2a9d5050dc
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 67540759151a ("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 19610184693c ("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: 67540759151a ("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>
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.