Re: [PATCH 7/9] perf tools: add support for reading from /proc/kcore

[Adrian Hunter]

On 30/07/2013 7:37 a.m., Namhyung Kim wrote:
> Hi,
>
> On Thu, 25 Jul 2013 17:01:28 +0300, Adrian Hunter wrote:
> > In the absence of vmlinux, perf tools uses kallsyms
> > for symbols.  If the user has access, now also map to
> > /proc/kcore.
> >
> > The dso data_type is now set to either
> > DSO_BINARY_TYPE__KCORE or DSO_BINARY_TYPE__GUEST_KCORE
> > as approprite.
>
> [SNIP]
> > +
> > +static bool is_host_buildid_str(const char *str)
> > +{
> > +	u8 host_build_id[BUILD_ID_SIZE];
> > +	char host_build_id_str[BUILD_ID_SIZE * 2 + 1];
> > +
> > +	if (sysfs__read_build_id("/sys/kernel/notes", host_build_id,
> > +				 sizeof(host_build_id)))
> > +		return false;
> > +
> > +	build_id__sprintf(host_build_id, sizeof(host_build_id),
> > +			  host_build_id_str);
> > +
> > +	return !strcmp(str, host_build_id_str);
> > +}
> > +
> > +/*
> > + * If kallsyms is referenced by name then we look for kcore in the same
> > + * directory.  Otherwise we use /proc/kcore but only if the buildid matches the
> > + * host.
> > + */
> > +static bool kcore_filename_from_kallsyms_filename(char *kcore_filename,
> > +						  const char *kallsyms_filename)
> > +{
> > +	char *name;
> > +
> > +	strcpy(kcore_filename, kallsyms_filename);
> > +	name = strrchr(kcore_filename, '/');
> > +	if (!name)
> > +		return false;
> > +
> > +	if (!strcmp(name, "/kallsyms")) {
> > +		strcpy(name, "/kcore");
> > +		return true;
> > +	}
> > +
> > +	if (is_host_buildid_str(name)) {
>
> IIUC the name should start with '/' but build-id is not.  So doesn't it
> always fail?

In fact I realized the whole thing is not necessary. Fixed in V2.

> Thanks,
> Namhyung
>
>
> > +		strcpy(kcore_filename, "/proc/kcore");
> > +		return true;
> > +	}
> > +
> > +	return false;
> > +}

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