Messages in this thread Patch in this message | | | From | Andy Lutomirski <> | Subject | [PATCH 2/3] selftests/x86/fsgsbase: Add a missing memory constraint | Date | Wed, 24 Jun 2020 15:50:49 -0700 |
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The manual call to set_thread_area() via int $0x80 was missing any indication that the descriptor was a pointer, causing gcc to occasionally generate wrong code. Add the missing constraint.
Signed-off-by: Andy Lutomirski <luto@kernel.org> --- tools/testing/selftests/x86/fsgsbase.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/tools/testing/selftests/x86/fsgsbase.c b/tools/testing/selftests/x86/fsgsbase.c index f47495d2f070..998319553523 100644 --- a/tools/testing/selftests/x86/fsgsbase.c +++ b/tools/testing/selftests/x86/fsgsbase.c @@ -285,7 +285,8 @@ static unsigned short load_gs(void) /* 32-bit set_thread_area */ long ret; asm volatile ("int $0x80" - : "=a" (ret) : "a" (243), "b" (low_desc) + : "=a" (ret), "+m" (*low_desc) + : "a" (243), "b" (low_desc) : "r8", "r9", "r10", "r11"); memcpy(&desc, low_desc, sizeof(desc)); munmap(low_desc, sizeof(desc)); -- 2.25.4
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