source: trunk/diffutils/m4/c-stack.m4@ 2695

Last change on this file since 2695 was 2556, checked in by bird, 20 years ago

diffutils 2.8.1
File size: 3.6 KB
Line 
1# Check prerequisites for compiling lib/c-stack.c.
2
3# Copyright (C) 2002 Free Software Foundation, Inc.
4
5# This program is free software; you can redistribute it and/or modify
6# it under the terms of the GNU General Public License as published by
7# the Free Software Foundation; either version 2, or (at your option)
8# any later version.
9
10# This program is distributed in the hope that it will be useful,
11# but WITHOUT ANY WARRANTY; without even the implied warranty of
12# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13# GNU General Public License for more details.
14
15# You should have received a copy of the GNU General Public License
16# along with this program; if not, write to the Free Software
17# Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
18# 02111-1307, USA.
19
20AC_DEFUN([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC],
21 [# for STACK_DIRECTION
22 AC_REQUIRE([AC_FUNC_ALLOCA])
23
24 AC_CACHE_CHECK([for working C stack overflow detection],
25 ac_cv_sys_xsi_stack_overflow_heuristic,
26 [AC_TRY_RUN(
27 [
28 #include <signal.h>
29 #include <ucontext.h>
30
31 static union
32 {
33 char buffer[SIGSTKSZ];
34 long double ld;
35 uintmax_t u;
36 void *p;
37 } alternate_signal_stack;
38
39 #if STACK_DIRECTION
40 # define find_stack_direction(ptr) STACK_DIRECTION
41 #else
42 static int
43 find_stack_direction (char const *addr)
44 {
45 char dummy;
46 return (! addr ? find_stack_direction (&dummy)
47 : addr < &dummy ? 1 : -1);
48 }
49 #endif
50
51 static void
52 segv_handler (int signo, siginfo_t *info, void *context)
53 {
54 if (0 < info->si_code)
55 {
56 ucontext_t const *user_context = context;
57 char const *stack_min = user_context->uc_stack.ss_sp;
58 size_t stack_size = user_context->uc_stack.ss_size;
59 char const *faulting_address = info->si_addr;
60 size_t s = faulting_address - stack_min;
61 size_t page_size = sysconf (_SC_PAGESIZE);
62 if (find_stack_direction (0) < 0)
63 s += page_size;
64 if (s < stack_size + page_size)
65 _exit (0);
66 }
67
68 _exit (1);
69 }
70
71 static int
72 c_stack_action (void)
73 {
74 stack_t st;
75 struct sigaction act;
76 int r;
77
78 st.ss_flags = 0;
79 st.ss_sp = alternate_signal_stack.buffer;
80 st.ss_size = sizeof alternate_signal_stack.buffer;
81 r = sigaltstack (&st, 0);
82 if (r != 0)
83 return r;
84
85 sigemptyset (&act.sa_mask);
86 act.sa_flags = SA_NODEFER | SA_ONSTACK | SA_RESETHAND | SA_SIGINFO;
87 act.sa_sigaction = segv_handler;
88 return sigaction (SIGSEGV, &act, 0);
89 }
90
91 static int
92 recurse (char *p)
93 {
94 char array[500];
95 array[0] = 1;
96 return *p + recurse (array);
97 }
98
99 int
100 main (void)
101 {
102 c_stack_action ();
103 return recurse ("\1");
104 }
105 ],
106 [ac_cv_sys_xsi_stack_overflow_heuristic=yes],
107 [ac_cv_sys_xsi_stack_overflow_heuristic=no],
108 [ac_cv_sys_xsi_stack_overflow_heuristic=cross-compiling])])
109
110 if test $ac_cv_sys_xsi_stack_overflow_heuristic = yes; then
111 AC_DEFINE(HAVE_XSI_STACK_OVERFLOW_HEURISTIC, 1,
112 [Define to 1 if extending the stack slightly past the limit causes
113 a SIGSEGV, and an alternate stack can be established with sigaltstack,
114 and the signal handler is passed a context that specifies the
115 run time stack. This behavior is defined by POSIX 1003.1-2001
116 with the X/Open System Interface (XSI) option
117 and is a standardized way to implement a SEGV-based stack
118 overflow detection heuristic.])
119 fi])
120
121
122AC_DEFUN([jm_PREREQ_C_STACK],
123 [AC_REQUIRE([jm_AC_TYPE_UINTMAX_T])
124 AC_REQUIRE([AC_SYS_XSI_STACK_OVERFLOW_HEURISTIC])
125
126 # for STACK_DIRECTION
127 AC_REQUIRE([AC_FUNC_ALLOCA])
128
129 AC_CHECK_HEADERS(unistd.h)
130
131 AC_CHECK_TYPES([siginfo_t, stack_t], , , [#include <signal.h>])])
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