Messages in this thread Patch in this message | | | From | Sasha Levin <> | Subject | [PATCH v11 15/18] selftests/x86/fsgsbase: Test ptracer-induced GS base write with FSGSBASE | Date | Sat, 9 May 2020 13:36:52 -0400 |
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From: "Chang S. Bae" <chang.seok.bae@intel.com>
This validates that GS selector and base are independently preserved in ptrace commands.
Suggested-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 | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/x86/fsgsbase.c b/tools/testing/selftests/x86/fsgsbase.c index 950a48b2e3662..9a4349813a30a 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; + unsigned long gs, base; unsigned long gs_offset = USER_REGS_OFFSET(gs); unsigned long base_offset = USER_REGS_OFFSET(gs_base); @@ -481,6 +481,7 @@ 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 @@ -501,8 +502,14 @@ static void test_ptrace_write_gsbase(void) */ if (gs == 0) printf("\tNote: this is expected behavior on older kernels.\n"); + } else if (have_fsgsbase && (base != 0xFF)) { + nerrs++; + printf("[FAIL]\tGSBASE changed to %lx\n", base); } else { - printf("[OK]\tGS remained 0x%hx\n", *shared_scratch); + printf("[OK]\tGS remained 0x%hx", *shared_scratch); + if (have_fsgsbase) + printf(" and GSBASE changed to 0xFF"); + printf("\n"); } } -- 2.20.1
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