mirror of
https://github.com/Zenithsiz/ftmemsim-valgrind.git
synced 2026-02-04 02:18:37 +00:00
e7674cfdbb
The function is used in VG_(client_syscall) to avoid extending the stack when it is clear that the current value of the stack pointer does not point into a segment that looks like a stack segment. See the comments in the code there. As a side effect of this we can now revert r15018 which increased the stack size of the alternate stack in memcheck/tests/sigaltstack.c. The reason is that the belief at the time: "alternate stack is too small" was not correct. What instead happened was that VG_(client_syscall) called VG_(extend_stack) without need (the syscall was tgkill) and the new stack pointer happened to be in a file segment. In other words: the current stack pointer was still within the alternate stack, i.e. the alternate stack was (barely) large enough. git-svn-id: svn://svn.valgrind.org/valgrind/trunk@15034
46 lines
1.3 KiB
C
46 lines
1.3 KiB
C
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#include <stdio.h>
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#include <stdlib.h>
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#include <signal.h>
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#include "tests/sys_mman.h"
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void sig_handler(int sig){
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int var;
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fprintf(stderr, "caught signal, local var is on %p\n", &var);
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}
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int main(int argv, char** argc) {
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int res, i;
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stack_t sigstk;
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struct sigaction act;
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static const int size = SIGSTKSZ*2;
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// We give EXEC permissions because this won't work on ppc32 unless you
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// ask for an alt stack with EXEC permissions,
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// since signal returning requires execution of code on the stack.
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char *stk = (char *)mmap(0, size, PROT_READ|PROT_WRITE|PROT_EXEC,
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MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
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sigstk.ss_sp = stk;
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sigstk.ss_size = size;
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sigstk.ss_flags = 0;
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fprintf(stderr, "calling sigaltstack, stack base is %p\n", sigstk.ss_sp);
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if (sigaltstack(&sigstk,0)<0) perror("sigaltstack");
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fprintf(stderr,"setting sigaction\n");
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act.sa_flags=SA_ONSTACK;
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act.sa_handler=&sig_handler;
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sigemptyset(&act.sa_mask);
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res = sigaction(SIGUSR1,&act,0);
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fprintf(stderr, "res = %d\n", res);
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fprintf(stderr, "raising the signal\n");
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raise(SIGUSR1);
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/* Loop long enough so valgrind has a forced context switch and
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actually delivers the signal before the thread exits. */
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for (i = 0; i < 1000000; i++) ;
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fprintf(stderr, "done\n");
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return 0;
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}
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