| 1 | |
| 2 | |
| 3 | * Copyright (C) 2025 Intel Corporation
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| 4 |
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| 5 | #define _GNU_SOURCE
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| 6 |
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| 7 | #include <err.h>
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| 8 | #include <signal.h>
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| 9 | #include <stdio.h>
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| 10 | #include <stdlib.h>
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| 11 | #include <string.h>
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| 12 | #include <sys/ucontext.h>
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| 13 |
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| 14 | #ifdef __x86_64__
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| 15 | # define REG_IP REG_RIP
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| 16 | #else
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| 17 | # define REG_IP REG_EIP
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| 18 | #endif
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| 19 |
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| 20 | static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), int flags)
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| 21 | {
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| 22 | struct sigaction sa;
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| 23 |
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| 24 | memset(&sa, 0, sizeof(sa));
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| 25 | sa.sa_sigaction = handler;
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| 26 | sa.sa_flags = SA_SIGINFO | flags;
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| 27 | sigemptyset(&sa.sa_mask);
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| 28 |
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| 29 | if (sigaction(sig, &sa, 0))
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| 30 | err(1, "sigaction");
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| 31 |
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| 32 | return;
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| 33 | }
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| 34 |
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| 35 | static void sigtrap(int sig, siginfo_t *info, void *ctx_void)
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| 36 | {
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| 37 | ucontext_t *ctx = (ucontext_t *)ctx_void;
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| 38 | static unsigned int loop_count_on_same_ip;
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| 39 | static unsigned long last_trap_ip;
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| 40 |
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| 41 | if (last_trap_ip == ctx->uc_mcontext.gregs[REG_IP]) {
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| 42 | printf("\tTrapped at %016lx\n", last_trap_ip);
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| 43 |
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| 44 | |
| 45 | * If the same IP is hit more than 10 times in a row, it is
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| 46 | * _considered_ an infinite loop.
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| 47 |
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| 48 | if (++loop_count_on_same_ip > 10) {
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| 49 | printf("[FAIL]\tDetected SIGTRAP infinite loop\n");
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| 50 | exit(1);
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| 51 | }
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| 52 |
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| 53 | return;
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| 54 | }
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| 55 |
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| 56 | loop_count_on_same_ip = 0;
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| 57 | last_trap_ip = ctx->uc_mcontext.gregs[REG_IP];
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| 58 | printf("\tTrapped at %016lx\n", last_trap_ip);
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| 59 | }
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| 60 |
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| 61 | int main(int argc, char *argv[])
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| 62 | {
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| 63 | sethandler(SIGTRAP, sigtrap, 0);
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| 64 |
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| 65 | |
| 66 | * Set the Trap Flag (TF) to single-step the test code, therefore to
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| 67 | * trigger a SIGTRAP signal after each instruction until the TF is
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| 68 | * cleared.
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| 69 | *
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| 70 | * Because the arithmetic flags are not significant here, the TF is
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| 71 | * set by pushing 0x302 onto the stack and then popping it into the
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| 72 | * flags register.
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| 73 | *
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| 74 | * Four instructions in the following asm code are executed with the
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| 75 | * TF set, thus the SIGTRAP handler is expected to run four times.
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| 76 |
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| 77 | printf("[RUN]\tSIGTRAP infinite loop detection\n");
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| 78 | asm volatile(
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| 79 | #ifdef __x86_64__
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| 80 | |
| 81 | * Avoid clobbering the redzone
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| 82 | *
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| 83 | * Equivalent to "sub $128, %rsp", however -128 can be encoded
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| 84 | * in a single byte immediate while 128 uses 4 bytes.
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| 85 |
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| 86 | "add $-128, %rsp\n\t"
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| 87 | #endif
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| 88 | "push $0x302\n\t"
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| 89 | "popf\n\t"
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| 90 | "nop\n\t"
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| 91 | "nop\n\t"
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| 92 | "push $0x202\n\t"
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| 93 | "popf\n\t"
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| 94 | #ifdef __x86_64__
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| 95 | "sub $-128, %rsp\n\t"
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| 96 | #endif
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| 97 | );
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| 98 |
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| 99 | printf("[OK]\tNo SIGTRAP infinite loop detected\n");
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| 100 | return 0;
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| 101 | }
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