From: tip-bot for Thomas Richter <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: tglx@linutronix.de, mingo@kernel.org, brueckner@linux.ibm.com,
tmricht@linux.ibm.com, linux-kernel@vger.kernel.org,
heiko.carstens@de.ibm.com, acme@redhat.com, hpa@zytor.com
Subject: [tip:perf/urgent] perf record: Fix s390 missing module symbol and warning for non-root users
Date: Tue, 28 May 2019 14:30:25 -0700 [thread overview]
Message-ID: <tip-6738028dd57df064b969d8392c943ef3b3ae705d@git.kernel.org> (raw)
In-Reply-To: <20190522144601.50763-4-tmricht@linux.ibm.com>
Commit-ID: 6738028dd57df064b969d8392c943ef3b3ae705d
Gitweb: https://git.kernel.org/tip/6738028dd57df064b969d8392c943ef3b3ae705d
Author: Thomas Richter <tmricht@linux.ibm.com>
AuthorDate: Wed, 22 May 2019 16:46:01 +0200
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
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 <tmricht@linux.ibm.com>
Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Link: http://lkml.kernel.org/r/20190522144601.50763-4-tmricht@linux.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
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;
}
prev parent reply other threads:[~2019-05-28 21:30 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-22 14:45 [PATCH 0/3] Fix OOM in perf report on s390 Thomas Richter
2019-05-22 14:45 ` [PATCH 1/3] perf report: Fix OOM error in TUI mode " Thomas Richter
2019-05-22 18:08 ` Arnaldo Carvalho de Melo
2019-05-23 8:12 ` Thomas-Mich Richter
2019-05-22 14:46 ` [PATCH 2/3] perf record: Fix kallsym map size for s390 Thomas Richter
2019-05-22 14:46 ` [PATCH 3/3] perf record: Fix s390 missing module symbol and warning for non-root users Thomas Richter
2019-05-22 18:03 ` Arnaldo Carvalho de Melo
2019-05-28 21:30 ` tip-bot for Thomas Richter [this message]
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