Re: [RFC] perf probe: Fix offline module name missmatch issue
On Tuesday 26 April 2016 04:16 PM, Masami Hiramatsu wrote: On Tue, 26 Apr 2016 14:26:48 +0530 Ravi Bangoriawrote: Thanks Masami for reviewing. Please find my replies to your comment. On Tuesday 26 April 2016 02:54 AM, Masami Hiramatsu wrote: Hi Ravi, On Mon, 25 Apr 2016 16:08:27 +0530 Ravi Bangoria wrote: Perf can add a probe on kernel module which has not been loaded yet. Current implementation finds module name from path. But if filename is different from actual module name then perf fails to register probe while loading module because of mismatch in names. For example, samples/kobject/kobject-example.ko is loaded as kobject_example. Ah! right, good catch! Have some comment below; diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c index 8319fbb..05d0905 100644 --- a/tools/perf/util/probe-event.c +++ b/tools/perf/util/probe-event.c @@ -265,6 +265,65 @@ static bool kprobe_warn_out_range(const char *symbol, unsigned long address) return true; } +/* + * NOTE: + * '.gnu.linkonce.this_module' section of kernel module elf directly + * maps to 'struct module' from linux/module.h. This section contains + * actual module name which will be used by kernel after loading it. + * But, we cannot use 'struct module' here since linux/module.h is not + * exposed to user-space. Offset of 'name' has remained same from long + * time, so hardcoding it here. + */ +#ifdef __LP64__ +#define MOD_NAME_OFFSET 24 +#else +#define MOD_NAME_OFFSET 12 +#endif + +/* + * @module can be module name of module file path. In case of path, + * inspect elf and find out what is actual module name. + * Caller has to free mod_name after using it. + */ +char *find_module_name(const char *module) Could you make this function static, since there is no caller outside this file? Yes. no caller outside of this file. But, In this patch, function find_module_name is defined outside of #ifdef HAVE_DWARF_SUPPORT while it's being called from inside of #ifdef HAVE_DWARF_SUPPORT. If I make it static and if there is no dwarf support, there will be compilation error about function defined but not used. And in second patch("perf probe: Fix module probe issue if no dwarf support"), I'm calling it from outside of #ifdef HAVE_DWARF_SUPPORT. So I have two options: 1. merge both the patches and make definition as static 2. make function static in second patch I've chose second approach and sent v2. But please let me know if there is better way to do it. Ah, I see. In that case, you can swap the patch in the series and move find_module_name in the other patch ;) Thanks :) Sent patch with changes. Please review it. Regards, Ravi
Re: [RFC] perf probe: Fix offline module name missmatch issue
On Tuesday 26 April 2016 04:16 PM, Masami Hiramatsu wrote: On Tue, 26 Apr 2016 14:26:48 +0530 Ravi Bangoria wrote: Thanks Masami for reviewing. Please find my replies to your comment. On Tuesday 26 April 2016 02:54 AM, Masami Hiramatsu wrote: Hi Ravi, On Mon, 25 Apr 2016 16:08:27 +0530 Ravi Bangoria wrote: Perf can add a probe on kernel module which has not been loaded yet. Current implementation finds module name from path. But if filename is different from actual module name then perf fails to register probe while loading module because of mismatch in names. For example, samples/kobject/kobject-example.ko is loaded as kobject_example. Ah! right, good catch! Have some comment below; diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c index 8319fbb..05d0905 100644 --- a/tools/perf/util/probe-event.c +++ b/tools/perf/util/probe-event.c @@ -265,6 +265,65 @@ static bool kprobe_warn_out_range(const char *symbol, unsigned long address) return true; } +/* + * NOTE: + * '.gnu.linkonce.this_module' section of kernel module elf directly + * maps to 'struct module' from linux/module.h. This section contains + * actual module name which will be used by kernel after loading it. + * But, we cannot use 'struct module' here since linux/module.h is not + * exposed to user-space. Offset of 'name' has remained same from long + * time, so hardcoding it here. + */ +#ifdef __LP64__ +#define MOD_NAME_OFFSET 24 +#else +#define MOD_NAME_OFFSET 12 +#endif + +/* + * @module can be module name of module file path. In case of path, + * inspect elf and find out what is actual module name. + * Caller has to free mod_name after using it. + */ +char *find_module_name(const char *module) Could you make this function static, since there is no caller outside this file? Yes. no caller outside of this file. But, In this patch, function find_module_name is defined outside of #ifdef HAVE_DWARF_SUPPORT while it's being called from inside of #ifdef HAVE_DWARF_SUPPORT. If I make it static and if there is no dwarf support, there will be compilation error about function defined but not used. And in second patch("perf probe: Fix module probe issue if no dwarf support"), I'm calling it from outside of #ifdef HAVE_DWARF_SUPPORT. So I have two options: 1. merge both the patches and make definition as static 2. make function static in second patch I've chose second approach and sent v2. But please let me know if there is better way to do it. Ah, I see. In that case, you can swap the patch in the series and move find_module_name in the other patch ;) Thanks :) Sent patch with changes. Please review it. Regards, Ravi
