X-Git-Url: https://oss.titaniummirror.com/gitweb?a=blobdiff_plain;f=gcc%2Fconfig%2Fhost-linux.c;fp=gcc%2Fconfig%2Fhost-linux.c;h=9f6ef0a1319960226f8ddecb38e6aa1c8aed6de5;hb=6fed43773c9b0ce596dca5686f37ac3fc0fa11c0;hp=0000000000000000000000000000000000000000;hpb=27b11d56b743098deb193d510b337ba22dc52e5c;p=msp430-gcc.git

diff --git a/gcc/config/host-linux.c b/gcc/config/host-linux.c
new file mode 100644
index 00000000..9f6ef0a1
--- /dev/null
+++ b/gcc/config/host-linux.c
@@ -0,0 +1,220 @@
+/* Linux host-specific hook definitions.
+   Copyright (C) 2004, 2005, 2007, 2008 Free Software Foundation, Inc.
+
+   This file is part of GCC.
+
+   GCC is free software; you can redistribute it and/or modify it
+   under the terms of the GNU General Public License as published
+   by the Free Software Foundation; either version 3, or (at your
+   option) any later version.
+
+   GCC is distributed in the hope that it will be useful, but WITHOUT
+   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+   or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+   License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with GCC; see the file COPYING3.  If not see
+   <http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include <sys/mman.h>
+#include <limits.h>
+#include "hosthooks.h"
+#include "hosthooks-def.h"
+
+
+/* Linux has a feature called exec-shield-randomize that perturbs the
+   address of non-fixed mapped segments by a (relatively) small amount.
+   The feature is intended to make it harder to attack the system with
+   buffer overflow attacks, since every invocation of a program will
+   have its libraries and data segments at slightly different addresses.
+
+   This feature causes us problems with PCH because it makes it that
+   much harder to acquire a stable location at which to map our PCH
+   data file.
+
+   [ The feature causes other points of non-determinism within the
+     compiler as well, so we'd *really* like to be able to have the
+     driver disable exec-shield-randomize for the process group, but
+     that isn't possible at present.  ]
+
+   We're going to try several things:
+
+      * Select an architecture specific address as "likely" and see
+	if that's free.  For our 64-bit hosts, we can easily choose
+	an address in Never Never Land.
+
+      * If exec-shield-randomize is disabled, then just use the
+	address chosen by mmap in step one.
+
+      * If exec-shield-randomize is enabled, then temporarily allocate
+	32M of memory as a buffer, then allocate PCH memory, then
+	free the buffer.  The theory here is that the perturbation is
+	no more than 16M, and so by allocating our buffer larger than
+	that we make it considerably more likely that the address will
+	be free when we want to load the data back.
+*/
+
+#undef HOST_HOOKS_GT_PCH_GET_ADDRESS
+#define HOST_HOOKS_GT_PCH_GET_ADDRESS linux_gt_pch_get_address
+
+#undef HOST_HOOKS_GT_PCH_USE_ADDRESS
+#define HOST_HOOKS_GT_PCH_USE_ADDRESS linux_gt_pch_use_address
+
+/* For various ports, try to guess a fixed spot in the vm space
+   that's probably free.  */
+#if defined(__alpha)
+# define TRY_EMPTY_VM_SPACE	0x10000000000
+#elif defined(__ia64)
+# define TRY_EMPTY_VM_SPACE	0x2000000100000000
+#elif defined(__x86_64)
+# define TRY_EMPTY_VM_SPACE	0x1000000000
+#elif defined(__i386)
+# define TRY_EMPTY_VM_SPACE	0x60000000
+#elif defined(__powerpc__)
+# define TRY_EMPTY_VM_SPACE	0x60000000
+#elif defined(__s390x__)
+# define TRY_EMPTY_VM_SPACE	0x8000000000
+#elif defined(__s390__)
+# define TRY_EMPTY_VM_SPACE	0x60000000
+#elif defined(__sparc__) && defined(__LP64__)
+# define TRY_EMPTY_VM_SPACE	0x8000000000
+#elif defined(__sparc__)
+# define TRY_EMPTY_VM_SPACE	0x60000000
+#elif defined(__mc68000__)
+# define TRY_EMPTY_VM_SPACE	0x40000000
+#else
+# define TRY_EMPTY_VM_SPACE	0
+#endif
+
+/* Determine a location where we might be able to reliably allocate SIZE
