mirror of
https://https.git.savannah.gnu.org/git/diffutils.git
synced 2026-01-27 09:54:25 +00:00
(__attribute__): New macro.
(EOVERFLOW): Define if not defined.(stack_t): Define to struct sigaltstack if not defined or declared. Include <sys/resource.h>, <ucontext.h> if available. Include <stdio.h> if DEBUG. Do not include <inttypes.h> or <stdint.h>. (c_stack_die): Remove info and context args. All uses changed. (segv_action): Likewise. (alternate_signal_stack): Change uintmax_t to long, to ease porting. (get_stack_location, min_address_from_argv, max_address_from_argv, null_action): New functions. (stack_base, stack_size): New vars. (segv_handler): context arg may not be used. Use global stack_base, stack_size if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC. Add debug code. Invoke die (rather than segv_action) to exit. (c_stack_action): Accept new argv arg, and simpler handler arg. All uses changed. Move code into new functions above. Allow null action. [! (defined SA_ONSTACK && defined _SC_PAGESIZE)]: Assume all segvs are stack overflows. (main) [DEBUG]: Describe what output should be like.
This commit is contained in:
Paul Eggert
parent
6cce27301e
commit
88ead75505
394
lib/c-stack.c
394
lib/c-stack.c
@ -18,17 +18,36 @@
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/* Written by Paul Eggert. */
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/* This module assumes that each stack frame is smaller than a page.
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If you use alloca, dynamic arrays, or large local variables, your
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program may extend the stack by more than a page at a time. If so,
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the code below may incorrectly report a program error, or worse
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yet, may not detect the overflow at all. To avoid this problem,
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don't use large local arrays. */
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/* NOTES:
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A program that uses alloca, dynamic arrays, or large local
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variables may extend the stack by more than a page at a time. If
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so, when the stack overflows the operating system may not detect
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the overflow until the program uses the array, and this module may
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incorrectly report a program error instead of a stack overflow.
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To avoid this problem, allocate only small objects on the stack; a
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program should be OK if it limits single allocations to a page or
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less. Allocate larger arrays in static storage, or on the heap
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(e.g., with malloc). Yes, this is a pain, but we don't know of any
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better solution that is portable.
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No attempt has been made to deal with multithreaded applications.
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If ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC, the current implementation
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assumes that, if the RLIMIT_STACK limit changes during execution,
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then c_stack_action is invoked immediately afterwards. */
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#if HAVE_CONFIG_H
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# include <config.h>
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#endif
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#ifndef __attribute__
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# if __GNUC__ < 3 || __STRICT_ANSI__
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# define __attribute__(x)
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# endif
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#endif
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#include "gettext.h"
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#define _(msgid) gettext (msgid)
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@ -36,19 +55,26 @@
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#ifndef ENOTSUP
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# define ENOTSUP EINVAL
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#endif
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#if HAVE_INTTYPES_H
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# include <inttypes.h>
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#else
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# if HAVE_STDINT_H
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# include <stdint.h>
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# endif
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#ifndef EOVERFLOW
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# define EOVERFLOW EINVAL
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#endif
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#include <signal.h>
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#if ! HAVE_STACK_T && ! defined stack_t
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typedef struct sigaltstack stack_t;
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#endif
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#include <stdlib.h>
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#include <string.h>
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#if HAVE_SYS_RESOURCE_H
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# include <sys/resource.h>
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#endif
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#if HAVE_UCONTEXT_H
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# include <ucontext.h>
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#endif
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#if HAVE_UNISTD_H
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# include <unistd.h>
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#endif
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@ -56,29 +82,47 @@
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# define STDERR_FILENO 2
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#endif
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#if DEBUG
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# include <stdio.h>
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#endif
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#include "c-stack.h"
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#include "exitfail.h"
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extern char *program_name;
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#if HAVE_XSI_STACK_OVERFLOW_HEURISTIC
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/* The user-specified action to take when a SEGV-related program error
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or stack overflow occurs. */
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static void (* volatile segv_action) (int);
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# include <ucontext.h>
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/* Translated messages for program errors and stack overflow. Do not
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translate them in the signal handler, since gettext is not
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async-signal-safe. */
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static char const * volatile program_error_message;
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static char const * volatile stack_overflow_message;
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/* Output an error message, then exit with status EXIT_FAILURE if it
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appears to have been a stack overflow, or with a core dump
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otherwise. This function is async-signal-safe. */
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/* Storage for the alternate signal stack. */
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static union
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static void die (int) __attribute__ ((noreturn));
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static void
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die (int signo)
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{
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char buffer[SIGSTKSZ];
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/* These other members are for proper alignment. There's no
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standard way to guarantee stack alignment, but this seems enough