Re: [RFC] perf probe: Fix offline module name missmatch issue
On Tue, 26 Apr 2016 14:26:48 +0530 Ravi Bangoriawrote: > Thanks Masami for reviewing. > > Please find my replies to your comment. > > On Tuesday 26 April 2016 02:54 AM, Masami Hiramatsu wrote: > > Hi Ravi, > > > > On Mon, 25 Apr 2016 16:08:27 +0530 > > Ravi Bangoria wrote: > > > >> Perf can add a probe on kernel module which has not been loaded yet. > >> Current implementation finds module name from path. But if filename > >> is different from actual module name then perf fails to register > >> probe while loading module because of mismatch in names. For example, > >> samples/kobject/kobject-example.ko is loaded as kobject_example. > > Ah! right, good catch! > > Have some comment below; > > > >> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c > >> index 8319fbb..05d0905 100644 > >> --- a/tools/perf/util/probe-event.c > >> +++ b/tools/perf/util/probe-event.c > >> @@ -265,6 +265,65 @@ static bool kprobe_warn_out_range(const char *symbol, > >> unsigned long address) > >>return true; > >> } > >> > >> +/* > >> + * NOTE: > >> + * '.gnu.linkonce.this_module' section of kernel module elf directly > >> + * maps to 'struct module' from linux/module.h. This section contains > >> + * actual module name which will be used by kernel after loading it. > >> + * But, we cannot use 'struct module' here since linux/module.h is not > >> + * exposed to user-space. Offset of 'name' has remained same from long > >> + * time, so hardcoding it here. > >> + */ > >> +#ifdef __LP64__ > >> +#define MOD_NAME_OFFSET 24 > >> +#else > >> +#define MOD_NAME_OFFSET 12 > >> +#endif > >> + > >> +/* > >> + * @module can be module name of module file path. In case of path, > >> + * inspect elf and find out what is actual module name. > >> + * Caller has to free mod_name after using it. > >> + */ > >> +char *find_module_name(const char *module) > > Could you make this function static, since there is no caller outside > > this file? > > Yes. no caller outside of this file. But, > > In this patch, function find_module_name is defined outside of > #ifdef HAVE_DWARF_SUPPORT while it's being called from inside of > #ifdef HAVE_DWARF_SUPPORT. > > If I make it static and if there is no dwarf support, there will be > compilation > error about function defined but not used. > > And in second patch("perf probe: Fix module probe issue if no dwarf > support"), > I'm calling it from outside of #ifdef HAVE_DWARF_SUPPORT. > > So I have two options: > 1. merge both the patches and make definition as static > 2. make function static in second patch > > I've chose second approach and sent v2. But please let me know if there is > better way to do it. Ah, I see. In that case, you can swap the patch in the series and move find_module_name in the other patch ;) Thanks! -- Masami Hiramatsu
Re: [RFC] perf probe: Fix offline module name missmatch issue
On Tue, 26 Apr 2016 14:26:48 +0530 Ravi Bangoria wrote: > Thanks Masami for reviewing. > > Please find my replies to your comment. > > On Tuesday 26 April 2016 02:54 AM, Masami Hiramatsu wrote: > > Hi Ravi, > > > > On Mon, 25 Apr 2016 16:08:27 +0530 > > Ravi Bangoria wrote: > > > >> Perf can add a probe on kernel module which has not been loaded yet. > >> Current implementation finds module name from path. But if filename > >> is different from actual module name then perf fails to register > >> probe while loading module because of mismatch in names. For example, > >> samples/kobject/kobject-example.ko is loaded as kobject_example. > > Ah! right, good catch! > > Have some comment below; > > > >> diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c > >> index 8319fbb..05d0905 100644 > >> --- a/tools/perf/util/probe-event.c > >> +++ b/tools/perf/util/probe-event.c > >> @@ -265,6 +265,65 @@ static bool kprobe_warn_out_range(const char *symbol, > >> unsigned long address) > >>return true; > >> } > >> > >> +/* > >> + * NOTE: > >> + * '.gnu.linkonce.this_module' section of kernel module elf directly > >> + * maps to 'struct module' from linux/module.h. This section contains > >> + * actual module name which will be used by kernel after loading it. > >> + * But, we cannot use 'struct module' here since linux/module.h is not > >> + * exposed to user-space. Offset of 'name' has remained same from long > >> + * time, so hardcoding it here. > >> + */ > >> +#ifdef __LP64__ > >> +#define MOD_NAME_OFFSET 24 > >> +#else > >> +#define MOD_NAME_OFFSET 12 > >> +#endif > >> + > >> +/* > >> + * @module can be module name of module file path. In case of path, > >> + * inspect