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  1. 05 7月, 2016 2 次提交
    • H
      perf sdt: ELF support for SDT · 060fa0c7
      由 Hemant Kumar 提交于 
      This patch serves the initial support to identify and list SDT events in
binaries.  When programs containing SDT markers are compiled, gcc with
the help of assembler directives identifies them and places them in the
section ".note.stapsdt".

To find these markers from the binaries, one needs to traverse through
this section and parse the relevant details like the name, type and
location of the marker. Also, the original location could be skewed due
to the effect of prelinking. If that is the case, the locations need to
be adjusted.

The functions in this patch open a given ELF, find out the SDT section,
parse the relevant details, adjust the location (if necessary) and
populate them in a list.

A typical note entry in ".note.stapsdt" section is as follows :

                                 |--nhdr.n_namesz--|
                ------------------------------------
                |      nhdr      |     "stapsdt"   |
        -----   |----------------------------------|
         |      |  <location>       <base_address> |
         |      |  <semaphore>                     |
nhdr.n_descsize |  "provider_name"   "note_name"   |
         |      |   <args>                         |
        -----   |----------------------------------|
                |      nhdr      |     "stapsdt"   |
                |...

The above shows an excerpt from the section ".note.stapsdt".  'nhdr' is
a structure which has the note name size (n_namesz), note description
size (n_desc_sz) and note type (n_type).

So, in order to parse the note note info, we need nhdr to tell us where
to start from.  As can be seen from <sys/sdt.h>, the name of the SDT
notes given is "stapsdt".  But this is not the identifier of the note.

After that, we go to description of the note to find out its location, the
address of the ".stapsdt.base" section and the semaphore address.
Then, we find the provider name and the SDT marker name and then follow the
arguments.
Signed-off-by: NHemant Kumar <hemant@linux.vnet.ibm.com>
Reviewed-by: NMasami Hiramatsu <mhiramat@kernel.org>
Acked-by: NNamhyung Kim <namhyung@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/146736022628.27797.1201368329092908163.stgit@devboxSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
      060fa0c7
    • A
      perf build: Add feature detection for libelf's elf_getshdrstrndx() · 2492c465
      由 Arnaldo Carvalho de Melo 提交于 
      That appeared after 0.140, and will be used in the SDT code, so, to
avoid bisection break on older systems, add a feature detection and
provide a stub with a pr_debug() to keep it building.

Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Hemant Kumar <hemant@linux.vnet.ibm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-80y0eldgweorqnwha9rvfxjr@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>
      2492c465
  3. 01 7月, 2016 11 次提交
  5. 30 6月, 2016 2 次提交
  7. 29 6月, 2016 3 次提交
  9. 28 6月, 2016 15 次提交
  11. 27 6月, 2016 7 次提交