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 <gon...@linux.vnet.ibm.com> >> Acked-by: Jiri Olsa <jo...@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 >