commit a9967a049a826989952d8976fda332f015c8e45a
author Barret Rhoden <brho@cs.berkeley.edu> Fri Jul 01 14:51:18 2016 -0400
committer Barret Rhoden <brho@cs.berkeley.edu> Thu Jul 07 12:39:01 2016 -0400
tree 903f7f1b62e3761a6b209e72d120af2b3bd5bbe0
parent bcab4ec6bf0a1c8621542870a2a4e788ae866c74

Use mmap(), not malloc(), in vfprintf (XCC)

Using malloc created an ordering between any of the printf calls and
malloc.  If malloc itself did anything that called back into printf, such
as a diagnostic warning, a SIGSEGV (which leads to printing), an snprintf
to talk to a kernel device, etc, then malloc would be calling itself.  That
could trigger a deadlock, depending on what malloc does internally.

By relying on mmap() only, we limit the amount of code that printf depends
on.  Note that if you ever put a printf in glibc's mmap() stub, you might
have issues.  Imagine a generic printf call: grabs glibc's IO lock, mmaps,
tries to print, then deadlocks on the *IO lock*.

Rebuild glibc.

Signed-off-by: Barret Rhoden <brho@cs.berkeley.edu>

tools/compilers/gcc-glibc/glibc-2.19-akaros/sysdeps/akaros/vfprintf.c

diff --git a/tools/compilers/gcc-glibc/glibc-2.19-akaros/sysdeps/akaros/vfprintf.c b/tools/compilers/gcc-glibc/glibc-2.19-akaros/sysdeps/akaros/vfprintf.c
index 6e20aba..200e98d 100644
--- a/tools/compilers/gcc-glibc/glibc-2.19-akaros/sysdeps/akaros/vfprintf.c
+++ b/tools/compilers/gcc-glibc/glibc-2.19-akaros/sysdeps/akaros/vfprintf.c
@@ -29,8 +29,11 @@
 #include <_itoa.h>
 #include <locale/localeinfo.h>
 #include <stdio.h>
+#include <ros/common.h>
+#include <sys/mman.h>
 
-/* Modified for AKAROS, uses malloc in place of large stack allocations */
+/* Modified for AKAROS, uses mmap in place of large stack allocations */
+static char *failmsg = "vfprintf mmap failed!";
 
 /* This code is shared between the standard stdio implementation found
    in GNU C library and the libio implementation originally found in
@@ -245,9 +248,15 @@
   const UCHAR_T *end_of_spec;
 
   /* Buffer intermediate results.  */
-  /* AKAROS malloc work_buf */
+  /* AKAROS mmap work_buf */
   //CHAR_T work_buffer[1000];
-  CHAR_T *work_buffer = malloc(1000);
+  CHAR_T *work_buffer = mmap(0, PGSIZE, PROT_WRITE | PROT_READ, MAP_PRIVATE,
+                             -1, 0);
+
+  if (work_buffer == MAP_FAILED) {
+    write(2, failmsg, sizeof(failmsg));
+    exit(-1);
+  }
 
   CHAR_T *workstart = NULL;
   CHAR_T *workend;
@@ -2059,7 +2068,7 @@
   _IO_cleanup_region_end (0);
 
   /* AKAROS */
-  free(work_buffer);
+  munmap(work_buffer, PGSIZE);
   return done;
 }
 
@@ -2283,9 +2292,16 @@
 buffered_vfprintf (_IO_FILE *s, const CHAR_T *format,
 		   _IO_va_list args)
 {
-	/* AKAROS: malloc the buf.  */
+  /* AKAROS: mmap the buf.  */
   //CHAR_T buf[_IO_BUFSIZ];
-  CHAR_T *buf = malloc(_IO_BUFSIZ);
+  CHAR_T *buf;
+
+  buf = mmap(0, ROUNDUP(_IO_BUFSIZ, PGSIZE), PROT_WRITE | PROT_READ,
+             MAP_PRIVATE, -1, 0);
+  if (buf == MAP_FAILED) {
+    write(2, failmsg, sizeof(failmsg));
+    exit(-1);
+  }
 
   struct helper_file helper;
   _IO_FILE *hp = (_IO_FILE *) &helper._f;
@@ -2348,7 +2364,7 @@
   _IO_funlockfile (s);
   __libc_cleanup_region_end (0);
 
-  free(buf); /* AKAROS */
+  munmap(buf, ROUNDUP(_IO_BUFSIZ, PGSIZE)); /* AKAROS */
   return result;
 }