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authorThomas Richter <tmricht@linux.ibm.com>2019-05-22 16:46:01 +0200
committerPaul Gortmaker <paul.gortmaker@windriver.com>2019-09-16 12:21:40 -0400
commit33557df8bcea567422f412a105e82dcb09e57e63 (patch)
tree9514492fa21e58d2d171997d9934137bd990fae5
parenta76b628c9f0e5c63e611aa7636b7fbf82e8af61b (diff)
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perf record: Fix s390 missing module symbol and warning for non-root users
commit 6738028dd57df064b969d8392c943ef3b3ae705d upstream. 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> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
-rw-r--r--tools/perf/arch/s390/util/machine.c9
1 files 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;
}