Attachment 578300 Details for Bug 810668 – Better reproducer

Better reproducer

fp2.c (text/plain), 1.66 KB, created by Chuck Ebbert on 2012-04-18 10:09:49 UTC

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Creator: Chuck Ebbert

Created: 2012-04-18 10:09:49 UTC

Size: 1.66 KB

patch

obsolete

>/* Make sure x86 ptrace(PTRACE_SETFPREGS) is working.
>   Tracer runs on cpu1, tracee on cpu0.
>*/
>#define _GNU_SOURCE
>#include <sched.h>
>#include <unistd.h>
>#include <assert.h>
>#include <sys/wait.h>
>#include <sys/procfs.h>
>#include <sys/ptrace.h>
>
>#define LOOPS 12
>#define setaffinity(c) ({cpu_set_t _s; CPU_ZERO(&_s); CPU_SET((c), &_s); \
>		sched_setaffinity(0, sizeof(cpu_set_t), &_s);})
>
>int main(int argc, char **argv)
>{
>	pid_t child;
>	int i, j, status;
>	elf_fpregset_t fpregs;
>	__float80 two = 2.0;
>
>	child = fork();
>	assert(child != -1);
>
>	if (child == 0) {
>		assert(!setaffinity(0));
>		assert(!ptrace(PTRACE_TRACEME, 0, NULL, NULL));
>		__asm__ __volatile__("fldz; fld1; fldt %0;" : : "m" (two)); /* stack: 0 1 2 <--top */
>
>		for (i = 0; i < LOOPS; i++) {
>			assert(!kill(getpid(), SIGSTOP));
>			__asm__ __volatile__("fadd %st(2), %st;"); /* use FPU; do nothing */
>		}
>
>		__asm__ __volatile__("fstpt %0;" : "=m" (two));
>		assert(two == 42.0); /* make sure child also sees 42 on stack top */
>
>		return 0;
>	}
>
>#define fpstack(n) (*(__float80 *)((char *)(&fpregs.st_space) + (n)*16))
>	assert(!setaffinity(1)); /* needs two CPUs because tracer uses FPU */
>
>	for (j = 0; j < LOOPS+1; j++) {
>		waitpid(child, &status, 0);
>		if (WIFEXITED(status) || WIFSIGNALED(status))
>			break;
>
>		assert(!ptrace(PTRACE_GETFPREGS, child, NULL, &fpregs));
>		assert(fpstack(1) == 1.0 && fpstack(2) == 0.0);
>
>		if (j == LOOPS/2) { /* replace 2 on stack top with 42 */
>			assert(fpstack(0) == two);
>			fpstack(0) = 42.0;
>			assert(!ptrace(PTRACE_SETFPREGS, child, NULL, &fpregs));
>		} else if (j > LOOPS/2)
>			assert(fpstack(0) == 42.0);
>
>		ptrace(PTRACE_CONT, child, NULL, NULL);
>	}
>
>	assert(j == LOOPS);
>	return 0;
>}

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Attachments on bug 810668: 575976 | 577270 | 577491 | 578300