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

Started byArnaldo Carvalho de Melo <acme@kernel.org>
First post2016-07-26 22:00 +0200
Last post2016-07-27 12:10 +0200
Articles 10 — 4 participants

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  Re: [PATCH] s390/perf: fix 'start' address of module's map Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-07-26 22:00 +0200
    Re: [PATCH] s390/perf: fix 'start' address of module's map Christian Borntraeger <borntraeger@de.ibm.com> - 2016-07-26 22:20 +0200
      Re: [PATCH] s390/perf: fix 'start' address of module's map Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-07-26 22:30 +0200
        Re: [PATCH] s390/perf: fix 'start' address of module's map Michael Ellerman <mpe@ellerman.id.au> - 2016-07-27 11:30 +0200
          Re: [PATCH] s390/perf: fix 'start' address of module's map Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-07-27 15:10 +0200
        Re: [PATCH] s390/perf: fix 'start' address of module's map Songshan Gong <gongss@linux.vnet.ibm.com> - 2016-07-27 12:20 +0200
        Re: [PATCH] s390/perf: fix 'start' address of module's map Songshan Gong <gongss@linux.vnet.ibm.com> - 2016-07-27 12:50 +0200
          Re: [PATCH] s390/perf: fix 'start' address of module's map Arnaldo Carvalho de Melo <acme@kernel.org> - 2016-07-27 15:10 +0200
            Re: [PATCH] s390/perf: fix 'start' address of module's map Songshan Gong <gongss@linux.vnet.ibm.com> - 2016-07-28 04:10 +0200
    Re: [PATCH] s390/perf: fix 'start' address of module's map Songshan Gong <gongss@linux.vnet.ibm.com> - 2016-07-27 12:10 +0200

#1450830 — Re: [PATCH] s390/perf: fix 'start' address of module's map

FromArnaldo Carvalho de Melo <acme@kernel.org>
Date2016-07-26 22:00 +0200
SubjectRe: [PATCH] s390/perf: fix 'start' address of module's map
Message-ID<rZgGe-6gj-15@gated-at.bofh.it>
Em Thu, Jul 21, 2016 at 11:10:51AM +0800, Song Shan Gong escreveu:
> 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.

I'll apply this as it fixes the problem for you and we need to get fixes
in ASAP to get this into 4.8, but why can't we just use your method for
all arches and get rid of this arch__ hook? I.e. if I look here in my
x86_64 notebook I see:

[acme@jouet linux]$ cat /sys/module/tun/sections/.text 
0xffffffffc0af2000
[acme@jouet linux]$ grep tun /proc/modules 
tun 28672 4 vhost_net, Live 0xffffffffc0af2000
[acme@jouet linux]$ 

So I could as well use what is in /sys/module/tun/sections/.text instead
of reading it from /proc/modules and, in s390, reading it from
/sys/module/tun/sections/.text.

Do you see any problem with using this approach for _all_ arches?

- Arnaldo
 
> 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@linux.vnet.ibm.com>
> Acked-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  tools/perf/arch/s390/util/Build     |  2 ++
>  tools/perf/arch/s390/util/machine.c | 19 +++++++++++++++++++
>  tools/perf/util/machine.c           |  8 ++++++++
>  tools/perf/util/machine.h           |  1 +
>  4 files changed, 30 insertions(+)
>  create mode 100644 tools/perf/arch/s390/util/machine.c
> 
> diff --git a/tools/perf/arch/s390/util/Build b/tools/perf/arch/s390/util/Build
> index 8a61372..5bd7b92 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 += machine.o
> diff --git a/tools/perf/arch/s390/util/machine.c b/tools/perf/arch/s390/util/machine.c
> new file mode 100644
> index 0000000..b9a95a1
> --- /dev/null
> +++ b/tools/perf/arch/s390/util/machine.c
> @@ -0,0 +1,19 @@
> +#include <unistd.h>
> +#include <stdio.h>
> +#include <string.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];
> +
> +	snprintf(path, PATH_MAX, "module/%.*s/sections/.text",
> +				(int)strlen(name) - 2, name + 1);
> +
> +	if (sysfs__read_ull(path, (unsigned long long *)start) < 0)
> +		return -1;
> +
> +	return 0;
> +}
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index b177218..97cc9f0 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1091,12 +1091,20 @@ static int machine__set_modules_path(struct machine *machine)
>  
>  	return map_groups__set_modules_path_dir(&machine->kmaps, modules_path, 0);
>  }
> +int __weak arch__fix_module_text_start(u64 *start __maybe_unused,
> +				const char *name __maybe_unused)
> +{
> +	return 0;
> +}
>  
>  static int machine__create_module(void *arg, const char *name, u64 start)
>  {
>  	struct machine *machine = arg;
>  	struct map *map;
>  
> +	if (arch__fix_module_text_start(&start, name) < 0)
> +		return -1;
> +
>  	map = machine__findnew_module_map(machine, start, name);
>  	if (map == NULL)
>  		return -1;
> diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
> index 41ac9cf..20739f7 100644
> --- a/tools/perf/util/machine.h
> +++ b/tools/perf/util/machine.h
> @@ -216,6 +216,7 @@ struct symbol *machine__find_kernel_function_by_name(struct machine *machine,
>  
>  struct map *machine__findnew_module_map(struct machine *machine, u64 start,
>  					const char *filename);
> +int arch__fix_module_text_start(u64 *start, const char *name);
>  
>  int __machine__load_kallsyms(struct machine *machine, const char *filename,
>  			     enum map_type type, bool no_kcore, symbol_filter_t filter);
> -- 
> 2.3.0

