diff options
| author | Andy Lutomirski <luto@kernel.org> | 2017-11-04 04:19:49 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-11-07 11:13:42 +0100 |
| commit | d60ad744c9741586010d4bea286f09a063a90fbd (patch) | |
| tree | 151677d1e329c26a86024662a12c74387ea3bd2d /tools/testing | |
| parent | 693cb5580fdb026922363aa103add64b3ecd572e (diff) | |
selftests/x86/ldt_gdt: Robustify against set_thread_area() and LAR oddities
Bits 19:16 of LAR's result are undefined, and some upcoming
improvements to the test case seem to trigger this. Mask off those
bits to avoid spurious failures.
commit 5b781c7e317f ("x86/tls: Forcibly set the accessed bit in TLS
segments") adds a valid case in which LAR's output doesn't quite
agree with set_thread_area()'s input. This isn't triggered in the
test as is, but it will be if we start calling set_thread_area()
with the accessed bit clear. Work around this discrepency.
I've added a Fixes tag so that -stable can pick this up if neccesary.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 5b781c7e317f ("x86/tls: Forcibly set the accessed bit in TLS segments")
Link: http://lkml.kernel.org/r/b82f3f89c034b53580970ac865139fd8863f44e2.1509794321.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'tools/testing')
| -rw-r--r-- | tools/testing/selftests/x86/ldt_gdt.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/tools/testing/selftests/x86/ldt_gdt.c b/tools/testing/selftests/x86/ldt_gdt.c index 961e3ee26c27..b0334338a4b0 100644 --- a/tools/testing/selftests/x86/ldt_gdt.c +++ b/tools/testing/selftests/x86/ldt_gdt.c @@ -115,7 +115,15 @@ static void check_valid_segment(uint16_t index, int ldt, return; } - if (ar != expected_ar) { + /* The SDM says "bits 19:16 are undefined". Thanks. */ + ar &= ~0xF0000; + + /* + * NB: Different Linux versions do different things with the + * accessed bit in set_thread_area(). + */ + if (ar != expected_ar && + (ldt || ar != (expected_ar | AR_ACCESSED))) { printf("[FAIL]\t%s entry %hu has AR 0x%08X but expected 0x%08X\n", (ldt ? "LDT" : "GDT"), index, ar, expected_ar); nerrs++; |