Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752491AbdILQ7K (ORCPT ); Tue, 12 Sep 2017 12:59:10 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:48816 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751830AbdILQ7F (ORCPT ); Tue, 12 Sep 2017 12:59:05 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Andy Lutomirski , Borislav Petkov , Borislav Petkov , Brian Gerst , Chang Seok , Denys Vlasenko , "H. Peter Anvin" , Josh Poimboeuf , Linus Torvalds , Peter Zijlstra , Thomas Gleixner , Ingo Molnar Subject: [PATCH 4.9 06/14] selftests/x86/fsgsbase: Test selectors 1, 2, and 3 Date: Tue, 12 Sep 2017 09:58:20 -0700 Message-Id: <20170912165254.052683853@linuxfoundation.org> X-Mailer: git-send-email 2.14.1 In-Reply-To: <20170912165253.709627159@linuxfoundation.org> References: <20170912165253.709627159@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3568 Lines: 114 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Andy Lutomirski commit 23d98c204386a98d9ef9f9e744f41443ece4929f upstream. 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: Andy Lutomirski Cc: Borislav Petkov Cc: Borislav Petkov Cc: Brian Gerst Cc: Chang Seok Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- tools/testing/selftests/x86/fsgsbase.c | 41 ++++++++++++++++++++++++++++----- 1 file changed, 35 insertions(+), 6 deletions(-) --- a/tools/testing/selftests/x86/fsgsbase.c +++ b/tools/testing/selftests/x86/fsgsbase.c @@ -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(unsigne 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(unsigne 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); } } @@ -381,8 +403,15 @@ 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], - bases_with_hard_zero[remote]); + 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]); + } } }