Command 'perf record' and 'perf report' on a system without kernel
debuginfo packages uses /proc/kallsyms and /proc/modules to find
addresses for kernel and module symbols. On x86 this works for root
and non-root users.
On s390, when invoked as non-root user, many of the following warnings
are shown and module symbols are missing:
proc/{kallsyms,modules} inconsistency while looking for
"[sha1_s390]" module!
Command 'perf record' creates a list of module start addresses by
parsing the output of /proc/modules and creates a PERF_RECORD_MMAP
record for the kernel and each module. The following function call
sequence is executed:
machine__create_kernel_maps
machine__create_module
modules__parse
machine__create_module --> for each line in /proc/modules
arch__fix_module_text_start
Function arch__fix_module_text_start() is s390 specific. It opens
file /sys/module/<name>/sections/.text to extract the module's .text
section start address. On s390 the module loader prepends a header
before the first section, whereas on x86 the module's text section
address is identical the the module's load address.
However module section files are root readable only. For non-root the
read operation fails and machine__create_module() returns an error.
Command perf record does not generate any PERF_RECORD_MMAP record
for loaded modules. Later command perf report complains about missing
module maps.
To fix this function arch__fix_module_text_start() always returns
success. For root users there is no change, for non-root users
the module's load address is used as module's text start address
(the prepended header then counts as part of the text section).
This enable non-root users to use module symbols and avoid the
warning when perf report is executed.
Output before:
[tmricht@m83lp54 perf]$ ./perf report -D | fgrep MMAP
0 0x168 [0x50]: PERF_RECORD_MMAP ... x [kernel.kallsyms]_text
Output after:
[tmricht@m83lp54 perf]$ ./perf report -D | fgrep MMAP
0 0x168 [0x50]: PERF_RECORD_MMAP ... x [kernel.kallsyms]_text
0 0x1b8 [0x98]: PERF_RECORD_MMAP ... x /lib/modules/.../autofs4.ko.xz
0 0x250 [0xa8]: PERF_RECORD_MMAP ... x /lib/modules/.../sha_common.ko.xz
0 0x2f8 [0x98]: PERF_RECORD_MMAP ... x /lib/modules/.../des_generic.ko.xz
Signed-off-by: Thomas Richter <[email protected]>
Reviewed-by: Hendrik Brueckner <[email protected]>
---
tools/perf/arch/s390/util/machine.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/tools/perf/arch/s390/util/machine.c b/tools/perf/arch/s390/util/machine.c
index 0b2054007314..a19690a17291 100644
--- a/tools/perf/arch/s390/util/machine.c
+++ b/tools/perf/arch/s390/util/machine.c
@@ -5,16 +5,19 @@
#include "util.h"
#include "machine.h"
#include "api/fs/fs.h"
+#include "debug.h"
int arch__fix_module_text_start(u64 *start, const char *name)
{
+ u64 m_start = *start;
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;
+ if (sysfs__read_ull(path, (unsigned long long *)start) < 0) {
+ pr_debug2("Using module %s start:%#lx\n", path, m_start);
+ *start = m_start;
+ }
return 0;
}
--
2.19.1
Em Wed, May 22, 2019 at 04:46:01PM +0200, Thomas Richter escreveu:
> Command 'perf record' and 'perf report' on a system without kernel
> debuginfo packages uses /proc/kallsyms and /proc/modules to find
> addresses for kernel and module symbols. On x86 this works for root
> and non-root users.
>
> On s390, when invoked as non-root user, many of the following warnings
> are shown and module symbols are missing:
>
> proc/{kallsyms,modules} inconsistency while looking for
> "[sha1_s390]" module!
>
> Command 'perf record' creates a list of module start addresses by
> parsing the output of /proc/modules and creates a PERF_RECORD_MMAP
> record for the kernel and each module. The following function call
> sequence is executed:
>
> machine__create_kernel_maps
> machine__create_module
> modules__parse
> machine__create_module --> for each line in /proc/modules
> arch__fix_module_text_start
>
> Function arch__fix_module_text_start() is s390 specific. It opens
> file /sys/module/<name>/sections/.text to extract the module's .text
> section start address. On s390 the module loader prepends a header
> before the first section, whereas on x86 the module's text section
> address is identical the the module's load address.