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#1450839

FromChristian Borntraeger <borntraeger@de.ibm.com>
Date2016-07-26 22:20 +0200
Message-ID<rZgZA-6D5-3@gated-at.bofh.it>
In reply to#1450830
On 07/26/2016 09:50 PM, Arnaldo Carvalho de Melo wrote:
> Em Thu, Jul 21, 2016 at 11:10:51AM +0800, Song Shan Gong escreveu:
>> 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.
> 
> I'll apply this as it fixes the problem for you and we need to get fixes
> in ASAP to get this into 4.8, but why can't we just use your method for
> all arches and get rid of this arch__ hook? I.e. if I look here in my
> x86_64 notebook I see:
> 
> [acme@jouet linux]$ cat /sys/module/tun/sections/.text 
> 0xffffffffc0af2000
> [acme@jouet linux]$ grep tun /proc/modules 
> tun 28672 4 vhost_net, Live 0xffffffffc0af2000
> [acme@jouet linux]$ 
> 
> So I could as well use what is in /sys/module/tun/sections/.text instead
> of reading it from /proc/modules and, in s390, reading it from
> /sys/module/tun/sections/.text.
> 
> Do you see any problem with using this approach for _all_ arches?

I think it should work well for _all_ arches but it will probably be
hard to test this without help. 
I wouldn't be surprised if other architectures than s390 actually have
the same issue, so doing this for everybody might atually fix this somewhere
else.

> 
> - Arnaldo
> 
>> 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@linux.vnet.ibm.com>
>> Acked-by: Jiri Olsa <jolsa@kernel.org>
>> ---
>>  tools/perf/arch/s390/util/Build     |  2 ++
>>  tools/perf/arch/s390/util/machine.c | 19 +++++++++++++++++++
>>  tools/perf/util/machine.c           |  8 ++++++++
>>  tools/perf/util/machine.h           |  1 +
>>  4 files changed, 30 insertions(+)
>>  create mode 100644 tools/perf/arch/s390/util/machine.c
>>
>> diff --git a/tools/perf/arch/s390/util/Build b/tools/perf/arch/s390/util/Build
>> index 8a61372..5bd7b92 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 += machine.o
>> diff --git a/tools/perf/arch/s390/util/machine.c b/tools/perf/arch/s390/util/machine.c
>> new file mode 100644
>> index 0000000..b9a95a1
>> --- /dev/null
>> +++ b/tools/perf/arch/s390/util/machine.c
>> @@ -0,0 +1,19 @@
>> +#include <unistd.h>
>> +#include <stdio.h>
>> +#include <string.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];
>> +
>> +	snprintf(path, PATH_MAX, "module/%.*s/sections/.text",
>> +				(int)strlen(name) - 2, name + 1);
>> +
>> +	if (sysfs__read_ull(path, (unsigned long long *)start) < 0)
>> +		return -1;
>> +
>> +	return 0;
>> +}
>> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
>> index b177218..97cc9f0 100644
>> --- a/tools/perf/util/machine.c
>> +++ b/tools/perf/util/machine.c
>> @@ -1091,12 +1091,20 @@ static int machine__set_modules_path(struct machine *machine)
>>  
>>  	return map_groups__set_modules_path_dir(&machine->kmaps, modules_path, 0);
>>  }
>> +int __weak arch__fix_module_text_start(u64 *start __maybe_unused,
>> +				const char *name __maybe_unused)
>> +{
>> +	return 0;
>> +}
>>  
>>  static int machine__create_module(void *arg, const char *name, u64 start)
>>  {
>>  	struct machine *machine = arg;
>>  	struct map *map;
>>  
>> +	if (arch__fix_module_text_start(&start, name) < 0)
>> +		return -1;
>> +
>>  	map = machine__findnew_module_map(machine, start, name);
>>  	if (map == NULL)
>>  		return -1;
>> diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
>> index 41ac9cf..20739f7 100644
>> --- a/tools/perf/util/machine.h
>> +++ b/tools/perf/util/machine.h
>> @@ -216,6 +216,7 @@ struct symbol *machine__find_kernel_function_by_name(struct machine *machine,
>>  
>>  struct map *machine__findnew_module_map(struct machine *machine, u64 start,
>>  					const char *filename);
>> +int arch__fix_module_text_start(u64 *start, const char *name);
>>  
>>  int __machine__load_kallsyms(struct machine *machine, const char *filename,
>>  			     enum map_type type, bool no_kcore, symbol_filter_t filter);
>> -- 
>> 2.3.0
>

