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Commit 23d98c20 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
Browse files

selftests/x86/fsgsbase: Test selectors 1, 2, and 3 



Those are funny cases.  Make sure they work.

(Something is screwy with signal handling if a selector is 1, 2, or 3.
Anyone who wants to dive into that rabbit hole is welcome to do so.)

Signed-off-by: default avatarAndy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Chang Seok <chang.seok.bae@intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 9584d98b

tools/testing/selftests/x86/fsgsbase.c

+35 −6
Original line number Diff line number Diff line
@@ -285,9 +285,12 @@ static void *threadproc(void *ctx) 
	}

}



static void set_gs_and_switch_to(unsigned long local, unsigned long remote)

static void set_gs_and_switch_to(unsigned long local,

				 unsigned short force_sel,

				 unsigned long remote)

{

	unsigned long base;

	unsigned short sel_pre_sched, sel_post_sched;



	bool hard_zero = false;

	if (local == HARD_ZERO) {
@@ -297,6 +300,8 @@ static void set_gs_and_switch_to(unsigned long local, unsigned long remote) 


	printf("[RUN]\tARCH_SET_GS(0x%lx)%s, then schedule to 0x%lx\n",

	       local, hard_zero ? " and clear gs" : "", remote);

	if (force_sel)

		printf("\tBefore schedule, set selector to 0x%hx\n", force_sel);

	if (syscall(SYS_arch_prctl, ARCH_SET_GS, local) != 0)

		err(1, "ARCH_SET_GS");

	if (hard_zero)
@@ -307,18 +312,35 @@ static void set_gs_and_switch_to(unsigned long local, unsigned long remote) 
		printf("[FAIL]\tGSBASE wasn't set as expected\n");

	}



	if (force_sel) {

		asm volatile ("mov %0, %%gs" : : "rm" (force_sel));

		sel_pre_sched = force_sel;

		local = read_base(GS);



		/*

		 * Signal delivery seems to mess up weird selectors.  Put it

		 * back.

		 */

		asm volatile ("mov %0, %%gs" : : "rm" (force_sel));

	} else {

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

	}



	remote_base = remote;

	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" (sel_post_sched));

	base = read_base(GS);

	if (base == local) {

		printf("[OK]\tGSBASE remained 0x%lx\n", local);

	if (base == local && sel_pre_sched == sel_post_sched) {

		printf("[OK]\tGS/BASE remained 0x%hx/0x%lx\n",

		       sel_pre_sched, local);

	} else {

		nerrs++;

		printf("[FAIL]\tGSBASE changed to 0x%lx\n", base);

		printf("[FAIL]\tGS/BASE changed from 0x%hx/0x%lx to 0x%hx/0x%lx\n",

		       sel_pre_sched, local, sel_post_sched, base);

	}

}
@@ -381,10 +403,17 @@ int main() 


	for (int local = 0; local < 4; local++) {

		for (int remote = 0; remote < 4; remote++) {

			set_gs_and_switch_to(bases_with_hard_zero[local],

			for (unsigned short s = 0; s < 5; s++) {

				unsigned short sel = s;

				if (s == 4)

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

				set_gs_and_switch_to(

					bases_with_hard_zero[local],

					sel,

					bases_with_hard_zero[remote]);

			}

		}

	}



	test_unexpected_base();