Eric Blake <ebb9 <at> byu.net> writes:
> Here's the minimal patch needed to CVS libsigsegv to expose the bug, as
> well as work around it for Irix 5.3. I still need to port something like
> this for c-stack in the non-libsigsegv case.
Now that libsigsegv is cleaned up, here's what I'm applying to gnulib. I've
tested that on Irix 5.3, both with and without libsigsegv, a tarball of m4
built today no longer fails any tests (but without libsigsegv, test-c-stack2.sh
skips, since Irix does not provide the XSI hooks for detecting stack overflow
from siginfo_t).
>From ad73682838ae0e66832aad97a8fbc5fb935130c6 Mon Sep 17 00:00:00 2001
From: Eric Blake <[EMAIL PROTECTED]>
Date: Tue, 23 Sep 2008 08:47:26 -0600
Subject: [PATCH] c-stack: work around Irix sigaltstack bug
* m4/c-stack.m4 (AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC): Check
whether sigaltstack uses wrong end of stack_t (copied in part from
libsigsegv).
* lib/c-stack.c (c_stack_action) [!HAVE_LIBSIGSEGV]: Work around
Irix bug, without requiring an over-allocation.
* doc/posix-functions/sigaltstack.texi (sigaltstack): Document the
bug.
Signed-off-by: Eric Blake <[EMAIL PROTECTED]>
---
ChangeLog | 13 ++++-
doc/posix-functions/sigaltstack.texi | 8 +++-
lib/c-stack.c | 7 +++
m4/c-stack.m4 | 94 ++++++++++++++++++++++++++++-----
4 files changed, 104 insertions(+), 18 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 38dd15e..1dbbb60 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,14 @@
2008-09-23 Eric Blake <[EMAIL PROTECTED]>
+ c-stack: work around Irix sigaltstack bug
+ * m4/c-stack.m4 (AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC): Check
+ whether sigaltstack uses wrong end of stack_t (copied in part from
+ libsigsegv).
+ * lib/c-stack.c (c_stack_action) [!HAVE_LIBSIGSEGV]: Work around
+ Irix bug, without requiring an over-allocation.
+ * doc/posix-functions/sigaltstack.texi (sigaltstack): Document the
+ bug.
+
fopen: document mingw bug on directories
* doc/posix-functions/fopen.texi (fopen): Mention mingw bug for
not allowing a stream visiting a directory, even though reading
diff --git a/doc/posix-functions/sigaltstack.texi b/doc/posix-
functions/sigaltstack.texi
index 53d91c7..e318ebe 100644
--- a/doc/posix-functions/sigaltstack.texi
+++ b/doc/posix-functions/sigaltstack.texi
@@ -16,5 +16,11 @@ Portability problems not fixed by Gnulib:
This function is missing on some platforms:
Cygwin, mingw, Interix 3.5, BeOS.
@item
[EMAIL PROTECTED] doesn't work on HP-UX 11/IA-64 and OpenBSD 3.6/Sparc64.
[EMAIL PROTECTED] doesn't work on HP-UX 11/IA-64 and OpenBSD
+3.6/Sparc64.
[EMAIL PROTECTED]
+This function interprets the @code{ss_sp} member of @code{stack_t} as
+the upper bound instead of the lower bound of the alternate stack on
+some platforms:
+Irix 6.5
@end itemize
diff --git a/lib/c-stack.c b/lib/c-stack.c
index 6802665..11cb9ef 100644
--- a/lib/c-stack.c
+++ b/lib/c-stack.c
@@ -291,8 +291,15 @@ c_stack_action (void (*action) (int))
stack_t st;
struct sigaction act;
st.ss_flags = 0;
+# if SIGALTSTACK_SS_REVERSED
+ /* Irix mistakenly treats ss_sp as the upper bound, rather than
+ lower bound, of the alternate stack. */
+ st.ss_sp = alternate_signal_stack.buffer + SIGSTKSZ - sizeof (void *);
+ st.ss_size = sizeof alternate_signal_stack.buffer - sizeof (void *);
+# else
st.ss_sp = alternate_signal_stack.buffer;
st.ss_size = sizeof alternate_signal_stack.buffer;
+# endif
r = sigaltstack (&st, NULL);
if (r != 0)
return r;
