kern/src/syscall.c

/* See COPYRIGHT for copyright information. */

#ifdef __SHARC__
#pragma nosharc
#endif

//#define DEBUG
#include <ros/common.h>
#include <arch/types.h>
#include <arch/arch.h>
#include <arch/mmu.h>
#include <arch/console.h>
#include <time.h>
#include <error.h>

#include <elf.h>
#include <string.h>
#include <assert.h>
#include <process.h>
#include <schedule.h>
#include <pmap.h>
#include <umem.h>
#include <mm.h>
#include <trap.h>
#include <syscall.h>
#include <kmalloc.h>
#include <stdio.h>
#include <frontend.h>
#include <colored_caches.h>
#include <hashtable.h>
#include <bitmask.h>
#include <vfs.h>
#include <devfs.h>
#include <smp.h>
#include <arsc_server.h>
#include <event.h>
#include <termios.h>
#include <socket.h>

#ifdef CONFIG_NETWORKING
#include <net/nic_common.h>
extern int (*send_frame)(const char *CT(len) data, size_t len);
extern unsigned char device_mac[6];
#endif

/* Tracing Globals */
int systrace_flags = 0;
struct systrace_record *systrace_buffer = 0;
uint32_t systrace_bufidx = 0;
size_t systrace_bufsize = 0;
struct proc *systrace_procs[MAX_NUM_TRACED] = {0};
spinlock_t systrace_lock = SPINLOCK_INITIALIZER_IRQSAVE;

/* Not enforcing the packing of systrace_procs yet, but don't rely on that */
static bool proc_is_traced(struct proc *p)
{
	for (int i = 0; i < MAX_NUM_TRACED; i++)
		if (systrace_procs[i] == p)
			return true;
	return false;
}

/* Helper to finish a syscall, signalling if appropriate */
static void finish_sysc(struct syscall *sysc, struct proc *p)
{
	/* Atomically turn on the LOCK and SC_DONE flag.  The lock tells userspace
	 * we're messing with the flags and to not proceed.  We use it instead of
	 * CASing with userspace.  We need the atomics since we're racing with
	 * userspace for the event_queue registration.  The 'lock' tells userspace
	 * to not muck with the flags while we're signalling. */
	atomic_or(&sysc->flags, SC_K_LOCK | SC_DONE);
	__signal_syscall(sysc, p);
	atomic_and(&sysc->flags, ~SC_K_LOCK); 
}

/* Helper that "finishes" the current async syscall.  This should be used with
 * care when we are not using the normal syscall completion path.
 *
 * Do *NOT* complete the same syscall twice.  This is catastrophic for _Ms, and
 * a bad idea for _S.
 *
 * It is possible for another user thread to see the syscall being done early -
 * they just need to be careful with the weird proc management calls (as in,
 * don't trust an async fork).
 *
 * *sysc is in user memory, and should be pinned (TODO: UMEM).  There may be
 * issues with unpinning this if we never return. */
static void finish_current_sysc(int retval)
{
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
	assert(pcpui->cur_kthread->sysc);
	pcpui->cur_kthread->sysc->retval = retval;
	finish_sysc(pcpui->cur_kthread->sysc, pcpui->cur_proc);
}

/* Callable by any function while executing a syscall (or otherwise, actually).
 */
void set_errno(int errno)
{
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
	if (pcpui->cur_kthread && pcpui->cur_kthread->sysc)
		pcpui->cur_kthread->sysc->err = errno;
}

void unset_errno(void)
{
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
	if (!pcpui->cur_kthread || !pcpui->cur_kthread->sysc)
		return;
	pcpui->cur_kthread->sysc->err = 0;
	pcpui->cur_kthread->sysc->errstr[0] = '\0';
}

void set_errstr(char *fmt, ...)
{
	va_list ap;
	int rc;

	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
	if (!pcpui->cur_kthread || !pcpui->cur_kthread->sysc)
		return;

	va_start(ap, fmt);
	rc = vsnprintf(pcpui->cur_kthread->sysc->errstr, MAX_ERRSTR_LEN, fmt, ap);
	va_end(ap);

	/* TODO: likely not needed */
	pcpui->cur_kthread->sysc->errstr[MAX_ERRSTR_LEN - 1] = '\0';
}

char *current_errstr(void)
{
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
	/* no one should call this that doesn't have a sysc */
	assert(pcpui->cur_kthread->sysc);
	return pcpui->cur_kthread->sysc->errstr;
}

struct errbuf *get_cur_errbuf(void)
{
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
	return (struct errbuf*)pcpui->cur_kthread->errbuf;
}

void set_cur_errbuf(struct errbuf *ebuf)
{
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
	pcpui->cur_kthread->errbuf = ebuf;
}

char *get_cur_genbuf(void)
{
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
	assert(pcpui->cur_kthread);
	return pcpui->cur_kthread->generic_buf;
}

/************** Utility Syscalls **************/

static int sys_null(void)
{
	return 0;
}

/* Diagnostic function: blocks the kthread/syscall, to help userspace test its
 * async I/O handling. */
static int sys_block(struct proc *p, unsigned int usec)
{
	struct timer_chain *tchain = &per_cpu_info[core_id()].tchain;
	struct alarm_waiter a_waiter;
	init_awaiter(&a_waiter, 0);
	/* Note printing takes a few ms, so your printds won't be perfect. */
	printd("[kernel] sys_block(), sleeping at %llu\n", read_tsc());
	set_awaiter_rel(&a_waiter, usec);
	set_alarm(tchain, &a_waiter);
	sleep_on_awaiter(&a_waiter);
	printd("[kernel] sys_block(), waking up at %llu\n", read_tsc());
	return 0;
}

// Writes 'val' to 'num_writes' entries of the well-known array in the kernel
// address space.  It's just #defined to be some random 4MB chunk (which ought
// to be boot_alloced or something).  Meant to grab exclusive access to cache
// lines, to simulate doing something useful.
static int sys_cache_buster(struct proc *p, uint32_t num_writes,
                             uint32_t num_pages, uint32_t flags)
{
	#define BUSTER_ADDR		0xd0000000L  // around 512 MB deep
	#define MAX_WRITES		1048576*8
	#define MAX_PAGES		32
	#define INSERT_ADDR 	(UINFO + 2*PGSIZE) // should be free for these tests
	uint32_t* buster = (uint32_t*)BUSTER_ADDR;
	static spinlock_t buster_lock = SPINLOCK_INITIALIZER;
	uint64_t ticks = -1;
	page_t* a_page[MAX_PAGES];

	/* Strided Accesses or Not (adjust to step by cachelines) */
	uint32_t stride = 1;
	if (flags & BUSTER_STRIDED) {
		stride = 16;
		num_writes *= 16;
	}

	/* Shared Accesses or Not (adjust to use per-core regions)
	 * Careful, since this gives 8MB to each core, starting around 512MB.
	 * Also, doesn't separate memory for core 0 if it's an async call.
	 */
	if (!(flags & BUSTER_SHARED))
		buster = (uint32_t*)(BUSTER_ADDR + core_id() * 0x00800000);

	/* Start the timer, if we're asked to print this info*/
	if (flags & BUSTER_PRINT_TICKS)
		ticks = start_timing();

	/* Allocate num_pages (up to MAX_PAGES), to simulate doing some more
	 * realistic work.  Note we don't write to these pages, even if we pick
	 * unshared.  Mostly due to the inconvenience of having to match up the
	 * number of pages with the number of writes.  And it's unnecessary.
	 */
	if (num_pages) {
		spin_lock(&buster_lock);
		for (int i = 0; i < MIN(num_pages, MAX_PAGES); i++) {
			upage_alloc(p, &a_page[i],1);
			page_insert(p->env_pgdir, a_page[i], (void*)INSERT_ADDR + PGSIZE*i,
			            PTE_USER_RW);
			page_decref(a_page[i]);
		}
		spin_unlock(&buster_lock);
	}

	if (flags & BUSTER_LOCKED)
		spin_lock(&buster_lock);
	for (int i = 0; i < MIN(num_writes, MAX_WRITES); i=i+stride)
		buster[i] = 0xdeadbeef;
	if (flags & BUSTER_LOCKED)
		spin_unlock(&buster_lock);

	if (num_pages) {
		spin_lock(&buster_lock);
		for (int i = 0; i < MIN(num_pages, MAX_PAGES); i++) {
			page_remove(p->env_pgdir, (void*)(INSERT_ADDR + PGSIZE * i));
			page_decref(a_page[i]);
		}
		spin_unlock(&buster_lock);
	}

	/* Print info */
	if (flags & BUSTER_PRINT_TICKS) {
		ticks = stop_timing(ticks);
		printk("%llu,", ticks);
	}
	return 0;
}

static int sys_cache_invalidate(void)
{
	#ifdef CONFIG_X86
		wbinvd();
	#endif
	return 0;
}

/* sys_reboot(): called directly from dispatch table. */

/* Print a string to the system console. */
static ssize_t sys_cputs(struct proc *p, const char *DANGEROUS string,
                         size_t strlen)
{
	char *t_string;
	t_string = user_strdup_errno(p, string, strlen);
	if (!t_string)
		return -1;
	printk("%.*s", strlen, t_string);
	user_memdup_free(p, t_string);
	return (ssize_t)strlen;
}

// Read a character from the system console.
// Returns the character.
/* TODO: remove me */
static uint16_t sys_cgetc(struct proc *p)
{
	uint16_t c;

	// The cons_get_any_char() primitive doesn't wait for a character,
	// but the sys_cgetc() system call does.
	while ((c = cons_get_any_char()) == 0)
		cpu_relax();

	return c;
}

/* Returns the id of the physical core this syscall is executed on. */
static uint32_t sys_getpcoreid(void)
{
	return core_id();
}

// TODO: Temporary hack until thread-local storage is implemented on i386 and
// this is removed from the user interface
static size_t sys_getvcoreid(struct proc *p)
{
	return proc_get_vcoreid(p);
}

