443bc639e5
For branch mode, if the symbol is not found, it prints
the address.
For example, 0x0000555eee0365a0 in below output.
Overhead Command Source Shared Object Source Symbol Target Symbol
17.55% div libc-2.27.so [.] __random [.] __random
6.11% div div [.] 0x0000555eee0365a0 [.] rand
6.10% div libc-2.27.so [.] rand [.] 0x0000555eee036769
5.80% div libc-2.27.so [.] __random_r [.] __random
5.72% div libc-2.27.so [.] __random [.] __random_r
5.62% div libc-2.27.so [.] __random_r [.] __random_r
5.38% div libc-2.27.so [.] __random [.] rand
4.56% div libc-2.27.so [.] __random [.] __random
4.49% div div [.] 0x0000555eee036779 [.] 0x0000555eee0365ff
4.25% div div [.] 0x0000555eee0365fa [.] 0x0000555eee036760
But it's not very easy to understand what the instructions
are in the binary. So this patch uses the al_addr instead.
With this patch, the output is
Overhead Command Source Shared Object Source Symbol Target Symbol
17.55% div libc-2.27.so [.] __random [.] __random
6.11% div div [.] 0x00000000000005a0 [.] rand
6.10% div libc-2.27.so [.] rand [.] 0x0000000000000769
5.80% div libc-2.27.so [.] __random_r [.] __random
5.72% div libc-2.27.so [.] __random [.] __random_r
5.62% div libc-2.27.so [.] __random_r [.] __random_r
5.38% div libc-2.27.so [.] __random [.] rand
4.56% div libc-2.27.so [.] __random [.] __random
4.49% div div [.] 0x0000000000000779 [.] 0x00000000000005ff
4.25% div div [.] 0x00000000000005fa [.] 0x0000000000000760
Now we can use objdump to dump the object starting from 0x5a0.
For example,
objdump -d --start-address 0x5a0 div
00000000000005a0 <rand@plt>:
5a0: ff 25 2a 0a 20 00 jmpq *0x200a2a(%rip) # 200fd0 <__cxa_finalize@plt+0x200a20>
5a6: 68 02 00 00 00 pushq $0x2
5ab: e9 c0 ff ff ff jmpq 570 <srand@plt-0x10>
...
Committer testing:
[root@seventh ~]# perf record -a -b sleep 1
[root@seventh ~]# perf report --header-only | grep cpudesc
# cpudesc : Intel(R) Core(TM) i5-7500 CPU @ 3.40GHz
[root@seventh ~]# perf evlist -v
cycles: size: 120, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|CPU|PERIOD|BRANCH_STACK, read_format: ID, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, task: 1, precise_ip: 3, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1, branch_sample_type: ANY
[root@seventh ~]#
Before:
[root@seventh ~]# perf report --stdio --dso libsystemd-shared-241.so | head -20
# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 0
#
# Samples: 2K of event 'cycles'
# Event count (approx.): 2240
#
# Overhead Command Source Shared Object Source Symbol Target Symbol Basic Block Cycles
# ........ ............... ........................ ...................... ...................... ..................
#
0.13% systemd-journal libc-2.29.so [.] cfree@GLIBC_2.2.5 [.] _int_free 1
0.09% systemd libsystemd-shared-241.so [.] 0x00007fe406465c82 [.] 0x00007fe406465d80 1
0.09% systemd libsystemd-shared-241.so [.] 0x00007fe406465ded [.] 0x00007fe406465c30 1
0.09% systemd libsystemd-shared-241.so [.] 0x00007fe406465e4e [.] 0x00007fe406465de0 1
0.09% systemd-journal systemd-journald [.] free@plt [.] cfree@GLIBC_2.2.5 1
0.09% systemd-journal libc-2.29.so [.] _int_free [.] _int_free 18
0.09% systemd-journal libc-2.29.so [.] _int_free [.] _int_free 2
0.04% systemd libsystemd-shared-241.so [.] bus_resolve@plt [.] bus_resolve 204
0.04% systemd libsystemd-shared-241.so [.] getpid_cached@plt [.] getpid_cached 7
[root@seventh ~]#
After:
[root@seventh ~]# perf report --stdio --dso libsystemd-shared-241.so | head -20
# To display the perf.data header info, please use --header/--header-only options.
#
#
# Total Lost Samples: 0
#
# Samples: 2K of event 'cycles'
# Event count (approx.): 2240
#
# Overhead Command Source Shared Object Source Symbol Target Symbol Basic Block Cycles
# ........ ............... ........................ ...................... ...................... ..................
#
0.13% systemd-journal libc-2.29.so [.] cfree@GLIBC_2.2.5 [.] _int_free 1
0.09% systemd libsystemd-shared-241.so [.] 0x00000000000f7c82 [.] 0x00000000000f7d80 1
0.09% systemd libsystemd-shared-241.so [.] 0x00000000000f7ded [.] 0x00000000000f7c30 1
0.09% systemd libsystemd-shared-241.so [.] 0x00000000000f7e4e [.] 0x00000000000f7de0 1
0.09% systemd-journal systemd-journald [.] free@plt [.] cfree@GLIBC_2.2.5 1
0.09% systemd-journal libc-2.29.so [.] _int_free [.] _int_free 18
0.09% systemd-journal libc-2.29.so [.] _int_free [.] _int_free 2
0.04% systemd libsystemd-shared-241.so [.] bus_resolve@plt [.] bus_resolve 204
0.04% systemd libsystemd-shared-241.so [.] getpid_cached@plt [.] getpid_cached 7
[root@seventh ~]#
Lets use -v to get full paths and then try objdump on the unresolved address:
[root@seventh ~]# perf report -v --stdio --dso libsystemd-shared-241.so |& grep libsystemd-shared-241.so | tail -1
0.04% systemd-journal /usr/lib/systemd/libsystemd-shared-241.so 0x80c1a B [.] 0x0000000000080c1a 0x80a95 B [.] 0x0000000000080a95 61
[root@seventh ~]#
[root@seventh ~]# objdump -d --start-address 0x00000000000f7d80 /usr/lib/systemd/libsystemd-shared-241.so | head -20
/usr/lib/systemd/libsystemd-shared-241.so: file format elf64-x86-64
Disassembly of section .text:
00000000000f7d80 <proc_cmdline_parse_given@@SD_SHARED+0x330>:
f7d80: 41 39 11 cmp %edx,(%r9)
f7d83: 0f 84 ff fe ff ff je f7c88 <proc_cmdline_parse_given@@SD_SHARED+0x238>
f7d89: 4c 8d 05 97 09 0c 00 lea 0xc0997(%rip),%r8 # 1b8727 <utf8_skip_data@@SD_SHARED+0x3147>
f7d90: b9 49 00 00 00 mov $0x49,%ecx
f7d95: 48 8d 15 c9 f5 0b 00 lea 0xbf5c9(%rip),%rdx # 1b7365 <utf8_skip_data@@SD_SHARED+0x1d85>
f7d9c: 31 ff xor %edi,%edi
f7d9e: 48 8d 35 9b ff 0b 00 lea 0xbff9b(%rip),%rsi # 1b7d40 <utf8_skip_data@@SD_SHARED+0x2760>
f7da5: e8 a6 d6 f4 ff callq 45450 <log_assert_failed_realm@plt>
f7daa: 66 0f 1f 44 00 00 nopw 0x0(%rax,%rax,1)
f7db0: 41 56 push %r14
f7db2: 41 55 push %r13
f7db4: 41 54 push %r12
f7db6: 55 push %rbp
[root@seventh ~]#
If we tried the the reported address before this patch:
[root@seventh ~]# objdump -d --start-address 0x00007fe406465d80 /usr/lib/systemd/libsystemd-shared-241.so | head -20
/usr/lib/systemd/libsystemd-shared-241.so: file format elf64-x86-64
[root@seventh ~]#
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200227043939.4403-2-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.