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in practice. */
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long double ld;
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uintmax_t u;
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void *p;
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} alternate_signal_stack;
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char const *message =
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signo ? program_error_message : stack_overflow_message;
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segv_action (signo);
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write (STDERR_FILENO, program_name, strlen (program_name));
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write (STDERR_FILENO, ": ", 2);
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write (STDERR_FILENO, message, strlen (message));
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write (STDERR_FILENO, "\n", 1);
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if (! signo)
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_exit (exit_failure);
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kill (getpid (), signo);
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abort ();
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}
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#if HAVE_DECL_SIGALTSTACK
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/* Direction of the C runtime stack. This function is
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async-signal-safe. */
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@ -94,14 +138,154 @@ find_stack_direction (char const *addr)
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}
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# endif
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/* The SIGSEGV handler. */
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static void (* volatile segv_action) (int, siginfo_t *, void *);
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# if HAVE_XSI_STACK_OVERFLOW_HEURISTIC
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# define get_stack_location(argv) 0
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# else
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# if defined RLIMIT_STACK && defined _SC_PAGESIZE
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/* Return the minimum machine address deducible from ARGV. This
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includes the addresses of all the strings that ARGV points at, as
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well as the address of ARGV itself. */
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static char const *
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min_address_from_argv (char * const *argv)
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{
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char const *min = (char const *) argv;
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char const *p;
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while ((p = *argv++))
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if (p < min)
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min = p;
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return min;
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}
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/* Return the maximum machine address deducible from ARGV. */
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static char const *
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max_address_from_argv (char * const *argv)
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{
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char const *max = *argv;
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char const *max1;
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char const *p;
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while ((p = *argv++))
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if (max < p)
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max = p;
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max1 = (char const *) (argv + 1);
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return max && max1 < max ? max + strlen (max) + 1 : max1;
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}
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# endif
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/* The base and size of the stack, determined at startup. */
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static char const * volatile stack_base;
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static size_t volatile stack_size;
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/* Store the base and size of the stack into the static variables
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STACK_BASE and STACK_SIZE. The base is the numerically lowest
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address in the stack. Return -1 (setting errno) if this cannot be
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done. */
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static int
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get_stack_location (char * const *argv)
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{
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# if ! (defined RLIMIT_STACK && defined _SC_PAGESIZE)
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errno = ENOTSUP;
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return -1;
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# else
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struct rlimit rlimit;
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int r = getrlimit (RLIMIT_STACK, &rlimit);
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if (r == 0)
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{
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char const *base;
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size_t size = rlimit.rlim_cur;
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extern char **environ;
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size_t page_size = sysconf (_SC_PAGESIZE);
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int stack_direction = find_stack_direction (0);
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#if HAVE_DECL_GETCONTEXT
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ucontext_t context;
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if (getcontext (&context) == 0)
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{
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base = context.uc_stack.ss_sp;
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if (stack_direction < 0)
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base -= size - context.uc_stack.ss_size;
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}
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else
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#endif
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{
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if (stack_direction < 0)
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{
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char const *a = max_address_from_argv (argv);
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char const *b = max_address_from_argv (environ);
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base = (a < b ? b : a) - size;
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base += - (size_t) base % page_size;
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}
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else
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{
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char const *a = min_address_from_argv (argv);
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char const *b = min_address_from_argv (environ);
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base = a < b ? a : b;
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base -= (size_t) base % page_size;
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}
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}
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if (size != rlimit.rlim_cur
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|| rlimit.rlim_cur < 0
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|| base + size < base
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# ifdef RLIM_SAVED_CUR
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|| rlimit.rlim_cur == RLIM_SAVED_CUR
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# endif
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# ifdef RLIM_SAVED_MAX
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|| rlimit.rlim_cur == RLIM_SAVED_MAX
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# endif
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# ifdef RLIM_INFINITY