elf and find out what is actual module name. > >> + * Caller has to free mod_name after using it. > >> + */ > >> +char *find_module_name(const char *module) > > Could you make this function static, since there is no caller outside > > this file? > > Yes. no caller outside of this file. But, > > In this patch, function find_module_name is defined outside of > #ifdef HAVE_DWARF_SUPPORT while it's being called from inside of > #ifdef HAVE_DWARF_SUPPORT. > > If I make it static and if there is no dwarf support, there will be > compilation > error about function defined but not used. > > And in second patch("perf probe: Fix module probe issue if no dwarf > support"), > I'm calling it from outside of #ifdef HAVE_DWARF_SUPPORT. > > So I have two options: > 1. merge both the patches and make definition as static > 2. make function static in second patch > > I've chose second approach and sent v2. But please let me know if there is > better way to do it. Ah, I see. In that case, you can swap the patch in the series and move find_module_name in the other patch ;) Thanks! -- Masami Hiramatsu
Re: [RFC] perf probe: Fix offline module name missmatch issue
On Tuesday 26 April 2016 02:45 PM, Wangnan (F) wrote: On 2016/4/26 16:56, Ravi Bangoria wrote: Thanks Masami for reviewing. Please find my replies to your comment. On Tuesday 26 April 2016 02:54 AM, Masami Hiramatsu wrote: Hi Ravi, On Mon, 25 Apr 2016 16:08:27 +0530 Ravi Bangoriawrote: Perf can add a probe on kernel module which has not been loaded yet. Current implementation finds module name from path. But if filename is different from actual module name then perf fails to register probe while loading module because of mismatch in names. For example, samples/kobject/kobject-example.ko is loaded as kobject_example. Ah! right, good catch! Have some comment below; diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c index 8319fbb..05d0905 100644 --- a/tools/perf/util/probe-event.c +++ b/tools/perf/util/probe-event.c @@ -265,6 +265,65 @@ static bool kprobe_warn_out_range(const char *symbol, unsigned long address) return true; } +/* + * NOTE: + * '.gnu.linkonce.this_module' section of kernel module elf directly + * maps to 'struct module' from linux/module.h. This section contains + * actual module name which will be used by kernel after loading it. + * But, we cannot use 'struct module' here since linux/module.h is not + * exposed to user-space. Offset of 'name' has remained same from long + * time, so hardcoding it here. + */ +#ifdef __LP64__ +#define MOD_NAME_OFFSET 24 +#else +#define MOD_NAME_OFFSET 12 +#endif + +/* + * @module can be module name of module file path. In case of path, + * inspect elf and find out what is actual module name. + * Caller has to free mod_name after using it. + */ +char *find_module_name(const char *module) Could you make this function static, since there is no caller outside this file? Yes. no caller outside of this file. But, In this patch, function find_module_name is defined outside of #ifdef HAVE_DWARF_SUPPORT while it's being called from inside of #ifdef HAVE_DWARF_SUPPORT. If I make it static and if there is no dwarf support, there will be compilation error about function defined but not used. And in second patch("perf probe: Fix module probe issue if no dwarf support"), I'm calling it from outside of #ifdef HAVE_DWARF_SUPPORT. So I have two options: 1. merge both the patches and make definition as static 2. make function static in second patch I've chose second approach and sent v2. But please let me know if there is better way to do it. Try __maybe_unused directive? Thanks Wangnan for suggestion, Actually I tried to use __maybe_unused with definition of find_module_name but it throws following compilation error: util/probe-event.c:289:1: error: expected ‘,’ or ‘;’ before ‘{’ token { ^ util/probe-event.c:288:14: error: ‘find_module_name’ declared ‘static’ but never defined [-Werror=unused-function] static char *find_module_name(const char *module) __maybe_unused ^ CC util/zlib.o cc1: all warnings being treated as errors I've to declare prototype of function with __maybe_unused before it's definition to resolve this error. And, anyway this is temporary and need to be removed in patch 2, I think no need to do this change. Regards, Ravi
Re: [RFC] perf probe: Fix offline module name missmatch issue
