#include <arch/arch.h>
#include <trap.h>
#include <process.h>
#include <pmap.h>
#include <smp.h>
#include <arch/fsgsbase.h>

#include <string.h>
#include <assert.h>
#include <stdio.h>

static void __attribute__((noreturn)) proc_pop_hwtf(struct hw_trapframe *tf)
{
	/* for both HW and SW, note we pass an offset into the TF, beyond the fs
	 * and gs bases */
	if (x86_hwtf_is_partial(tf)) {
		swap_gs();
	} else {
		write_gsbase(tf->tf_gsbase);
		write_fsbase(tf->tf_fsbase);
	}
	asm volatile (".globl __asm_pop_hwtf_start;"
	              "__asm_pop_hwtf_start:    "
	              "movq %0, %%rsp;          "
	              "popq %%rax;              "
	              "popq %%rbx;              "
	              "popq %%rcx;              "
	              "popq %%rdx;              "
	              "popq %%rbp;              "
	              "popq %%rsi;              "
	              "popq %%rdi;              "
	              "popq %%r8;               "
	              "popq %%r9;               "
	              "popq %%r10;              "
	              "popq %%r11;              "
	              "popq %%r12;              "
	              "popq %%r13;              "
	              "popq %%r14;              "
	              "popq %%r15;              "
	              "addq $0x10, %%rsp;       "
	              "iretq;                   "
	              ".globl __asm_pop_hwtf_end;"
	              "__asm_pop_hwtf_end:      "
	              : : "g" (&tf->tf_rax) : "memory");
	panic("iretq failed");
}

static void __attribute__((noreturn)) proc_pop_swtf(struct sw_trapframe *tf)
{
	if (x86_swtf_is_partial(tf)) {
		swap_gs();
	} else {
		write_gsbase(tf->tf_gsbase);
		write_fsbase(tf->tf_fsbase);
	}
	/* We need to 0 out any registers that aren't part of the sw_tf and that
	 * we won't use/clobber on the out-path.  While these aren't part of the
	 * sw_tf, we also don't want to leak any kernel register content. */
	asm volatile (".globl __asm_pop_swtf_start;"
	              "__asm_pop_swtf_start:    "
	              "movq %0, %%rsp;          "
	              "movq $0, %%rax;          "
	              "movq $0, %%rdx;          "
	              "movq $0, %%rsi;          "
	              "movq $0, %%rdi;          "
	              "movq $0, %%r8;           "
	              "movq $0, %%r9;           "
	              "movq $0, %%r10;          "
	              "popq %%rbx;              "
	              "popq %%rbp;              "
	              "popq %%r12;              "
	              "popq %%r13;              "
	              "popq %%r14;              "
	              "popq %%r15;              "
	              "movq %1, %%r11;          "
	              "popq %%rcx;              "
	              "popq %%rsp;              "
	              "rex.w sysret;            "
	              ".globl __asm_pop_swtf_end;"
	              "__asm_pop_swtf_end:      "
	              : : "g"(&tf->tf_rbx), "i"(FL_IF) : "memory");
	panic("sysret failed");
}

/* If popping a VM TF fails for some reason, we need to reflect it back to the
 * user.  It is possible that the reflection fails.  We still need to run
 * something, and it's a lousy time to try something else.  So We'll give them a
 * TF that will probably fault right away and kill them. */
static void __attribute__((noreturn)) handle_bad_vm_tf(struct vm_trapframe *tf)
{
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];

	tf->tf_exit_reason |= VMX_EXIT_REASONS_FAILED_VMENTRY;
	tf->tf_flags |= VMCTX_FL_HAS_FAULT;
	if (reflect_current_context()) {
		printk("[kernel] Unable to reflect after a bad VM enter\n");
		proc_init_ctx(pcpui->cur_ctx, 0, 0xcafebabe, 0, 0);
	}
	proc_pop_ctx(pcpui->cur_ctx);
}

static void __attribute__((noreturn)) proc_pop_vmtf(struct vm_trapframe *tf)
{
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
	struct proc *p = pcpui->cur_proc;
	struct guest_pcore *gpc;