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|| rlimit.rlim_cur == RLIM_INFINITY
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# endif
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)
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{
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errno = EOVERFLOW;
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return -1;
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}
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stack_base = base;
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stack_size = size;
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# if DEBUG
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fprintf (stderr, "get_stack_location base=%p size=%lx\n",
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base, (unsigned long) size);
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# endif
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}
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return r;
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# endif
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}
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# endif
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/* Storage for the alternate signal stack. */
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static union
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{
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char buffer[SIGSTKSZ];
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/* These other members are for proper alignment. There's no
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standard way to guarantee stack alignment, but this seems enough
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in practice. */
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long double ld;
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long l;
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void *p;
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} alternate_signal_stack;
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# if defined SA_ONSTACK && defined _SC_PAGESIZE
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/* Handle a segmentation violation and exit. This function is
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async-signal-safe. */
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static void segv_handler (int, siginfo_t *, void *) __attribute__((noreturn));
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static void
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segv_handler (int signo, siginfo_t *info, void *context)
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segv_handler (int signo, siginfo_t *info,
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void *context __attribute__ ((unused)))
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{
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/* Clear SIGNO if it seems to have been a stack overflow. */
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if (0 < info->si_code)
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@ -109,101 +293,109 @@ segv_handler (int signo, siginfo_t *info, void *context)
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/* If the faulting address is within the stack, or within one
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page of the stack end, assume that it is a stack
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overflow. */
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# if HAVE_XSI_STACK_OVERFLOW_HEURISTIC
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ucontext_t const *user_context = context;
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char const *stack_min = user_context->uc_stack.ss_sp;
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char const *stack_base = user_context->uc_stack.ss_sp;
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size_t stack_size = user_context->uc_stack.ss_size;
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# endif
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char const *faulting_address = info->si_addr;
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size_t s = faulting_address - stack_min;
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size_t s = faulting_address - stack_base;
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size_t page_size = sysconf (_SC_PAGESIZE);
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if (find_stack_direction (0) < 0)
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s += page_size;
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if (s < stack_size + page_size)
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signo = 0;
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# if DEBUG
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{
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char buf[1024];
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sprintf (buf,
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"segv_handler fault=%p base=%p size=%lx page=%lx signo=%d\n",
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faulting_address, stack_base, (unsigned long) stack_size,
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(unsigned long) page_size, signo);
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write (STDERR_FILENO, buf, strlen (buf));
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}
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# endif
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}
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segv_action (signo, info, context);
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die (signo);
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}
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# endif
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#endif /* HAVE_XSI_STACK_OVERFLOW_HEURISTIC */
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/* Translated messages for program errors and stack overflow. Do not
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translate them in the signal handler, since gettext is not
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async-signal-safe. */
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static char const * volatile program_error_message;
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static char const * volatile stack_overflow_message;
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/* Output an error message, then exit with status EXIT_FAILURE if it
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appears to have been a stack overflow, or with a core dump
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otherwise. This function is async-signal-safe. */
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void
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c_stack_die (int signo, siginfo_t *info, void *context)
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static void
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null_action (int signo __attribute__ ((unused)))
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{
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char const *message =
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signo ? program_error_message : stack_overflow_message;
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write (STDERR_FILENO, program_name, strlen (program_name));
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write (STDERR_FILENO, ": ", 2);
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write (STDERR_FILENO, message, strlen (message));
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write (STDERR_FILENO, "\n", 1);
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if (! signo)
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_exit (exit_failure);
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#if HAVE_SIGINFO_T
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if (context && info && 0 <= info->si_code)
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{
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/* Re-raise the exception at the same address. */
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char *addr = info->si_addr;
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*addr = 0;
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}
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#endif
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kill (getpid (), signo);
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}
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/* Assuming ARGV is the argument vector of `main', set up ACTION so
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that it is invoked on C stack overflow. Return -1 (setting errno)
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if this cannot be done.
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/* Set up ACTION so that it is invoked on C stack overflow. Return -1
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(setting errno) if this cannot be done.
