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Subject[PATCH v7 15/18] selftests/x86/fsgsbase: Test ptracer-induced GSBASE write with FSGSBASE
Date
This validates that GS and GSBASE are independently preserved in
ptracer commands.

Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Andi Kleen <andi@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 daff504..7cd36be 100644
--- a/tools/testing/selftests/x86/fsgsbase.c
+++ b/tools/testing/selftests/x86/fsgsbase.c
@@ -470,7 +470,7 @@ 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);

@@ -486,6 +486,7 @@ 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
@@ -496,8 +497,14 @@ static void test_ptrace_write_gsbase(void)
if (gs != 0x7) {
nerrs++;
printf("[FAIL]\tGS changed to %lx\n", gs);
+ } else if (have_fsgsbase && (base != 0xFF)) {
+ nerrs++;
+ printf("[FAIL]\tGSBASE changed to %lx\n", base);
} else {
- printf("[OK]\tGS remained 0x7\n");
+ printf("[OK]\tGS remained 0x7 %s");
+ if (have_fsgsbase)
+ printf("and GSBASE changed to 0xFF");
+ printf("\n");
}
}

--
2.7.4
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