On Tuesday 26 April 2016 02:45 PM, Wangnan (F) wrote: On 2016/4/26 16:56, Ravi Bangoria wrote: Thanks Masami for reviewing. Please find my replies to your comment. On Tuesday 26 April 2016 02:54 AM, Masami Hiramatsu wrote: Hi Ravi, On Mon, 25 Apr 2016 16:08:27 +0530 Ravi Bangoria wrote: Perf can add a probe on kernel module which has not been loaded yet. Current implementation finds module name from path. But if filename is different from actual module name then perf fails to register probe while loading module because of mismatch in names. For example, samples/kobject/kobject-example.ko is loaded as kobject_example. Ah! right, good catch! Have some comment below; diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c index 8319fbb..05d0905 100644 --- a/tools/perf/util/probe-event.c +++ b/tools/perf/util/probe-event.c @@ -265,6 +265,65 @@ static bool kprobe_warn_out_range(const char *symbol, unsigned long address) return true; } +/* + * NOTE: + * '.gnu.linkonce.this_module' section of kernel module elf directly + * maps to 'struct module' from linux/module.h. This section contains + * actual module name which will be used by kernel after loading it. + * But, we cannot use 'struct module' here since linux/module.h is not + * exposed to user-space. Offset of 'name' has remained same from long + * time, so hardcoding it here. + */ +#ifdef __LP64__ +#define MOD_NAME_OFFSET 24 +#else +#define MOD_NAME_OFFSET 12 +#endif + +/* + * @module can be module name of module file path. In case of path, + * inspect elf and find out what is actual module name. + * Caller has to free mod_name after using it. + */ +char *find_module_name(const char *module) Could you make this function static, since there is no caller outside this file? Yes. no caller outside of this file. But, In this patch, function find_module_name is defined outside of #ifdef HAVE_DWARF_SUPPORT while it's being called from inside of #ifdef HAVE_DWARF_SUPPORT. If I make it static and if there is no dwarf support, there will be compilation error about function defined but not used. And in second patch("perf probe: Fix module probe issue if no dwarf support"), I'm calling it from outside of #ifdef HAVE_DWARF_SUPPORT. So I have two options: 1. merge both the patches and make definition as static 2. make function static in second patch I've chose second approach and sent v2. But please let me know if there is better way to do it. Try __maybe_unused directive? Thanks Wangnan for suggestion, Actually I tried to use __maybe_unused with definition of find_module_name but it throws following compilation error: util/probe-event.c:289:1: error: expected ‘,’ or ‘;’ before ‘{’ token { ^ util/probe-event.c:288:14: error: ‘find_module_name’ declared ‘static’ but never defined [-Werror=unused-function] static char *find_module_name(const char *module) __maybe_unused ^ CC util/zlib.o cc1: all warnings being treated as errors I've to declare prototype of function with __maybe_unused before it's definition to resolve this error. And, anyway this is temporary and need to be removed in patch 2, I think no need to do this change. Regards, Ravi
Re: [RFC] perf probe: Fix offline module name missmatch issue
On 2016/4/26 16:56, Ravi Bangoria wrote: Thanks Masami for reviewing. Please find my replies to your comment. On Tuesday 26 April 2016 02:54 AM, Masami Hiramatsu wrote: Hi Ravi, On Mon, 25 Apr 2016 16:08:27 +0530 Ravi Bangoriawrote: Perf can add a probe on kernel module which has not been loaded yet. Current implementation finds module name from path. But if filename is different from actual module name then perf fails to register probe while loading module because of mismatch in names. For example, samples/kobject/kobject-example.ko is loaded as kobject_example. Ah! right, good catch! Have some comment below; diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c index 8319fbb..05d0905 100644 --- a/tools/perf/util/probe-event.c +++ b/tools/perf/util/probe-event.c @@ -265,6 +265,65 @@ static bool kprobe_warn_out_range(const char *symbol, unsigned long address) return true; } +/* + * NOTE: + * '.gnu.linkonce.this_module' section of kernel module elf directly + * maps to 'struct module' from linux/module.h. This section contains + * actual module name which will be used by kernel after loading it. + * But, we cannot use 'struct module' here since linux/module.h is not + * exposed to user-space. Offset of 'name' has remained same from long + * time, so hardcoding it here. + */ +#ifdef __LP64__ +#define MOD_NAME_OFFSET 24 +#else +#define MOD_NAME_OFFSET 12 +#endif + +/* + * @module can be module name of module file path. In case of path, + * inspect elf and find out what is actual module name. + * Caller has to free mod_name after using it. + */ +char *find_module_name(const char *module) Could you make this function static, since there is no caller outside this file? Yes. no caller outside of this file. But, In this patch, function find_module_name is defined outside of #ifdef HAVE_DWARF_SUPPORT while it's being called from inside of #ifdef HAVE_DWARF_SUPPORT. If I make it static and if there is no dwarf support, there will be compilation error about function defined but not used. And in second patch("perf probe: Fix module probe issue if no dwarf support"), I'm calling it from outside of #ifdef HAVE_DWARF_SUPPORT. So I have two options: 1. merge both the patches and make definition as static 2. make function static in second patch I've chose second approach and sent v2. But please let me know if there is better way to do it. Try __maybe_unused directive? Thank you.
