mirror of
https://github.com/ioacademy-jikim/debugging
synced 2025-06-08 08:26:14 +00:00
91 lines
2.3 KiB
C
91 lines
2.3 KiB
C
/* Test if definedness of rflags values is correctly propagated in and out
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of a signal handler. Note that actually only the propagation of the
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overflow and sign flags is tested.
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This test must use alarm(2) to trigger the signal and not kill(2) as other
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tests do because in the latter case the signal is actually delivered after
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the syscall finished. This means that Valgrind had to save a correct carry
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flag value (indicating if the syscall succeeded) in the rflags. This save
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operation unfortunately makes all rflags initialised (due to imprecise
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simulation). */
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#include <assert.h>
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#include <signal.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <sys/syscall.h>
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#include <sys/ucontext.h>
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#define OBIT(rflags) (!!((rflags) & (1 << 11)))
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#define SBIT(rflags) (!!((rflags) & (1 << 7)))
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static siginfo_t si;
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static ucontext_t uc;
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void break_out(void);
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static void sighandler(int sig, siginfo_t *sip, ucontext_t *ucp)
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{
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si = *sip;
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uc = *ucp;
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/* Break out of the endless loop. */
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*(uintptr_t*)&ucp->uc_mcontext.gregs[REG_RIP] = (uintptr_t)break_out;
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}
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int main(void)
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{
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struct sigaction sa;
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long rflags;
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int x1;
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/* Uninitialised, but we know px[0] is 0x0. */
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int *px = malloc(sizeof(*px));
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x1 = px[0] + 1;
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sa.sa_handler = sighandler;
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sa.sa_flags = SA_SIGINFO;
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if (sigfillset(&sa.sa_mask)) {
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perror("sigfillset");
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return 1;
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}
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if (sigaction(SIGALRM, &sa, NULL)) {
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perror("sigaction");
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return 1;
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}
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alarm(2);
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__asm__ __volatile__(
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/* Set overflow and sign flags. */
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"movl %[x1], %%edx\n"
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"addl $0x7fffffff, %%edx\n"
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/* Loopity loop, this is where the SIGALRM is triggered. */
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"1:\n"
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"jmp 1b\n"
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"break_out:\n"
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"pushfq\n"
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"popq %%rdx\n"
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: "=d" (rflags)
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: [x1] "m" (x1)
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: "cc", "memory");
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/* Check that the overflow and sign flags are uninitialised.
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Note: This actually fails because the rflags are only approximate
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(always initialised) in the signal handler. */
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if (!OBIT(uc.uc_mcontext.gregs[REG_RFL]) ||
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!SBIT(uc.uc_mcontext.gregs[REG_RFL]))
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assert(0);
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/* Check that the overflow and sign flags are uninitialised. */
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if (!OBIT(rflags) || !SBIT(rflags))
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assert(0);
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return 0;
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}
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