When using 'perf mem' and 'perf c2c', an issue is observed that tool
reports the wrong offset for global data symbols. This is a common
issue on both x86 and Arm64 platforms.
Let's see an example, for a test program, below is the disassembly for
its .bss section which is dumped with objdump:
...
Disassembly of section .bss:
0000000000004040 <completed.0>:
...
0000000000004080 <buf1>:
...
00000000000040c0 <buf2>:
...
0000000000004100 <thread>:
...
First we used 'perf mem record' to run the test program and then used
'perf --debug verbose=4 mem report' to observe what's the symbol info
for 'buf1' and 'buf2' structures.
# ./perf mem record -e ldlat-loads,ldlat-stores -- false_sharing.exe 8
# ./perf --debug verbose=4 mem report
...
dso__load_sym_internal: adjusting symbol: st_value: 0x40c0 sh_addr: 0x4040 sh_offset: 0x3028
symbol__new: buf2 0x30a8-0x30e8
...
dso__load_sym_internal: adjusting symbol: st_value: 0x4080 sh_addr: 0x4040 sh_offset: 0x3028
symbol__new: buf1 0x3068-0x30a8
...
The perf tool relies on libelf to parse symbols, in executable and
shared object files, 'st_value' holds a virtual address; 'sh_addr' is
the address at which section's first byte should reside in memory, and
'sh_offset' is the byte offset from the beginning of the file to the
first byte in the section. The perf tool uses below formula to convert
a symbol's memory address to a file address:
file_address = st_value - sh_addr + sh_offset
^
` Memory address
We can see the final adjusted address ranges for buf1 and buf2 are
[0x30a8-0x30e8) and [0x3068-0x30a8) respectively, apparently this is
incorrect, in the code, the structure for 'buf1' and 'buf2' specifies
compiler attribute with 64-byte alignment.
The problem happens for 'sh_offset', libelf returns it as 0x3028 which
is not 64-byte aligned, combining with disassembly, it's likely libelf
doesn't respect the alignment for .bss section, therefore, it doesn't
return the aligned value for 'sh_offset'.
Suggested by Fangrui Song, ELF file contains program header which
contains PT_LOAD segments, the fields p_vaddr and p_offset in PT_LOAD
segments contain the execution info. A better choice for converting
memory address to file address is using the formula:
file_address = st_value - p_vaddr + p_offset
This patch introduces elf_read_program_header() which returns the
program header based on the passed 'st_value', then it uses the formula
above to calculate the symbol file address; and the debugging log is
updated respectively.
After applying the change:
# ./perf --debug verbose=4 mem report
...
dso__load_sym_internal: adjusting symbol: st_value: 0x40c0 p_vaddr: 0x3d28 p_offset: 0x2d28
symbol__new: buf2 0x30c0-0x3100
...
dso__load_sym_internal: adjusting symbol: st_value: 0x4080 p_vaddr: 0x3d28 p_offset: 0x2d28
symbol__new: buf1 0x3080-0x30c0
...
Fixes: f17e04afaf ("perf report: Fix ELF symbol parsing")
Reported-by: Chang Rui <changruinj@gmail.com>
Suggested-by: Fangrui Song <maskray@google.com>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220724060013.171050-2-leo.yan@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
On powerpc, 'perf trace' is crashing with a SIGSEGV when trying to
process a perf.data file created with 'perf trace record -p':
#0 0x00000001225b8988 in syscall_arg__scnprintf_augmented_string <snip> at builtin-trace.c:1492
#1 syscall_arg__scnprintf_filename <snip> at builtin-trace.c:1492
#2 syscall_arg__scnprintf_filename <snip> at builtin-trace.c:1486
#3 0x00000001225bdd9c in syscall_arg_fmt__scnprintf_val <snip> at builtin-trace.c:1973
#4 syscall__scnprintf_args <snip> at builtin-trace.c:2041
#5 0x00000001225bff04 in trace__sys_enter <snip> at builtin-trace.c:2319
That points to the below code in tools/perf/builtin-trace.c:
/*
* If this is raw_syscalls.sys_enter, then it always comes with the 6 possible
* arguments, even if the syscall being handled, say "openat", uses only 4 arguments
* this breaks syscall__augmented_args() check for augmented args, as we calculate
* syscall->args_size using each syscalls:sys_enter_NAME tracefs format file,
* so when handling, say the openat syscall, we end up getting 6 args for the
* raw_syscalls:sys_enter event, when we expected just 4, we end up mistakenly
* thinking that the extra 2 u64 args are the augmented filename, so just check
* here and avoid using augmented syscalls when the evsel is the raw_syscalls one.
*/
if (evsel != trace->syscalls.events.sys_enter)
augmented_args = syscall__augmented_args(sc, sample, &augmented_args_size, trace->raw_augmented_syscalls_args_size);
As the comment points out, we should not be trying to augment the args
for raw_syscalls. However, when processing a perf.data file, we are not
initializing those properly. Fix the same.
