linux-kernel - Re: [PATCH V2 1/3] perf symbols: Ignore mapping symbols on aarch64

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Message-ID: <20150122152715.GZ26493@n2100.arm.linux.org.uk>
Date:	Thu, 22 Jan 2015 15:27:15 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Victor Kamensky <victor.kamensky@...aro.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	David Ahern <dsahern@...il.com>,
	Will Deacon <will.deacon@....com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Avi Kivity <avi@...udius-systems.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Anton Blanchard <anton@...ba.org>,
	Dave Martin <Dave.Martin@....com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V2 1/3] perf symbols: Ignore mapping symbols on aarch64

On Wed, Jan 21, 2015 at 08:52:56PM -0800, Victor Kamensky wrote:
> Aarch64 ELF files use mapping symbols with special names $x, $d
> to identify regions of Aarch64 code (see Aarch64 ELF ABI - "ARM
> IHI 0056B", section "4.5.4 Mapping symbols").
> 
> The patch filters out these symbols at load time, similar to
> "696b97a perf symbols: Ignore mapping symbols on ARM" changes
> done for ARM before V8.

I thought I'd commented that this should probably use the same test that
we already have established elsewhere in the kernel, namely in the
kallsyms and module code:

/*
 * This ignores the intensely annoying "mapping symbols" found
 * in ARM ELF files: $a, $t and $d.
 */
static inline int is_arm_mapping_symbol(const char *str)
{ 
        return str[0] == '$' && strchr("axtd", str[1])
               && (str[2] == '\0' || str[2] == '.');
}

We really shouldn't be writing the same check for the same symbols in
different ways.

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