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SubjectRe: [PATCH] x86/selftests: add clobbers for int80 on x86_64
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On 02/10/2017 02:52 PM, Dmitry Safonov wrote:
> Kernel erases R8..R11 registers prior returning to userspace
> from int80: https://lkml.org/lkml/2009/10/1/164
>
> GCC can reuse this registers and doesn't expect them to change
> during syscall invocation. I met this kind of bug in CRIU once
> gcc 6.1 and clang stored local variables in those registers
> and the kernel zerofied them during syscall:
> https://github.com/xemul/criu/commit/990d33f1a1cdd17bca6c2eb059ab3be2564f7fa2
>
> By that reason I suggest to add those registers to clobbers
> in selftests.
>
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: x86@kernel.org
> Cc: linux-kselftest@vger.kernel.org
> Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
> ---
> tools/testing/selftests/x86/fsgsbase.c | 2 +-
> tools/testing/selftests/x86/iopl.c | 10 ++++++++--

Drop this one: iopl doesn't do int80 - it's my failure in grepping.
Will resend.

> tools/testing/selftests/x86/ldt_gdt.c | 16 +++++++++++-----
> tools/testing/selftests/x86/ptrace_syscall.c | 3 ++-
> tools/testing/selftests/x86/single_step_syscall.c | 5 ++++-
> 5 files changed, 26 insertions(+), 10 deletions(-)
>

--
Dmitry

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