+   bytes.  FD is the PCH file, though we should return with the file 
+   unmapped.  */
+
+static void *
+linux_gt_pch_get_address (size_t size, int fd)
+{
+  size_t buffer_size = 32 * 1024 * 1024;
+  void *addr, *buffer;
+  FILE *f;
+  bool randomize_on;
+
+  addr = mmap ((void *)TRY_EMPTY_VM_SPACE, size, PROT_READ | PROT_WRITE,
+	       MAP_PRIVATE, fd, 0);
+
+  /* If we failed the map, that means there's *no* free space.  */
+  if (addr == (void *) MAP_FAILED)
+    return NULL;
+  /* Unmap the area before returning.  */
+  munmap (addr, size);
+
+  /* If we got the exact area we requested, then that's great.  */
+  if (TRY_EMPTY_VM_SPACE && addr == (void *) TRY_EMPTY_VM_SPACE)
+    return addr;
+
+  /* If we didn't, then we need to look to see if virtual address
+     randomization is on.  That is recorded in
+     kernel.randomize_va_space.  An older implementation used
+     kernel.exec-shield-randomize.  */
+  f = fopen ("/proc/sys/kernel/randomize_va_space", "r");
+  if (f == NULL)
+    f = fopen ("/proc/sys/kernel/exec-shield-randomize", "r");
+  randomize_on = false;
+  if (f != NULL)
+    {
+      char buf[100];
+      size_t c;
+
+      c = fread (buf, 1, sizeof buf - 1, f);
+      if (c > 0)
+	{
+	  buf[c] = '\0';
+	  randomize_on = (atoi (buf) > 0);
+	}
+      fclose (f);
+    }
+
+  /* If it isn't, then accept the address that mmap selected as fine.  */
+  if (!randomize_on)
+    return addr;
+
+  /* Otherwise, we need to try again with buffer space.  */
+  buffer = mmap (0, buffer_size, PROT_NONE, MAP_PRIVATE | MAP_ANON, -1, 0);
+  addr = mmap (0, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
+  if (buffer != (void *) MAP_FAILED)
+    munmap (buffer, buffer_size);
+  if (addr == (void *) MAP_FAILED)
+    return NULL;
+  munmap (addr, size);
+
+  return addr;
+}
+
+/* Map SIZE bytes of FD+OFFSET at BASE.  Return 1 if we succeeded at
+   mapping the data at BASE, -1 if we couldn't.
+
+   It's not possibly to reliably mmap a file using MAP_PRIVATE to
+   a specific START address on either hpux or linux.  First we see
+   if mmap with MAP_PRIVATE works.  If it does, we are off to the
+   races.  If it doesn't, we try an anonymous private mmap since the
+   kernel is more likely to honor the BASE address in anonymous maps.
+   We then copy the data to the anonymous private map.  This assumes
+   of course that we don't need to change the data in the PCH file
+   after it is created.
+
+   This approach obviously causes a performance penalty but there is
+   little else we can do given the current PCH implementation.  */
+
+static int
+linux_gt_pch_use_address (void *base, size_t size, int fd, size_t offset)
+{
+  void *addr;
+
+  /* We're called with size == 0 if we're not planning to load a PCH
+     file at all.  This allows the hook to free any static space that
+     we might have allocated at link time.  */
+  if (size == 0)
+    return -1;
+
+  /* Try to map the file with MAP_PRIVATE.  */
+  addr = mmap (base, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, offset);
+
+  if (addr == base)
+    return 1;
+
+  if (addr != (void *) MAP_FAILED)
+    munmap (addr, size);
+
+  /* Try to make an anonymous private mmap at the desired location.  */
+  addr = mmap (base, size, PROT_READ | PROT_WRITE,
+	       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+  if (addr != base)
+    {
+      if (addr != (void *) MAP_FAILED)
+        munmap (addr, size);
+      return -1;
+    }
+
+  if (lseek (fd, offset, SEEK_SET) == (off_t)-1)
+    return -1;
+
+  while (size)
+    {
+      ssize_t nbytes;
+
+      nbytes = read (fd, base, MIN (size, SSIZE_MAX));
+      if (nbytes <= 0)
+        return -1;
+      base = (char *) base + nbytes;
+      size -= nbytes;
+    }
+
+  return 1;
+}
+
+
+const struct host_hooks host_hooks = HOST_HOOKS_INITIALIZER;