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#1450853

FromArnaldo Carvalho de Melo <acme@kernel.org>
Date2016-07-26 22:30 +0200
Message-ID<rZh9g-6Gn-3@gated-at.bofh.it>
In reply to#1450839
Em Tue, Jul 26, 2016 at 10:14:18PM +0200, Christian Borntraeger escreveu:
> On 07/26/2016 09:50 PM, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Jul 21, 2016 at 11:10:51AM +0800, Song Shan Gong escreveu:
> >> 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.
> > 
> > I'll apply this as it fixes the problem for you and we need to get fixes
> > in ASAP to get this into 4.8, but why can't we just use your method for
> > all arches and get rid of this arch__ hook? I.e. if I look here in my
> > x86_64 notebook I see:
> > 
> > [acme@jouet linux]$ cat /sys/module/tun/sections/.text 
> > 0xffffffffc0af2000
> > [acme@jouet linux]$ grep tun /proc/modules 
> > tun 28672 4 vhost_net, Live 0xffffffffc0af2000
> > [acme@jouet linux]$ 
> > 
> > So I could as well use what is in /sys/module/tun/sections/.text instead
> > of reading it from /proc/modules and, in s390, reading it from
> > /sys/module/tun/sections/.text.
> > 
> > Do you see any problem with using this approach for _all_ arches?
> 
> I think it should work well for _all_ arches but it will probably be
> hard to test this without help. 

Well, we could check for the cases we don't know, i.e. read from both
and warn about cases where it is different, except for s390 where we now
which is the right one to pick.

> I wouldn't be surprised if other architectures than s390 actually have
> the same issue, so doing this for everybody might atually fix this somewhere
> else.

Would be nice to get info from other arch people, Michael, how this goes
on ppc?

- Arnaldo
 
> > 
> > - Arnaldo
> > 
> >> 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@linux.vnet.ibm.com>
> >> Acked-by: Jiri Olsa <jolsa@kernel.org>
> >> ---
> >>  tools/perf/arch/s390/util/Build     |  2 ++
> >>  tools/perf/arch/s390/util/machine.c | 19 +++++++++++++++++++
> >>  tools/perf/util/machine.c           |  8 ++++++++
> >>  tools/perf/util/machine.h           |  1 +
> >>  4 files changed, 30 insertions(+)
> >>  create mode 100644 tools/perf/arch/s390/util/machine.c
> >>
> >> diff --git a/tools/perf/arch/s390/util/Build b/tools/perf/arch/s390/util/Build
> >> index 8a61372..5bd7b92 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 += machine.o
> >> diff --git a/tools/perf/arch/s390/util/machine.c b/tools/perf/arch/s390/util/machine.c
> >> new file mode 100644
> >> index 0000000..b9a95a1
> >> --- /dev/null
> >> +++ b/tools/perf/arch/s390/util/machine.c
> >> @@ -0,0 +1,19 @@
> >> +#include <unistd.h>
> >> +#include <stdio.h>
> >> +#include <string.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];
> >> +
> >> +	snprintf(path, PATH_MAX, "module/%.*s/sections/.text",
> >> +				(int)strlen(name) - 2, name + 1);
> >> +
> >> +	if (sysfs__read_ull(path, (unsigned long long *)start) < 0)
> >> +		return -1;
> >> +
> >> +	return 0;
> >> +}
> >> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> >> index b177218..97cc9f0 100644
> >> --- a/tools/perf/util/machine.c
> >> +++ b/tools/perf/util/machine.c
> >> @@ -1091,12 +1091,20 @@ static int machine__set_modules_path(struct machine *machine)
> >>  
> >>  	return map_groups__set_modules_path_dir(&machine->kmaps, modules_path, 0);
> >>  }
> >> +int __weak arch__fix_module_text_start(u64 *start __maybe_unused,
> >> +				const char *name __maybe_unused)
> >> +{
> >> +	return 0;
> >> +}
> >>  
> >>  static int machine__create_module(void *arg, const char *name, u64 start)
> >>  {
> >>  	struct machine *machine = arg;
> >>  	struct map *map;
> >>  
> >> +	if (arch__fix_module_text_start(&start, name) < 0)
> >> +		return -1;
> >> +
> >>  	map = machine__findnew_module_map(machine, start, name);
> >>  	if (map == NULL)
> >>  		return -1;
> >> diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
> >> index 41ac9cf..20739f7 100644
> >> --- a/tools/perf/util/machine.h
> >> +++ b/tools/perf/util/machine.h
> >> @@ -216,6 +216,7 @@ struct symbol *machine__find_kernel_function_by_name(struct machine *machine,
> >>  
> >>  struct map *machine__findnew_module_map(struct machine *machine, u64 start,
> >>  					const char *filename);
> >> +int arch__fix_module_text_start(u64 *start, const char *name);
> >>  
> >>  int __machine__load_kallsyms(struct machine *machine, const char *filename,
> >>  			     enum map_type type, bool no_kcore, symbol_filter_t filter);
> >> -- 
> >> 2.3.0
> >

