From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, tglx@linutronix.de, bp@alien8.de,
luto@kernel.org
Cc: hpa@zytor.com, dave.hansen@intel.com, tony.luck@intel.com,
ak@linux.intel.com, ravi.v.shankar@intel.com,
chang.seok.bae@intel.com, Sasha Levin <sashal@kernel.org>
Subject: [PATCH v12 02/18] selftests/x86/fsgsbase: Test GS selector on ptracer-induced GS base write
Date: Mon, 11 May 2020 00:52:55 -0400 [thread overview]
Message-ID: <20200511045311.4785-3-sashal@kernel.org> (raw)
In-Reply-To: <20200511045311.4785-1-sashal@kernel.org>
From: "Chang S. Bae" <chang.seok.bae@intel.com>
The test validates that the selector is not changed when a ptracer writes
the ptracee's GS base.
Originally-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
---
tools/testing/selftests/x86/fsgsbase.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/tools/testing/selftests/x86/fsgsbase.c b/tools/testing/selftests/x86/fsgsbase.c
index 15a329da59fa3..950a48b2e3662 100644
--- a/tools/testing/selftests/x86/fsgsbase.c
+++ b/tools/testing/selftests/x86/fsgsbase.c
@@ -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);
}
}
--
2.20.1
next prev parent reply other threads:[~2020-05-11 4:53 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-11 4:52 [PATCH v12 00/18] Enable FSGSBASE instructions Sasha Levin
2020-05-11 4:52 ` [PATCH v12 01/18] x86/ptrace: Prevent ptrace from clearing the FS/GS selector Sasha Levin
2020-05-11 4:52 ` Sasha Levin [this message]
2020-05-11 4:52 ` [PATCH v12 03/18] x86/cpu: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Sasha Levin
2020-05-11 4:52 ` [PATCH v12 04/18] x86/entry/64: Clean up paranoid exit Sasha Levin
2020-05-11 4:52 ` [PATCH v12 05/18] x86/entry/64: Switch CR3 before SWAPGS in paranoid entry Sasha Levin
2020-05-11 4:52 ` [PATCH v12 06/18] x86/entry/64: Introduce the FIND_PERCPU_BASE macro Sasha Levin
2020-05-11 4:53 ` [PATCH v12 07/18] x86/entry/64: Handle FSGSBASE enabled paranoid entry/exit Sasha Levin
2020-05-11 4:53 ` [PATCH v12 08/18] x86/entry/64: Document GSBASE handling in the paranoid path Sasha Levin
2020-05-11 4:53 ` [PATCH v12 09/18] x86/fsgsbase/64: Add intrinsics for FSGSBASE instructions Sasha Levin
2020-05-11 4:53 ` [PATCH v12 10/18] x86/fsgsbase/64: Enable FSGSBASE instructions in helper functions Sasha Levin
2020-05-18 18:20 ` Thomas Gleixner
2020-05-18 20:24 ` Sasha Levin
2020-05-18 22:59 ` Thomas Gleixner
2020-05-19 12:20 ` David Laight
2020-05-19 14:48 ` Thomas Gleixner
2020-05-20 9:13 ` David Laight
2020-05-11 4:53 ` [PATCH v12 11/18] x86/fsgsbase/64: Use FSGSBASE in switch_to() if available Sasha Levin
2020-05-11 4:53 ` [PATCH v12 12/18] x86/fsgsbase/64: move save_fsgs to header file Sasha Levin
2020-05-11 4:53 ` [PATCH v12 13/18] x86/fsgsbase/64: Use FSGSBASE instructions on thread copy and ptrace Sasha Levin
2020-05-11 4:53 ` [PATCH v12 14/18] x86/speculation/swapgs: Check FSGSBASE in enabling SWAPGS mitigation Sasha Levin
2020-05-11 4:53 ` [PATCH v12 15/18] selftests/x86/fsgsbase: Test ptracer-induced GS base write with FSGSBASE Sasha Levin
2020-05-11 4:53 ` [PATCH v12 16/18] x86/fsgsbase/64: Enable FSGSBASE on 64bit by default and add a chicken bit Sasha Levin
2020-05-11 4:53 ` [PATCH v12 17/18] x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 Sasha Levin
2020-05-11 4:53 ` [PATCH v12 18/18] Documentation/x86/64: Add documentation for GS/FS addressing mode Sasha Levin
2020-05-15 9:24 ` [PATCH v12 00/18] Enable FSGSBASE instructions Jarkko Sakkinen
2020-05-15 16:40 ` Sasha Levin
2020-05-15 17:55 ` Andi Kleen
2020-05-15 23:07 ` Sasha Levin
2020-05-16 12:21 ` Jarkko Sakkinen
2020-05-16 9:50 ` Jarkko Sakkinen
2020-05-18 15:34 ` Andi Kleen
2020-05-18 20:01 ` Jarkko Sakkinen
2020-05-18 23:03 ` Thomas Gleixner
2020-05-19 16:48 ` Jarkko Sakkinen
2020-05-22 20:14 ` Don Porter
2020-05-22 20:55 ` Dave Hansen
2020-05-23 0:45 ` Thomas Gleixner
2020-05-24 19:45 ` hpa
2020-05-24 21:19 ` Sasha Levin
2020-05-24 23:44 ` hpa
2020-05-25 7:54 ` Richard Weinberger
2020-05-25 21:56 ` Tony Luck
2020-05-26 8:12 ` David Laight
2020-05-26 8:23 ` Richard Weinberger
2020-05-27 8:31 ` Jarkko Sakkinen
2020-05-26 12:42 ` Don Porter
2020-05-26 20:27 ` Sasha Levin
2020-05-26 22:03 ` Don Porter
2020-05-26 22:51 ` Sasha Levin
2020-05-28 17:37 ` Don Porter
2020-05-28 10:29 ` Thomas Gleixner
2020-05-28 17:40 ` Don Porter
2020-05-28 18:38 ` Andy Lutomirski
2020-05-29 15:27 ` Wojtek Porczyk
2020-06-25 15:27 ` Don Porter
2020-06-25 21:37 ` Jarkko Sakkinen
2020-07-18 18:19 ` Don Porter
2020-07-23 3:23 ` Jarkko Sakkinen
2020-05-28 19:19 ` Jarkko Sakkinen
2020-05-28 19:41 ` Sasha Levin
2020-05-29 3:07 ` Jarkko Sakkinen
2020-05-29 3:10 ` Jarkko Sakkinen
2020-06-25 15:30 ` Don Porter
2020-06-25 21:40 ` Jarkko Sakkinen
2020-05-23 4:19 ` Andi Kleen
2020-05-28 10:36 ` Thomas Gleixner
2020-05-27 8:20 ` Jarkko Sakkinen
2020-05-27 12:42 ` Wojtek Porczyk
2020-05-18 9:51 ` Thomas Gleixner
2020-05-18 15:16 ` Sasha Levin
2020-05-18 18:28 ` Thomas Gleixner
2020-05-18 19:36 ` Jarkko Sakkinen
2020-05-18 6:18 ` Christoph Hellwig
2020-05-18 12:33 ` Sasha Levin
2020-05-18 14:53 ` Thomas Gleixner
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