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This new test checks that all x86 registers are preserved across
32-bit syscalls. It tests syscalls through VDSO (if available)
and through INT 0x80, normally and under ptrace.
If kernel is a 64-bit one, high registers (r8..r15) are poisoned
before the syscall is called and are checked afterwards.
They must be either preserved, or cleared to zero (but r11 is
special); r12..15 must be preserved for INT 0x80.
EFLAGS is checked for changes too, but change there is not
considered to be a bug (paravirt kernels do not preserve
arithmetic flags).
Run-tested on 64-bit kernel:
$ ./test_syscall_vdso_32
[RUN] Executing 6-argument 32-bit syscall via VDSO
[OK] Arguments are preserved across syscall
[NOTE] R11 has changed:0000000000200ed7 - assuming clobbered by
SYSRET insn [OK] R8..R15 did not leak kernel data
[RUN] Executing 6-argument 32-bit syscall via INT 80
[OK] Arguments are preserved across syscall
[OK] R8..R15 did not leak kernel data
[RUN] Running tests under ptrace
[RUN] Executing 6-argument 32-bit syscall via VDSO
[OK] Arguments are preserved across syscall
[OK] R8..R15 did not leak kernel data
[RUN] Executing 6-argument 32-bit syscall via INT 80
[OK] Arguments are preserved across syscall
[OK] R8..R15 did not leak kernel data
On 32-bit paravirt kernel:
$ ./test_syscall_vdso_32
[NOTE] Not a 64-bit kernel, won't test R8..R15 leaks
[RUN] Executing 6-argument 32-bit syscall via VDSO
[WARN] Flags before=0000000000200ed7 id 0 00 o d i s z 0 a 0 p 1 c
[WARN] Flags after=0000000000200246 id 0 00 i z 0 0 p 1
[WARN] Flags change=0000000000000c91 0 00 o d s 0 a 0 0 c
[OK] Arguments are preserved across syscall
[RUN] Executing 6-argument 32-bit syscall via INT 80
[OK] Arguments are preserved across syscall
[RUN] Running tests under ptrace
[RUN] Executing 6-argument 32-bit syscall via VDSO
[OK] Arguments are preserved across syscall
[RUN] Executing 6-argument 32-bit syscall via INT 80
[OK] Arguments are preserved across syscall
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Acked-by: Andy Lutomirski <luto@amacapital.net>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/1442427809-2027-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Thomas Gleixner
Denys Vlasenko