diff --git a/m4/c-stack.m4 b/m4/c-stack.m4
index 4f0300b..f1bda7b 100644
--- a/m4/c-stack.m4
+++ b/m4/c-stack.m4
@@ -7,7 +7,7 @@
# Written by Paul Eggert.
-# serial 6
+# serial 7
AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
[# for STACK_DIRECTION
@@ -26,13 +26,13 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
# include <sys/time.h>
# include <sys/resource.h>
#endif
- #ifndef SIGSTKSZ
- # define SIGSTKSZ 16384
- #endif
+ #ifndef SIGSTKSZ
+ # define SIGSTKSZ 16384
+ #endif
static union
{
- char buffer[SIGSTKSZ];
+ char buffer[2 * SIGSTKSZ];
long double ld;
long u;
void *p;
@@ -52,8 +52,9 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
int r;
st.ss_flags = 0;
- st.ss_sp = alternate_signal_stack.buffer;
- st.ss_size = sizeof alternate_signal_stack.buffer;
+ /* Use the midpoint to avoid Irix sigaltstack bug. */
+ st.ss_sp = alternate_signal_stack.buffer + SIGSTKSZ;
+ st.ss_size = SIGSTKSZ;
r = sigaltstack (&st, 0);
if (r != 0)
return r;
@@ -98,6 +99,68 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
a SIGSEGV which can be handled on an alternate stack established
with sigaltstack.])
+ dnl The ss_sp field of a stack_t is, according to POSIX, the lowest address
+ dnl of the memory block designated as an alternate stack. But IRIX 5.3
+ dnl interprets it as the highest address!
+ AC_CACHE_CHECK([for correct stack_t interpretation],
+ [gl_cv_sigaltstack_low_base], [
+ AC_RUN_IFELSE([
+ AC_LANG_SOURCE([[
+#include <stdlib.h>
+#include <signal.h>
+#if HAVE_SYS_SIGNAL_H
+# include <sys/signal.h>
+#endif
+#ifndef SIGSTKSZ
+# define SIGSTKSZ 16384
+#endif
+volatile char *stack_lower_bound;
+volatile char *stack_upper_bound;
+static void check_stack_location (volatile char *addr)
+{
+ if (addr >= stack_lower_bound && addr <= stack_upper_bound)
+ exit (0);
+ else
+ exit (1);
+}
+static void stackoverflow_handler (int sig)
+{
+ char dummy;
+ check_stack_location (&dummy);
+}
+int main ()
+{
+ char mystack[2 * SIGSTKSZ];
+ stack_t altstack;
+ struct sigaction action;
+ /* Install the alternate stack. */
+ altstack.ss_sp = mystack + SIGSTKSZ;
+ altstack.ss_size = SIGSTKSZ;
+ stack_lower_bound = (char *) altstack.ss_sp;
+ stack_upper_bound = (char *) altstack.ss_sp + altstack.ss_size - 1;
+ altstack.ss_flags = 0; /* no SS_DISABLE */
+ if (sigaltstack (&altstack, NULL) < 0)
+ exit (2);
+ /* Install the SIGSEGV handler. */
+ sigemptyset (&action.sa_mask);
+ action.sa_handler = &stackoverflow_handler;
+ action.sa_flags = SA_ONSTACK;
+ if (sigaction (SIGSEGV, &action, (struct sigaction *) NULL) < 0)
+ exit(3);
+ /* Provoke a SIGSEGV. */
+ raise (SIGSEGV);
+ exit (3);
+}]])],
+ [gl_cv_sigaltstack_low_base=yes],
+ [gl_cv_sigaltstack_low_base=no],
+ [gl_cv_sigaltstack_low_base=cross-compiling])])
+ if test "$gl_cv_sigaltstack_low_base" = no; then
+ AC_DEFINE([SIGALTSTACK_SS_REVERSED], [1],
+ [Define if sigaltstack() interprets the stack_t.ss_sp field
+ incorrectly, as the highest address of the alternate stack range
+ rather than as the lowest address.])
+ fi
+
AC_CACHE_CHECK([for precise C stack overflow detection],
ac_cv_sys_xsi_stack_overflow_heuristic,
[AC_TRY_RUN(
@@ -112,13 +175,13 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
# include <sys/time.h>
# include <sys/resource.h>
#endif
- #ifndef SIGSTKSZ
- # define SIGSTKSZ 16384
- #endif
+ #ifndef SIGSTKSZ
+ # define SIGSTKSZ 16384
+ #endif
static union
{
- char buffer[SIGSTKSZ];
+ char buffer[2 * SIGSTKSZ];
long double ld;
long u;
void *p;
@@ -167,8 +230,9 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
int r;
st.ss_flags = 0;
- st.ss_sp = alternate_signal_stack.buffer;
- st.ss_size = sizeof alternate_signal_stack.buffer;
+ /* Use the midpoint to avoid Irix sigaltstack bug. */
+ st.ss_sp = alternate_signal_stack.buffer + SIGSTKSZ;
+ st.ss_size = SIGSTKSZ;
r = sigaltstack (&st, 0);
if (r != 0)
return r;
--
1.6.0.2
>From 91a109c0426e8b8cd8b317e29c8a91bd99757f0a Mon Sep 17 00:00:00 2001
From: Eric Blake <[EMAIL PROTECTED]>
Date: Tue, 23 Sep 2008 08:56:10 -0600
Subject: [PATCH] c-stack: avoid compiler optimizations when provoking overflow
* m4/c-stack.m4 (AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC): Make
recursion harder to optimize, to ensure a stack overflow occurs.