Re: [RFC] perf probe: Fix offline module name missmatch issue
On 2016/4/26 16:56, Ravi Bangoria wrote: Thanks Masami for reviewing. Please find my replies to your comment. On Tuesday 26 April 2016 02:54 AM, Masami Hiramatsu wrote: Hi Ravi, On Mon, 25 Apr 2016 16:08:27 +0530 Ravi Bangoria wrote: Perf can add a probe on kernel module which has not been loaded yet. Current implementation finds module name from path. But if filename is different from actual module name then perf fails to register probe while loading module because of mismatch in names. For example, samples/kobject/kobject-example.ko is loaded as kobject_example. Ah! right, good catch! Have some comment below; diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c index 8319fbb..05d0905 100644 --- a/tools/perf/util/probe-event.c +++ b/tools/perf/util/probe-event.c @@ -265,6 +265,65 @@ static bool kprobe_warn_out_range(const char *symbol, unsigned long address) return true; } +/* + * NOTE: + * '.gnu.linkonce.this_module' section of kernel module elf directly + * maps to 'struct module' from linux/module.h. This section contains + * actual module name which will be used by kernel after loading it. + * But, we cannot use 'struct module' here since linux/module.h is not + * exposed to user-space. Offset of 'name' has remained same from long + * time, so hardcoding it here. + */ +#ifdef __LP64__ +#define MOD_NAME_OFFSET 24 +#else +#define MOD_NAME_OFFSET 12 +#endif + +/* + * @module can be module name of module file path. In case of path, + * inspect elf and find out what is actual module name. + * Caller has to free mod_name after using it. + */ +char *find_module_name(const char *module) Could you make this function static, since there is no caller outside this file? Yes. no caller outside of this file. But, In this patch, function find_module_name is defined outside of #ifdef HAVE_DWARF_SUPPORT while it's being called from inside of #ifdef HAVE_DWARF_SUPPORT. If I make it static and if there is no dwarf support, there will be compilation error about function defined but not used. And in second patch("perf probe: Fix module probe issue if no dwarf support"), I'm calling it from outside of #ifdef HAVE_DWARF_SUPPORT. So I have two options: 1. merge both the patches and make definition as static 2. make function static in second patch I've chose second approach and sent v2. But please let me know if there is better way to do it. Try __maybe_unused directive? Thank you.
Re: [RFC] perf probe: Fix offline module name missmatch issue
Thanks Masami, On Tuesday 26 April 2016 07:49 AM, Masami Hiramatsu wrote: On Tue, 26 Apr 2016 06:24:38 +0900 Masami Hiramatsuwrote: +/* + * NOTE: + * '.gnu.linkonce.this_module' section of kernel module elf directly + * maps to 'struct module' from linux/module.h. This section contains + * actual module name which will be used by kernel after loading it. + * But, we cannot use 'struct module' here since linux/module.h is not + * exposed to user-space. Offset of 'name' has remained same from long + * time, so hardcoding it here. + */ BTW, is there no way to get the module name avoiding to access this "hidden" data structure? This looks very tricky way... So this is the same approach kernel use to find module name when module is loaded. Please refer this function for more detail: kernel/module.c :: static struct module *setup_load_info(...) Regards, Ravi
Re: [RFC] perf probe: Fix offline module name missmatch issue
Thanks Masami, On Tuesday 26 April 2016 07:49 AM, Masami Hiramatsu wrote: On Tue, 26 Apr 2016 06:24:38 +0900 Masami Hiramatsu wrote: +/* + * NOTE: + * '.gnu.linkonce.this_module' section of kernel module elf directly + * maps to 'struct module' from linux/module.h. This section contains + * actual module name which will be used by kernel after loading it. + * But, we cannot use 'struct module' here since linux/module.h is not + * exposed to user-space. Offset of 'name' has remained same from long + * time, so hardcoding it here. + */ BTW, is there no way to get the module name avoiding to access this "hidden" data structure? This looks very tricky way... So this is the same approach kernel use to find module name when module is loaded. Please refer this function for more detail: kernel/module.c :: static struct module *setup_load_info(...) Regards, Ravi
Re: [RFC] perf probe: Fix offline module name missmatch issue
