| From foo@baz Wed Dec 6 18:04:41 CET 2017 |
| From: Andy Lutomirski <luto@kernel.org> |
| Date: Sat, 4 Nov 2017 04:19:49 -0700 |
| Subject: selftests/x86/ldt_gdt: Robustify against set_thread_area() and LAR oddities |
| |
| From: Andy Lutomirski <luto@kernel.org> |
| |
| |
| [ Upstream commit d60ad744c9741586010d4bea286f09a063a90fbd ] |
| |
| 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> |
| Signed-off-by: Sasha Levin <alexander.levin@verizon.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| tools/testing/selftests/x86/ldt_gdt.c | 10 +++++++++- |
| 1 file changed, 9 insertions(+), 1 deletion(-) |
| |
| --- 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 |
| 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++; |