/************** Process management syscalls **************/

/* Returns the calling process's pid */
static pid_t sys_getpid(struct proc *p)
{
	return p->pid;
}

/* Creates a process from the file 'path'.  The process is not runnable by
 * default, so it needs it's status to be changed so that the next call to
 * schedule() will try to run it.  TODO: take args/envs from userspace. */
static int sys_proc_create(struct proc *p, char *path, size_t path_l,
                           struct procinfo *pi)
{
	int pid = 0;
	char *t_path;
	struct file *program;
	struct proc *new_p;

	/* Copy in the path.  Consider putting an upper bound on path_l. */
	t_path = user_strdup_errno(p, path, path_l);
	if (!t_path)
		return -1;
	/* TODO: 9ns support */
	program = do_file_open(t_path, 0, 0);
	user_memdup_free(p, t_path);
	if (!program)
		return -1;			/* presumably, errno is already set */
	/* TODO: need to split the proc creation, since you must load after setting
	 * args/env, since auxp gets set up there. */
	//new_p = proc_create(program, 0, 0);
	if (proc_alloc(&new_p, current))
		goto mid_error;
	/* Set the argument stuff needed by glibc */
	if (memcpy_from_user_errno(p, new_p->procinfo->argp, pi->argp,
	                           sizeof(pi->argp)))
		goto late_error;
	if (memcpy_from_user_errno(p, new_p->procinfo->argbuf, pi->argbuf,
	                           sizeof(pi->argbuf)))
		goto late_error;
	if (load_elf(new_p, program))
		goto late_error;
	kref_put(&program->f_kref);
	/* Connect to stdin, stdout, stderr (part of proc_create()) */
	assert(insert_file(&new_p->open_files, dev_stdin,  0) == 0);
	assert(insert_file(&new_p->open_files, dev_stdout, 0) == 1);
	assert(insert_file(&new_p->open_files, dev_stderr, 0) == 2);
	__proc_ready(new_p);
	pid = new_p->pid;
	proc_decref(new_p);	/* give up the reference created in proc_create() */
	return pid;
late_error:
	proc_destroy(new_p);
	proc_decref(new_p);	/* give up the reference created in proc_create() */
mid_error:
	kref_put(&program->f_kref);
	return -1;
}

/* Makes process PID runnable.  Consider moving the functionality to process.c */
static error_t sys_proc_run(struct proc *p, unsigned pid)
{
	struct proc *target = pid2proc(pid);
	error_t retval = 0;

	if (!target) {
		set_errno(ESRCH);
		return -1;
	}
	/* make sure we have access and it's in the right state to be activated */
	if (!proc_controls(p, target)) {
		set_errno(EPERM);
		goto out_error;
	} else if (target->state != PROC_CREATED) {
		set_errno(EINVAL);
		goto out_error;
	}
	/* Note a proc can spam this for someone it controls.  Seems safe - if it
	 * isn't we can change it. */
	proc_wakeup(target);
	proc_decref(target);
	return 0;
out_error:
	proc_decref(target);
	return -1;
}

/* Destroy proc pid.  If this is called by the dying process, it will never
 * return.  o/w it will return 0 on success, or an error.  Errors include:
 * - ESRCH: if there is no such process with pid
 * - EPERM: if caller does not control pid */
static error_t sys_proc_destroy(struct proc *p, pid_t pid, int exitcode)
{
	error_t r;
	struct proc *p_to_die = pid2proc(pid);

	if (!p_to_die) {
		set_errno(ESRCH);
		return -1;
	}
	if (!proc_controls(p, p_to_die)) {
		proc_decref(p_to_die);
		set_errno(EPERM);
		return -1;
	}
	if (p_to_die == p) {
		p->exitcode = exitcode;
		printd("[PID %d] proc exiting gracefully (code %d)\n", p->pid,exitcode);
	} else {
		p_to_die->exitcode = exitcode; 	/* so its parent has some clue */
		printd("[%d] destroying proc %d\n", p->pid, p_to_die->pid);
	}
	proc_destroy(p_to_die);
	/* we only get here if we weren't the one to die */
	proc_decref(p_to_die);
	return 0;
}

static int sys_proc_yield(struct proc *p, bool being_nice)
{
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
	/* proc_yield() often doesn't return - we need to set the syscall retval
	 * early.  If it doesn't return, it expects to eat our reference (for now).
	 */
	finish_sysc(pcpui->cur_kthread->sysc, pcpui->cur_proc);
	pcpui->cur_kthread->sysc = 0;	/* don't touch sysc again */
	proc_incref(p, 1);
	proc_yield(p, being_nice);
	proc_decref(p);
	/* Shouldn't return, to prevent the chance of mucking with cur_sysc. */
	smp_idle();
	assert(0);
}

static int sys_change_vcore(struct proc *p, uint32_t vcoreid,
                             bool enable_my_notif)
{
	/* Note retvals can be negative, but we don't mess with errno in case
	 * callers use this in low-level code and want to extract the 'errno'. */
	return proc_change_to_vcore(p, vcoreid, enable_my_notif);
}

static ssize_t sys_fork(env_t* e)
{
	struct proc *temp;
	int8_t state = 0;

	// TODO: right now we only support fork for single-core processes
	if (e->state != PROC_RUNNING_S) {
		set_errno(EINVAL);
		return -1;
	}
	env_t* env;
	assert(!proc_alloc(&env, current));
	assert(env != NULL);

	env->heap_top = e->heap_top;
	env->ppid = e->pid;
	disable_irqsave(&state);	/* protect cur_ctx */
	/* Can't really fork if we don't have a current_ctx to fork */
	if (!current_ctx) {
		set_errno(EINVAL);
		return -1;
	}
	env->scp_ctx = *current_ctx;
	enable_irqsave(&state);

	env->cache_colors_map = cache_colors_map_alloc();
	for(int i=0; i < llc_cache->num_colors; i++)
		if(GET_BITMASK_BIT(e->cache_colors_map,i))
			cache_color_alloc(llc_cache, env->cache_colors_map);

	/* Make the new process have the same VMRs as the older.  This will copy the
	 * contents of non MAP_SHARED pages to the new VMRs. */
	if (duplicate_vmrs(e, env)) {
		proc_destroy(env);	/* this is prob what you want, not decref by 2 */
		proc_decref(env);
		set_errno(ENOMEM);
		return -1;
	}
	/* Switch to the new proc's address space and finish the syscall.  We'll
	 * never naturally finish this syscall for the new proc, since its memory
	 * is cloned before we return for the original process.  If we ever do CoW
	 * for forked memory, this will be the first place that gets CoW'd. */
	temp = switch_to(env);
	finish_current_sysc(0);
	switch_back(env, temp);

	/* In general, a forked process should be a fresh process, and we copy over
	 * whatever stuff is needed between procinfo/procdata. */
	/* Copy over the procinfo argument stuff in case they don't exec */
	memcpy(env->procinfo->argp, e->procinfo->argp, sizeof(e->procinfo->argp));
	memcpy(env->procinfo->argbuf, e->procinfo->argbuf,
	       sizeof(e->procinfo->argbuf));
	#ifdef CONFIG_X86
	/* new guy needs to know about ldt (everything else in procdata is fresh */
	env->procdata->ldt = e->procdata->ldt;
	#endif

	clone_files(&e->open_files, &env->open_files);
	/* FYI: once we call ready, the proc is open for concurrent usage */
	__proc_ready(env);
	proc_wakeup(env);

	// don't decref the new process.
	// that will happen when the parent waits for it.
	// TODO: if the parent doesn't wait, we need to change the child's parent
	// when the parent dies, or at least decref it

	printd("[PID %d] fork PID %d\n", e->pid, env->pid);
	return env->pid;
}

/* Load the binary "path" into the current process, and start executing it.
 * argv and envp are magically bundled in procinfo for now.  Keep in sync with
 * glibc's sysdeps/ros/execve.c.  Once past a certain point, this function won't
 * return.  It assumes (and checks) that it is current.  Don't give it an extra
 * refcnt'd *p (syscall won't do that). 
 * Note: if someone batched syscalls with this call, they could clobber their
 * old memory (and will likely PF and die).  Don't do it... */
static int sys_exec(struct proc *p, char *path, size_t path_l,
                    struct procinfo *pi)
{
	int ret = -1;
	char *t_path;
	struct file *program;
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
	int8_t state = 0;

