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authorAndy Lutomirski <luto@kernel.org>2017-11-04 04:19:49 -0700
committerIngo Molnar <mingo@kernel.org>2017-11-07 11:13:42 +0100
commitd60ad744c9741586010d4bea286f09a063a90fbd (patch)
tree151677d1e329c26a86024662a12c74387ea3bd2d /tools
parent693cb5580fdb026922363aa103add64b3ecd572e (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')
-rw-r--r--tools/testing/selftests/x86/ldt_gdt.c10
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++;