* tests/test-c-stack.c (recurse): Likewise.
Borrowed from libsigsegv.
Signed-off-by: Eric Blake <[EMAIL PROTECTED]>
---
ChangeLog | 6 ++++++
m4/c-stack.m4 | 36 ++++++++++++++++++++++--------------
tests/test-c-stack.c | 22 +++++++++++++++-------
3 files changed, 43 insertions(+), 21 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 1dbbb60..8586143 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
2008-09-23 Eric Blake <[EMAIL PROTECTED]>
+ c-stack: avoid compiler optimizations when provoking overflow
+ * m4/c-stack.m4 (AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC): Make
+ recursion harder to optimize, to ensure a stack overflow occurs.
+ * tests/test-c-stack.c (recurse): Likewise.
+ Borrowed from libsigsegv.
+
c-stack: work around Irix sigaltstack bug
* m4/c-stack.m4 (AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC): Check
whether sigaltstack uses wrong end of stack_t (copied in part from
diff --git a/m4/c-stack.m4 b/m4/c-stack.m4
index f1bda7b..5069333 100644
--- a/m4/c-stack.m4
+++ b/m4/c-stack.m4
@@ -64,15 +64,19 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
act.sa_handler = segv_handler;
return sigaction (SIGSEGV, &act, 0);
}
-
+ static volatile int *
+ recurse_1 (volatile int n, volatile int *p)
+ {
+ if (n >= 0)
+ *recurse_1 (n + 1, p) += n;
+ return p;
+ }
static int
- recurse (char *p)
+ recurse (volatile int n)
{
- char array[500];
- array[0] = 1;
- return *p + recurse (array);
+ int sum = 0;
+ return *recurse_1 (n, &sum);
}
-
int
main ()
{
@@ -86,7 +90,7 @@ AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
setrlimit (RLIMIT_STACK, &rl);
#endif
- return c_stack_action () || recurse ("\1");
+ return c_stack_action () || recurse (0);
}
],
[ac_cv_sys_stack_overflow_works=yes],
@@ -242,15 +246,19 @@ int main ()
act.sa_sigaction = segv_handler;
return sigaction (SIGSEGV, &act, 0);
}
-
+ static volatile int *
+ recurse_1 (volatile int n, volatile int *p)
+ {
+ if (n >= 0)
+ *recurse_1 (n + 1, p) += n;
+ return p;
+ }
static int
- recurse (char *p)
+ recurse (volatile int n)
{
- char array[500];
- array[0] = 1;
- return *p + recurse (array);
+ int sum = 0;
+ return *recurse_1 (n, &sum);
}
-
int
main ()
{
@@ -264,7 +272,7 @@ int main ()
setrlimit (RLIMIT_STACK, &rl);
#endif
- return c_stack_action () || recurse ("\1");
+ return c_stack_action () || recurse (0);
}
],
[ac_cv_sys_xsi_stack_overflow_heuristic=yes],
diff --git a/tests/test-c-stack.c b/tests/test-c-stack.c
index fe782c9..96ab152 100644
--- a/tests/test-c-stack.c
+++ b/tests/test-c-stack.c
@@ -41,15 +41,22 @@
} \
while (0)
-static long
-recurse (char *p)
+char *program_name;
+
+static volatile int *
+recurse_1 (volatile int n, volatile int *p)
{
- char array[500];
- array[0] = 1;
- return *p + recurse (array);
+ if (n >= 0)
+ *recurse_1 (n + 1, p) += n;
+ return p;
}
-char *program_name;
+static int
+recurse (volatile int n)
+{
+ int sum = 0;
+ return *recurse_1 (n, &sum);
+}
int
main (int argc, char **argv)
@@ -72,8 +79,9 @@ main (int argc, char **argv)
exit_failure = 77;
++*argv[argc]; /* Intentionally dereference NULL. */
}
- return recurse ("\1");
+ return recurse (0);
}
+ fputs ("skipping test: ", stderr);
perror ("c_stack_action");
return 77;
}
--
1.6.0.2
