selftests/x86/fsgsbase: Test PTRACE_PEEKUSER for GSBASE with invalid LDT GS (1b9abd17) · Commits · 戴 / test

tools/testing/selftests/x86/fsgsbase.c

+65 −0

Original line number	Diff line number	Diff line
		@@ -443,6 +443,68 @@ static void test_unexpected_base(void)

		#define USER_REGS_OFFSET(r) offsetof(struct user_regs_struct, r)

		static void test_ptrace_write_gs_read_base(void)
		{
		int status;
		pid_t child = fork();

		if (child < 0)
		err(1, "fork");

		if (child == 0) {
		printf("[RUN]\tPTRACE_POKE GS, read GSBASE back\n");

		printf("[RUN]\tARCH_SET_GS to 1\n");
		if (syscall(SYS_arch_prctl, ARCH_SET_GS, 1) != 0)
		err(1, "ARCH_SET_GS");

		if (ptrace(PTRACE_TRACEME, 0, NULL, NULL) != 0)
		err(1, "PTRACE_TRACEME");

		raise(SIGTRAP);
		_exit(0);
		}

		wait(&status);

		if (WSTOPSIG(status) == SIGTRAP) {
		unsigned long base;
		unsigned long gs_offset = USER_REGS_OFFSET(gs);
		unsigned long base_offset = USER_REGS_OFFSET(gs_base);

		/* Read the initial base. It should be 1. */
		base = ptrace(PTRACE_PEEKUSER, child, base_offset, NULL);
		if (base == 1) {
		printf("[OK]\tGSBASE started at 1\n");
		} else {
		nerrs++;
		printf("[FAIL]\tGSBASE started at 0x%lx\n", base);
		}

		printf("[RUN]\tSet GS = 0x7, read GSBASE\n");

		/* Poke an LDT selector into GS. */
		if (ptrace(PTRACE_POKEUSER, child, gs_offset, 0x7) != 0)
		err(1, "PTRACE_POKEUSER");

		/* And read the base. */
		base = ptrace(PTRACE_PEEKUSER, child, base_offset, NULL);

		if (base == 0 \|\| base == 1) {
		printf("[OK]\tGSBASE reads as 0x%lx with invalid GS\n", base);
		} else {
		nerrs++;
		printf("[FAIL]\tGSBASE=0x%lx (should be 0 or 1)\n", base);
		}
		}

		ptrace(PTRACE_CONT, child, NULL, NULL);

		wait(&status);
		if (!WIFEXITED(status))
		printf("[WARN]\tChild didn't exit cleanly.\n");
		}

		static void test_ptrace_write_gsbase(void)
		{
		int status;
		@@ -529,6 +591,9 @@ int main()
		shared_scratch = mmap(NULL, 4096, PROT_READ \| PROT_WRITE,
		MAP_ANONYMOUS \| MAP_SHARED, -1, 0);

		/* Do these tests before we have an LDT. */
		test_ptrace_write_gs_read_base();

		/* Probe FSGSBASE */
		sethandler(SIGILL, sigill, 0);
		if (sigsetjmp(jmpbuf, 1) == 0) {

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