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Tiezhu Yang 0c5f1acc2a perf top: Skip side-band event setup if HAVE_LIBBPF_SUPPORT is not set 
When I execute 'perf top' without HAVE_LIBBPF_SUPPORT, there exists the
following segmentation fault, skip the side-band event setup to fix it,
this is similar with commit 1101c872c8 ("perf record: Skip side-band
event setup if HAVE_LIBBPF_SUPPORT is not set").

  [yangtiezhu@linux perf]$ ./perf top
  <SNIP>
  perf: Segmentation fault
  Obtained 6 stack frames.
  ./perf(sighandler_dump_stack+0x5c) [0x12011b604]
  [0xffffffc010]
  ./perf(perf_mmap__read_init+0x3e) [0x1201feeae]
  ./perf() [0x1200d715c]
  /lib64/libpthread.so.0(+0xab9c) [0xffee10ab9c]
  /lib64/libc.so.6(+0x128f4c) [0xffedc08f4c]
  Segmentation fault
  [yangtiezhu@linux perf]$

I use git bisect to find commit b38d85ef49 ("perf bpf: Decouple
creating the evlist from adding the SB event") is the first bad commit,
so also add the Fixes tag.

Committer testing:

First build perf explicitely disabling libbpf:

  $ make NO_LIBBPF=1 O=/tmp/build/perf -C tools/perf install-bin && perf test python

Now make sure it isn't linked:

  $ perf -vv | grep -w bpf
                   bpf: [ OFF ]  # HAVE_LIBBPF_SUPPORT
  $
  $ nm ~/bin/perf | grep libbpf
  $

And now try to run 'perf top':

  # perf top
  perf: Segmentation fault
  -------- backtrace --------
  perf[0x5bcd6d]
  /lib64/libc.so.6(+0x3ca6f)[0x7fd0f5a66a6f]
  perf(perf_mmap__read_init+0x1e)[0x5e1afe]
  perf[0x4cc468]
  /lib64/libpthread.so.0(+0x9431)[0x7fd0f645a431]
  /lib64/libc.so.6(clone+0x42)[0x7fd0f5b2b912]
  #

Applying this patch fixes the issue.

Fixes: b38d85ef49 ("perf bpf: Decouple creating the evlist from adding the SB event")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Xuefeng Li <lixuefeng@loongson.cn>
Link: http://lore.kernel.org/lkml/1597753837-16222-1-git-send-email-yangtiezhu@loongson.cn
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-08-21 10:22:23 -03:00
arch x86/boot/compressed: Use builtin mem functions for decompressor 2020-08-19 11:23:45 -07:00
block block-5.9-2020-08-14 2020-08-15 20:36:42 -07:00
certs .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-08-14 13:09:15 -07:00
Documentation spi: Fixes for v5.9 2020-08-18 14:27:12 -07:00
drivers pci-v5.9-fixes-1 2020-08-20 14:17:03 -07:00
fs afs: Fix key ref leak in afs_put_operation() 2020-08-20 10:41:45 -07:00
include dma-mapping fixes for 5.9 2020-08-20 10:48:17 -07:00
init OpenRISC updates for 5.9 2020-08-14 14:04:53 -07:00
ipc ipc/shm.c: remove the superfluous break 2020-08-12 10:58:02 -07:00
kernel dma-mapping fixes for 5.9 2020-08-20 10:48:17 -07:00
lib lib/string.c: Use freestanding environment 2020-08-19 11:23:45 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm/memory.c: skip spurious TLB flush for retried page fault 2020-08-18 12:02:27 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-17 17:09:50 -07:00
samples Kbuild updates for v5.9 2020-08-09 14:10:26 -07:00
scripts Kconfig updates for v5.9 2020-08-14 11:04:45 -07:00
security Merge branch 'akpm' (patches from Andrew) 2020-08-12 11:24:12 -07:00
sound sound fixes for 5.9-rc1 2020-08-14 15:58:57 -07:00
tools perf top: Skip side-band event setup if HAVE_LIBBPF_SUPPORT is not set 2020-08-21 10:22:23 -03:00
usr Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
virt Merge branch 'akpm' (patches from Andrew) 2020-08-12 11:24:12 -07:00
.clang-format block: add bio_for_each_bvec_all() 2020-05-25 11:25:24 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: Add ZSTD-compressed files 2020-07-31 11:50:49 +02:00
.mailmap mailmap: Add WeiXiong Liao 2020-08-17 14:32:44 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS CREDITS: Replace HTTP links with HTTPS ones 2020-07-23 14:53:58 -06:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS perf tools changes for v5.9: 2nd batch 2020-08-15 11:17:15 -07:00
Makefile Linux 5.9-rc1 2020-08-16 13:04:57 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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.

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.