| 1 | # Check prerequisites for compiling lib/c-stack.c.
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| 2 |
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| 3 | # Copyright (C) 2002 Free Software Foundation, Inc.
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| 4 |
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| 5 | # This program is free software; you can redistribute it and/or modify
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| 6 | # it under the terms of the GNU General Public License as published by
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| 7 | # the Free Software Foundation; either version 2, or (at your option)
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| 8 | # any later version.
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| 9 |
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| 10 | # This program is distributed in the hope that it will be useful,
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| 11 | # but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 12 | # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 13 | # GNU General Public License for more details.
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| 14 |
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| 15 | # You should have received a copy of the GNU General Public License
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| 16 | # along with this program; if not, write to the Free Software
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| 17 | # Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
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| 18 | # 02111-1307, USA.
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| 19 |
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| 20 | AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
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| 21 | [# for STACK_DIRECTION
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| 22 | AC_REQUIRE([AC_FUNC_ALLOCA])
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| 23 |
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| 24 | AC_CACHE_CHECK([for working C stack overflow detection],
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| 25 | ac_cv_sys_xsi_stack_overflow_heuristic,
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| 26 | [AC_TRY_RUN(
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| 27 | [
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| 28 | #include <signal.h>
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| 29 | #include <ucontext.h>
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| 30 |
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| 31 | static union
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| 32 | {
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| 33 | char buffer[SIGSTKSZ];
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| 34 | long double ld;
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| 35 | uintmax_t u;
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| 36 | void *p;
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| 37 | } alternate_signal_stack;
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| 38 |
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| 39 | #if STACK_DIRECTION
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| 40 | # define find_stack_direction(ptr) STACK_DIRECTION
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| 41 | #else
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| 42 | static int
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| 43 | find_stack_direction (char const *addr)
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| 44 | {
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| 45 | char dummy;
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| 46 | return (! addr ? find_stack_direction (&dummy)
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| 47 | : addr < &dummy ? 1 : -1);
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| 48 | }
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| 49 | #endif
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| 50 |
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| 51 | static void
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| 52 | segv_handler (int signo, siginfo_t *info, void *context)
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| 53 | {
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| 54 | if (0 < info->si_code)
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| 55 | {
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| 56 | ucontext_t const *user_context = context;
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| 57 | char const *stack_min = user_context->uc_stack.ss_sp;
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| 58 | size_t stack_size = user_context->uc_stack.ss_size;
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| 59 | char const *faulting_address = info->si_addr;
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| 60 | size_t s = faulting_address - stack_min;
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| 61 | size_t page_size = sysconf (_SC_PAGESIZE);
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| 62 | if (find_stack_direction (0) < 0)
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| 63 | s += page_size;
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| 64 | if (s < stack_size + page_size)
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| 65 | _exit (0);
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| 66 | }
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| 67 |
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| 68 | _exit (1);
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| 69 | }
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| 70 |
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| 71 | static int
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| 72 | c_stack_action (void)
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| 73 | {
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| 74 | stack_t st;
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| 75 | struct sigaction act;
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| 76 | int r;
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| 77 |
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| 78 | st.ss_flags = 0;
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| 79 | st.ss_sp = alternate_signal_stack.buffer;
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| 80 | st.ss_size = sizeof alternate_signal_stack.buffer;
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| 81 | r = sigaltstack (&st, 0);
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| 82 | if (r != 0)
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| 83 | return r;
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| 84 |
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| 85 | sigemptyset (&act.sa_mask);
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| 86 | act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
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