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Sandipan Das 2a9d5050dc perf script: Show correct offsets for DWARF-based unwinding 
When perf/data is recorded with the dwarf call-graph option, the
callchain shown by 'perf script' still shows the binary offsets of the
userspace symbols instead of their virtual addresses. Since the symbol
offset calculation is based on using virtual address as the ip, we see
incorrect offsets as well.

The use of virtual addresses affects the ability to find out the
line number in the corresponding source file to which an address
maps to as described in commit 6754075915 ("perf unwind: Use
addr_location::addr instead of ip for entries").

This has also been addressed by temporarily converting the virtual
address to the correponding binary offset so that it can be mapped
to the source line number correctly.

This is a follow-up for commit 1961018469 ("perf script: Show
virtual addresses instead of offsets").

This can be verified on a powerpc64le system running Fedora 27 as
shown below:

  # perf probe -x /usr/lib64/libc-2.26.so -a inet_pton
  # perf record -e probe_libc:inet_pton --call-graph=dwarf ping -6 -c 1 ::1

Before:

  # perf report --stdio --no-children -s sym,srcline -g address

  # Samples: 1  of event 'probe_libc:inet_pton'
  # Event count (approx.): 1
  #
  # Overhead  Symbol                Source:Line
  # ........  ....................  ...........
  #
     100.00%  [.] __GI___inet_pton  inet_pton.c
              |
              ---gaih_inet getaddrinfo.c:537 (inlined)
                 __GI_getaddrinfo getaddrinfo.c:2304 (inlined)
                 main ping.c:519
                 generic_start_main libc-start.c:308 (inlined)
                 __libc_start_main libc-start.c:102
  ...

  # perf script -F comm,ip,sym,symoff,srcline,dso

  ping
                    15af28 __GI___inet_pton+0xffff000099160008 (/usr/lib64/libc-2.26.so)
    libc-2.26.so[ffff80004ca0af28]
                    10fa53 gaih_inet+0xffff000099160f43
    libc-2.26.so[ffff80004c9bfa53] (inlined)
                    1105b3 __GI_getaddrinfo+0xffff000099160163
    libc-2.26.so[ffff80004c9c05b3] (inlined)
                      2d6f main+0xfffffffd9f1003df (/usr/bin/ping)
    ping[fffffffecf882d6f]
                     2369f generic_start_main+0xffff00009916013f
    libc-2.26.so[ffff80004c8d369f] (inlined)
                     23897 __libc_start_main+0xffff0000991600b7 (/usr/lib64/libc-2.26.so)
    libc-2.26.so[ffff80004c8d3897]

After:

  # perf report --stdio --no-children -s sym,srcline -g address

  # Samples: 1  of event 'probe_libc:inet_pton'
  # Event count (approx.): 1
  #
  # Overhead  Symbol                Source:Line
  # ........  ....................  ...........
  #
     100.00%  [.] __GI___inet_pton  inet_pton.c
              |
              ---gaih_inet.constprop.7 getaddrinfo.c:537
                 getaddrinfo getaddrinfo.c:2304
                 main ping.c:519
                 generic_start_main.isra.0 libc-start.c:308
                 __libc_start_main libc-start.c:102
  ...

  # perf script -F comm,ip,sym,symoff,srcline,dso

  ping
              7fffb38aaf28 __GI___inet_pton+0x8 (/usr/lib64/libc-2.26.so)
    inet_pton.c:68
              7fffb385fa53 gaih_inet.constprop.7+0xf43 (/usr/lib64/libc-2.26.so)
    getaddrinfo.c:537
              7fffb38605b3 getaddrinfo+0x163 (/usr/lib64/libc-2.26.so)
    getaddrinfo.c:2304
                 130782d6f main+0x3df (/usr/bin/ping)
    ping.c:519
              7fffb377369f generic_start_main.isra.0+0x13f (/usr/lib64/libc-2.26.so)
    libc-start.c:308
              7fffb3773897 __libc_start_main+0xb7 (/usr/lib64/libc-2.26.so)
    libc-start.c:102

Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Fixes: 6754075915 ("perf unwind: Use addr_location::addr instead of ip for entries")
Link: http://lkml.kernel.org/r/20180703120555.32971-1-sandipan@linux.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2018-07-24 14:53:11 -03:00
arch Merge remote-tracking branch 'tip/perf/urgent' into perf/core 2018-07-24 14:34:32 -03:00
block for-linus-20180713 2018-07-14 12:28:00 -07:00
certs certs/blacklist: fix const confusion 2018-06-26 09:43:03 -07:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2018-07-19 07:32:44 -07:00
Documentation Merge remote-tracking branch 'tip/perf/urgent' into perf/core 2018-07-24 14:34:32 -03:00
drivers NVMe fixes for 4.18-rc6: 2018-07-22 13:21:45 -07:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-07-22 12:04:51 -07:00
include Merge remote-tracking branch 'tip/perf/urgent' into perf/core 2018-07-24 14:34:32 -03:00
init Kbuild fixes for v4.18 2018-06-30 13:05:30 -07:00
ipc ipc: use new return type vm_fault_t 2018-06-15 07:55:25 +09:00
kernel Merge remote-tracking branch 'tip/perf/urgent' into perf/core 2018-07-24 14:34:32 -03:00
lib Merge remote-tracking branch 'tip/perf/urgent' into perf/core 2018-07-24 14:34:32 -03:00
LICENSES LICENSES: Add Linux-OpenIB license text 2018-04-27 16:41:53 -06:00
mm mm: make vm_area_alloc() initialize core fields 2018-07-21 15:24:03 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-07-18 19:32:54 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-07-18 19:32:54 -07:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-07-18 19:32:54 -07:00
security selinux/stable-4.18 PR 20180629 2018-06-30 11:15:12 -07:00
sound ALSA: hda/realtek - Yet another Clevo P950 quirk entry 2018-07-18 12:17:46 +02:00
tools perf script: Show correct offsets for DWARF-based unwinding 2018-07-24 14:53:11 -03:00
usr kbuild: rename built-in.o to built-in.a 2018-03-26 02:01:19 +09:00
virt Miscellaneous bugfixes, plus a small patchlet related to Spectre v2. 2018-07-18 11:08:44 -07:00
.clang-format clang-format: add configuration file 2018-04-11 10:28:35 -07:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap Merge branch 'asoc-4.17' into asoc-4.18 for compress dependencies 2018-04-26 12:24:28 +01:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS/CREDITS: Drop METAG ARCHITECTURE 2018-03-05 16:34:24 +00:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: add basic helper macros to scripts/Kconfig.include 2018-05-29 03:31:19 +09:00
MAINTAINERS MAINTAINERS: Add Naveen N. Rao as kprobes co-maintainer 2018-07-24 17:01:28 +02:00
Makefile Linux 4.18-rc6 2018-07-22 14:12:20 -07:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

README 

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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.