	/* We probably want it to never be allowed to exec if it ever was _M */
	if (p->state != PROC_RUNNING_S) {
		set_errno(EINVAL);
		return -1;
	}
	if (p != pcpui->cur_proc) {
		set_errno(EINVAL);
		return -1;
	}
	/* Copy in the path.  Consider putting an upper bound on path_l. */
	t_path = user_strdup_errno(p, path, path_l);
	if (!t_path)
		return -1;
	disable_irqsave(&state);	/* protect cur_ctx */
	/* Can't exec if we don't have a current_ctx to restart (if we fail).  This
	 * isn't 100% true, but I'm okay with it. */
	if (!pcpui->cur_ctx) {
		enable_irqsave(&state);
		set_errno(EINVAL);
		return -1;
	}
	/* Preemptively copy out the cur_ctx, in case we fail later (easier on
	 * cur_ctx if we do this now) */
	p->scp_ctx = *pcpui->cur_ctx;
	/* Clear the current_ctx.  We won't be returning the 'normal' way.  Even if
	 * we want to return with an error, we need to go back differently in case
	 * we succeed.  This needs to be done before we could possibly block, but
	 * unfortunately happens before the point of no return. */
	pcpui->cur_ctx = 0;
	enable_irqsave(&state);
	/* This could block: */
	/* TODO: 9ns support */
	program = do_file_open(t_path, 0, 0);
	user_memdup_free(p, t_path);
	if (!program)
		goto early_error;
	/* Set the argument stuff needed by glibc */
	if (memcpy_from_user_errno(p, p->procinfo->argp, pi->argp,
	                           sizeof(pi->argp)))
		goto mid_error;
	if (memcpy_from_user_errno(p, p->procinfo->argbuf, pi->argbuf,
	                           sizeof(pi->argbuf)))
		goto mid_error;
	/* This is the point of no return for the process. */
	#ifdef CONFIG_X86
	/* clear this, so the new program knows to get an LDT */
	p->procdata->ldt = 0;
	#endif
	/* When we destroy our memory regions, accessing cur_sysc would PF */
	pcpui->cur_kthread->sysc = 0;
	unmap_and_destroy_vmrs(p);
	close_9ns_files(p, TRUE);
	close_all_files(&p->open_files, TRUE);
	env_user_mem_free(p, 0, UMAPTOP);
	if (load_elf(p, program)) {
		kref_put(&program->f_kref);
		/* Note this is an inedible reference, but proc_destroy now returns */
		proc_destroy(p);
		/* We don't want to do anything else - we just need to not accidentally
		 * return to the user (hence the all_out) */
		goto all_out;
	}
	printd("[PID %d] exec %s\n", p->pid, file_name(program));
	kref_put(&program->f_kref);
	goto success;
	/* These error and out paths are so we can handle the async interface, both
	 * for when we want to error/return to the proc, as well as when we succeed
	 * and want to start the newly exec'd _S */
mid_error:
	/* These two error paths are for when we want to restart the process with an
	 * error value (errno is already set). */
	kref_put(&program->f_kref);
early_error:
	finish_current_sysc(-1);
success:
	/* Here's how we restart the new (on success) or old (on failure) proc: */
	spin_lock(&p->proc_lock);
	__unmap_vcore(p, 0);	/* VC# keep in sync with proc_run_s */
	__proc_set_state(p, PROC_WAITING);	/* fake a yield */
	spin_unlock(&p->proc_lock);
	proc_wakeup(p);
all_out:
	/* we can't return, since we'd write retvals to the old location of the
	 * syscall struct (which has been freed and is in the old userspace) (or has
	 * already been written to).*/
	disable_irq();			/* abandon_core/clear_own wants irqs disabled */
	clear_owning_proc(core_id());
	abandon_core();
	smp_idle();				/* will reenable interrupts */
}

/* Helper, will attempt a particular wait on a proc.  Returns the pid of the
 * process if we waited on it successfully, and the status will be passed back
 * in ret_status (kernel memory).  Returns 0 if the wait failed and we should
 * try again.  Returns -1 if we should abort.  Only handles DYING.  Callers
 * need to lock to protect the children tailq and reaping bits. */
static pid_t try_wait(struct proc *parent, struct proc *child, int *ret_status,
                      int options)
{
	if (child->state == PROC_DYING) {
		/* Disown returns -1 if it's already been disowned or we should o/w
		 * abort.  This can happen if we have concurrent waiters, both with
		 * pointers to the child (only one should reap).  Note that if we don't
		 * do this, we could go to sleep and never receive a cv_signal. */
		if (__proc_disown_child(parent, child))
			return -1;
		/* despite disowning, the child won't be freed til we drop this ref
		 * held by this function, so it is safe to access the memory.
		 *
		 * Note the exit code one byte in the 0xff00 spot.  Check out glibc's
		 * posix/sys/wait.h and bits/waitstatus.h for more info.  If we ever
		 * deal with signalling and stopping, we'll need to do some more work
		 * here.*/
		*ret_status = (child->exitcode & 0xff) << 8;
		return child->pid;
	}
	return 0;
}

/* Helper, like try_wait, but attempts a wait on any of the children, returning
 * the specific PID we waited on, 0 to try again (a waitable exists), and -1 to
 * abort (no children/waitables exist).  Callers need to lock to protect the
 * children tailq and reaping bits.*/
static pid_t try_wait_any(struct proc *parent, int *ret_status, int options)
{
	struct proc *i, *temp;
	pid_t retval;
	if (TAILQ_EMPTY(&parent->children))
		return -1;
	/* Could have concurrent waiters mucking with the tailq, caller must lock */
	TAILQ_FOREACH_SAFE(i, &parent->children, sibling_link, temp) {
		retval = try_wait(parent, i, ret_status, options);
		/* This catches a thread causing a wait to fail but not taking the
		 * child off the list before unlocking.  Should never happen. */
		assert(retval != -1);
		/* Succeeded, return the pid of the child we waited on */
		if (retval)
			return retval;
	}
	assert(retval == 0);
	return 0;
}

/* Waits on a particular child, returns the pid of the child waited on, and
 * puts the ret status in *ret_status.  Returns the pid if we succeeded, 0 if
 * the child was not waitable and WNOHANG, and -1 on error. */
static pid_t wait_one(struct proc *parent, struct proc *child, int *ret_status,
                      int options)
{
	pid_t retval;
	cv_lock(&parent->child_wait);
	/* retval == 0 means we should block */
	retval = try_wait(parent, child, ret_status, options);
	if ((retval == 0) && (options & WNOHANG))
		goto out_unlock;
	while (!retval) {
		cpu_relax();
		cv_wait(&parent->child_wait);
		/* If we're dying, then we don't need to worry about waiting.  We don't
		 * do this yet, but we'll need this outlet when we deal with orphaned
		 * children and having init inherit them. */
		if (parent->state == PROC_DYING)
			goto out_unlock;
		/* Any child can wake us up, but we check for the particular child we
		 * care about */
		retval = try_wait(parent, child, ret_status, options);
	}
	if (retval == -1) {
		/* Child was already waited on by a concurrent syscall. */
		set_errno(ECHILD);
	}
	/* Fallthrough */
out_unlock:
	cv_unlock(&parent->child_wait);
	return retval;
}

/* Waits on any child, returns the pid of the child waited on, and puts the ret
 * status in *ret_status.  Is basically a waitpid(-1, ... );  See wait_one for
 * more details.  Returns -1 if there are no children to wait on, and returns 0
 * if there are children and we need to block but WNOHANG was set. */
static pid_t wait_any(struct proc *parent, int *ret_status, int options)
{
	pid_t retval;
	cv_lock(&parent->child_wait);
	retval = try_wait_any(parent, ret_status, options);
	if ((retval == 0) && (options & WNOHANG))
		goto out_unlock;
	while (!retval) {
		cpu_relax();
		cv_wait(&parent->child_wait);
		if (parent->state == PROC_DYING)
			goto out_unlock;
		/* Any child can wake us up from the CV.  This is a linear try_wait
		 * scan.  If we have a lot of children, we could optimize this. */
		retval = try_wait_any(parent, ret_status, options);
	}
	if (retval == -1)
		assert(TAILQ_EMPTY(&parent->children));
	/* Fallthrough */
out_unlock:
	cv_unlock(&parent->child_wait);
	return retval;
}

/* Note: we only allow waiting on children (no such thing as threads, for
 * instance).  Right now we only allow waiting on termination (not signals),
 * and we don't have a way for parents to disown their children (such as
 * ignoring SIGCHLD, see man 2 waitpid's Notes).
 *
 * We don't bother with stop/start signals here, though we can probably build
 * it in the helper above.
 *
 * Returns the pid of who we waited on, or -1 on error, or 0 if we couldn't
 * wait (WNOHANG). */
static pid_t sys_waitpid(struct proc *parent, pid_t pid, int *status,
                         int options)
{
	struct proc *child;
	pid_t retval = 0;
	int ret_status = 0;

	/* -1 is the signal for 'any child' */
	if (pid == -1) {
		retval = wait_any(parent, &ret_status, options);
		goto out;
	}
	child = pid2proc(pid);
	if (!child) {
		set_errno(ECHILD);	/* ECHILD also used for no proc */
		retval = -1;
		goto out;
	}
	if (!(parent->pid == child->ppid)) {
		set_errno(ECHILD);
		retval = -1;
		goto out_decref;
	}
	retval = wait_one(parent, child, &ret_status, options);
	/* fall-through */
out_decref:
	proc_decref(child);
out:
	/* ignoring / don't care about memcpy's retval here. */
	if (status)
		memcpy_to_user(parent, status, &ret_status, sizeof(ret_status));
	printd("[PID %d] waited for PID %d, got retval %d (status 0x%x)\n",
	       parent->pid, pid, retval, ret_status);
	return retval;
}

/************** Memory Management Syscalls **************/

static void *sys_mmap(struct proc *p, uintptr_t addr, size_t len, int prot,
                      int flags, int fd, off_t offset)
{
	return mmap(p, addr, len, prot, flags, fd, offset);
}

static intreg_t sys_mprotect(struct proc *p, void *addr, size_t len, int prot)
{
	return mprotect(p, (uintptr_t)addr, len, prot);
}

static intreg_t sys_munmap(struct proc *p, void *addr, size_t len)
{
	return munmap(p, (uintptr_t)addr, len);
}

static ssize_t sys_shared_page_alloc(env_t* p1,
                                     void**DANGEROUS _addr, pid_t p2_id,
                                     int p1_flags, int p2_flags
                                    )
{
	printk("[kernel] shared page alloc is deprecated/unimplemented.\n");
	return -1;
}

static int sys_shared_page_free(env_t* p1, void*DANGEROUS addr, pid_t p2)
{
	return -1;
}

/* Helper, to do the actual provisioning of a resource to a proc */
static int prov_resource(struct proc *target, unsigned int res_type,
                         long res_val)
{
	switch (res_type) {
		case (RES_CORES):
			/* in the off chance we have a kernel scheduler that can't
			 * provision, we'll need to change this. */
			return provision_core(target, res_val);
		default:
			printk("[kernel] received provisioning for unknown resource %d\n",
			       res_type);
			set_errno(ENOENT);	/* or EINVAL? */
			return -1;
	}
}

