Messages in this thread | | | Subject | Re: [PATCH] s390/perf: fix 'start' address of module's map | From | Songshan Gong <> | Date | Wed, 27 Jul 2016 18:10:07 +0800 |
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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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