linux/tools/perf
Ravi Bangoria 99e608b595 perf probe ppc64le: Fix probe location when using DWARF
Powerpc has Global Entry Point and Local Entry Point for functions.  LEP
catches call from both the GEP and the LEP. Symbol table of ELF contains
GEP and Offset from which we can calculate LEP, but debuginfo does not
have LEP info.

Currently, perf prioritize symbol table over dwarf to probe on LEP for
ppc64le. But when user tries to probe with function parameter, we fall
back to using dwarf(i.e. GEP) and when function called via LEP, probe
will never hit.

For example:

  $ objdump -d vmlinux
    ...
    do_sys_open():
    c0000000002eb4a0:       e8 00 4c 3c     addis   r2,r12,232
    c0000000002eb4a4:       60 00 42 38     addi    r2,r2,96
    c0000000002eb4a8:       a6 02 08 7c     mflr    r0
    c0000000002eb4ac:       d0 ff 41 fb     std     r26,-48(r1)

  $ sudo ./perf probe do_sys_open
  $ sudo cat /sys/kernel/debug/tracing/kprobe_events
    p:probe/do_sys_open _text+3060904

  $ sudo ./perf probe 'do_sys_open filename:string'
  $ sudo cat /sys/kernel/debug/tracing/kprobe_events
    p:probe/do_sys_open _text+3060896 filename_string=+0(%gpr4):string

For second case, perf probed on GEP. So when function will be called via
LEP, probe won't hit.

  $ sudo ./perf record -a -e probe:do_sys_open ls
    [ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 0.195 MB perf.data ]

To resolve this issue, let's not prioritize symbol table, let perf
decide what it wants to use. Perf is already converting GEP to LEP when
it uses symbol table. When perf uses debuginfo, let it find LEP offset
form symbol table. This way we fall back to probe on LEP for all cases.

After patch:

  $ sudo ./perf probe 'do_sys_open filename:string'
  $ sudo cat /sys/kernel/debug/tracing/kprobe_events
    p:probe/do_sys_open _text+3060904 filename_string=+0(%gpr4):string

  $ sudo ./perf record -a -e probe:do_sys_open ls
    [ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 0.197 MB perf.data (11 samples) ]

Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/1470723805-5081-2-git-send-email-ravi.bangoria@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2016-08-09 12:14:29 -03:00
..
arch perf probe ppc64le: Fix probe location when using DWARF 2016-08-09 12:14:29 -03:00
bench perf bench: Copy kernel files needed to build mem{cpy,set} x86_64 benchmarks 2016-07-12 15:20:32 -03:00
Documentation perf probe: Support signedness casting 2016-08-09 10:52:22 -03:00
jvmti perf jit: Remove some no-op error handling 2016-07-18 12:20:00 -03:00
python perf python: Add tracepoint example 2016-07-12 16:23:35 -03:00
scripts perf/core improvements and fixes: 2016-08-04 11:02:38 +02:00
tests perf tests bpf: Use SyS_epoll_wait alias 2016-08-03 19:40:48 -03:00
trace perf trace beauty seccomp: Remove seccomp.h include 2016-07-12 15:20:38 -03:00
ui perf annotate: Introduce strerror for handling symbol__disassemble() errors 2016-08-01 18:18:16 -03:00
util perf probe ppc64le: Fix probe location when using DWARF 2016-08-09 12:14:29 -03:00
.gitignore perf tools: Add arch/*/include/generated/ to .gitignore 2016-05-30 12:41:46 -03:00
Build perf tools: Set and pass DOCDIR to builtin-report.c 2016-01-12 12:42:07 -03:00
builtin-annotate.c perf annotate: Introduce --stdio-color to setup the color output mode selection 2016-07-12 00:00:39 -03:00
builtin-bench.c perf subcmd: Create subcmd library 2015-12-17 14:27:14 -03:00
builtin-buildid-cache.c tools: Introduce str_error_r() 2016-07-12 15:19:47 -03:00
builtin-buildid-list.c perf subcmd: Create subcmd library 2015-12-17 14:27:14 -03:00
builtin-config.c perf config: Reimplement show_config() using config_set__for_each 2016-06-23 17:23:00 -03:00
builtin-data.c perf data ctf: Add '--all' option for 'perf data convert' 2016-06-28 10:54:57 -03:00
builtin-diff.c perf evlist: Rename for_each() macros to for_each_entry() 2016-06-23 11:26:15 -03:00
builtin-evlist.c perf evlist: Rename for_each() macros to for_each_entry() 2016-06-23 11:26:15 -03:00
builtin-help.c tools: Introduce str_error_r() 2016-07-12 15:19:47 -03:00
builtin-inject.c perf evlist: Rename for_each() macros to for_each_entry() 2016-06-23 11:26:15 -03:00
builtin-kmem.c mm, thp: remove __GFP_NORETRY from khugepaged and madvised allocations 2016-07-28 16:07:41 -07:00
builtin-kvm.c tools: Introduce str_error_r() 2016-07-12 15:19:47 -03:00
builtin-list.c perf list: Show SDT and pre-cached events 2016-07-13 23:09:07 -03:00
builtin-lock.c perf subcmd: Create subcmd library 2015-12-17 14:27:14 -03:00
builtin-mem.c perf mem: Add --ldlat option 2016-06-15 10:35:27 -03:00
builtin-probe.c perf probe: Make --list show only available cached events 2016-07-13 23:09:05 -03:00
builtin-record.c perf record: Add --sample-cpu option 2016-08-02 16:33:29 -03:00
builtin-report.c perf report: Introduce --stdio-color to setup the color output mode selection 2016-07-12 00:00:39 -03:00
builtin-sched.c tools: Introduce str_error_r() 2016-07-12 15:19:47 -03:00
builtin-script.c perf script: Add 'bpf-output' field to usage message 2016-08-09 10:46:43 -03:00
builtin-stat.c perf stat: Avoid skew when reading events 2016-08-09 10:48:32 -03:00
builtin-timechart.c perf tools: Set buildid dir under symfs when --symfs is provided 2016-05-20 11:43:58 -03:00
builtin-top.c perf annotate: Introduce strerror for handling symbol__disassemble() errors 2016-08-01 18:18:16 -03:00
builtin-trace.c perf trace: Remove unused sys/ptrace.h include 2016-07-12 15:20:35 -03:00
builtin-version.c perf tools: Move cmd_version() to builtin-version.c 2015-12-09 13:42:03 -03:00
builtin.h perf tools: Remove needless 'extern' from function prototypes 2016-03-23 15:06:35 -03:00
command-list.txt perf tools: Do not show trace command if it's not compiled in 2016-01-08 12:46:17 -03:00
CREDITS
design.txt
Makefile perf build tests: Do parallell builds with 'build-test' 2016-02-04 15:57:00 -03:00
Makefile.config perf tools: Move config/Makefile into Makefile.config 2016-08-02 16:33:28 -03:00
Makefile.perf perf tools: Move config/Makefile into Makefile.config 2016-08-02 16:33:28 -03:00
MANIFEST tools: Copy linux/{hash,poison}.h and check for drift 2016-07-18 18:41:50 -03:00
perf-archive.sh
perf-completion.sh perf tools: Avoid confusion with preloaded bash function for perf bash completion 2015-03-19 13:53:27 -03:00
perf-read-vdso.c
perf-sys.h perf tools: Add missing linux/compiler.h include to perf-sys.h 2016-07-18 17:40:49 -03:00
perf-with-kcore.sh perf tools: Fix perf-with-kcore handling of arguments containing spaces 2015-08-06 16:48:27 -03:00
perf.c perf tools: Just pr_debug() about not being able to read cacheline_size 2016-07-15 10:08:29 -03:00
perf.h perf record: Add --sample-cpu option 2016-08-02 16:33:29 -03:00