/* Rough syscall to provision res_val of type res_type to target_pid */
static int sys_provision(struct proc *p, int target_pid,
                         unsigned int res_type, long res_val)
{
	struct proc *target = pid2proc(target_pid);
	int retval;
	if (!target) {
		if (target_pid == 0)
			return prov_resource(0, res_type, res_val);
		/* debugging interface */
		if (target_pid == -1)
			print_prov_map();
		set_errno(ESRCH);
		return -1;
	}
	retval = prov_resource(target, res_type, res_val);
	proc_decref(target);
	return retval;
}

/* Untested.  Will notify the target on the given vcore, if the caller controls
 * the target.  Will honor the target's wanted/vcoreid.  u_ne can be NULL. */
static int sys_notify(struct proc *p, int target_pid, unsigned int ev_type,
                      struct event_msg *u_msg)
{
	struct event_msg local_msg = {0};
	struct proc *target = pid2proc(target_pid);
	if (!target) {
		set_errno(ESRCH);
		return -1;
	}
	if (!proc_controls(p, target)) {
		proc_decref(target);
		set_errno(EPERM);
		return -1;
	}
	/* if the user provided an ev_msg, copy it in and use that */
	if (u_msg) {
		if (memcpy_from_user(p, &local_msg, u_msg, sizeof(struct event_msg))) {
			proc_decref(target);
			set_errno(EINVAL);
			return -1;
		}
	} else {
		local_msg.ev_type = ev_type;
	}
	send_kernel_event(target, &local_msg, 0);
	proc_decref(target);
	return 0;
}

/* Will notify the calling process on the given vcore, independently of WANTED
 * or advertised vcoreid.  If you change the parameters, change pop_user_ctx().
 */
static int sys_self_notify(struct proc *p, uint32_t vcoreid,
                           unsigned int ev_type, struct event_msg *u_msg,
                           bool priv)
{
	struct event_msg local_msg = {0};
	/* if the user provided an ev_msg, copy it in and use that */
	if (u_msg) {
		if (memcpy_from_user(p, &local_msg, u_msg, sizeof(struct event_msg))) {
			set_errno(EINVAL);
			return -1;
		}
	} else {
		local_msg.ev_type = ev_type;
	}
	if (local_msg.ev_type >= MAX_NR_EVENT) {
		printk("[kernel] received self-notify for vcoreid %d, ev_type %d, "
		       "u_msg %p, u_msg->type %d\n", vcoreid, ev_type, u_msg,
		       u_msg ? u_msg->ev_type : 0);
		return -1;
	}
	/* this will post a message and IPI, regardless of wants/needs/debutantes.*/
	post_vcore_event(p, &local_msg, vcoreid, priv ? EVENT_VCORE_PRIVATE : 0);
	proc_notify(p, vcoreid);
	return 0;
}

/* Puts the calling core into vcore context, if it wasn't already, via a
 * self-IPI / active notification.  Barring any weird unmappings, we just send
 * ourselves a __notify. */
static int sys_vc_entry(struct proc *p)
{
	send_kernel_message(core_id(), __notify, (long)p, 0, 0, KMSG_ROUTINE);
	return 0;
}

/* This will set a local timer for usec, then shut down the core.  There's a
 * slight race between spinner and halt.  For now, the core will wake up for
 * other interrupts and service them, but will not process routine messages or
 * do anything other than halt until the alarm goes off.  We could just unset
 * the alarm and return early.  On hardware, there are a lot of interrupts that
 * come in.  If we ever use this, we can take a closer look.  */
static int sys_halt_core(struct proc *p, unsigned int usec)
{
	struct timer_chain *tchain = &per_cpu_info[core_id()].tchain;
	struct alarm_waiter a_waiter;
	bool spinner = TRUE;
	void unblock(struct alarm_waiter *waiter)
	{
		spinner = FALSE;
	}
	init_awaiter(&a_waiter, unblock);
	set_awaiter_rel(&a_waiter, MAX(usec, 100));
	set_alarm(tchain, &a_waiter);
	enable_irq();
	/* Could wake up due to another interrupt, but we want to sleep still. */
	while (spinner) {
		cpu_halt();	/* slight race between spinner and halt */
		cpu_relax();
	}
	printd("Returning from halting\n");
	return 0;
}

/* Changes a process into _M mode, or -EINVAL if it already is an mcp.
 * __proc_change_to_m() returns and we'll eventually finish the sysc later.  The
 * original context may restart on a remote core before we return and finish,
 * but that's fine thanks to the async kernel interface. */
static int sys_change_to_m(struct proc *p)
{
	int retval = proc_change_to_m(p);
	/* convert the kernel error code into (-1, errno) */
	if (retval) {
		set_errno(-retval);
		retval = -1;
	}
	return retval;
}

/* Pokes the ksched for the given resource for target_pid.  If the target pid
 * == 0, we just poke for the calling process.  The common case is poking for
 * self, so we avoid the lookup. 
 *
 * Not sure if you could harm someone via asking the kernel to look at them, so
 * we'll do a 'controls' check for now.  In the future, we might have something
 * in the ksched that limits or penalizes excessive pokes. */
static int sys_poke_ksched(struct proc *p, int target_pid,
                           unsigned int res_type)
{
	struct proc *target;
	int retval = 0;
	if (!target_pid) {
		poke_ksched(p, res_type);
		return 0;
	}
	target = pid2proc(target_pid);
	if (!target) {
		set_errno(ESRCH);
		return -1;
	}
	if (!proc_controls(p, target)) {
		set_errno(EPERM);
		retval = -1;
		goto out;
	}
	poke_ksched(target, res_type);
out:
	proc_decref(target);
	return retval;
}

static int sys_abort_sysc(struct proc *p, struct syscall *sysc)
{
	return abort_sysc(p, sysc);
}

/************** Platform Specific Syscalls **************/

//Read a buffer over the serial port
static ssize_t sys_serial_read(env_t* e, char *DANGEROUS _buf, size_t len)
{
	printk("[kernel] serial reading is deprecated.\n");
	if (len == 0)
		return 0;

	#ifdef CONFIG_SERIAL_IO
	    char *COUNT(len) buf = user_mem_assert(e, _buf, len, 1, PTE_USER_RO);
		size_t bytes_read = 0;
		int c;
		while((c = serial_read_byte()) != -1) {
			buf[bytes_read++] = (uint8_t)c;
			if(bytes_read == len) break;
		}
		return (ssize_t)bytes_read;
	#else
		return -EINVAL;
	#endif
}

//Write a buffer over the serial port
static ssize_t sys_serial_write(env_t* e, const char *DANGEROUS buf, size_t len)
{
	printk("[kernel] serial writing is deprecated.\n");
	if (len == 0)
		return 0;
	#ifdef CONFIG_SERIAL_IO
		char *COUNT(len) _buf = user_mem_assert(e, buf, len, 1, PTE_USER_RO);
		for(int i =0; i<len; i++)
			serial_send_byte(buf[i]);
		return (ssize_t)len;
	#else
		return -EINVAL;
	#endif
}

#ifdef CONFIG_NETWORKING
// This is not a syscall we want. Its hacky. Here just for syscall stuff until get a stack.
static ssize_t sys_eth_read(env_t* e, char *DANGEROUS buf)
{
	if (eth_up) {

		uint32_t len;
		char *ptr;

		spin_lock(&packet_buffers_lock);

		if (num_packet_buffers == 0) {
			spin_unlock(&packet_buffers_lock);
			return 0;
		}

		ptr = packet_buffers[packet_buffers_head];
		len = packet_buffers_sizes[packet_buffers_head];

		num_packet_buffers--;
		packet_buffers_head = (packet_buffers_head + 1) % MAX_PACKET_BUFFERS;

		spin_unlock(&packet_buffers_lock);

		char* _buf = user_mem_assert(e, buf, len, 1, PTE_U);

		memcpy(_buf, ptr, len);

		kfree(ptr);

		return len;
	}
	else
		return -EINVAL;
}

// This is not a syscall we want. Its hacky. Here just for syscall stuff until get a stack.
static ssize_t sys_eth_write(env_t* e, const char *DANGEROUS buf, size_t len)
{
	if (eth_up) {

		if (len == 0)
			return 0;

		// HACK TO BYPASS HACK
		int just_sent = send_frame(buf, len);

		if (just_sent < 0) {
			printk("Packet send fail\n");
			return 0;
		}

		return just_sent;

		// END OF RECURSIVE HACK
/*
		char *COUNT(len) _buf = user_mem_assert(e, buf, len, PTE_U);
		int total_sent = 0;
		int just_sent = 0;
		int cur_packet_len = 0;
		while (total_sent != len) {
			cur_packet_len = ((len - total_sent) > MTU) ? MTU : (len - total_sent);
			char dest_mac[6] = APPSERVER_MAC_ADDRESS;
			char* wrap_buffer = eth_wrap(_buf + total_sent, cur_packet_len, device_mac, dest_mac, APPSERVER_PORT);
			just_sent = send_frame(wrap_buffer, cur_packet_len + sizeof(struct ETH_Header));

			if (just_sent < 0)
				return 0; // This should be an error code of its own

			if (wrap_buffer)
				kfree(wrap_buffer);

			total_sent += cur_packet_len;
		}

		return (ssize_t)len;
*/
	}
	else
		return -EINVAL;
}

static ssize_t sys_eth_get_mac_addr(env_t* e, char *DANGEROUS buf) 
{
	if (eth_up) {
		for (int i = 0; i < 6; i++)
			buf[i] = device_mac[i];
		return 0;
	}
	else
		return -EINVAL;
}

static int sys_eth_recv_check(env_t* e) 
{
	if (num_packet_buffers != 0) 
		return 1;
	else
		return 0;
}

