X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;ds=sidebyside;f=lib%2Fc-stack.c;h=e48b97c3b73f9865d3e6555253c7429aa1e1c695;hb=a918da4d61d28be61a12605c9d35e2cf3966d866;hp=1ee356074da3e52e1b06286a9568b3ed9cbd2e9b;hpb=1398c0de968352891dfaaf26d4f8bf6676e5b060;p=gnulib.git

diff --git a/lib/c-stack.c b/lib/c-stack.c
index 1ee356074..e48b97c3b 100644
--- a/lib/c-stack.c
+++ b/lib/c-stack.c
@@ -1,7 +1,6 @@
 /* Stack overflow handling.
 
-   Copyright (C) 2002, 2004, 2006, 2008, 2009 Free Software
-   Foundation, Inc.
+   Copyright (C) 2002, 2004, 2006, 2008-2011 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -53,6 +52,12 @@ typedef struct sigaltstack stack_t;
 #endif
 #ifndef SIGSTKSZ
 # define SIGSTKSZ 16384
+#elif HAVE_LIBSIGSEGV && SIGSTKSZ < 16384
+/* libsigsegv 2.6 through 2.8 have a bug where some architectures use
+   more than the Linux default of an 8k alternate stack when deciding
+   if a fault was caused by stack overflow.  */
+# undef SIGSTKSZ
+# define SIGSTKSZ 16384
 #endif
 
 #include <stdlib.h>
@@ -75,9 +80,9 @@ typedef struct sigaltstack stack_t;
 #include "ignore-value.h"
 
 #if defined SA_ONSTACK && defined SA_SIGINFO
-# define SIGACTION_WORKS 1
+# define SIGINFO_WORKS 1
 #else
-# define SIGACTION_WORKS 0
+# define SIGINFO_WORKS 0
 # ifndef SA_ONSTACK
 #  define SA_ONSTACK 0
 # endif
@@ -104,6 +109,12 @@ static void
 die (int signo)
 {
   char const *message;
+#if !SIGINFO_WORKS && !HAVE_LIBSIGSEGV
+  /* We can't easily determine whether it is a stack overflow; so
+     assume that the rest of our program is perfect (!) and that
+     this segmentation violation is a stack overflow.  */
+  signo = 0;
+#endif /* !SIGINFO_WORKS && !HAVE_LIBSIGSEGV */
   segv_action (signo);
   message = signo ? program_error_message : stack_overflow_message;
   ignore_value (write (STDERR_FILENO, program_name, strlen (program_name)));
@@ -151,7 +162,7 @@ static volatile int segv_handler_missing;
    overflow.  This function is async-signal-safe.  */
 
 static int segv_handler (void *address __attribute__ ((unused)),
-			 int serious)
+                         int serious)
 {
 # if DEBUG
   {
@@ -175,13 +186,13 @@ static void overflow_handler (int, stackoverflow_context_t)
   __attribute__ ((noreturn));
 static void
 overflow_handler (int emergency,
-		  stackoverflow_context_t context __attribute__ ((unused)))
+                  stackoverflow_context_t context __attribute__ ((unused)))
 {
 # if DEBUG
   {
     char buf[1024];
     sprintf (buf, "overflow_handler emergency=%d segv_handler_missing=%d\n",
-	     emergency, segv_handler_missing);
+             emergency, segv_handler_missing);
     write (STDERR_FILENO, buf, strlen (buf));
   }
 # endif
@@ -212,23 +223,7 @@ c_stack_action (void (*action) (int))
 
 #elif HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK && HAVE_STACK_OVERFLOW_HANDLING
 
-/* Direction of the C runtime stack.  This function is
-   async-signal-safe.  */
-
-# if STACK_DIRECTION
-#  define find_stack_direction(ptr) STACK_DIRECTION
-# else
-#  if ! SIGACTION_WORKS || HAVE_XSI_STACK_OVERFLOW_HEURISTIC
-static int
-find_stack_direction (char const *addr)
-{
-  char dummy;
-  return ! addr ? find_stack_direction (&dummy) : addr < &dummy ? 1 : -1;
-}
-#  endif
-# endif
-
-# if SIGACTION_WORKS
+# if SIGINFO_WORKS
 
 /* Handle a segmentation violation and exit.  This function is
    async-signal-safe.  */
@@ -236,7 +231,7 @@ find_stack_direction (char const *addr)
 static void segv_handler (int, siginfo_t *, void *) __attribute__((noreturn));
 static void
 segv_handler (int signo, siginfo_t *info,
-	      void *context __attribute__ ((unused)))
+              void *context __attribute__ ((unused)))
 {
   /* Clear SIGNO if it seems to have been a stack overflow.  */
 #  if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
@@ -255,27 +250,24 @@ segv_handler (int signo, siginfo_t *info,
   if (0 < info->si_code)
     {
       /* If the faulting address is within the stack, or within one
-	 page of the stack end, assume that it is a stack
-	 overflow.  */
+         page of the stack, assume that it is a stack overflow.  */
       ucontext_t const *user_context = context;
       char const *stack_base = user_context->uc_stack.ss_sp;
       size_t stack_size = user_context->uc_stack.ss_size;
       char const *faulting_address = info->si_addr;
-      size_t s = faulting_address - stack_base;
       size_t page_size = sysconf (_SC_PAGESIZE);
-      if (find_stack_direction (NULL) < 0)
-	s += page_size;
-      if (s < stack_size + page_size)
-	signo = 0;
+      size_t s = faulting_address - stack_base + page_size;
+      if (s < stack_size + 2 * page_size)
+        signo = 0;
 
 #   if DEBUG
       {
-	char buf[1024];
-	sprintf (buf,
-		 "segv_handler fault=%p base=%p size=%lx page=%lx signo=%d\n",
-		 faulting_address, stack_base, (unsigned long) stack_size,
-		 (unsigned long) page_size, signo);
-	write (STDERR_FILENO, buf, strlen (buf));
+        char buf[1024];
+        sprintf (buf,
+                 "segv_handler fault=%p base=%p size=%lx page=%lx signo=%d\n",
+                 faulting_address, stack_base, (unsigned long) stack_size,
+                 (unsigned long) page_size, signo);
+        write (STDERR_FILENO, buf, strlen (buf));
       }
 #   endif
     }
@@ -311,7 +303,7 @@ c_stack_action (void (*action) (int))
 
   sigemptyset (&act.sa_mask);
 
-# if SIGACTION_WORKS
+# if SIGINFO_WORKS
   /* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but
      this is not true on Solaris 8 at least.  It doesn't hurt to use
      SA_NODEFER here, so leave it in.  */
@@ -330,7 +322,7 @@ c_stack_action (void (*action) (int))
 }
 
 #else /* ! ((HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK
-	     && HAVE_STACK_OVERFLOW_HANDLING) || HAVE_LIBSIGSEGV) */
+             && HAVE_STACK_OVERFLOW_HANDLING) || HAVE_LIBSIGSEGV) */
 
 int
 c_stack_action (void (*action) (int)  __attribute__ ((unused)))