Re: [PATCH 14/14] perf annotate-data: Add stack canary type

From: Namhyung Kim <namhyung@kernel.org>
To: Ian Rogers <irogers@google.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>,
	Jiri Olsa <jolsa@kernel.org>,
	 Adrian Hunter <adrian.hunter@intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	 Ingo Molnar <mingo@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	 linux-perf-users@vger.kernel.org,
	 Linus Torvalds <torvalds@linux-foundation.org>,
	Stephane Eranian <eranian@google.com>,
	 Masami Hiramatsu <mhiramat@kernel.org>,
	linux-toolchains@vger.kernel.org,
	 linux-trace-devel@vger.kernel.org
Subject: Re: [PATCH 14/14] perf annotate-data: Add stack canary type
Date: Tue, 6 Feb 2024 15:18:47 -0800	[thread overview]
Message-ID: <CAM9d7cgF_PYm2fG1Vgu25u1hVZUK0wmFBqY7DHW2eVpRV=iERA@mail.gmail.com> (raw)
In-Reply-To: <CAP-5=fUWaKW7d6_YkET0o26=fjBwX6PPJ1gXQ9wndQM_Oi2O3A@mail.gmail.com>

On Fri, Feb 2, 2024 at 7:21 PM Ian Rogers <irogers@google.com> wrote:
>
> On Fri, Feb 2, 2024 at 2:05 PM Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > When the stack protector is enabled, compiler would generate code to
> > check stack overflow with a special value called 'stack carary' at
> > runtime.  On x86_64, GCC hard-codes the stack canary as %gs:40.
> >
> > While there's a definition of fixed_percpu_data in asm/processor.h,
> > it seems that the header is not included everywhere and many places
> > it cannot find the type info.  As it's in the well-known location (at
> > %gs:40), let's add a pseudo stack canary type to handle it specially.
>
> I wonder if cases like this can be handled by debug info rather than
> special cases in the tool. Special cases are fine too, but are
> potentially less portable.

Agreed, but I couldn't find anything special in DWARF.

Thanks,
Namhyung