#endif // Network

static intreg_t sys_read(struct proc *p, int fd, void *buf, int len)
{
	ssize_t ret;
	struct file *file = get_file_from_fd(&p->open_files, fd);
	/* VFS */
	if (file) {
		if (!file->f_op->read) {
			kref_put(&file->f_kref);
			set_errno(EINVAL);
			return -1;
		}
		/* TODO: (UMEM) currently, read() handles user memcpy
		 * issues, but we probably should user_mem_check and
		 * pin the region here, so read doesn't worry about
		 * it */
		ret = file->f_op->read(file, buf, len, &file->f_pos);
		kref_put(&file->f_kref);
		return ret;
	}
	/* plan9, should also handle errors (EBADF) */
    ret = sysread(fd, buf, len, ~0LL);
	return ret;
}

static intreg_t sys_write(struct proc *p, int fd, const void *buf, int len)
{
	ssize_t ret;
	struct file *file = get_file_from_fd(&p->open_files, fd);
	/* VFS */
	if (file) {
		if (!file->f_op->write) {
			kref_put(&file->f_kref);
			set_errno(EINVAL);
			return -1;
		}
		/* TODO: (UMEM) */
		ret = file->f_op->write(file, buf, len, &file->f_pos);
		kref_put(&file->f_kref);
		return ret;
	}
	/* plan9, should also handle errors */
	ret = syswrite(fd, (void*)buf, len, (off_t) -1);
	return ret;
}

/* Checks args/reads in the path, opens the file, and inserts it into the
 * process's open file list. */
static intreg_t sys_open(struct proc *p, const char *path, size_t path_l,
                         int oflag, int mode)
{
	int fd;
	struct file *file;

	printd("File %s Open attempt oflag %x mode %x\n", path, oflag, mode);
	char *t_path = user_strdup_errno(p, path, path_l);
	if (!t_path)
		return -1;
	mode &= ~p->fs_env.umask;
	file = do_file_open(t_path, oflag, mode);
	/* VFS */
	if (file) {
		fd = insert_file(&p->open_files, file, 0);	/* stores the ref to file */
		kref_put(&file->f_kref);	/* drop our ref */
		if (fd < 0)
			warn("File insertion failed");
	} else {
		unset_errno();	/* Go can't handle extra errnos */
		fd = sysopen(t_path, oflag);
	}
	user_memdup_free(p, t_path);
	printd("File %s Open, fd=%d\n", path, fd);
	return fd;
}

static intreg_t sys_close(struct proc *p, int fd)
{
	struct file *file = get_file_from_fd(&p->open_files, fd);
	int retval = 0;
	printd("sys_close %d\n", fd);
	/* VFS */
	if (file) {
		put_file_from_fd(&p->open_files, fd);
		kref_put(&file->f_kref);	/* Drop the ref from get_file */
		return 0;
	}
	/* 9ns, should also handle errors (bad FD, etc) */
	retval = sysclose(fd);
	return retval;
}

/* kept around til we remove the last ufe */
#define ufe(which,a0,a1,a2,a3) \
	frontend_syscall_errno(p,APPSERVER_SYSCALL_##which,\
	                   (int)(a0),(int)(a1),(int)(a2),(int)(a3))

static intreg_t sys_fstat(struct proc *p, int fd, struct kstat *u_stat)
{
	struct kstat *kbuf;
	struct file *file;
	kbuf = kmalloc(sizeof(struct kstat), 0);
	if (!kbuf) {
		set_errno(ENOMEM);
		return -1;
	}
	file = get_file_from_fd(&p->open_files, fd);
	/* VFS */
	if (file) {
		stat_inode(file->f_dentry->d_inode, kbuf);
		kref_put(&file->f_kref);
	} else {
	    if (sysfstat(fd, (uint8_t*)kbuf, sizeof(*kbuf)) < 0) {
			kfree(kbuf);
			return -1;
		}
	}
	/* TODO: UMEM: pin the memory, copy directly, and skip the kernel buffer */
	if (memcpy_to_user_errno(p, u_stat, kbuf, sizeof(struct kstat))) {
		kfree(kbuf);
		return -1;
	}
	kfree(kbuf);
	return 0;
}

/* sys_stat() and sys_lstat() do nearly the same thing, differing in how they
 * treat a symlink for the final item, which (probably) will be controlled by
 * the lookup flags */
static intreg_t stat_helper(struct proc *p, const char *path, size_t path_l,
                            struct kstat *u_stat, int flags)
{
	struct kstat *kbuf;
	struct dentry *path_d;
	char *t_path = user_strdup_errno(p, path, path_l);
	int retval = 0;
	if (!t_path)
		return -1;
	kbuf = kmalloc(sizeof(struct kstat), 0);
	if (!kbuf) {
		set_errno(ENOMEM);
		retval = -1;
		goto out_with_path;
	}
	/* Check VFS for path */
	path_d = lookup_dentry(t_path, flags);
	if (path_d) {
		stat_inode(path_d->d_inode, kbuf);
		kref_put(&path_d->d_kref);
	} else {
		/* VFS failed, checking 9ns */
		unset_errno();	/* Go can't handle extra errnos */
		retval = sysstat(t_path, (uint8_t*)kbuf, sizeof(*kbuf));
		printd("sysstat returns %d\n", retval);
		/* both VFS and 9ns failed, bail out */
		if (retval < 0)
			goto out_with_kbuf;
	}
	/* TODO: UMEM: pin the memory, copy directly, and skip the kernel buffer */
	if (memcpy_to_user_errno(p, u_stat, kbuf, sizeof(struct kstat)))
		retval = -1;
	/* Fall-through */
out_with_kbuf:
	kfree(kbuf);
out_with_path:
	user_memdup_free(p, t_path);
	return retval;
}

/* Follow a final symlink */
static intreg_t sys_stat(struct proc *p, const char *path, size_t path_l,
                         struct kstat *u_stat)
{
	return stat_helper(p, path, path_l, u_stat, LOOKUP_FOLLOW);
}

/* Don't follow a final symlink */
static intreg_t sys_lstat(struct proc *p, const char *path, size_t path_l,
                          struct kstat *u_stat)
{
	return stat_helper(p, path, path_l, u_stat, 0);
}

intreg_t sys_fcntl(struct proc *p, int fd, int cmd, int arg)
{
	int retval = 0;
	int newfd;
	struct file *file = get_file_from_fd(&p->open_files, fd);

	if (!file) {
		/* 9ns hack */
		switch (cmd) {
			case (F_DUPFD):
				return sysdup(fd, -1);
			case (F_GETFD):
			case (F_SETFD):
			case (F_GETFL):
			case (F_SETFL):
				return 0;
			default:
				warn("Unsupported fcntl cmd %d\n", cmd);
		}
		/* not really ever calling this, even for badf, due to the switch */
		set_errno(EBADF);
		return -1;
	}

	switch (cmd) {
		case (F_DUPFD):
			retval = insert_file(&p->open_files, file, arg);
			if (retval < 0) {
				set_errno(-retval);
				retval = -1;
			}
			break;
		case (F_GETFD):
			retval = p->open_files.fd[fd].fd_flags;
			break;
		case (F_SETFD):
			if (arg == FD_CLOEXEC)
				file->f_flags |= O_CLOEXEC;
			break;
		case (F_GETFL):
			retval = file->f_flags;
			break;
		case (F_SETFL):
			/* only allowed to set certain flags. */
			arg &= O_FCNTL_FLAGS;
			file->f_flags = (file->f_flags & ~O_FCNTL_FLAGS) | arg;
			break;
		default:
			warn("Unsupported fcntl cmd %d\n", cmd);
	}
	kref_put(&file->f_kref);
	return retval;
}

static intreg_t sys_access(struct proc *p, const char *path, size_t path_l,
                           int mode)
{
	int retval;
	char *t_path = user_strdup_errno(p, path, path_l);
	if (!t_path)
		return -1;
	/* TODO: 9ns support */
	retval = do_access(t_path, mode);
	user_memdup_free(p, t_path);
	printd("Access for path: %s retval: %d\n", path, retval);
	if (retval < 0) {
		set_errno(-retval);
		return -1;
	}
	return retval;
}

intreg_t sys_umask(struct proc *p, int mask)
{
	int old_mask = p->fs_env.umask;
	p->fs_env.umask = mask & S_PMASK;
	return old_mask;
}

intreg_t sys_chmod(struct proc *p, const char *path, size_t path_l, int mode)
{
	int retval;
	char *t_path = user_strdup_errno(p, path, path_l);
	if (!t_path)
		return -1;
	/* TODO: 9ns support */
	retval = do_chmod(t_path, mode);
	user_memdup_free(p, t_path);
	if (retval < 0) {
		set_errno(-retval);
		return -1;
	}
	return retval;
}