	if (x86_vmtf_is_partial(tf)) {
		gpc = lookup_guest_pcore(p, tf->tf_guest_pcoreid);
		assert(gpc);
		assert(pcpui->guest_pcoreid == tf->tf_guest_pcoreid);
		assert(gpc->should_vmresume);
	} else {
		gpc = load_guest_pcore(p, tf->tf_guest_pcoreid);
		if (!gpc) {
			tf->tf_exit_reason = EXIT_REASON_GUEST_IN_USE;
			handle_bad_vm_tf(tf);
		}
	}
	vmcs_write(GUEST_RSP, tf->tf_rsp);
	vmcs_write(GUEST_CR3, tf->tf_cr3);
	vmcs_write(GUEST_RIP, tf->tf_rip);
	vmcs_write(GUEST_RFLAGS, tf->tf_rflags);
	/* The host stacktop could have changed, even if we are still a partial
	 * context.  Consider a vmcall that blocks.  We'll restart the partial
	 * context, but be on a new stack.  set_stack_top() doesn't really know
	 * about the VMCS. */
	vmcs_write(HOST_RSP, pcpui->stacktop);
	/* cr2 is not part of the VMCS state; we need to save/restore it
	 * manually */
	lcr2(tf->tf_cr2);
	vmcs_write(VM_ENTRY_INTR_INFO_FIELD, tf->tf_trap_inject);
	/* Someone may have tried poking the guest and posting an IRQ, but the
	 * IPI missed (concurrent vmexit).  In these cases, the 'outstanding
	 * notification' bit should still be set, and we can resend the IPI.
	 * This will arrive after we vmenter, since IRQs are currently disabled.
	 * */
	if (test_bit(VMX_POSTED_OUTSTANDING_NOTIF, gpc->posted_irq_desc))
		send_self_ipi(I_POKE_GUEST);
	/* The first time a VMCS is started after being loaded, it must be
	 * launched.  Subsequent starts must be resumes.  Once the VMCS is
	 * cleared, we start with a launch again.  Note this is the VMCS, not
	 * the GPC unload. */
	if (gpc->should_vmresume) {
		tf->tf_flags |= VMCTX_FL_VMRESUME;
	} else {
		tf->tf_flags &= ~VMCTX_FL_VMRESUME;
		gpc->should_vmresume = TRUE;
	}
	/* vmlaunch/resume can fail, so we need to be able to return from this.
	 * Thus we can't clobber rsp via the popq style of setting the
	 * registers.  Likewise, we don't want to lose rbp via the clobber list.
	 *
	 * Partial contexts have already been launched, so we resume them. */
	asm volatile (".globl __asm_pop_vmtf_start;"
	              "__asm_pop_vmtf_start:     "
	              "testl $"STRINGIFY(VMCTX_FL_VMRESUME)", %c[flags](%0);"
	              "pushq %%rbp;              " /* save in case we fail */
	              "movq %c[rbx](%0), %%rbx;  "
	              "movq %c[rcx](%0), %%rcx;  "
	              "movq %c[rdx](%0), %%rdx;  "
	              "movq %c[rbp](%0), %%rbp;  "
	              "movq %c[rsi](%0), %%rsi;  "
	              "movq %c[rdi](%0), %%rdi;  "
	              "movq %c[r8](%0),  %%r8;   "
	              "movq %c[r9](%0),  %%r9;   "
	              "movq %c[r10](%0), %%r10;  "
	              "movq %c[r11](%0), %%r11;  "
	              "movq %c[r12](%0), %%r12;  "
	              "movq %c[r13](%0), %%r13;  "
	              "movq %c[r14](%0), %%r14;  "
	              "movq %c[r15](%0), %%r15;  "
	              "movq %c[rax](%0), %%rax;  " /* clobber our *tf last */
	              "jnz 1f;                   " /* jump if resume */
	              ASM_VMX_VMLAUNCH";         " /* non-resume gets launched*/
	              "jmp 2f;                   "
	              "1: "ASM_VMX_VMRESUME";    "
	              "2: popq %%rbp;            " /* vmlaunch failed */
	              ".globl __asm_pop_vmtf_end;"
	              "__asm_pop_vmtf_end:       "
	              :
	              : "a" (tf),
	                [rax]"i"(offsetof(struct vm_trapframe, tf_rax)),
	                [rbx]"i"(offsetof(struct vm_trapframe, tf_rbx)),
	                [rcx]"i"(offsetof(struct vm_trapframe, tf_rcx)),
	                [rdx]"i"(offsetof(struct vm_trapframe, tf_rdx)),
	                [rbp]"i"(offsetof(struct vm_trapframe, tf_rbp)),
	                [rsi]"i"(offsetof(struct vm_trapframe, tf_rsi)),
	                [rdi]"i"(offsetof(struct vm_trapframe, tf_rdi)),
	                 [r8]"i"(offsetof(struct vm_trapframe, tf_r8)),
	                 [r9]"i"(offsetof(struct vm_trapframe, tf_r9)),
	                [r10]"i"(offsetof(struct vm_trapframe, tf_r10)),
	                [r11]"i"(offsetof(struct vm_trapframe, tf_r11)),
	                [r12]"i"(offsetof(struct vm_trapframe, tf_r12)),
	                [r13]"i"(offsetof(struct vm_trapframe, tf_r13)),
	                [r14]"i"(offsetof(struct vm_trapframe, tf_r14)),
	                [r15]"i"(offsetof(struct vm_trapframe, tf_r15)),
	                [flags]"i"(offsetof(struct vm_trapframe, tf_flags))
	              : "cc", "memory", "rbx", "rcx", "rdx", "rsi", "rdi",
	                "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15");
	/* vmlaunch/resume failed.  It could be for a few reasons, including
	 * things like launching instead of resuming, not having a VMCS loaded,
	 * failing a host-state area check, etc.  Those are kernel problems.
	 *
	 * The user should not be able to trigger these problems.  The user
	 * could trigger a problem loading the guest-state area, such as a
	 * non-canonical address for RIP.  Those sorts of errors should appear
	 * to be a normal vmexit with some flags set.
	 *
	 * Any failed vmlaunch/resume is likely a kernel bug, but we'll still
	 * reflect it to the user for debugability.
	 *
	 * Also we should always have a non-shadow VMCS, so ZF should be 1 and
	 * we can read the error register. */
	assert(read_flags() & FL_ZF);
	tf->tf_exit_reason = EXIT_REASON_VMENTER_FAILED;
	tf->tf_exit_qual = vmcs_read(VM_INSTRUCTION_ERROR);
	tf->tf_flags |= VMCTX_FL_PARTIAL;
	warn("vmlaunch / vmresume failed!, check userspace's reflected fault");
	handle_bad_vm_tf(tf);
}