Thanks Masami for reviewing. Please find my replies to your comment. On Tuesday 26 April 2016 02:54 AM, Masami Hiramatsu wrote: Hi Ravi, On Mon, 25 Apr 2016 16:08:27 +0530 Ravi Bangoriawrote: Perf can add a probe on kernel module which has not been loaded yet. Current implementation finds module name from path. But if filename is different from actual module name then perf fails to register probe while loading module because of mismatch in names. For example, samples/kobject/kobject-example.ko is loaded as kobject_example. Ah! right, good catch! Have some comment below; diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c index 8319fbb..05d0905 100644 --- a/tools/perf/util/probe-event.c +++ b/tools/perf/util/probe-event.c @@ -265,6 +265,65 @@ static bool kprobe_warn_out_range(const char *symbol, unsigned long address) return true; } +/* + * NOTE: + * '.gnu.linkonce.this_module' section of kernel module elf directly + * maps to 'struct module' from linux/module.h. This section contains + * actual module name which will be used by kernel after loading it. + * But, we cannot use 'struct module' here since linux/module.h is not + * exposed to user-space. Offset of 'name' has remained same from long + * time, so hardcoding it here. + */ +#ifdef __LP64__ +#define MOD_NAME_OFFSET 24 +#else +#define MOD_NAME_OFFSET 12 +#endif + +/* + * @module can be module name of module file path. In case of path, + * inspect elf and find out what is actual module name. + * Caller has to free mod_name after using it. + */ +char *find_module_name(const char *module) Could you make this function static, since there is no caller outside this file? Yes. no caller outside of this file. But, In this patch, function find_module_name is defined outside of #ifdef HAVE_DWARF_SUPPORT while it's being called from inside of #ifdef HAVE_DWARF_SUPPORT. If I make it static and if there is no dwarf support, there will be compilation error about function defined but not used. And in second patch("perf probe: Fix module probe issue if no dwarf support"), I'm calling it from outside of #ifdef HAVE_DWARF_SUPPORT. So I have two options: 1. merge both the patches and make definition as static 2. make function static in second patch I've chose second approach and sent v2. But please let me know if there is better way to do it. Regards, Ravi
Re: [RFC] perf probe: Fix offline module name missmatch issue
Thanks Masami for reviewing. Please find my replies to your comment. On Tuesday 26 April 2016 02:54 AM, Masami Hiramatsu wrote: Hi Ravi, On Mon, 25 Apr 2016 16:08:27 +0530 Ravi Bangoria wrote: Perf can add a probe on kernel module which has not been loaded yet. Current implementation finds module name from path. But if filename is different from actual module name then perf fails to register probe while loading module because of mismatch in names. For example, samples/kobject/kobject-example.ko is loaded as kobject_example. Ah! right, good catch! Have some comment below; diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c index 8319fbb..05d0905 100644 --- a/tools/perf/util/probe-event.c +++ b/tools/perf/util/probe-event.c @@ -265,6 +265,65 @@ static bool kprobe_warn_out_range(const char *symbol, unsigned long address) return true; } +/* + * NOTE: + * '.gnu.linkonce.this_module' section of kernel module elf directly + * maps to 'struct module' from linux/module.h. This section contains + * actual module name which will be used by kernel after loading it. + * But, we cannot use 'struct module' here since linux/module.h is not + * exposed to user-space. Offset of 'name' has remained same from long + * time, so hardcoding it here. + */ +#ifdef __LP64__ +#define MOD_NAME_OFFSET 24 +#else +#define MOD_NAME_OFFSET 12 +#endif + +/* + * @module can be module name of module file path. In case of path, + * inspect elf and find out what is actual module name. + * Caller has to free mod_name after using it. + */ +char *find_module_name(const char *module) Could you make this function static, since there is no caller outside this file? Yes. no caller outside of this file. But, In this patch, function find_module_name is defined outside of #ifdef HAVE_DWARF_SUPPORT while it's being called from inside of #ifdef HAVE_DWARF_SUPPORT. If I make it static and if there is no dwarf support, there will be compilation error about function defined but not used. And in second patch("perf probe: Fix module probe issue if no dwarf support"), I'm calling it from outside of #ifdef HAVE_DWARF_SUPPORT. So I have two options: 1. merge both the patches and make definition as static 2. make function static in second patch I've chose second approach and sent v2. But please let me know if there is better way to do it. Regards, Ravi