/* 64 bit seek, with the off64_t passed in via two (potentially 32 bit) off_ts.
 * We're supporting both 32 and 64 bit kernels/userspaces, but both use the
 * llseek syscall with 64 bit parameters. */
static intreg_t sys_llseek(struct proc *p, int fd, off_t offset_hi,
                           off_t offset_lo, off64_t *result, int whence)
{
	off64_t retoff = 0;
	off64_t tempoff = 0;
	int ret = 0;
	struct file *file = get_file_from_fd(&p->open_files, fd);
	if (!file) {
		set_errno(EBADF);
		return -1;
	}
	tempoff = offset_hi;
	tempoff <<= 32;
	tempoff |= offset_lo;
	ret = file->f_op->llseek(file, tempoff, &retoff, whence);
	kref_put(&file->f_kref);
	if (ret)
		return -1;
	if (memcpy_to_user_errno(p, result, &retoff, sizeof(off64_t)))
		return -1;
	return 0;
}

intreg_t sys_link(struct proc *p, char *old_path, size_t old_l,
                  char *new_path, size_t new_l)
{
	int ret;
	char *t_oldpath = user_strdup_errno(p, old_path, old_l);
	if (t_oldpath == NULL)
		return -1;
	char *t_newpath = user_strdup_errno(p, new_path, new_l);
	if (t_newpath == NULL) {
		user_memdup_free(p, t_oldpath);
		return -1;
	}
	ret = do_link(t_oldpath, t_newpath);
	user_memdup_free(p, t_oldpath);
	user_memdup_free(p, t_newpath);
	return ret;
}

intreg_t sys_unlink(struct proc *p, const char *path, size_t path_l)
{
	int retval;
	char *t_path = user_strdup_errno(p, path, path_l);
	if (!t_path)
		return -1;
	/* TODO: 9ns support */
	retval = do_unlink(t_path);
	user_memdup_free(p, t_path);
	return retval;
}

intreg_t sys_symlink(struct proc *p, char *old_path, size_t old_l,
                     char *new_path, size_t new_l)
{
	int ret;
	char *t_oldpath = user_strdup_errno(p, old_path, old_l);
	if (t_oldpath == NULL)
		return -1;
	char *t_newpath = user_strdup_errno(p, new_path, new_l);
	if (t_newpath == NULL) {
		user_memdup_free(p, t_oldpath);
		return -1;
	}
	ret = do_symlink(t_newpath, t_oldpath, S_IRWXU | S_IRWXG | S_IRWXO);
	user_memdup_free(p, t_oldpath);
	user_memdup_free(p, t_newpath);
	return ret;
}

intreg_t sys_readlink(struct proc *p, char *path, size_t path_l,
                      char *u_buf, size_t buf_l)
{
	char *symname;
	ssize_t copy_amt;
	struct dentry *path_d;
	char *t_path = user_strdup_errno(p, path, path_l);
	if (t_path == NULL)
		return -1;
	/* TODO: 9ns support */
	path_d = lookup_dentry(t_path, 0);
	user_memdup_free(p, t_path);
	if (!path_d)
		return -1;
	symname = path_d->d_inode->i_op->readlink(path_d);
	copy_amt = strnlen(symname, buf_l - 1) + 1;
	if (memcpy_to_user_errno(p, u_buf, symname, copy_amt)) {
		kref_put(&path_d->d_kref);
		return -1;
	}
	kref_put(&path_d->d_kref);
	printd("READLINK returning %s\n", u_buf);
	return copy_amt;
}

intreg_t sys_chdir(struct proc *p, const char *path, size_t path_l)
{
	int retval;
	char *t_path = user_strdup_errno(p, path, path_l);
	if (!t_path)
		return -1;
	/* TODO: 9ns support */
	retval = do_chdir(&p->fs_env, t_path);
	user_memdup_free(p, t_path);
	if (retval) {
		set_errno(-retval);
		return -1;
	}
	return 0;
}

/* Note cwd_l is not a strlen, it's an absolute size */
intreg_t sys_getcwd(struct proc *p, char *u_cwd, size_t cwd_l)
{
	int retval = 0;
	char *kfree_this;
	char *k_cwd = do_getcwd(&p->fs_env, &kfree_this, cwd_l);
	if (!k_cwd)
		return -1;		/* errno set by do_getcwd */
	if (memcpy_to_user_errno(p, u_cwd, k_cwd, strnlen(k_cwd, cwd_l - 1) + 1))
		retval = -1;
	kfree(kfree_this);
	return retval;
}

intreg_t sys_mkdir(struct proc *p, const char *path, size_t path_l, int mode)
{
	int retval;
	char *t_path = user_strdup_errno(p, path, path_l);
	if (!t_path)
		return -1;
	mode &= ~p->fs_env.umask;
	/* TODO: 9ns support */
	retval = do_mkdir(t_path, mode);
	user_memdup_free(p, t_path);
	return retval;
}

intreg_t sys_rmdir(struct proc *p, const char *path, size_t path_l)
{
	int retval;
	char *t_path = user_strdup_errno(p, path, path_l);
	if (!t_path)
		return -1;
	/* TODO: 9ns support */
	retval = do_rmdir(t_path);
	user_memdup_free(p, t_path);
	return retval;
}

intreg_t sys_pipe(struct proc *p, int *u_pipefd, int flags)
{
	int pipefd[2] = {0};
	int fd;
	int retval = 0;
	struct file *pipe_files[2] = {0};

	if (do_pipe(pipe_files, flags))
		return -1;
	fd = insert_file(&p->open_files, pipe_files[0], 0);
	if (!fd) {
		set_errno(ENFILE);
		goto failed_first;
	}
	pipefd[0] = fd;
	fd = insert_file(&p->open_files, pipe_files[1], 0);
	if (!fd) {
		set_errno(ENFILE);
		goto failed_second;
	}
	pipefd[1] = fd;
	if (memcpy_to_user_errno(p, u_pipefd, pipefd, sizeof(pipefd))) {
		set_errno(EFAULT);
		goto failed_memcpy;
	}
	goto all_out;

failed_memcpy:
	put_file_from_fd(&p->open_files, pipefd[1]);
failed_second:
	put_file_from_fd(&p->open_files, pipefd[0]);
failed_first:
	retval = -1;
all_out:
	kref_put(&pipe_files[0]->f_kref);
	kref_put(&pipe_files[1]->f_kref);
	return retval;
}

intreg_t sys_gettimeofday(struct proc *p, int *buf)
{
	static spinlock_t gtod_lock = SPINLOCK_INITIALIZER;
	static int t0 = 0;

	spin_lock(&gtod_lock);
	if(t0 == 0)

#if (defined CONFIG_APPSERVER)
	t0 = ufe(time,0,0,0,0);
#else
	// Nanwan's birthday, bitches!!
	t0 = 1242129600;
#endif
	spin_unlock(&gtod_lock);

	long long dt = read_tsc();
	/* TODO: This probably wants its own function, using a struct timeval */
	long kbuf[2] = {t0+dt/system_timing.tsc_freq,
	    (dt%system_timing.tsc_freq)*1000000/system_timing.tsc_freq};

	return memcpy_to_user_errno(p,buf,kbuf,sizeof(kbuf));
}

intreg_t sys_tcgetattr(struct proc *p, int fd, void *termios_p)
{
	int retval = 0;
	/* TODO: actually support this call on tty FDs.  Right now, we just fake
	 * what my linux box reports for a bash pty. */
	struct termios *kbuf = kmalloc(sizeof(struct termios), 0);
	kbuf->c_iflag = 0x2d02;
	kbuf->c_oflag = 0x0005;
	kbuf->c_cflag = 0x04bf;
	kbuf->c_lflag = 0x8a3b;
	kbuf->c_line = 0x0;
	kbuf->c_ispeed = 0xf;
	kbuf->c_ospeed = 0xf;
	kbuf->c_cc[0] = 0x03;
	kbuf->c_cc[1] = 0x1c;
	kbuf->c_cc[2] = 0x7f;
	kbuf->c_cc[3] = 0x15;
	kbuf->c_cc[4] = 0x04;
	kbuf->c_cc[5] = 0x00;
	kbuf->c_cc[6] = 0x01;
	kbuf->c_cc[7] = 0xff;
	kbuf->c_cc[8] = 0x11;
	kbuf->c_cc[9] = 0x13;
	kbuf->c_cc[10] = 0x1a;
	kbuf->c_cc[11] = 0xff;
	kbuf->c_cc[12] = 0x12;
	kbuf->c_cc[13] = 0x0f;
	kbuf->c_cc[14] = 0x17;
	kbuf->c_cc[15] = 0x16;
	kbuf->c_cc[16] = 0xff;
	kbuf->c_cc[17] = 0x00;
	kbuf->c_cc[18] = 0x00;
	kbuf->c_cc[19] = 0x00;
	kbuf->c_cc[20] = 0x00;
	kbuf->c_cc[21] = 0x00;
	kbuf->c_cc[22] = 0x00;
	kbuf->c_cc[23] = 0x00;
	kbuf->c_cc[24] = 0x00;
	kbuf->c_cc[25] = 0x00;
	kbuf->c_cc[26] = 0x00;
	kbuf->c_cc[27] = 0x00;
	kbuf->c_cc[28] = 0x00;
	kbuf->c_cc[29] = 0x00;
	kbuf->c_cc[30] = 0x00;
	kbuf->c_cc[31] = 0x00;

	if (memcpy_to_user_errno(p, termios_p, kbuf, sizeof(struct termios)))
		retval = -1;
	kfree(kbuf);
	return retval;
}

intreg_t sys_tcsetattr(struct proc *p, int fd, int optional_actions,
                       const void *termios_p)
{
	/* TODO: do this properly too.  For now, we just say 'it worked' */
	return 0;
}

/* TODO: we don't have any notion of UIDs or GIDs yet, but don't let that stop a
 * process from thinking it can do these.  The other alternative is to have
 * glibc return 0 right away, though someone might want to do something with
 * these calls.  Someday. */
intreg_t sys_setuid(struct proc *p, uid_t uid)
{
	return 0;
}

intreg_t sys_setgid(struct proc *p, gid_t gid)
{
	return 0;
}

/* long bind(char* src_path, char* onto_path, int flag);
 *
 * The naming for the args in bind is messy historically.  We do:
 * 		bind src_path onto_path
 * plan9 says bind NEW OLD, where new is *src*, and old is *onto*.
 * Linux says mount --bind OLD NEW, where OLD is *src* and NEW is *onto*. */
intreg_t sys_nbind(struct proc *p,
                   char *src_path, size_t src_l,
                   char *onto_path, size_t onto_l,
                   unsigned int flag)

{
	int ret;
	char *t_srcpath = user_strdup_errno(p, src_path, src_l);
	if (t_srcpath == NULL) {
		printd("srcpath dup failed ptr %p size %d\n", src_path, src_l);
		return -1;
	}
	char *t_ontopath = user_strdup_errno(p, onto_path, onto_l);
	if (t_ontopath == NULL) {
		user_memdup_free(p, t_srcpath);
		printd("ontopath dup failed ptr %p size %d\n", onto_path, onto_l);
		return -1;
	}
	printd("sys_nbind: %s -> %s flag %d\n", t_srcpath, t_ontopath, flag);
	ret = bindmount(0, -1, -1, t_srcpath, t_ontopath, flag, NULL);
	user_memdup_free(p, t_srcpath);
	user_memdup_free(p, t_ontopath);
	return ret;
}

