Re: [RFC PATCH V2] s390/perf: fix 'start' address of module's map

[Songshan Gong]

å 7/19/2016 9:50 AM, Songshan Gong åé:
> å 7/19/2016 9:37 AM, Songshan Gong åé:
> > å 7/18/2016 10:07 PM, Jiri Olsa åé:
> > > On Fri, Jul 15, 2016 at 06:15:11PM +0800, Song Shan Gong wrote:
> > > > At preset, when creating module's map, perf gets 'start' address by
> > > > parsing
> > > > '/proc/modules', but it's module base address, isn't the start
> > > > address of
> > > > '.text' section. In most archs, it's OK. But for s390, it places
> > > > 'GOT' and
> > > > 'PLT' relocations before '.text' section. So there exists an offset
> > > > between
> > > > module base address and '.text' section, which will incur wrong symbol
> > > > resolution for modules.
> > > >
> > > > Fix this bug by getting 'start' address of module's map from parsing
> > > > '/sys/module/[module name]/sections/.text', not from '/proc/modules'.
> > > >
> > > > Signed-off-by: Song Shan Gong <gongss@xxxxxxxxxxxxxxxxxx>
> > > > ---
> > > >  tools/perf/arch/s390/util/Build          |  2 ++
> > > >  tools/perf/arch/s390/util/sym-handling.c | 27
> > > > +++++++++++++++++++++++++++
> > > >  tools/perf/util/machine.c                |  8 ++++++++
> > > >  tools/perf/util/machine.h                |  1 +
> > > >  4 files changed, 38 insertions(+)
> > > >  create mode 100644 tools/perf/arch/s390/util/sym-handling.c
> > > >
> > > > diff --git a/tools/perf/arch/s390/util/Build
> > > > b/tools/perf/arch/s390/util/Build
> > > > index 8a61372..5e322ed 100644
> > > > --- a/tools/perf/arch/s390/util/Build
> > > > +++ b/tools/perf/arch/s390/util/Build
> > > > @@ -2,3 +2,5 @@ libperf-y += header.o
> > > >  libperf-y += kvm-stat.o
> > > >
> > > >  libperf-$(CONFIG_DWARF) += dwarf-regs.o
> > > > +
> > > > +libperf-y += sym-handling.o
> > > > diff --git a/tools/perf/arch/s390/util/sym-handling.c
> > > > b/tools/perf/arch/s390/util/sym-handling.c
> > > > new file mode 100644
> > > > index 0000000..ff51336
> > > > --- /dev/null
> > > > +++ b/tools/perf/arch/s390/util/sym-handling.c
> > > > @@ -0,0 +1,27 @@
> > > > +#include <stdio.h>
> > > > +#include <stdlib.h>
> > > > +#include <unistd.h>
> > > > +#include "util.h"
> > > > +#include "machine.h"
> > > > +#include "api/fs/fs.h"
> > > > +
> > > > +int arch__fix_module_text_start(u64 *start, const char *name)
> > > > +{
> > > > +    char path[PATH_MAX];
> > > > +    char *module_name = NULL;
> > > > +    int len;
> > > > +
> > > > +    if (!(module_name = strdup(name)))
> > > > +        return -1;
> > > > +
> > > > +    len = strlen(module_name);
> > > > +    module_name[len - 1] = '\0';
> > > > +    snprintf(path, PATH_MAX, "module/%s/sections/.text",
> > > > +                module_name + 1);
> > >
> > > why can't you use 'name' in here? I can't see the reason
> > > you allocated module_name..
> >
> > Oh, yes.
> Sorry, just ignore the upper reply.
>
> I use the 'module_name' here instead of 'name', because 'name' is
> something like '[module_name]', I need strip the '[' and ']', so I have
> to set the tail ']' to '\0' to indicate the string end, which will need
> change the constant variable 'name'.
eeee, I found a new way to implement it.

I could use '%.*s' to format the 'path', 'name' is enough indeed.

It's so concise now. Appreciate.
> > > > +
> > > > +    if (sysfs__read_ull(path, (unsigned long long *)start) < 0) {
> > > > +        free(module_name);
> > > > +        return -1;
> > > > +    }
> > >
> > > leaking module_name in here
> >
> > yes, thanks.
> > > > +    return 0;
> > > > +}
> > >
> > > SNIP
> > >
> > > thanks,
> > > jirka

--
SongShan Gong