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#1451172

FromMichael Ellerman <mpe@ellerman.id.au>
Date2016-07-27 11:30 +0200
Message-ID<rZtk8-5Wg-71@gated-at.bofh.it>
In reply to#1450853
Arnaldo Carvalho de Melo <acme@kernel.org> writes:

> Em Tue, Jul 26, 2016 at 10:14:18PM +0200, Christian Borntraeger escreveu:
>> On 07/26/2016 09:50 PM, Arnaldo Carvalho de Melo wrote:
>> > Em Thu, Jul 21, 2016 at 11:10:51AM +0800, Song Shan Gong escreveu:
>> >> 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.
>> > 
>> > I'll apply this as it fixes the problem for you and we need to get fixes
>> > in ASAP to get this into 4.8, but why can't we just use your method for
>> > all arches and get rid of this arch__ hook? I.e. if I look here in my
>> > x86_64 notebook I see:
>> > 
>> > [acme@jouet linux]$ cat /sys/module/tun/sections/.text 
>> > 0xffffffffc0af2000
>> > [acme@jouet linux]$ grep tun /proc/modules 
>> > tun 28672 4 vhost_net, Live 0xffffffffc0af2000
>> > [acme@jouet linux]$ 
>> > 
>> > So I could as well use what is in /sys/module/tun/sections/.text instead
>> > of reading it from /proc/modules and, in s390, reading it from
>> > /sys/module/tun/sections/.text.
>> > 
>> > Do you see any problem with using this approach for _all_ arches?
>> 
>> I think it should work well for _all_ arches but it will probably be
>> hard to test this without help. 
>
> Well, we could check for the cases we don't know, i.e. read from both
> and warn about cases where it is different, except for s390 where we now
> which is the right one to pick.
>
>> I wouldn't be surprised if other architectures than s390 actually have
>> the same issue, so doing this for everybody might atually fix this somewhere
>> else.
>
> Would be nice to get info from other arch people, Michael, how this goes
> on ppc?

It doesn't look like this is a problem on powerpc - at least I haven't
heard of it.

Looking at a system I have here, for all modules (26) the value in
/proc/modules matches the .text section in /sys.

So I think using /sys should be fine for us.

cheers

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#1451270

FromArnaldo Carvalho de Melo <acme@kernel.org>
Date2016-07-27 15:10 +0200
Message-ID<rZwKZ-8gP-31@gated-at.bofh.it>
In reply to#1451172
Em Wed, Jul 27, 2016 at 07:24:26PM +1000, Michael Ellerman escreveu:
> Arnaldo Carvalho de Melo <acme@kernel.org> writes:
> > Em Tue, Jul 26, 2016 at 10:14:18PM +0200, Christian Borntraeger escreveu:
> >> On 07/26/2016 09:50 PM, Arnaldo Carvalho de Melo wrote:
> >> > So I could as well use what is in /sys/module/tun/sections/.text instead
> >> > of reading it from /proc/modules and, in s390, reading it from
> >> > /sys/module/tun/sections/.text.

> >> > Do you see any problem with using this approach for _all_ arches?

> >> I think it should work well for _all_ arches but it will probably be
> >> hard to test this without help. 

> > Well, we could check for the cases we don't know, i.e. read from both
> > and warn about cases where it is different, except for s390 where we now
> > which is the right one to pick.

> >> I wouldn't be surprised if other architectures than s390 actually have
> >> the same issue, so doing this for everybody might atually fix this somewhere
> >> else.

> > Would be nice to get info from other arch people, Michael, how this goes
> > on ppc?

> It doesn't look like this is a problem on powerpc - at least I haven't
> heard of it.

> Looking at a system I have here, for all modules (26) the value in
> /proc/modules matches the .text section in /sys.

> So I think using /sys should be fine for us.

Thanks for checking.