>
> However module section files are root readable only. For non-root the
> read operation fails and machine__create_module() returns an error.
> Command perf record does not generate any PERF_RECORD_MMAP record
> for loaded modules. Later command perf report complains about missing
> module maps.
>
> To fix this function arch__fix_module_text_start() always returns
> success. For root users there is no change, for non-root users
> the module's load address is used as module's text start address
> (the prepended header then counts as part of the text section).
Thanks, applied.
- Arnaldo
Commit-ID: 6738028dd57df064b969d8392c943ef3b3ae705d
Gitweb: https://git.kernel.org/tip/6738028dd57df064b969d8392c943ef3b3ae705d
Author: Thomas Richter <[email protected]>
AuthorDate: Wed, 22 May 2019 16:46:01 +0200
Committer: Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Tue, 28 May 2019 09:52:23 -0300
perf record: Fix s390 missing module symbol and warning for non-root users
Command 'perf record' and 'perf report' on a system without kernel
debuginfo packages uses /proc/kallsyms and /proc/modules to find
addresses for kernel and module symbols. On x86 this works for root and
non-root users.
On s390, when invoked as non-root user, many of the following warnings
are shown and module symbols are missing:
proc/{kallsyms,modules} inconsistency while looking for
"[sha1_s390]" module!
Command 'perf record' creates a list of module start addresses by
parsing the output of /proc/modules and creates a PERF_RECORD_MMAP
record for the kernel and each module. The following function call
sequence is executed:
machine__create_kernel_maps
machine__create_module
modules__parse
machine__create_module --> for each line in /proc/modules
arch__fix_module_text_start
Function arch__fix_module_text_start() is s390 specific. It opens
file /sys/module/<name>/sections/.text to extract the module's .text
section start address. On s390 the module loader prepends a header
before the first section, whereas on x86 the module's text section
address is identical the the module's load address.
However module section files are root readable only. For non-root the
read operation fails and machine__create_module() returns an error.
Command perf record does not generate any PERF_RECORD_MMAP record
for loaded modules. Later command perf report complains about missing
module maps.
To fix this function arch__fix_module_text_start() always returns
success. For root users there is no change, for non-root users
the module's load address is used as module's text start address
(the prepended header then counts as part of the text section).
This enable non-root users to use module symbols and avoid the
warning when perf report is executed.
Output before:
[tmricht@m83lp54 perf]$ ./perf report -D | fgrep MMAP
0 0x168 [0x50]: PERF_RECORD_MMAP ... x [kernel.kallsyms]_text
Output after:
[tmricht@m83lp54 perf]$ ./perf report -D | fgrep MMAP
0 0x168 [0x50]: PERF_RECORD_MMAP ... x [kernel.kallsyms]_text
0 0x1b8 [0x98]: PERF_RECORD_MMAP ... x /lib/modules/.../autofs4.ko.xz
0 0x250 [0xa8]: PERF_RECORD_MMAP ... x /lib/modules/.../sha_common.ko.xz
0 0x2f8 [0x98]: PERF_RECORD_MMAP ... x /lib/modules/.../des_generic.ko.xz
Signed-off-by: Thomas Richter <[email protected]>
Reviewed-by: Hendrik Brueckner <[email protected]>
Cc: Heiko Carstens <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>
---
tools/perf/arch/s390/util/machine.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/tools/perf/arch/s390/util/machine.c b/tools/perf/arch/s390/util/machine.c
index 0b2054007314..a19690a17291 100644
--- a/tools/perf/arch/s390/util/machine.c
+++ b/tools/perf/arch/s390/util/machine.c
@@ -5,16 +5,19 @@
#include "util.h"
#include "machine.h"
#include "api/fs/fs.h"
+#include "debug.h"
int arch__fix_module_text_start(u64 *start, const char *name)
{
+ u64 m_start = *start;
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;
+ if (sysfs__read_ull(path, (unsigned long long *)start) < 0) {
+ pr_debug2("Using module %s start:%#lx\n", path, m_start);
+ *start = m_start;
+ }
return 0;
}