Re: [RFC] perf probe: Fix offline module name missmatch issue
On Tue, 26 Apr 2016 06:24:38 +0900 Masami Hiramatsuwrote: > > +/* > > + * NOTE: > > + * '.gnu.linkonce.this_module' section of kernel module elf directly > > + * maps to 'struct module' from linux/module.h. This section contains > > + * actual module name which will be used by kernel after loading it. > > + * But, we cannot use 'struct module' here since linux/module.h is not > > + * exposed to user-space. Offset of 'name' has remained same from long > > + * time, so hardcoding it here. > > + */ BTW, is there no way to get the module name avoiding to access this "hidden" data structure? This looks very tricky way... Thanks, -- Masami Hiramatsu
Re: [RFC] perf probe: Fix offline module name missmatch issue
On Tue, 26 Apr 2016 06:24:38 +0900 Masami Hiramatsu wrote: > > +/* > > + * NOTE: > > + * '.gnu.linkonce.this_module' section of kernel module elf directly > > + * maps to 'struct module' from linux/module.h. This section contains > > + * actual module name which will be used by kernel after loading it. > > + * But, we cannot use 'struct module' here since linux/module.h is not > > + * exposed to user-space. Offset of 'name' has remained same from long > > + * time, so hardcoding it here. > > + */ BTW, is there no way to get the module name avoiding to access this "hidden" data structure? This looks very tricky way... Thanks, -- Masami Hiramatsu
Re: [RFC] perf probe: Fix offline module name missmatch issue
Hi Ravi, On Mon, 25 Apr 2016 16:08:27 +0530 Ravi Bangoriawrote: > Perf can add a probe on kernel module which has not been loaded yet. > Current implementation finds module name from path. But if filename > is different from actual module name then perf fails to register > probe while loading module because of mismatch in names. For example, > samples/kobject/kobject-example.ko is loaded as kobject_example. Ah! right, good catch! Have some comment below; > > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c > index 8319fbb..05d0905 100644 > --- a/tools/perf/util/probe-event.c > +++ b/tools/perf/util/probe-event.c > @@ -265,6 +265,65 @@ static bool kprobe_warn_out_range(const char *symbol, > unsigned long address) > return true; > } > > +/* > + * NOTE: > + * '.gnu.linkonce.this_module' section of kernel module elf directly > + * maps to 'struct module' from linux/module.h. This section contains > + * actual module name which will be used by kernel after loading it. > + * But, we cannot use 'struct module' here since linux/module.h is not > + * exposed to user-space. Offset of 'name' has remained same from long > + * time, so hardcoding it here. > + */ > +#ifdef __LP64__ > +#define MOD_NAME_OFFSET 24 > +#else > +#define MOD_NAME_OFFSET 12 > +#endif > + > +/* > + * @module can be module name of module file path. In case of path, > + * inspect elf and find out what is actual module name. > + * Caller has to free mod_name after using it. > + */ > +char *find_module_name(const char *module) Could you make this function static, since there is no caller outside this file? > +{ > + int fd; > + Elf *elf; > + GElf_Ehdr ehdr; > + GElf_Shdr shdr; > + Elf_Data *data; > + Elf_Scn *sec; > + char *mod_name = NULL; > + > + fd = open(module, O_RDONLY); > + if (fd < 0) > + return NULL; > + > + elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); > + if (elf == NULL) > + goto elf_err; > + > + if (gelf_getehdr(elf, ) == NULL) > + goto ret_err; > + > + sec = elf_section_by_name(elf, , , > + ".gnu.linkonce.this_module", NULL); > + if (!sec) > + goto ret_err; > + > + data = elf_getdata(sec, NULL); > + if (!data || !data->d_buf) > + goto ret_err; > + > + mod_name = strdup((char *)data->d_buf + MOD_NAME_OFFSET); > + > +ret_err: > + elf_end(elf); > +elf_err: > + close(fd); > + return mod_name; > +} > + > #ifdef HAVE_DWARF_SUPPORT > > static int kernel_get_module_dso(const char *module, struct dso **pdso) > @@ -583,32 +642,23 @@ static int add_module_to_probe_trace_events(struct > probe_trace_event *tevs, > int ntevs, const char *module) > { > int i, ret = 0; > - char *tmp; > + char *mod_name; > > if (!module) > return 0; > > - tmp = strrchr(module, '/'); > - if (tmp) { > - /* This is a module path -- get the module name */ > - module = strdup(tmp + 1); > - if (!module) > - return -ENOMEM; > - tmp = strchr(module, '.'); > - if (tmp) > - *tmp = '\0'; > - tmp = (char *)module; /* For free() */ > - } > + mod_name = find_module_name(module); > > for (i = 0; i < ntevs; i++) { > - tevs[i].point.module = strdup(module); > + tevs[i].point.module = > + strdup(mod_name ? mod_name : module); > if (!tevs[i].point.module) { > ret = -ENOMEM; > break; > } > } > > - free(tmp); > + free(mod_name); > return ret; > } > > diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h > index e54e7b0..0468fa3 100644 > --- a/tools/perf/util/probe-event.h > +++ b/tools/perf/util/probe-event.h > @@ -166,4 +166,6 @@ int e_snprintf(char *str, size_t size, const char > *format, ...) > int copy_to_probe_trace_arg(struct probe_trace_arg *tvar, > struct perf_probe_arg *pvar); > > +char *find_module_name(const char *module); And remove this. Others looks good to me! Thank you, > + > #endif /*_PROBE_EVENT_H */ > -- > 2.1.4 > -- Masami Hiramatsu
Re: [RFC] perf probe: Fix offline module name missmatch issue
Hi Ravi, On Mon, 25 Apr 2016 16:08:27 +0530 Ravi Bangoria wrote: > Perf can add a probe on kernel module which has not been loaded yet. > Current implementation finds module name from path. But if filename > is different from actual module name then perf fails to register > probe while loading module because of mismatch in names. For example, > samples/kobject/kobject-example.ko is loaded as kobject_example. Ah! right, good catch! Have some comment below; > > diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c > index 8319fbb..05d0905 100644 > --- a/tools/perf/util/probe-event.c > +++ b/tools/perf/util/probe-event.c > @@ -265,6 +265,65 @@ static bool kprobe_warn_out_range(const char *symbol, > unsigned long address) > return true; > } > > +/* > + * NOTE: > + * '.gnu.linkonce.this_module' section of kernel module elf directly > + * maps to 'struct module' from linux/module.h. This section contains > + * actual module name which will be used by kernel after loading it. > + * But, we cannot use 'struct module' here since linux/module.h is not > + * exposed to user-space. Offset of 'name' has remained same from long > + * time, so hardcoding it here. > + */ > +#ifdef __LP64__ > +#define MOD_NAME_OFFSET 24 > +#else > +#define MOD_NAME_OFFSET 12 > +#endif > + > +/* > + * @module can be module name of module file path. In case of path, > + * inspect elf and find out what is actual module name. > + * Caller has to free mod_name after using it. > + */ > +char *find_module_name(const char *module) Could you make this function static, since there is no caller outside this file? > +{ > + int fd; > + Elf *elf; > + GElf_Ehdr ehdr; > + GElf_Shdr shdr; > + Elf_Data *data; > + Elf_Scn *sec; > + char *mod_name = NULL; > + > + fd = open(module, O_RDONLY); > + if (fd < 0) > + return NULL; > + > + elf = elf_begin(fd, PERF_ELF_C_READ_MMAP, NULL); > + if (elf == NULL) > + goto elf_err; > + > + if (gelf_getehdr(elf, ) == NULL) > + goto ret_err; > + > + sec = elf_section_by_name(elf, , , > + ".gnu.linkonce.this_module", NULL); > + if (!sec) > + goto ret_err; > + > + data = elf_getdata(sec, NULL); > + if (!data || !data->d_buf) > + goto ret_err; > + > + mod_name = strdup((char *)data->d_buf + MOD_NAME_OFFSET); > + > +ret_err: > + elf_end(elf); > +elf_err: > + close(fd); > + return mod_name; > +} > + > #ifdef HAVE_DWARF_SUPPORT > > static int kernel_get_module_dso(const char *module, struct dso **pdso) > @@ -583,32 +642,23 @@ static int add_module_to_probe_trace_events(struct > probe_trace_event *tevs, > int ntevs, const char *module) > { > int i, ret = 0; > - char *tmp; > + char *mod_name; > > if (!module) > return 0; > > - tmp = strrchr(module, '/'); > - if (tmp) { > - /* This is a module path -- get the module name */ > - module = strdup(tmp + 1); > - if (!module) > - return -ENOMEM; > - tmp = strchr(module, '.'); > - if (tmp) > - *tmp = '\0'; > - tmp = (char *)module; /* For free() */ > - } > + mod_name = find_module_name(module); > > for (i = 0; i < ntevs; i++) { > - tevs[i].point.module = strdup(module); > + tevs[i].point.module = > + strdup(mod_name ? mod_name : module); > if (!tevs[i].point.module) { > ret = -ENOMEM; > break; > } > } > > - free(tmp); > + free(mod_name); > return ret; > } > > diff --git a/tools/perf/util/probe-event.h b/tools/perf/util/probe-event.h > index e54e7b0..0468fa3 100644 > --- a/tools/perf/util/probe-event.h > +++ b/tools/perf/util/probe-event.h > @@ -166,4 +166,6 @@ int e_snprintf(char *str, size_t size, const char > *format, ...) > int copy_to_probe_trace_arg(struct probe_trace_arg *tvar, > struct perf_probe_arg *pvar); > > +char *find_module_name(const char *module); And remove this. Others looks good to me! Thank you, > + > #endif /*_PROBE_EVENT_H */ > -- > 2.1.4 > -- Masami Hiramatsu