- Arnaldo

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#1451210

FromSongshan Gong <gongss@linux.vnet.ibm.com>
Date2016-07-27 12:20 +0200
Message-ID<rZu6t-6ul-7@gated-at.bofh.it>
In reply to#1450853

在 7/27/2016 4:29 AM, Arnaldo Carvalho de Melo 写道:
> Em Tue, Jul 26, 2016 at 10:14:18PM +0200, Christian Borntraeger escreveu:
>> On 07/26/2016 09:50 PM, Arnaldo Carvalho de Melo wrote:
>>> Em Thu, Jul 21, 2016 at 11:10:51AM +0800, Song Shan Gong escreveu:
>>>> 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.
>>>
>>> I'll apply this as it fixes the problem for you and we need to get fixes
>>> in ASAP to get this into 4.8, but why can't we just use your method for
>>> all arches and get rid of this arch__ hook? I.e. if I look here in my
>>> x86_64 notebook I see:
>>>
>>> [acme@jouet linux]$ cat /sys/module/tun/sections/.text
>>> 0xffffffffc0af2000
>>> [acme@jouet linux]$ grep tun /proc/modules
>>> tun 28672 4 vhost_net, Live 0xffffffffc0af2000
>>> [acme@jouet linux]$
>>>
>>> So I could as well use what is in /sys/module/tun/sections/.text instead
>>> of reading it from /proc/modules and, in s390, reading it from
>>> /sys/module/tun/sections/.text.
>>>
>>> Do you see any problem with using this approach for _all_ arches?
>>
>> I think it should work well for _all_ arches but it will probably be
>> hard to test this without help.
>
> Well, we could check for the cases we don't know, i.e. read from both
> and warn about cases where it is different, except for s390 where we now
> which is the right one to pick.

Good idea!

>
>> I wouldn't be surprised if other architectures than s390 actually have
>> the same issue, so doing this for everybody might atually fix this somewhere
>> else.
>
> Would be nice to get info from other arch people, Michael, how this goes
> on ppc?
>
> - Arnaldo
>
>>>
>>> - Arnaldo
>>>
>>>> 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@linux.vnet.ibm.com>
>>>> Acked-by: Jiri Olsa <jolsa@kernel.org>
>>>> ---
>>>>  tools/perf/arch/s390/util/Build     |  2 ++
>>>>  tools/perf/arch/s390/util/machine.c | 19 +++++++++++++++++++
>>>>  tools/perf/util/machine.c           |  8 ++++++++
>>>>  tools/perf/util/machine.h           |  1 +
>>>>  4 files changed, 30 insertions(+)
>>>>  create mode 100644 tools/perf/arch/s390/util/machine.c
>>>>
>>>> diff --git a/tools/perf/arch/s390/util/Build b/tools/perf/arch/s390/util/Build
>>>> index 8a61372..5bd7b92 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 += machine.o
>>>> diff --git a/tools/perf/arch/s390/util/machine.c b/tools/perf/arch/s390/util/machine.c
>>>> new file mode 100644
>>>> index 0000000..b9a95a1
>>>> --- /dev/null
>>>> +++ b/tools/perf/arch/s390/util/machine.c
>>>> @@ -0,0 +1,19 @@
>>>> +#include <unistd.h>
>>>> +#include <stdio.h>
>>>> +#include <string.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];
>>>> +
>>>> +	snprintf(path, PATH_MAX, "module/%.*s/sections/.text",
>>>> +				(int)strlen(name) - 2, name + 1);
>>>> +
>>>> +	if (sysfs__read_ull(path, (unsigned long long *)start) < 0)
>>>> +		return -1;
>>>> +
>>>> +	return 0;
>>>> +}
>>>> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
>>>> index b177218..97cc9f0 100644
>>>> --- a/tools/perf/util/machine.c
>>>> +++ b/tools/perf/util/machine.c
>>>> @@ -1091,12 +1091,20 @@ static int machine__set_modules_path(struct machine *machine)
>>>>
>>>>  	return map_groups__set_modules_path_dir(&machine->kmaps, modules_path, 0);
>>>>  }
>>>> +int __weak arch__fix_module_text_start(u64 *start __maybe_unused,
>>>> +				const char *name __maybe_unused)
>>>> +{
>>>> +	return 0;
>>>> +}
>>>>
>>>>  static int machine__create_module(void *arg, const char *name, u64 start)
>>>>  {
>>>>  	struct machine *machine = arg;
>>>>  	struct map *map;
>>>>
>>>> +	if (arch__fix_module_text_start(&start, name) < 0)
>>>> +		return -1;
>>>> +
>>>>  	map = machine__findnew_module_map(machine, start, name);
>>>>  	if (map == NULL)
>>>>  		return -1;
>>>> diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
>>>> index 41ac9cf..20739f7 100644
>>>> --- a/tools/perf/util/machine.h
>>>> +++ b/tools/perf/util/machine.h
>>>> @@ -216,6 +216,7 @@ struct symbol *machine__find_kernel_function_by_name(struct machine *machine,
>>>>
>>>>  struct map *machine__findnew_module_map(struct machine *machine, u64 start,
>>>>  					const char *filename);
>>>> +int arch__fix_module_text_start(u64 *start, const char *name);
>>>>
>>>>  int __machine__load_kallsyms(struct machine *machine, const char *filename,
>>>>  			     enum map_type type, bool no_kcore, symbol_filter_t filter);
>>>> --
>>>> 2.3.0
>>>
>

-- 
SongShan Gong

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#1451218

FromSongshan Gong <gongss@linux.vnet.ibm.com>
Date2016-07-27 12:50 +0200
Message-ID<rZuzv-6GJ-3@gated-at.bofh.it>
In reply to#1450853

