linux-kernel - Re: [PATCH v3 RESEND] x86/asm/entry/32, selftests: Add test_syscall

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Date:	Mon, 6 Jul 2015 14:46:41 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Shuah Khan <shuahkh@....samsung.com>
Subject: Re: [PATCH v3 RESEND] x86/asm/entry/32, selftests: Add
 test_syscall_vdso test


* Ingo Molnar <mingo@...nel.org> wrote:

> >  tools/testing/selftests/x86/test_syscall_vdso.c | 401 ++++++++++++++++++++++++
> >  tools/testing/selftests/x86/thunks_32.S         |  55 ++++
> >  2 files changed, 456 insertions(+)
> >  create mode 100644 tools/testing/selftests/x86/test_syscall_vdso.c
> >  create mode 100644 tools/testing/selftests/x86/thunks_32.S
> 
> Hm, what I don't see is any Makefile integration. How am I supposed to build this 
> test, and how will automated tests pick this testcase up?

Note that I prettied up its changelog (attached below), please use this for the 
next submission.

Thanks,

	Ingo


=======================>
Subject: x86/asm/entry/32, selftests: Add 'test_syscall_vdso' test
From: Denys Vlasenko <dvlasenk@...hat.com>
Date: Fri, 3 Jul 2015 22:02:52 +0200

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
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