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@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: linux-kselftest@xxxxxxxxxxxxxxx
Signed-off-by: Dmitry Safonov <dsafonov@xxxxxxxxxxxxx>
---
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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