From: Kees Cook <keescook@chromium.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Robert O'Callahan <rocallahan@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>,
linux-arch@vger.kernel.org, Will Deacon <will@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Mark Rutland <mark.rutland@arm.com>,
Keno Fischer <keno@juliacomputing.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kvm list <kvm@vger.kernel.org>,
Gabriel Krisman Bertazi <krisman@collabora.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Kyle Huey <me@kylehuey.com>
Subject: Re: [REGRESSION] x86/entry: Tracer no longer has opportunity to change the syscall number at entry via orig_ax
Date: Fri, 11 Sep 2020 17:10:52 -0700 [thread overview]
Message-ID: <202009111609.61E7875B3@keescook> (raw)
In-Reply-To: <87a6xzrr89.fsf@mpe.ellerman.id.au>
On Wed, Sep 09, 2020 at 11:53:42PM +1000, Michael Ellerman wrote:
> I can observe the difference between v5.8 and mainline, using the
> raw_syscall trace event and running the seccomp_bpf selftest which turns
> a getpid (39) into a getppid (110).
>
> With v5.8 we see getppid on entry and exit:
>
> seccomp_bpf-1307 [000] .... 22974.874393: sys_enter: NR 110 (7ffff22c46e0, 40a350, 4, fffffffffffff7ab, 7fa6ee0d4010, 0)
> seccomp_bpf-1307 [000] .N.. 22974.874401: sys_exit: NR 110 = 1304
>
> Whereas on mainline we see an enter for getpid and an exit for getppid:
>
> seccomp_bpf-1030 [000] .... 21.806766: sys_enter: NR 39 (7ffe2f6d1ad0, 40a350, 7ffe2f6d1ad0, 0, 0, 407299)
> seccomp_bpf-1030 [000] .... 21.806767: sys_exit: NR 110 = 1027
For my own notes, this is how I reproduced it:
# ./perf-$VER record -e raw_syscalls:sys_enter -e raw_syscalls:sys_exit &
# ./seccomp_bpf
# fg
ctrl-c
# ./perf-$VER script | grep seccomp_bpf | awk '{print $7}' | sort | uniq -c > $VER.log
*repeat*
# diff -u old.log new.log
...
(Is there an easier way to get those results?)
I will go see if I can figure out the best way to correct this.
--
Kees Cook
next prev parent reply other threads:[~2020-09-12 0:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-19 17:14 [REGRESSION] x86/entry: Tracer no longer has opportunity to change the syscall number at entry via orig_ax Kyle Huey
2020-08-19 19:44 ` Thomas Gleixner
2020-08-20 17:26 ` Kyle Huey
2020-08-20 21:09 ` Kees Cook
2020-08-21 0:35 ` Thomas Gleixner
[not found] ` <87a6xzrr89.fsf@mpe.ellerman.id.au>
2020-09-11 18:58 ` Kees Cook
2020-09-12 0:10 ` Kees Cook [this message]
2020-09-13 7:44 ` Michael Ellerman
2020-09-13 18:27 ` Thomas Gleixner
2020-09-14 20:04 ` Kees Cook
2020-09-17 0:39 ` Michael Ellerman
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