void proc_pop_ctx(struct user_context *ctx)
{
	disable_irq();
	switch (ctx->type) {
	case ROS_HW_CTX:
		proc_pop_hwtf(&ctx->tf.hw_tf);
		break;
	case ROS_SW_CTX:
		proc_pop_swtf(&ctx->tf.sw_tf);
		break;
	case ROS_VM_CTX:
		proc_pop_vmtf(&ctx->tf.vm_tf);
		break;
	default:
		/* We should have caught this when securing the ctx */
		panic("Unknown context type %d!", ctx->type);
	}
}

void proc_init_ctx(struct user_context *ctx, uint32_t vcoreid, uintptr_t entryp,
                   uintptr_t stack_top, uintptr_t tls_desc)
{
	struct sw_trapframe *sw_tf = &ctx->tf.sw_tf;

	/* zero the entire structure for any type, prevent potential disclosure
	 */
	memset(ctx, 0, sizeof(struct user_context));
	ctx->type = ROS_SW_CTX;
	/* Stack pointers in x86 C functions need to be such that adding or
	 * subtracting 8 will result in 16 byte alignment (AMD64 ABI), which we
	 * call an odd-8-byte alignment.  The reason is so that input arguments
	 * (on the stack) are 16 byte aligned.  The extra 8 bytes is the
	 * retaddr, pushed on the stack.  Compilers know they can subtract 8 to
	 * get 16 byte alignment for instructions like movaps.
	 *
	 * However, the kernel will start contexts at 16 byte aligned stacks.
	 * This is because glibc's _start (in ASM) expects this.  Parlib x86's
	 * vcore entry does the same.
	 *
	 * We init contexts for both an elf startup as well as vcore entry.  It
	 * is up to the caller (including the user) to make sure the stack is
	 * aligned properly.  elf.c doesn't know about these concerns, so if it
	 * messes up, there's nothing we can really do, since the args are just
	 * wrong.  ld will fail immediately though, so we'll find out quickly.
	 * */
	sw_tf->tf_rsp = stack_top;
	sw_tf->tf_rip = entryp;
	sw_tf->tf_rbp = 0;	/* for potential backtraces */
	sw_tf->tf_mxcsr = 0x00001f80;	/* x86 default mxcsr */
	sw_tf->tf_fpucw = 0x037f;		/* x86 default FP CW */
	/* Coupled closely with user's entry.S.  id is the vcoreid, which
	 * entry.S uses to determine what to do.  vcoreid == 0 is the main
	 * core/context. */
	sw_tf->tf_rbx = vcoreid;
	sw_tf->tf_fsbase = tls_desc;
	proc_secure_ctx(ctx);
}

