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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2025 Intel Corporation
*/
#define _GNU_SOURCE
#include <err.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ucontext.h>
#ifdef __x86_64__
# define REG_IP REG_RIP
#else
# define REG_IP REG_EIP
#endif
static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), int flags)
{
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_sigaction = handler;
sa.sa_flags = SA_SIGINFO | flags;
sigemptyset(&sa.sa_mask);
if (sigaction(sig, &sa, 0))
err(1, "sigaction");
return;
}
static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
{
ucontext_t *ctx = (ucontext_t *)ctx_void;
static unsigned int loop_count_on_same_ip;
static unsigned long last_trap_ip;
if (last_trap_ip == ctx->uc_mcontext.gregs[REG_IP]) {
printf("\tTrapped at %016lx\n", last_trap_ip);
/*
* If the same IP is hit more than 10 times in a row, it is
* _considered_ an infinite loop.
*/
if (++loop_count_on_same_ip > 10) {
printf("[FAIL]\tDetected SIGTRAP infinite loop\n");
exit(1);
}
return;
}
loop_count_on_same_ip = 0;
last_trap_ip = ctx->uc_mcontext.gregs[REG_IP];
printf("\tTrapped at %016lx\n", last_trap_ip);
}
int main(int argc, char *argv[])
{
sethandler(SIGTRAP, sigtrap, 0);
/*
* Set the Trap Flag (TF) to single-step the test code, therefore to
* trigger a SIGTRAP signal after each instruction until the TF is
* cleared.
*
* Because the arithmetic flags are not significant here, the TF is
* set by pushing 0x302 onto the stack and then popping it into the
* flags register.
*
* Four instructions in the following asm code are executed with the
* TF set, thus the SIGTRAP handler is expected to run four times.
*/
printf("[RUN]\tSIGTRAP infinite loop detection\n");
asm volatile(
#ifdef __x86_64__
/*
* Avoid clobbering the redzone
*
* Equivalent to "sub $128, %rsp", however -128 can be encoded
* in a single byte immediate while 128 uses 4 bytes.
*/
"add $-128, %rsp\n\t"
#endif
"push $0x302\n\t"
"popf\n\t"
"nop\n\t"
"nop\n\t"
"push $0x202\n\t"
"popf\n\t"
#ifdef __x86_64__
"sub $-128, %rsp\n\t"
#endif
);
printf("[OK]\tNo SIGTRAP infinite loop detected\n");
return 0;
}
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