/* int npipe(int *fd) */
intreg_t sys_npipe(struct proc *p, int *retfd)

{
	/* TODO: validate addresses of retfd (UMEM) */
	return syspipe(retfd);
}

/* int mount(int fd, int afd, char* onto_path, int flag, char* aname); */
intreg_t sys_nmount(struct proc *p,
                    int fd,
                    char *onto_path, size_t onto_l,
                    unsigned int flag
			/* we ignore these */
			/* no easy way to pass this many args anyway. *
		    int afd,
                    char *auth, size_t auth_l*/)
{
	int ret;
	int afd;

	afd = -1;
	char *t_ontopath = user_strdup_errno(p, onto_path, onto_l);
	if (t_ontopath == NULL)
		return -1;
	ret = bindmount(1, fd, afd, NULL, t_ontopath, flag, /* spec or auth */"");
	user_memdup_free(p, t_ontopath);
	return ret;
}

/* int mount(int fd, int afd, char* old, int flag, char* aname); */
intreg_t sys_nunmount(struct proc *p, char *name, int name_l, char *old_path, int old_l)
{
	int ret;
	char *t_oldpath = user_strdup_errno(p, old_path, old_l);
	if (t_oldpath == NULL)
		return -1;
	char *t_name = user_strdup_errno(p, name, name_l);
	if (t_name == NULL) {
		user_memdup_free(p, t_oldpath);
		return -1;
	}
	ret = sysunmount(t_name, t_oldpath);
	printd("go do it\n");
	user_memdup_free(p, t_oldpath);
	user_memdup_free(p, t_name);
	return ret;
}

static int sys_fd2path(struct proc *p, int fd, void *u_buf, size_t len)
{
	int ret;
	struct chan *ch;
	ERRSTACK(1);
	/* UMEM: Check the range, can PF later and kill if the page isn't present */
	if (!is_user_rwaddr(u_buf, len)) {
		printk("[kernel] bad user addr %p (+%p) in %s (user bug)\n", u_buf,
		       len, __FUNCTION__);
		return -1;
	}
	/* fdtochan throws */
	if (waserror()) {
		poperror();
		return -1;
	}
	ch = fdtochan(fd, -1, FALSE, TRUE);
	ret = snprintf(u_buf, len, "%s", chanpath(ch));
	cclose(ch);
	poperror();
	return ret;
}

/************** Syscall Invokation **************/

const static struct sys_table_entry syscall_table[] = {
	[SYS_null] = {(syscall_t)sys_null, "null"},
	[SYS_block] = {(syscall_t)sys_block, "block"},
	[SYS_cache_buster] = {(syscall_t)sys_cache_buster, "buster"},
	[SYS_cache_invalidate] = {(syscall_t)sys_cache_invalidate, "wbinv"},
	[SYS_reboot] = {(syscall_t)reboot, "reboot!"},
	[SYS_cputs] = {(syscall_t)sys_cputs, "cputs"},
	[SYS_cgetc] = {(syscall_t)sys_cgetc, "cgetc"},
	[SYS_getpcoreid] = {(syscall_t)sys_getpcoreid, "getpcoreid"},
	[SYS_getvcoreid] = {(syscall_t)sys_getvcoreid, "getvcoreid"},
	[SYS_getpid] = {(syscall_t)sys_getpid, "getpid"},
	[SYS_proc_create] = {(syscall_t)sys_proc_create, "proc_create"},
	[SYS_proc_run] = {(syscall_t)sys_proc_run, "proc_run"},
	[SYS_proc_destroy] = {(syscall_t)sys_proc_destroy, "proc_destroy"},
	[SYS_yield] = {(syscall_t)sys_proc_yield, "proc_yield"},
	[SYS_change_vcore] = {(syscall_t)sys_change_vcore, "change_vcore"},
	[SYS_fork] = {(syscall_t)sys_fork, "fork"},
	[SYS_exec] = {(syscall_t)sys_exec, "exec"},
	[SYS_waitpid] = {(syscall_t)sys_waitpid, "waitpid"},
	[SYS_mmap] = {(syscall_t)sys_mmap, "mmap"},
	[SYS_munmap] = {(syscall_t)sys_munmap, "munmap"},
	[SYS_mprotect] = {(syscall_t)sys_mprotect, "mprotect"},
	[SYS_shared_page_alloc] = {(syscall_t)sys_shared_page_alloc, "pa"},
	[SYS_shared_page_free] = {(syscall_t)sys_shared_page_free, "pf"},
	[SYS_provision] = {(syscall_t)sys_provision, "provision"},
	[SYS_notify] = {(syscall_t)sys_notify, "notify"},
	[SYS_self_notify] = {(syscall_t)sys_self_notify, "self_notify"},
	[SYS_vc_entry] = {(syscall_t)sys_vc_entry, "vc_entry"},
	[SYS_halt_core] = {(syscall_t)sys_halt_core, "halt_core"},
#ifdef CONFIG_SERIAL_IO
	[SYS_serial_read] = {(syscall_t)sys_serial_read, "ser_read"},
	[SYS_serial_write] = {(syscall_t)sys_serial_write, "ser_write"},
#endif
#ifdef CONFIG_NETWORKING
	[SYS_eth_read] = {(syscall_t)sys_eth_read, "eth_read"},
	[SYS_eth_write] = {(syscall_t)sys_eth_write, "eth_write"},
	[SYS_eth_get_mac_addr] = {(syscall_t)sys_eth_get_mac_addr, "get_mac"},
	[SYS_eth_recv_check] = {(syscall_t)sys_eth_recv_check, "recv_check"},
#endif
#ifdef CONFIG_ARSC_SERVER
	[SYS_init_arsc] = {(syscall_t)sys_init_arsc, "init_arsc"},
#endif
	[SYS_change_to_m] = {(syscall_t)sys_change_to_m, "change_to_m"},
	[SYS_poke_ksched] = {(syscall_t)sys_poke_ksched, "poke_ksched"},
	[SYS_abort_sysc] = {(syscall_t)sys_abort_sysc, "abort_sysc"},

// socket related syscalls
	[SYS_socket] ={(syscall_t)sys_socket, "socket"},
	[SYS_sendto] ={(syscall_t)sys_sendto, "sendto"},
	[SYS_recvfrom] ={(syscall_t)sys_recvfrom, "recvfrom"},
	[SYS_select] ={(syscall_t)sys_select, "select"},
	[SYS_connect] = {(syscall_t)sys_connect, "connect"},
	[SYS_send] ={(syscall_t)sys_send, "send"},
	[SYS_recv] ={(syscall_t)sys_recv, "recvfrom"},
	[SYS_bind] ={(syscall_t)sys_bind, "bind"},
	[SYS_accept] ={(syscall_t)sys_accept, "accept"},
	[SYS_listen] ={(syscall_t)sys_listen, "listen"},


	[SYS_read] = {(syscall_t)sys_read, "read"},
	[SYS_write] = {(syscall_t)sys_write, "write"},
	[SYS_open] = {(syscall_t)sys_open, "open"},
	[SYS_close] = {(syscall_t)sys_close, "close"},
	[SYS_fstat] = {(syscall_t)sys_fstat, "fstat"},
	[SYS_stat] = {(syscall_t)sys_stat, "stat"},
	[SYS_lstat] = {(syscall_t)sys_lstat, "lstat"},
	[SYS_fcntl] = {(syscall_t)sys_fcntl, "fcntl"},
	[SYS_access] = {(syscall_t)sys_access, "access"},
	[SYS_umask] = {(syscall_t)sys_umask, "umask"},
	[SYS_chmod] = {(syscall_t)sys_chmod, "chmod"},
	[SYS_llseek] = {(syscall_t)sys_llseek, "llseek"},
	[SYS_link] = {(syscall_t)sys_link, "link"},
	[SYS_unlink] = {(syscall_t)sys_unlink, "unlink"},
	[SYS_symlink] = {(syscall_t)sys_symlink, "symlink"},
	[SYS_readlink] = {(syscall_t)sys_readlink, "readlink"},
	[SYS_chdir] = {(syscall_t)sys_chdir, "chdir"},
	[SYS_getcwd] = {(syscall_t)sys_getcwd, "getcwd"},
	[SYS_mkdir] = {(syscall_t)sys_mkdir, "mkdri"},
	[SYS_rmdir] = {(syscall_t)sys_rmdir, "rmdir"},
	[SYS_pipe] = {(syscall_t)sys_pipe, "pipe"},
	[SYS_gettimeofday] = {(syscall_t)sys_gettimeofday, "gettime"},
	[SYS_tcgetattr] = {(syscall_t)sys_tcgetattr, "tcgetattr"},
	[SYS_tcsetattr] = {(syscall_t)sys_tcsetattr, "tcsetattr"},
	[SYS_setuid] = {(syscall_t)sys_setuid, "setuid"},
	[SYS_setgid] = {(syscall_t)sys_setgid, "setgid"},
	/* special! */
	[SYS_nbind] ={(syscall_t)sys_nbind, "nbind"},
	[SYS_nmount] ={(syscall_t)sys_nmount, "nmount"},
	[SYS_nunmount] ={(syscall_t)sys_nunmount, "nunmount"},
	[SYS_npipe] ={(syscall_t)sys_npipe, "npipe"},
	[SYS_fd2path] ={(syscall_t)sys_fd2path, "fd2path"},

};