在 7/27/2016 4:29 AM, Arnaldo Carvalho de Melo 写道:
> Em Tue, Jul 26, 2016 at 10:14:18PM +0200, Christian Borntraeger escreveu:
>> On 07/26/2016 09:50 PM, Arnaldo Carvalho de Melo wrote:
>>> Em Thu, Jul 21, 2016 at 11:10:51AM +0800, Song Shan Gong escreveu:
>>>> 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.
>>>
>>> I'll apply this as it fixes the problem for you and we need to get fixes
>>> in ASAP to get this into 4.8, but why can't we just use your method for
>>> all arches and get rid of this arch__ hook? I.e. if I look here in my
>>> x86_64 notebook I see:
>>>
>>> [acme@jouet linux]$ cat /sys/module/tun/sections/.text
>>> 0xffffffffc0af2000
>>> [acme@jouet linux]$ grep tun /proc/modules
>>> tun 28672 4 vhost_net, Live 0xffffffffc0af2000
>>> [acme@jouet linux]$
>>>
>>> So I could as well use what is in /sys/module/tun/sections/.text instead
>>> of reading it from /proc/modules and, in s390, reading it from
>>> /sys/module/tun/sections/.text.
>>>
>>> Do you see any problem with using this approach for _all_ arches?
>>
>> I think it should work well for _all_ arches but it will probably be
>> hard to test this without help.
>
> Well, we could check for the cases we don't know, i.e. read from both
> and warn about cases where it is different, except for s390 where we now
> which is the right one to pick.
>
One question: how to get arch info except machine->env->arch? It seems 
that machine->env->arch could be NULL sometimes.


>> I wouldn't be surprised if other architectures than s390 actually have
>> the same issue, so doing this for everybody might atually fix this somewhere
>> else.
>
> Would be nice to get info from other arch people, Michael, how this goes
> on ppc?
>
> - Arnaldo
>
>>>
>>> - Arnaldo
>>>
>>>> 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@linux.vnet.ibm.com>
>>>> Acked-by: Jiri Olsa <jolsa@kernel.org>
>>>> ---
>>>>  tools/perf/arch/s390/util/Build     |  2 ++
>>>>  tools/perf/arch/s390/util/machine.c | 19 +++++++++++++++++++
>>>>  tools/perf/util/machine.c           |  8 ++++++++
>>>>  tools/perf/util/machine.h           |  1 +
>>>>  4 files changed, 30 insertions(+)
>>>>  create mode 100644 tools/perf/arch/s390/util/machine.c
>>>>
>>>> diff --git a/tools/perf/arch/s390/util/Build b/tools/perf/arch/s390/util/Build
>>>> index 8a61372..5bd7b92 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 += machine.o
>>>> diff --git a/tools/perf/arch/s390/util/machine.c b/tools/perf/arch/s390/util/machine.c
>>>> new file mode 100644
>>>> index 0000000..b9a95a1
>>>> --- /dev/null
>>>> +++ b/tools/perf/arch/s390/util/machine.c
>>>> @@ -0,0 +1,19 @@
>>>> +#include <unistd.h>
>>>> +#include <stdio.h>
>>>> +#include <string.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];
>>>> +
>>>> +	snprintf(path, PATH_MAX, "module/%.*s/sections/.text",
>>>> +				(int)strlen(name) - 2, name + 1);
>>>> +
>>>> +	if (sysfs__read_ull(path, (unsigned long long *)start) < 0)
>>>> +		return -1;
>>>> +
>>>> +	return 0;
>>>> +}
>>>> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
>>>> index b177218..97cc9f0 100644
>>>> --- a/tools/perf/util/machine.c
>>>> +++ b/tools/perf/util/machine.c
>>>> @@ -1091,12 +1091,20 @@ static int machine__set_modules_path(struct machine *machine)
>>>>
>>>>  	return map_groups__set_modules_path_dir(&machine->kmaps, modules_path, 0);
>>>>  }
>>>> +int __weak arch__fix_module_text_start(u64 *start __maybe_unused,
>>>> +				const char *name __maybe_unused)
>>>> +{
>>>> +	return 0;
>>>> +}
>>>>
>>>>  static int machine__create_module(void *arg, const char *name, u64 start)
>>>>  {
>>>>  	struct machine *machine = arg;
>>>>  	struct map *map;
>>>>
>>>> +	if (arch__fix_module_text_start(&start, name) < 0)
>>>> +		return -1;
>>>> +
>>>>  	map = machine__findnew_module_map(machine, start, name);
>>>>  	if (map == NULL)
>>>>  		return -1;
>>>> diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
>>>> index 41ac9cf..20739f7 100644
>>>> --- a/tools/perf/util/machine.h
>>>> +++ b/tools/perf/util/machine.h
>>>> @@ -216,6 +216,7 @@ struct symbol *machine__find_kernel_function_by_name(struct machine *machine,
>>>>
>>>>  struct map *machine__findnew_module_map(struct machine *machine, u64 start,
>>>>  					const char *filename);
>>>> +int arch__fix_module_text_start(u64 *start, const char *name);
>>>>
>>>>  int __machine__load_kallsyms(struct machine *machine, const char *filename,
>>>>  			     enum map_type type, bool no_kcore, symbol_filter_t filter);
>>>> --
>>>> 2.3.0
>>>
>

