4.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
[ Upstream commit 1f2ed153b916c95a49a1ca9d7107738664224b7f ]
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@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/148337043836.6752.383495516397005695.stgit@devbox
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
tools/perf/util/probe-event.c | 32 ++++++++++++++++----------------
1 file changed, 16 insertions(+), 16 deletions(-)
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -268,21 +268,6 @@ static bool kprobe_warn_out_range(const
}
/*
- * 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.
@@ -296,6 +281,7 @@ static char *find_module_name(const char
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
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);