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Peter Anvin" , Dave Hansen , Sasha Levin Subject: [PATCH v13 16/16] selftests/x86/fsgsbase: Test ptracer-induced GS base write with FSGSBASE Date: Thu, 28 May 2020 16:14:02 -0400 Message-Id: <20200528201402.1708239-17-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200528201402.1708239-1-sashal@kernel.org> References: <20200528201402.1708239-1-sashal@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Chang S. Bae" This validates that GS selector and base are independently preserved in ptrace commands. Suggested-by: Andy Lutomirski Signed-off-by: Chang S. Bae Reviewed-by: Tony Luck Cc: Thomas Gleixner Cc: Borislav Petkov Cc: Andy Lutomirski Cc: H. Peter Anvin Cc: Dave Hansen Cc: Tony Luck Cc: Andi Kleen Signed-off-by: Sasha Levin --- 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 950a48b2e366..9a4349813a30 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"); } } -- 2.25.1