linux-kernel - Re: [PATCH v3 42/51] x86/unwind: create stack frames for saved syscall registers

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Message-ID: <CALCETrXuCs0CS6+NR3Vv6tnLM_z8Cht1GEm6FfTpB_9rHLpF5w@mail.gmail.com>
Date:	Sun, 14 Aug 2016 01:23:11 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Josh Poimboeuf <jpoimboe@...hat.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	"H . Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Brian Gerst <brgerst@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Byungchul Park <byungchul.park@....com>,
	Nilay Vaish <nilayvaish@...il.com>
Subject: Re: [PATCH v3 42/51] x86/unwind: create stack frames for saved
 syscall registers

On Fri, Aug 12, 2016 at 7:29 AM, Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> The entry code doesn't encode pt_regs for syscalls.  But they're always
> at the same location, so we can add a manual check for them.

At first I thought these would be useless (they're the *user* state
and aren't directly relevant to the kernel), but then I realized that
they could be extremely valuable: they contain the syscall args.  Do
they display in OOPS dumps?  It might be nice to add orig_ax to the
regs display too so we get the syscall nr as well.

--Andy