selftests/x86/fsgsbase: Test GS selector on ptracer-induced GS base write (291fd835) · Commits · 戴 / test

tools/testing/selftests/x86/fsgsbase.c

+15 −6

Original line number	Diff line number	Diff line
		@@ -465,7 +465,7 @@ static void test_ptrace_write_gsbase(void)
		wait(&status);

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

		@@ -481,7 +481,6 @@ static void test_ptrace_write_gsbase(void)
		err(1, "PTRACE_POKEUSER");

		gs = ptrace(PTRACE_PEEKUSER, child, gs_offset, NULL);
		base = ptrace(PTRACE_PEEKUSER, child, base_offset, NULL);

		/*
		* In a non-FSGSBASE system, the nonzero selector will load
		@@ -489,11 +488,21 @@ static void test_ptrace_write_gsbase(void)
		* selector value is changed or not by the GSBASE write in
		* a ptracer.
		*/
		if (gs == 0 && base == 0xFF) {
		printf("[OK]\tGS was reset as expected\n");
		} else {
		if (gs != *shared_scratch) {
		nerrs++;
		printf("[FAIL]\tGS=0x%lx, GSBASE=0x%lx (should be 0, 0xFF)\n", gs, base);
		printf("[FAIL]\tGS changed to %lx\n", gs);

		/*
		* On older kernels, poking a nonzero value into the
		* base would zero the selector. On newer kernels,
		* this behavior has changed -- poking the base
		* changes only the base and, if FSGSBASE is not
		* available, this may not effect.
		*/
		if (gs == 0)
		printf("\tNote: this is expected behavior on older kernels.\n");
		} else {
		printf("[OK]\tGS remained 0x%hx\n", *shared_scratch);
		}
		}