linux-kernel - Re: [PATCH 2/2] perf:tools: figure out start address of kernel map from /proc/kallsyms

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Message-ID: <20101124141129.GA15875@ghostprotocols.net>
Date:	Wed, 24 Nov 2010 12:11:29 -0200
From:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
To:	tom.leiming@...il.com
Cc:	linux-kernel@...r.kernel.org, Ian Munsie <imunsie@....ibm.com>,
	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tom Zanussi <tzanussi@...il.com>
Subject: Re: [PATCH 2/2] perf:tools: figure out start address of kernel map
 from /proc/kallsyms

Em Wed, Nov 24, 2010 at 07:35:33PM +0800, tom.leiming@...il.com escreveu:
> From: Ming Lei <tom.leiming@...il.com>
> 
> On ARM, module symbol start address is ahead of kernel symbol start
> address, so we can't suppose that the start address of kenerl map
> always is zero, otherwise may cause incorrect .start and .end of kernel map
> (caused by fixup) when there are modules loaded, then map_groups__find
> may return incorrect map for symbol query.
> 
> This patch always figures out the start address of kernel map from
> /proc/kallsyms if the file is available, so fix the issues on ARM for
> module loaded case.
> 
> This patch fixes the following issues on ARM when modules are loaded:
> 
> 	- vmlinux symbol can't be found by kallsyms maps doing 'perf test'
> 	- module symbols are parsed mistakenlly when doing 'perf top'/'perf report'
> 
> Cc: Ian Munsie <imunsie@....ibm.com>
> Cc: Ingo Molnar <mingo@...e.hu>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Tom Zanussi <tzanussi@...il.com>
> Signed-off-by: Ming Lei <tom.leiming@...il.com>
> ---
>  tools/perf/util/symbol.c |   60 +++++++++++++++++++++++++++++++++++++++++++++-
>  1 files changed, 59 insertions(+), 1 deletions(-)
> 
> diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
> index c5b4ccb..1a8895c 100644
> --- a/tools/perf/util/symbol.c
> +++ b/tools/perf/util/symbol.c
> @@ -2183,14 +2183,72 @@ static struct dso *machine__create_kernel(struct machine *self)
>  	return kernel;
>  }
>  
> +/*figure out the start address of kernel map from /proc/kallsyms*/
> +static u64 __machine_get_kernel_start_addr(struct machine *self)
> +{
> +	char *line = NULL;
> +	size_t n;
> +	u64 start_addr = 0;
> +	FILE *file;
> +	const char *filename;
> +	char path[PATH_MAX];
> +
> +	if (machine__is_default_guest(self)) {
> +		filename = symbol_conf.default_guest_kallsyms;
> +		if (!filename)
> +			goto out_failure;
> +	} else {
> +		sprintf(path, "%s/proc/kallsyms", self->root_dir);
> +		filename = path;
> +	}
> +
> +	file = fopen(filename, "r");

Can you please use kallsyms__parse()? Please take a look at
event__synthesize_kernel_mmap as it also uses it.

> +	if (file == NULL)
> +		goto out_failure;
> +
> +	while (!feof(file)) {
> +		u64 start = 0;
> +		int line_len, len;
> +
> +		line_len = getline(&line, &n, file);
> +		if (line_len < 0 || !line)
> +			break;
> +
> +		line[--line_len] = '\0'; /* \n */
> +
> +		/*if the line is for module symbol, skip it*/
> +		if (strchr(line, '['))
> +			continue;
> +
> +		len = hex2u64(line, &start);
> +
> +		len++;
> +		if (len + 2 >= line_len)
> +			continue;
> +
> +		start_addr = start;
> +		break;
> +	}
> +
> +	free(line);
> +	fclose(file);

Out failure could be here, avoiding one return case.

> +	return start_addr;
> +
> +out_failure:
> +	return start_addr;
> +}
> +
>  int __machine__create_kernel_maps(struct machine *self, struct dso *kernel)
>  {
>  	enum map_type type;
> +	u64 start;
>  
> +	start = __machine_get_kernel_start_addr(self);
>  	for (type = 0; type < MAP__NR_TYPES; ++type) {
>  		struct kmap *kmap;
>  
> -		self->vmlinux_maps[type] = map__new2(0, kernel, type);
> +		self->vmlinux_maps[type] = map__new2(start, kernel, type);
>  		if (self->vmlinux_maps[type] == NULL)
>  			return -1;
>  
> -- 
> 1.7.3
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