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When ACTION is called, it is passed an argument equal to SIGSEGV
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for a segmentation violation that does not appear related to stack
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overflow, and is passed zero otherwise.
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ACTION must invoke only async-signal-safe functions. ACTION
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together with its callees must not require more than SIGSTKSZ bytes
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of stack space. */
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A null ACTION acts like an action that does nothing.
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ACTION must be async-signal-safe. ACTION together with its callees
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must not require more than SIGSTKSZ bytes of stack space. */
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int
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c_stack_action (void (*action) (int, siginfo_t *, void *))
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c_stack_action (char * const *argv __attribute__ ((unused)),
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void (*action) (int))
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{
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#if ! HAVE_XSI_STACK_OVERFLOW_HEURISTIC
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errno = ENOTSUP;
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return -1;
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#else
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struct sigaction act;
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stack_t st;
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int r;
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st.ss_flags = 0;
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st.ss_sp = alternate_signal_stack.buffer;
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st.ss_size = sizeof alternate_signal_stack.buffer;
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r = sigaltstack (&st, 0);
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int r = get_stack_location (argv);
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if (r != 0)
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return r;
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{
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stack_t st;
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st.ss_flags = 0;
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st.ss_sp = alternate_signal_stack.buffer;
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st.ss_size = sizeof alternate_signal_stack.buffer;
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r = sigaltstack (&st, 0);
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if (r != 0)
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return r;
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}
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segv_action = action ? action : null_action;
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program_error_message = _("program error");
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stack_overflow_message = _("stack overflow");
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segv_action = action;
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sigemptyset (&act.sa_mask);
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{
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# if ! (defined SA_ONSTACK && defined _SC_PAGESIZE)
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return signal (SIGSEGV, die) == SIG_ERR ? -1 : 0;
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# else
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struct sigaction act;
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sigemptyset (&act.sa_mask);
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/* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but this
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is not true on Solaris 8 at least. It doesn't hurt to use
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SA_NODEFER here, so leave it in. */
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act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
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/* POSIX 1003.1-2001 says SA_RESETHAND implies SA_NODEFER, but
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this is not true on Solaris 8 at least. It doesn't hurt to use
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SA_NODEFER here, so leave it in. */
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act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
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act.sa_sigaction = segv_handler;
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return sigaction (SIGSEGV, &act, 0);
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#endif
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act.sa_sigaction = segv_handler;
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return sigaction (SIGSEGV, &act, 0);
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# endif
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}
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}
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#if DEBUG
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#include <stdio.h>
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#else /* ! HAVE_DECL_SIGALTSTACK */
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int
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c_stack_action (char * const *argv __attribute__ ((unused)),
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void (*action) (int) __attribute__ ((unused)))
|
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{
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errno = ENOTSUP;
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return -1;
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}
|
||||
|
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#endif
|
||||
|
||||
|
||||
|
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#if DEBUG
|
||||
|
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int volatile exit_failure;
|
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|
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@ -218,20 +410,20 @@ recurse (char *p)
|
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char *program_name;
|
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|
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int
|
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main (int argc, char **argv)
|
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main (int argc __attribute__ ((unused)), char **argv)
|
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{
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program_name = argv[0];
|
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c_stack_action (c_stack_die);
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return recurse ("\1");
|
||||
fprintf (stderr, "The last line of output should be \"stack overflow\".\n");
|
||||
if (c_stack_action (argv, 0) == 0)
|
||||
return recurse ("\1");
|
||||
perror ("c_stack_action");
|
||||
return 1;
|
||||
}
|
||||
|
||||
#endif /* DEBUG */
|
||||
|
||||
/*
|
||||
Local Variables:
|
||||
compile-command: "gcc -D_GNU_SOURCE -DDEBUG \
|
||||
-DHAVE_INTTYPES_H -DHAVE_SIGINFO_T \
|
||||
-DHAVE_XSI_STACK_OVERFLOW_HEURISTIC -DHAVE_UNISTD_H \
|
||||
-Wall -W -g c-stack.c -o c-stack"
|
||||
compile-command: "gcc -DDEBUG -DHAVE_CONFIG_H -I.. -g -O -Wall -W c-stack.c"
|
||||
End:
|
||||
*/
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user