-- 
SongShan Gong

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#1451268

FromArnaldo Carvalho de Melo <acme@kernel.org>
Date2016-07-27 15:10 +0200
Message-ID<rZwKZ-8gP-23@gated-at.bofh.it>
In reply to#1451218
Em Wed, Jul 27, 2016 at 06:49:48PM +0800, Songshan Gong escreveu:
> 
> 
> 在 7/27/2016 4:29 AM, Arnaldo Carvalho de Melo 写道:
> > Em Tue, Jul 26, 2016 at 10:14:18PM +0200, Christian Borntraeger escreveu:
> > > On 07/26/2016 09:50 PM, Arnaldo Carvalho de Melo wrote:
> > > > Em Thu, Jul 21, 2016 at 11:10:51AM +0800, Song Shan Gong escreveu:
> > > > > 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.
> > > > 
> > > > I'll apply this as it fixes the problem for you and we need to get fixes
> > > > in ASAP to get this into 4.8, but why can't we just use your method for
> > > > all arches and get rid of this arch__ hook? I.e. if I look here in my
> > > > x86_64 notebook I see:
> > > > 
> > > > [acme@jouet linux]$ cat /sys/module/tun/sections/.text
> > > > 0xffffffffc0af2000
> > > > [acme@jouet linux]$ grep tun /proc/modules
> > > > tun 28672 4 vhost_net, Live 0xffffffffc0af2000
> > > > [acme@jouet linux]$
> > > > 
> > > > So I could as well use what is in /sys/module/tun/sections/.text instead
> > > > of reading it from /proc/modules and, in s390, reading it from
> > > > /sys/module/tun/sections/.text.
> > > > 
> > > > Do you see any problem with using this approach for _all_ arches?
> > > 
> > > I think it should work well for _all_ arches but it will probably be
> > > hard to test this without help.
> > 
> > Well, we could check for the cases we don't know, i.e. read from both
> > and warn about cases where it is different, except for s390 where we now
> > which is the right one to pick.
> > 
> One question: how to get arch info except machine->env->arch? It seems that
> machine->env->arch could be NULL sometimes.

That is not what you want to look at, as it is related to perf.data,
which may not be related to what you want, which is the running machine.

For that use uname() -> utsname.machine.

But then, why would you need it for reading /sys/module/*/sections/.text?
The arch name isn't there :-)

- Arnaldo

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#1451625

FromSongshan Gong <gongss@linux.vnet.ibm.com>
Date2016-07-28 04:10 +0200
Message-ID<rZIVQ-7X5-15@gated-at.bofh.it>
In reply to#1451268

在 7/27/2016 9:08 PM, Arnaldo Carvalho de Melo 写道:
> Em Wed, Jul 27, 2016 at 06:49:48PM +0800, Songshan Gong escreveu:
>>
>>
>> 在 7/27/2016 4:29 AM, Arnaldo Carvalho de Melo 写道:
>>> Em Tue, Jul 26, 2016 at 10:14:18PM +0200, Christian Borntraeger escreveu:
>>>> On 07/26/2016 09:50 PM, Arnaldo Carvalho de Melo wrote:
>>>>> Em Thu, Jul 21, 2016 at 11:10:51AM +0800, Song Shan Gong escreveu:
>>>>>> 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.
>>>>>
>>>>> I'll apply this as it fixes the problem for you and we need to get fixes
>>>>> in ASAP to get this into 4.8, but why can't we just use your method for
>>>>> all arches and get rid of this arch__ hook? I.e. if I look here in my
>>>>> x86_64 notebook I see:
>>>>>
>>>>> [acme@jouet linux]$ cat /sys/module/tun/sections/.text
>>>>> 0xffffffffc0af2000
>>>>> [acme@jouet linux]$ grep tun /proc/modules
>>>>> tun 28672 4 vhost_net, Live 0xffffffffc0af2000
>>>>> [acme@jouet linux]$
>>>>>
>>>>> So I could as well use what is in /sys/module/tun/sections/.text instead
>>>>> of reading it from /proc/modules and, in s390, reading it from
>>>>> /sys/module/tun/sections/.text.
>>>>>
>>>>> Do you see any problem with using this approach for _all_ arches?
>>>>
>>>> I think it should work well for _all_ arches but it will probably be
>>>> hard to test this without help.
>>>
>>> Well, we could check for the cases we don't know, i.e. read from both
>>> and warn about cases where it is different, except for s390 where we now
>>> which is the right one to pick.
>>>
>> One question: how to get arch info except machine->env->arch? It seems that
>> machine->env->arch could be NULL sometimes.
>
> That is not what you want to look at, as it is related to perf.data,
> which may not be related to what you want, which is the running machine.
>
> For that use uname() -> utsname.machine.
>
> But then, why would you need it for reading /sys/module/*/sections/.text?
> The arch name isn't there :-)