/* Executes the given syscall.
 *
 * Note tf is passed in, which points to the tf of the context on the kernel
 * stack.  If any syscall needs to block, it needs to save this info, as well as
 * any silly state.
 *
 * This syscall function is used by both local syscall and arsc, and should
 * remain oblivious of the caller. */
intreg_t syscall(struct proc *p, uintreg_t sc_num, uintreg_t a0, uintreg_t a1,
                 uintreg_t a2, uintreg_t a3, uintreg_t a4, uintreg_t a5)
{
	intreg_t ret = -1;
	ERRSTACK(1);
	const int max_syscall = sizeof(syscall_table)/sizeof(syscall_table[0]);

	uint32_t coreid, vcoreid;
	if (systrace_flags & SYSTRACE_ON) {
		if ((systrace_flags & SYSTRACE_ALLPROC) || (proc_is_traced(p))) {
			coreid = core_id();
			vcoreid = proc_get_vcoreid(p);
			if (systrace_flags & SYSTRACE_LOUD) {
				printk("[%16llu] Syscall %3d (%12s):(%p, %p, %p, %p, "
				       "%p, %p) proc: %d core: %d vcore: %d\n", read_tsc(),
				       sc_num, syscall_table[sc_num].name, a0, a1, a2, a3,
				       a4, a5, p->pid, coreid, vcoreid);
			} else {
				struct systrace_record *trace;
				uintptr_t idx, new_idx;
				do {
					idx = systrace_bufidx;
					new_idx = (idx + 1) % systrace_bufsize;
				} while (!atomic_cas_u32(&systrace_bufidx, idx, new_idx));
				trace = &systrace_buffer[idx];
				trace->timestamp = read_tsc();
				trace->syscallno = sc_num;
				trace->arg0 = a0;
				trace->arg1 = a1;
				trace->arg2 = a2;
				trace->arg3 = a3;
				trace->arg4 = a4;
				trace->arg5 = a5;
				trace->pid = p->pid;
				trace->coreid = coreid;
				trace->vcoreid = vcoreid;
			}
		}
	}
	if (sc_num > max_syscall || syscall_table[sc_num].call == NULL)
		panic("Invalid syscall number %d for proc %x!", sc_num, p);

	/* N.B. This is going away. */
	if (waserror()){
		printk("Plan 9 system call returned via waserror()\n");
		printk("String: '%s'\n", current_errstr());
		/* if we got here, then the errbuf was right.
		 * no need to check!
		 */
		return -1;
	}
	//printd("before syscall errstack %p\n", errstack);
	//printd("before syscall errstack base %p\n", get_cur_errbuf());
	ret = syscall_table[sc_num].call(p, a0, a1, a2, a3, a4, a5);
	//printd("after syscall errstack base %p\n", get_cur_errbuf());
	if (get_cur_errbuf() != &errstack[0]) {
		coreid = core_id();
		vcoreid = proc_get_vcoreid(p);
		printk("[%16llu] Syscall %3d (%12s):(%p, %p, %p, %p, "
		       "%p, %p) proc: %d core: %d vcore: %d\n", read_tsc(),
		       sc_num, syscall_table[sc_num].name, a0, a1, a2, a3,
		       a4, a5, p->pid, coreid, vcoreid);
		if (sc_num != SYS_fork)
			printk("YOU SHOULD PANIC: errstack mismatch");
	}
	return ret;
}

/* Execute the syscall on the local core */
void run_local_syscall(struct syscall *sysc)
{
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];

	/* TODO: (UMEM) assert / pin the memory for the sysc */
	assert(irq_is_enabled());	/* in case we proc destroy */
	/* Abort on mem check failure, for now */
	if (!user_mem_check(pcpui->cur_proc, sysc, sizeof(struct syscall),
	                    sizeof(uintptr_t), PTE_USER_RW))
		return;
	pcpui->cur_kthread->sysc = sysc;	/* let the core know which sysc it is */
	sysc->retval = syscall(pcpui->cur_proc, sysc->num, sysc->arg0, sysc->arg1,
	                       sysc->arg2, sysc->arg3, sysc->arg4, sysc->arg5);
	/* Need to re-load pcpui, in case we migrated */
	pcpui = &per_cpu_info[core_id()];
	/* Some 9ns paths set errstr, but not errno.  glibc will ignore errstr.
	 * this is somewhat hacky, since errno might get set unnecessarily */
	if ((current_errstr()[0] != 0) && (!sysc->err))
		sysc->err = EUNSPECIFIED;
	finish_sysc(sysc, pcpui->cur_proc);
	/* Can unpin (UMEM) at this point */
	pcpui->cur_kthread->sysc = 0;	/* no longer working on sysc */
}

/* A process can trap and call this function, which will set up the core to
 * handle all the syscalls.  a.k.a. "sys_debutante(needs, wants)".  If there is
 * at least one, it will run it directly. */
void prep_syscalls(struct proc *p, struct syscall *sysc, unsigned int nr_syscs)
{
	int retval;
	/* Careful with pcpui here, we could have migrated */
	if (!nr_syscs)
		return;
	/* For all after the first call, send ourselves a KMSG (TODO). */
	if (nr_syscs != 1)
		warn("Only one supported (Debutante calls: %d)\n", nr_syscs);
	/* Call the first one directly.  (we already checked to make sure there is
	 * 1) */
	run_local_syscall(sysc);
}

/* Call this when something happens on the syscall where userspace might want to
 * get signaled.  Passing p, since the caller should know who the syscall
 * belongs to (probably is current).
 *
 * You need to have SC_K_LOCK set when you call this. */
void __signal_syscall(struct syscall *sysc, struct proc *p)
{
	struct event_queue *ev_q;
	struct event_msg local_msg;
	/* User sets the ev_q then atomically sets the flag (races with SC_DONE) */
	if (atomic_read(&sysc->flags) & SC_UEVENT) {
		rmb();	/* read the ev_q after reading the flag */
		ev_q = sysc->ev_q;
		if (ev_q) {
			memset(&local_msg, 0, sizeof(struct event_msg));
			local_msg.ev_type = EV_SYSCALL;
			local_msg.ev_arg3 = sysc;
			send_event(p, ev_q, &local_msg, 0);
		}
	}
}

/* Syscall tracing */
static void __init_systrace(void)
{
	systrace_buffer = kmalloc(MAX_SYSTRACES*sizeof(struct systrace_record), 0);
	if (!systrace_buffer)
		panic("Unable to alloc a trace buffer\n");
	systrace_bufidx = 0;
	systrace_bufsize = MAX_SYSTRACES;
	/* Note we never free the buffer - it's around forever.  Feel free to change
	 * this if you want to change the size or something dynamically. */
}

/* If you call this while it is running, it will change the mode */
void systrace_start(bool silent)
{
	static bool init = FALSE;
	spin_lock_irqsave(&systrace_lock);
	if (!init) {
		__init_systrace();
		init = TRUE;
	}
	systrace_flags = silent ? SYSTRACE_ON : SYSTRACE_ON | SYSTRACE_LOUD;
	spin_unlock_irqsave(&systrace_lock);
}

int systrace_reg(bool all, struct proc *p)
{
	int retval = 0;
	spin_lock_irqsave(&systrace_lock);
	if (all) {
		printk("Tracing syscalls for all processes\n");
		systrace_flags |= SYSTRACE_ALLPROC;
		retval = 0;
	} else {
		for (int i = 0; i < MAX_NUM_TRACED; i++) {
			if (!systrace_procs[i]) {
				printk("Tracing syscalls for process %d\n", p->pid);
				systrace_procs[i] = p;
				retval = 0;
				break;
			}
		}
	}
	spin_unlock_irqsave(&systrace_lock);
	return retval;
}

void systrace_stop(void)
{
	spin_lock_irqsave(&systrace_lock);
	systrace_flags = 0;
	for (int i = 0; i < MAX_NUM_TRACED; i++)
		systrace_procs[i] = 0;
	spin_unlock_irqsave(&systrace_lock);
}

/* If you registered a process specifically, then you need to dereg it
 * specifically.  Or just fully stop, which will do it for all. */
int systrace_dereg(bool all, struct proc *p)
{
	spin_lock_irqsave(&systrace_lock);
	if (all) {
		printk("No longer tracing syscalls for all processes.\n");
		systrace_flags &= ~SYSTRACE_ALLPROC;
	} else {
		for (int i = 0; i < MAX_NUM_TRACED; i++) {
			if (systrace_procs[i] == p) {
				systrace_procs[i] = 0;
				printk("No longer tracing syscalls for process %d\n", p->pid);
			}
		}
	}
	spin_unlock_irqsave(&systrace_lock);
	return 0;
}

/* Regardless of locking, someone could be writing into the buffer */
void systrace_print(bool all, struct proc *p)
{
	spin_lock_irqsave(&systrace_lock);
	/* if you want to be clever, you could make this start from the earliest
	 * timestamp and loop around.  Careful of concurrent writes. */
	for (int i = 0; i < systrace_bufsize; i++)
		if (systrace_buffer[i].timestamp)
			printk("[%16llu] Syscall %3d (%12s):(%p, %p, %p, %p, %p,"
			       "%p) proc: %d core: %d vcore: %d\n",
			       systrace_buffer[i].timestamp,
			       systrace_buffer[i].syscallno,
			       syscall_table[systrace_buffer[i].syscallno].name,
			       systrace_buffer[i].arg0,
			       systrace_buffer[i].arg1,
			       systrace_buffer[i].arg2,
			       systrace_buffer[i].arg3,
			       systrace_buffer[i].arg4,
			       systrace_buffer[i].arg5,
			       systrace_buffer[i].pid,
			       systrace_buffer[i].coreid,
			       systrace_buffer[i].vcoreid);
	spin_unlock_irqsave(&systrace_lock);
}

void systrace_clear_buffer(void)
{
	spin_lock_irqsave(&systrace_lock);
	memset(systrace_buffer, 0, sizeof(struct systrace_record) * MAX_SYSTRACES);
	spin_unlock_irqsave(&systrace_lock);
}