static void proc_secure_hwtf(struct hw_trapframe *tf)
{
	enforce_user_canon(&tf->tf_gsbase);
	enforce_user_canon(&tf->tf_fsbase);
	enforce_user_canon(&tf->tf_rip);
	enforce_user_canon(&tf->tf_rsp);
	/* GD_UD is the user data segment selector in the GDT, and
	 * GD_UT is the user text segment selector (see inc/memlayout.h).
	 * The low 2 bits of each segment register contains the
	 * Requestor Privilege Level (RPL); 3 means user mode. */
	tf->tf_ss = GD_UD | 3;
	tf->tf_cs = GD_UT | 3;
	/* Always 1: interrupts */
	tf->tf_rflags |= FL_IF;
	/* Always 0: IOPL must be set to 0.  VM (virtual 8086) probably doesn't
	 * matter - SDM says it can't get modified via iret anyways.  VIF and
	 * VIP are also virtual-8086 mode stuff.  Supposedly NT is settable by
	 * userspace, but there's no good reason for it.  Rather be paranoid. */
	tf->tf_rflags &= ~(FL_IOPL_MASK | FL_VM | FL_NT | FL_VIF | FL_VIP);
	tf->tf_rflags |= FL_RSVD_1;
	tf->tf_rflags &= FL_RSVD_0;
	x86_hwtf_clear_partial(tf);
}

static void proc_secure_swtf(struct sw_trapframe *tf)
{
	enforce_user_canon(&tf->tf_gsbase);
	enforce_user_canon(&tf->tf_fsbase);
	enforce_user_canon(&tf->tf_rip);
	enforce_user_canon(&tf->tf_rsp);
	/* The kernel doesn't actually load the mxcsr or the fpucw, but we can
	 * still sanitize it in case we ever do load it. */
	tf->tf_mxcsr &= MXCSR_RSVD_0;
	x86_swtf_clear_partial(tf);
}

static void proc_secure_vmtf(struct vm_trapframe *tf)
{
	/* The user can say whatever it wants for the bulk of the TF.  If they
	 * mess up something in the guest-area, it'll be treated like a vmexit.
	 * There are a few things in the TF that we use on the kernel side.
	 *
	 * If guest_pcoreid is bad (not a guest_pcore), we'll fail to load the
	 * GPC and reflect the fault to userspace.
	 *
	 * Regarding tf_flags, some are informational for the user, some are
	 * used for our own use in the kernel.
	 * - VMCTX_FL_PARTIAL: We clear this below
	 * - VMCTX_FL_VMRESUME: Used to temporarily carry a bool in pop_vmtf,
	 *   but we never trust the value in the VM TF.
	 * These are write-only from the kernel and passed to the user:
	 * - VMCTX_FL_HAS_FAULT
	 * - VMCTX_FL_EPT_VMR_BACKED */
	x86_vmtf_clear_partial(tf);
}

void proc_secure_ctx(struct user_context *ctx)
{
	switch (ctx->type) {
	case ROS_HW_CTX:
		proc_secure_hwtf(&ctx->tf.hw_tf);
		break;
	case ROS_SW_CTX:
		proc_secure_swtf(&ctx->tf.sw_tf);
		break;
	case ROS_VM_CTX:
		proc_secure_vmtf(&ctx->tf.vm_tf);
		break;
	default:
		/* If we aren't another ctx type, we're assuming (and forcing) a
		 * HW ctx.  If this is somehow fucked up, userspace should die
		 * rather quickly. */
		ctx->type = ROS_HW_CTX;
		proc_secure_hwtf(&ctx->tf.hw_tf);
	}
}

/* Called when we are currently running an address space on our core and want to
 * abandon it.  We need a known good pgdir before releasing the old one.  We
 * decref, since current no longer tracks the proc (and current no longer
 * protects the cr3). */
void __abandon_core(void)
{
	struct per_cpu_info *pcpui = &per_cpu_info[core_id()];
	struct proc *old_proc;

	lcr3(boot_cr3);
	old_proc = pcpui->cur_proc;
	pcpui->cur_proc = NULL;
	proc_decref(old_proc);
}

void __clear_owning_proc(uint32_t coreid)
{
	vmx_clear_vmcs();
}