Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-12-28 05:41:55 +00:00
Code Issues Packages Projects Releases Wiki Activity

perf probe: Fix to get correct modname from elf header

Browse Source 
Since 'perf probe' supports cross-arch probes, it is possible to analyze
different arch kernel image which has different bits-per-long.

In that case, it fails to get the module name because it uses the
MOD_NAME_OFFSET macro based on the host machine bits-per-long, instead
of the target arch bits-per-long.

This fixes above issue by changing modname-offset based on the target
archs bit width. This is ok because linux kernel uses LP64 model on
64bit arch.

E.g. without this (on x86_64, and target module is arm32):

  $ perf probe -m build-arm/fs/configfs/configfs.ko -D configfs_lookup
  p:probe/configfs_lookup :configfs_lookup+0
                          ^-Here is an empty module name.

With this fix, you can see correct module name:

  $ perf probe -m build-arm/fs/configfs/configfs.ko -D configfs_lookup
  p:probe/configfs_lookup configfs:configfs_lookup+0

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/148337043836.6752.383495516397005695.stgit@devbox
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Masami Hiramatsu 2017-01-03 00:20:49 +09:00 committed by Arnaldo Carvalho de Melo
parent b6f4c66704
commit 1f2ed153b9
1 changed files with 16 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

32
tools/perf/util/probe-event.c
View File

@ -267,21 +267,6 @@ 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.
@ -296,6 +281,7 @@ static char *find_module_name(const char *module)
Elf_Data *data;
Elf_Scn *sec;
char *mod_name = NULL;
int name_offset;
fd = open(module, O_RDONLY);
if (fd < 0)
@ -317,7 +303,21 @@ static char *find_module_name(const char *module)
if (!data || !data->d_buf)
goto ret_err;
mod_name = strdup((char *)data->d_buf + MOD_NAME_OFFSET);
/*
* 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.
*/
if (ehdr.e_ident[EI_CLASS] == ELFCLASS32)
name_offset = 12;
else /* expect ELFCLASS64 by default */
name_offset = 24;
mod_name = strdup((char *)data->d_buf + name_offset);
ret_err:
elf_end(elf);