Reported-by: Claudio Carvalho <cclaudio@linux.ibm.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lore.kernel.org/lkml/20220707090900.572584-1-naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Commit dc2cf4ca86 ("perf unwind: Fix segbase for ld.lld linked
objects") uncovered the following issue on aarch64:
util/unwind-libunwind-local.c: In function 'find_proc_info':
util/unwind-libunwind-local.c:386:28: error: 'offset' may be used uninitialized in this function [-Werror=maybe-uninitialized]
386 | if (ofs > 0) {
| ^
util/unwind-libunwind-local.c:199:22: note: 'offset' was declared here
199 | u64 address, offset;
| ^~~~~~
util/unwind-libunwind-local.c:371:20: error: 'offset' may be used uninitialized in this function [-Werror=maybe-uninitialized]
371 | if (ofs <= 0) {
| ^
util/unwind-libunwind-local.c:199:22: note: 'offset' was declared here
199 | u64 address, offset;
| ^~~~~~
util/unwind-libunwind-local.c:363:20: error: 'offset' may be used uninitialized in this function [-Werror=maybe-uninitialized]
363 | if (ofs <= 0) {
| ^
util/unwind-libunwind-local.c:199:22: note: 'offset' was declared here
199 | u64 address, offset;
| ^~~~~~
In file included from util/libunwind/arm64.c:37:
Fixes: dc2cf4ca86 ("perf unwind: Fix segbase for ld.lld linked objects")
Signed-off-by: Ivan Babrou <ivan@cloudflare.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Fangrui Song <maskray@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: kernel-team@cloudflare.com
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20220701182046.12589-1-ivan@cloudflare.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
perf already support ignore_missing_thread for -p, but not yet
applied to `perf stat -p <pid>`. This patch enables ignore_missing_thread
for `perf stat -p <pid>`.
Committer notes:
And here is a refresher about the 'ignore_missing_thread' knob, from a
previous patch using it:
ca8000684e ("perf evsel: Enable ignore_missing_thread for pid option")
---
While monitoring a multithread process with pid option, perf sometimes
may return sys_perf_event_open failure with 3(No such process) if any of
the process's threads die before we open the event. However, we want
perf continue monitoring the remaining threads and do not exit with
error.
---
Signed-off-by: Gang Li <ligang.bdlg@bytedance.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220622030037.15005-1-ligang.bdlg@bytedance.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
For some reason using:
cat <<EoFuncBegin
static const char *errno_to_name__$arch(int err)
{
switch (err) {
EoFuncBegin
In tools/perf/trace/beauty/arch_errno_names.sh isn't working on ALT
Linux sisyphus (development version), which could be some distro
specific glitch, so just get this done in an alternative way that works
everywhere while giving notice to the people working on that distro to
try and figure our what really took place.
Cc: Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Build ID events associate a file name with a build ID. However, when
using perf inject, there is no guarantee that the file on the current
machine at the current time has that build ID. Fix by comparing the
build IDs and skip adding to the cache if they are different.
Example:
$ echo "int main() {return 0;}" > prog.c
$ gcc -o prog prog.c
$ perf record --buildid-all ./prog
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.019 MB perf.data ]
$ file-buildid() { file $1 | awk -F= '{print $2}' | awk -F, '{print $1}' ; }
$ file-buildid prog
444ad9be165d8058a48ce2ffb4e9f55854a3293e
$ file-buildid ~/.debug/$(pwd)/prog/444ad9be165d8058a48ce2ffb4e9f55854a3293e/elf
444ad9be165d8058a48ce2ffb4e9f55854a3293e
$ echo "int main() {return 1;}" > prog.c
$ gcc -o prog prog.c
$ file-buildid prog
885524d5aaa24008a3e2b06caa3ea95d013c0fc5
Before:
$ perf buildid-cache --purge $(pwd)/prog
$ perf inject -i perf.data -o junk
$ file-buildid ~/.debug/$(pwd)/prog/444ad9be165d8058a48ce2ffb4e9f55854a3293e/elf
885524d5aaa24008a3e2b06caa3ea95d013c0fc5
$
After:
$ perf buildid-cache --purge $(pwd)/prog
$ perf inject -i perf.data -o junk
$ file-buildid ~/.debug/$(pwd)/prog/444ad9be165d8058a48ce2ffb4e9f55854a3293e/elf
$
Fixes: 454c407ec1 ("perf: add perf-inject builtin")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Link: https://lore.kernel.org/r/20220621125144.5623-1-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The testcase 'Check Arm64 callgraphs are complete in fp mode' wants to
see the following output:
610 leaf
62f parent
648 main
However, without excluding kernel callchains, the output might look like:
ffffc2ff40ef1b5c arch_local_irq_enable
ffffc2ff419d032c __schedule
ffffc2ff419d06c0 schedule
ffffc2ff40e4da30 do_notify_resume
ffffc2ff40e421b0 work_pending
610 leaf
62f parent
648 main
Adding '--user-callchains' leaves only the wanted symbols in the chain.
Fixes: cd6382d827 ("perf test arm64: Test unwinding using fame-pointer (fp) mode")
Suggested-by: German Gomez <german.gomez@arm.com>
Reviewed-by: German Gomez <german.gomez@arm.com>
Reviewed-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Michael Petlan <mpetlan@redhat.com>
Cc: German Gomez <german.gomez@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/r/20220614105207.26223-1-mpetlan@redhat.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
To pick the changes in:
f94fd25cb0 ("tcp: pass back data left in socket after receive")
That don't result in any changes in the tables generated from that
header.
This silences this perf build warning:
Warning: Kernel ABI header at 'tools/perf/trace/beauty/include/linux/socket.h' differs from latest version at 'include/linux/socket.h'
diff -u tools/perf/trace/beauty/include/linux/socket.h include/linux/socket.h
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/all/YqORj9d58AiGYl8b@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Ian Rogers
Leo Yan
Naveen N. Rao
Adrian Hunter
Namhyung Kim
Ivan Babrou
Gang Li
Raul Silvera
Arnaldo Carvalho de Melo
Athira Rajeev
Michael Petlan