The following commit has been merged into the x86/fsgsbase branch of tip: Commit-ID: 5e7ec8578fa3dada50c50f5b234fa8d154b76349 Gitweb: https://git.kernel.org/tip/5e7ec8578fa3dada50c50f5b234fa8d154b76349 Author: Chang S. Bae <[email protected]> AuthorDate: Thu, 28 May 2020 16:14:02 -04:00 Committer: Thomas Gleixner <[email protected]> CommitterDate: Thu, 18 Jun 2020 15:47:07 +02:00
selftests/x86/fsgsbase: Test ptracer-induced GS base write with FSGSBASE This validates that GS selector and base are independently preserved in ptrace commands. Suggested-by: Andy Lutomirski <[email protected]> Signed-off-by: Chang S. Bae <[email protected]> Signed-off-by: Sasha Levin <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Reviewed-by: Tony Luck <[email protected]> Link: https://lkml.kernel.org/r/[email protected] --- 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 950a48b..9a43498 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"); } }
