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perf bpf: Add 'examples' directories 

The first one is the bare minimum that bpf infrastructure accepts before
it expects actual events to be set up:

  $ cat tools/perf/examples/bpf/empty.c
  char _license[] __attribute__((section("license"), used)) = "GPL";
  int _version __attribute__((section("version"), used)) = LINUX_VERSION_CODE;
  $

If you remove that "version" line, then it will be refused with:

  # perf trace -e tools/perf/examples/bpf/empty.c
  event syntax error: 'tools/perf/examples/bpf/empty.c'
                       \___ Failed to load tools/perf/examples/bpf/empty.c from source: 'version' section incorrect or lost

  (add -v to see detail)
  Run 'perf list' for a list of valid events

   Usage: perf trace [<options>] [<command>]
      or: perf trace [<options>] -- <command> [<options>]
      or: perf trace record [<options>] [<command>]
      or: perf trace record [<options>] -- <command> [<options>]

      -e, --event <event>   event/syscall selector. use 'perf list' to list available events
  #

The next ones will, step by step, show simple filters, then the needs
for headers will be made clear, it will be put in place and tested with
new examples, rinse, repeat.

Back to using this first one to test the perf+bpf infrastructure:

If we run it will fail, as no functions are present connecting with,
say, a tracepoint or a function using the kprobes or uprobes
infrastructure:

  # perf trace -e tools/perf/examples/bpf/empty.c
  WARNING: event parser found nothing
  invalid or unsupported event: 'tools/perf/examples/bpf/empty.c'
  Run 'perf list' for a list of valid events

   Usage: perf trace [<options>] [<command>]
      or: perf trace [<options>] -- <command> [<options>]
      or: perf trace record [<options>] [<command>]
      or: perf trace record [<options>] -- <command> [<options>]

      -e, --event <event>   event/syscall selector. use 'perf list' to list available events
  #

But, if we set things up to dump the generated object file to a file,
and do this after having run 'make install', still on the developer's
$HOME directory:

  # cat ~/.perfconfig
  [llvm]

	dump-obj = true
  #
  # perf trace -e ~acme/lib/examples/perf/bpf/empty.c
  LLVM: dumping /home/acme/lib/examples/perf/bpf/empty.o
  WARNING: event parser found nothing
  invalid or unsupported event: '/home/acme/lib/examples/perf/bpf/empty.c'
  <SNIP>
  #

We can look at the dumped object file:

  # ls -la ~acme/lib/examples/perf/bpf/empty.o
  -rw-r--r--. 1 root root 576 May  4 12:10 /home/acme/lib/examples/perf/bpf/empty.o
  # file ~acme/lib/examples/perf/bpf/empty.o
  /home/acme/lib/examples/perf/bpf/empty.o: ELF 64-bit LSB relocatable, *unknown arch 0xf7* version 1 (SYSV), not stripped
  # readelf -sw ~acme/lib/examples/perf/bpf/empty.o

  Symbol table '.symtab' contains 3 entries:
     Num:    Value          Size Type    Bind   Vis      Ndx Name
       0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
       1: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT    3 _license
       2: 0000000000000000     0 NOTYPE  GLOBAL DEFAULT    4 _version
  #
  # tools/bpf/bpftool/bpftool --pretty ~acme/lib/examples/perf/bpf/empty.o
  null
  #

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-y7dkhakejz3013o0w21n98xd@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Arnaldo Carvalho de Melo 2018-05-04 11:56:15 -03:00
parent 1b16fffa38
commit 8f12a2ff00
3 changed files with 12 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
tools/perf/Makefile.config
View File

@ -886,6 +886,7 @@ endif
# Among the variables below, these:
# perfexecdir
# perf_include_dir
# perf_examples_dir
# template_dir
# mandir
# infodir
@ -906,6 +907,7 @@ mandir = share/man
infodir = share/info
perfexecdir = libexec/perf-core
perf_include_dir = lib/include/perf
perf_examples_dir = lib/examples/perf
sharedir = $(prefix)/share
template_dir = share/perf-core/templates
STRACE_GROUPS_DIR = share/perf-core/strace/groups
@ -937,6 +939,7 @@ mandir_SQ = $(subst ','\'',$(mandir))
infodir_SQ = $(subst ','\'',$(infodir))
perfexecdir_SQ = $(subst ','\'',$(perfexecdir))
perf_include_dir_SQ = $(subst ','\'',$(perf_include_dir))
perf_examples_dir_SQ = $(subst ','\'',$(perf_examples_dir))
template_dir_SQ = $(subst ','\'',$(template_dir))
htmldir_SQ = $(subst ','\'',$(htmldir))
tipdir_SQ = $(subst ','\'',$(tipdir))
@ -948,16 +951,19 @@ srcdir_SQ = $(subst ','\'',$(srcdir))
ifneq ($(filter /%,$(firstword $(perfexecdir))),)
perfexec_instdir = $(perfexecdir)
perf_include_instdir = $(perf_include_dir)
perf_examples_instdir = $(perf_examples_dir)
STRACE_GROUPS_INSTDIR = $(STRACE_GROUPS_DIR)
tip_instdir = $(tipdir)
else
perfexec_instdir = $(prefix)/$(perfexecdir)
perf_include_instdir = $(prefix)/$(perf_include_dir)
perf_examples_instdir = $(prefix)/$(perf_examples_dir)
STRACE_GROUPS_INSTDIR = $(prefix)/$(STRACE_GROUPS_DIR)
tip_instdir = $(prefix)/$(tipdir)
endif
perfexec_instdir_SQ = $(subst ','\'',$(perfexec_instdir))
perf_include_instdir_SQ = $(subst ','\'',$(perf_include_instdir))
perf_examples_instdir_SQ = $(subst ','\'',$(perf_examples_instdir))
STRACE_GROUPS_INSTDIR_SQ = $(subst ','\'',$(STRACE_GROUPS_INSTDIR))
tip_instdir_SQ = $(subst ','\'',$(tip_instdir))
@ -1006,6 +1012,7 @@ $(call detected_var,STRACE_GROUPS_DIR_SQ)
$(call detected_var,prefix_SQ)
$(call detected_var,perfexecdir_SQ)
$(call detected_var,perf_include_dir_SQ)
$(call detected_var,perf_examples_dir_SQ)
$(call detected_var,tipdir_SQ)
$(call detected_var,srcdir_SQ)
$(call detected_var,LIBDIR)

3
tools/perf/Makefile.perf
View File

@ -770,6 +770,9 @@ endif
ifndef NO_LIBBPF
$(call QUIET_INSTALL, lib) \
$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(perf_include_instdir_SQ)/bpf'
$(call QUIET_INSTALL, lib) \
$(INSTALL) -d -m 755 '$(DESTDIR_SQ)$(perf_examples_instdir_SQ)/bpf'
$(INSTALL) examples/bpf/*.c '$(DESTDIR_SQ)$(perf_examples_instdir_SQ)/bpf'
endif
$(call QUIET_INSTALL, perf-archive) \
$(INSTALL) $(OUTPUT)perf-archive -t '$(DESTDIR_SQ)$(perfexec_instdir_SQ)'

2
tools/perf/examples/bpf/empty.c Normal file
View File

@ -0,0 +1,2 @@
char _license[] __attribute__((section("license"), used)) = "GPL";
int _version __attribute__((section("version"), used)) = LINUX_VERSION_CODE;