#if ! HAVE_STACK_T && ! defined stack_t
typedef struct sigaltstack stack_t;
#endif
+#ifndef SIGSTKSZ
+# define SIGSTKSZ 16384
+#endif
#include <stdlib.h>
#include <string.h>
# define STDERR_FILENO 2
#endif
+#if HAVE_LIBSIGSEGV
+# include <sigsegv.h>
+#endif
+
#include "c-stack.h"
#include "exitfail.h"
abort ();
}
-#if HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK
+#if (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK) || HAVE_LIBSIGSEGV
+
+/* Storage for the alternate signal stack. */
+static union
+{
+ char buffer[SIGSTKSZ];
+
+ /* These other members are for proper alignment. There's no
+ standard way to guarantee stack alignment, but this seems enough
+ in practice. */
+ long double ld;
+ long l;
+ void *p;
+} alternate_signal_stack;
+
+static void
+null_action (int signo __attribute__ ((unused)))
+{
+}
+
+#endif /* SIGALTSTACK || LIBSIGSEGV */
+
+/* Only use libsigsegv if we need it; platforms like Solaris can
+ detect stack overflow without the overhead of an external
+ library. */
+#if HAVE_LIBSIGSEGV && ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
+
+/* Nonzero if general segv handler could not be installed. */
+static volatile int segv_handler_missing;
+
+/* Handle a segmentation violation and exit if it cannot be stack
+ overflow. This function is async-signal-safe. */
+
+static int segv_handler (void *address __attribute__ ((unused)),
+ int serious)
+{
+# if DEBUG
+ {
+ char buf[1024];
+ sprintf (buf, "segv_handler serious=%d\n", serious);
+ write (STDERR_FILENO, buf, strlen (buf));
+ }
+# endif
+
+ /* If this fault is not serious, return 0 to let the stack overflow
+ handler take a shot at it. */
+ if (!serious)
+ return 0;
+ die (SIGSEGV);
+}
+
+/* Handle a segmentation violation that is likely to be a stack
+ overflow and exit. This function is async-signal-safe. */
+
+static void overflow_handler (int, stackoverflow_context_t)
+ __attribute__ ((noreturn));
+static void
+overflow_handler (int emergency,
+ 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);
+ write (STDERR_FILENO, buf, strlen (buf));
+ }
+# endif
+
+ die ((!emergency || segv_handler_missing) ? 0 : SIGSEGV);
+}
+
+/* Set up ACTION so that it is invoked on C stack overflow. Return -1
+ (setting errno) if this cannot be done.
+
+ When ACTION is called, it is passed an argument equal to SIGSEGV
+ for a segmentation violation that does not appear related to stack
+ overflow, and is passed zero otherwise. On many platforms it is
+ hard to tell; when in doubt, zero is passed.
+
+ A null ACTION acts like an action that does nothing.
+
+ ACTION must be async-signal-safe. ACTION together with its callees
+ must not require more than SIGSTKSZ bytes of stack space. Also,
+ ACTION should not call longjmp, because this implementation does
+ not guarantee that it is safe to return to the original stack. */
+
+int
+c_stack_action (void (*action) (int))
+{
+ segv_action = action ? action : null_action;
+ program_error_message = _("program error");
+ stack_overflow_message = _("stack overflow");
+
+ /* Always install the overflow handler. */
+ if (stackoverflow_install_handler (overflow_handler,
+ alternate_signal_stack.buffer,
+ sizeof alternate_signal_stack.buffer))
+ {
+ errno = ENOTSUP;
+ return -1;
+ }
+ /* Try installing a general handler; if it fails, then treat all
+ segv as stack overflow. */
+ segv_handler_missing = sigsegv_install_handler (segv_handler);
+ return 0;
+}
+
+#elif HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK
/* Direction of the C runtime stack. This function is
async-signal-safe. */
}
# endif
-/* Storage for the alternate signal stack. */
-static union
-{
- char buffer[SIGSTKSZ];
-
- /* These other members are for proper alignment. There's no
- standard way to guarantee stack alignment, but this seems enough
- in practice. */
- long double ld;
- long l;
- void *p;
-} alternate_signal_stack;
-
# if SIGACTION_WORKS
/* Handle a segmentation violation and exit. This function is
# if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
/* 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. */
+ this segmentation violation is a stack overflow.
+
+ Note that although both Linux and Solaris provide
+ sigaltstack, SA_ONSTACK, and SA_SIGINFO, currently only
+ Solaris satisfies the XSI heueristic. This is because
+ Solaris populates uc_stack with the details of the
+ interrupted stack, while Linux populates it with the details
+ of the current stack. */
signo = 0;
# else
/* If the faulting address is within the stack, or within one
}
# endif
-static void
-null_action (int signo __attribute__ ((unused)))
-{
-}
-
/* Set up ACTION so that it is invoked on C stack overflow. Return -1
(setting errno) if this cannot be done.
A null ACTION acts like an action that does nothing.
ACTION must be async-signal-safe. ACTION together with its callees
- must not require more than SIGSTKSZ bytes of stack space. */
+ must not require more than SIGSTKSZ bytes of stack space. Also,
+ ACTION should not call longjmp, because this implementation does
+ not guarantee that it is safe to return to the original stack. */
int
c_stack_action (void (*action) (int))
return sigaction (SIGSEGV, &act, NULL);
}
-#else /* ! (HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK) */
+#else /* ! ((HAVE_SIGALTSTACK && HAVE_DECL_SIGALTSTACK) || HAVE_LIBSIGSEGV) */
int
c_stack_action (void (*action) (int) __attribute__ ((unused)))
# Written by Paul Eggert.
-# serial 2
+# serial 3
AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
[# for STACK_DIRECTION
{
if (0 < info->si_code)
{
+ /* For XSI heuristics to work, we need uc_stack to describe
+ the interrupted stack (as on Solaris), and not the
+ currently executing stack (as on Linux). */
ucontext_t const *user_context = context;
char const *stack_min = user_context->uc_stack.ss_sp;
size_t stack_size = user_context->uc_stack.ss_size;
AC_DEFUN([gl_PREREQ_C_STACK],
[AC_REQUIRE([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC])
+ AC_REQUIRE([gl_LIBSIGSEGV])
# for STACK_DIRECTION
AC_REQUIRE([AC_FUNC_ALLOCA])
AC_CHECK_MEMBERS([struct sigaction.sa_sigaction], , , [#include <signal.h>])
- AC_CHECK_TYPES([stack_t], , , [#include <signal.h>])])
+ AC_CHECK_TYPES([stack_t], , , [#include <signal.h>])
+
+ dnl c-stack does not need -lsigsegv if the system has XSI heuristics.
+ if test "$gl_cv_lib_sigsegv" = yes \
+ && test $"ac_cv_sys_xsi_stack_overflow_heuristic" != yes ; then
+ AC_SUBST([LIBCSTACK], [$LIBSIGSEGV])
+ AC_SUBST([LTLIBCSTACK], [$LTLIBSIGSEGV])
+ fi
+])
AC_DEFUN([gl_C_STACK],
[
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