Yes, it's no use for this patch. Thanks a lot.
>
> - Arnaldo
>

-- 
SongShan Gong

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#1451208

FromSongshan Gong <gongss@linux.vnet.ibm.com>
Date2016-07-27 12:10 +0200
Message-ID<rZtWO-6qK-47@gated-at.bofh.it>
In reply to#1450830

在 7/27/2016 3:50 AM, Arnaldo Carvalho de Melo 写道:
> Em Thu, Jul 21, 2016 at 11:10:51AM +0800, Song Shan Gong escreveu:
>> 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.
>
> I'll apply this as it fixes the problem for you and we need to get fixes
> in ASAP to get this into 4.8, but why can't we just use your method for
> all arches and get rid of this arch__ hook? I.e. if I look here in my
> x86_64 notebook I see:
>
> [acme@jouet linux]$ cat /sys/module/tun/sections/.text
> 0xffffffffc0af2000
> [acme@jouet linux]$ grep tun /proc/modules
> tun 28672 4 vhost_net, Live 0xffffffffc0af2000
> [acme@jouet linux]$
>
> So I could as well use what is in /sys/module/tun/sections/.text instead
> of reading it from /proc/modules and, in s390, reading it from
> /sys/module/tun/sections/.text.
>

I also think it should be OK for most archs.

> Do you see any problem with using this approach for _all_ arches?
>
> - Arnaldo
>
>> 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@linux.vnet.ibm.com>
>> Acked-by: Jiri Olsa <jolsa@kernel.org>
>> ---
>>  tools/perf/arch/s390/util/Build     |  2 ++
>>  tools/perf/arch/s390/util/machine.c | 19 +++++++++++++++++++
>>  tools/perf/util/machine.c           |  8 ++++++++
>>  tools/perf/util/machine.h           |  1 +
>>  4 files changed, 30 insertions(+)
>>  create mode 100644 tools/perf/arch/s390/util/machine.c
>>
>> diff --git a/tools/perf/arch/s390/util/Build b/tools/perf/arch/s390/util/Build
>> index 8a61372..5bd7b92 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 += machine.o
>> diff --git a/tools/perf/arch/s390/util/machine.c b/tools/perf/arch/s390/util/machine.c
>> new file mode 100644
>> index 0000000..b9a95a1
>> --- /dev/null
>> +++ b/tools/perf/arch/s390/util/machine.c
>> @@ -0,0 +1,19 @@
>> +#include <unistd.h>
>> +#include <stdio.h>
>> +#include <string.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];
>> +
>> +	snprintf(path, PATH_MAX, "module/%.*s/sections/.text",
>> +				(int)strlen(name) - 2, name + 1);
>> +
>> +	if (sysfs__read_ull(path, (unsigned long long *)start) < 0)
>> +		return -1;
>> +
>> +	return 0;
>> +}
>> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
>> index b177218..97cc9f0 100644
>> --- a/tools/perf/util/machine.c
>> +++ b/tools/perf/util/machine.c
>> @@ -1091,12 +1091,20 @@ static int machine__set_modules_path(struct machine *machine)
>>
>>  	return map_groups__set_modules_path_dir(&machine->kmaps, modules_path, 0);
>>  }
>> +int __weak arch__fix_module_text_start(u64 *start __maybe_unused,
>> +				const char *name __maybe_unused)
>> +{
>> +	return 0;
>> +}
>>
>>  static int machine__create_module(void *arg, const char *name, u64 start)
>>  {
>>  	struct machine *machine = arg;
>>  	struct map *map;
>>
>> +	if (arch__fix_module_text_start(&start, name) < 0)
>> +		return -1;
>> +
>>  	map = machine__findnew_module_map(machine, start, name);
>>  	if (map == NULL)
>>  		return -1;
>> diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h
>> index 41ac9cf..20739f7 100644
>> --- a/tools/perf/util/machine.h
>> +++ b/tools/perf/util/machine.h
>> @@ -216,6 +216,7 @@ struct symbol *machine__find_kernel_function_by_name(struct machine *machine,
>>
>>  struct map *machine__findnew_module_map(struct machine *machine, u64 start,
>>  					const char *filename);
>> +int arch__fix_module_text_start(u64 *start, const char *name);
>>
>>  int __machine__load_kallsyms(struct machine *machine, const char *filename,
>>  			     enum map_type type, bool no_kcore, symbol_filter_t filter);
>> --
>> 2.3.0
>

-- 
SongShan Gong

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