selftests/x86/fsgsbase: Test RD/WRGSBASE (9ad75a09) · Commits · 戴 / test

tools/testing/selftests/x86/fsgsbase.c

+99 −3

Original line number	Diff line number	Diff line
		@@ -26,6 +26,7 @@
		#include <stddef.h>
		#include <sys/ptrace.h>
		#include <sys/wait.h>
		#include <setjmp.h>

		#ifndef __x86_64__
		# error This test is 64-bit only
		@@ -74,6 +75,43 @@ static void sigsegv(int sig, siginfo_t si, void ctx_void)

		}

		static jmp_buf jmpbuf;

		static void sigill(int sig, siginfo_t si, void ctx_void)
		{
		siglongjmp(jmpbuf, 1);
		}

		static bool have_fsgsbase;

		static inline unsigned long rdgsbase(void)
		{
		unsigned long gsbase;

		asm volatile("rdgsbase %0" : "=r" (gsbase) :: "memory");

		return gsbase;
		}

		static inline unsigned long rdfsbase(void)
		{
		unsigned long fsbase;

		asm volatile("rdfsbase %0" : "=r" (fsbase) :: "memory");

		return fsbase;
		}

		static inline void wrgsbase(unsigned long gsbase)
		{
		asm volatile("wrgsbase %0" :: "r" (gsbase) : "memory");
		}

		static inline void wrfsbase(unsigned long fsbase)
		{
		asm volatile("wrfsbase %0" :: "r" (fsbase) : "memory");
		}

		enum which_base { FS, GS };

		static unsigned long read_base(enum which_base which)
		@@ -202,14 +240,16 @@ static void do_remote_base()
		to_set, hard_zero ? " and clear gs" : "", sel);
		}

		void do_unexpected_base(void)
		static __thread int set_thread_area_entry_number = -1;

		static void do_unexpected_base(void)
		{
		/*
		* The goal here is to try to arrange for GS == 0, GSBASE !=
		* 0, and for the the kernel the think that GSBASE == 0.
		*
		* To make the test as reliable as possible, this uses
		* explicit descriptorss. (This is not the only way. This
		* explicit descriptors. (This is not the only way. This
		* could use ARCH_SET_GS with a low, nonzero base, but the
		* relevant side effect of ARCH_SET_GS could change.)
		*/
		@@ -242,7 +282,7 @@ void do_unexpected_base(void)
		MAP_PRIVATE \| MAP_ANONYMOUS \| MAP_32BIT, -1, 0);
		memcpy(low_desc, &desc, sizeof(desc));

		low_desc->entry_number = -1;
		low_desc->entry_number = set_thread_area_entry_number;

		/* 32-bit set_thread_area */
		long ret;
		@@ -257,6 +297,8 @@ void do_unexpected_base(void)
		return;
		}
		printf("\tother thread: using GDT slot %d\n", desc.entry_number);
		set_thread_area_entry_number = desc.entry_number;

		asm volatile ("mov %0, %%gs" : : "rm" ((unsigned short)((desc.entry_number << 3) \| 0x3)));
		}

		@@ -268,6 +310,34 @@ void do_unexpected_base(void)
		asm volatile ("mov %0, %%gs" : : "rm" ((unsigned short)0));
		}

		void test_wrbase(unsigned short index, unsigned long base)
		{
		unsigned short newindex;
		unsigned long newbase;

		printf("[RUN]\tGS = 0x%hx, GSBASE = 0x%lx\n", index, base);

		asm volatile ("mov %0, %%gs" : : "rm" (index));
		wrgsbase(base);

		remote_base = 0;
		ftx = 1;
		syscall(SYS_futex, &ftx, FUTEX_WAKE, 0, NULL, NULL, 0);
		while (ftx != 0)
		syscall(SYS_futex, &ftx, FUTEX_WAIT, 1, NULL, NULL, 0);

		asm volatile ("mov %%gs, %0" : "=rm" (newindex));
		newbase = rdgsbase();

		if (newindex == index && newbase == base) {
		printf("[OK]\tIndex and base were preserved\n");
		} else {
		printf("[FAIL]\tAfter switch, GS = 0x%hx and GSBASE = 0x%lx\n",
		newindex, newbase);
		nerrs++;
		}
		}

		static void threadproc(void ctx)
		{
		while (1) {
		@@ -439,6 +509,17 @@ int main()
		{
		pthread_t thread;

		/* Probe FSGSBASE */
		sethandler(SIGILL, sigill, 0);
		if (sigsetjmp(jmpbuf, 1) == 0) {
		rdfsbase();
		have_fsgsbase = true;
		printf("\tFSGSBASE instructions are enabled\n");
		} else {
		printf("\tFSGSBASE instructions are disabled\n");
		}
		clearhandler(SIGILL);

		sethandler(SIGSEGV, sigsegv, 0);

		check_gs_value(0);
		@@ -485,6 +566,21 @@ int main()

		test_unexpected_base();

		if (have_fsgsbase) {
		unsigned short ss;

		asm volatile ("mov %%ss, %0" : "=rm" (ss));

		test_wrbase(0, 0);
		test_wrbase(0, 1);
		test_wrbase(0, 0x200000000);
		test_wrbase(0, 0xffffffffffffffff);
		test_wrbase(ss, 0);
		test_wrbase(ss, 1);
		test_wrbase(ss, 0x200000000);
		test_wrbase(ss, 0xffffffffffffffff);
		}

		ftx = 3; /* Kill the thread. */
		syscall(SYS_futex, &ftx, FUTEX_WAKE, 0, NULL, NULL, 0);

Admin message