When loading symbols in a data mapping, ABS symbols (which has a value
of SHN_ABS in its st_shndx) failed at elf_getscn().  And it marks the
loading as a failure so already loaded symbols cannot be fixed up.

I'm not sure what should be done. Just ignore them for now. :)
Signed-off-by: NNamhyung Kim <namhyung@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1353502185-26521-19-git-send-email-eranian@google.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Build currently fails:
  $ make -C tools/perf O=/tmp/pbuild NO_LIBELF=1

  util/symbol.c: In function ‘dso__load’:
  util/symbol.c:1128:27: error: ‘struct symsrc’ has no member named ‘dynsym’
      CC /tmp/pbuild/util/pager.o
  make: *** [/tmp/pbuild/util/symbol.o] Error 1
  make: *** Waiting for unfinished jobs....

Moving the dynsym reference to symbol-elf.c reveals that NO_LIBELF requires
NO_LIBUNWIND:

  $ make -C tools/perf O=/tmp/pbuild NO_LIBELF=1

      LINK /tmp/pbuild/perf
  /tmp/pbuild/libperf.a(unwind.o): In function `elf_section_offset':
  /opt/sw/ahern/perf.git/tools/perf/util/unwind.c:176: undefined reference to `elf_begin'
  /opt/sw/ahern/perf.git/tools/perf/util/unwind.c:181: undefined reference to `gelf_getehdr'
  /tmp/pbuild/libperf.a(unwind.o): In function `elf_section_by_name':
  /opt/sw/ahern/perf.git/tools/perf/util/unwind.c:157: undefined reference to `elf_nextscn'
  /opt/sw/ahern/perf.git/tools/perf/util/unwind.c:160: undefined reference to `gelf_getshdr'
  /opt/sw/ahern/perf.git/tools/perf/util/unwind.c:161: undefined reference to `elf_strptr'
  /tmp/pbuild/libperf.a(unwind.o): In function `elf_section_offset':
  /opt/sw/ahern/perf.git/tools/perf/util/unwind.c:190: undefined reference to `elf_end'
  /tmp/pbuild/libperf.a(unwind.o): In function `read_unwind_spec':
  /opt/sw/ahern/perf.git/tools/perf/util/unwind.c:190: undefined reference to `elf_end'
  collect2: ld returned 1 exit status
  make: *** [/tmp/pbuild/perf] Error 1
  make: Leaving directory `/opt/sw/ahern/perf.git/tools/perf'

This patch fixes both.
Reviewed-by: NNamhyung Kim <namhyung@kernel.org>
Signed-off-by: NDavid Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1345391234-71906-1-git-send-email-dsahern@gmail.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

We keep both a 'runtime' elf image as well as a 'debug' elf image around
and generate symbols by looking at both of these.

This eliminates the need for the want_symtab/goto restart mechanism
combined with iterating over and reopening the elf images a second time.

Also give dso__synthsize_plt_symbols() the runtime image (which has
dynsyms) instead of the symbol image (which may only have a symtab and
no dynsyms).

Previously if a debug image was found all runtime images were ignored.

This fixes 2 issues:

 - Symbol resolution to failure on PowerPC systems with debug symbols
   installed, as the debug images lack a '.opd' section which contains
   function descriptors.

 - On all archs, plt synthesis failed when a debug image was loaded and
   that debug image lacks a dynsym section while a runtime image has a
   dynsym section.

Assumptions:

 - If a .opd section exists, it is contained in the highest priority
   image with a dynsym section.

 - This generally implies that the debug image lacks a dynsym section
   (ie: it is marked as NO_BITS).
Signed-off-by: NCody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Hansen <dave@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matt Hellsley <matthltc@us.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1344637382-22789-17-git-send-email-cody@linux.vnet.ibm.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

To properly handle platforms with an opd section, both a runtime image
(which contains the opd section but possibly lacks symbols) and a symbol
image (which probably lacks an opd section but has symbols).

The next patch ("perf symbol: use both runtime and debug images")
adjusts the callsite in dso__load() to take advantage of being able to
pass both runtime & debug images.

Assumptions made here:

 - The opd section, if it exists in the runtime image, has headers in
   both the runtime image and the debug/syms image.

 - The index of the opd section (again, only if it exists in the runtime
   image) is the same in both the runtime and debug/symbols image.

Both of these are true on RHEL, but it is unclear how accurate they are
in general (on platforms with function descriptors in opd sections).
Signed-off-by: NCody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Hansen <dave@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matt Hellsley <matthltc@us.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1344637382-22789-16-git-send-email-cody@linux.vnet.ibm.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Only one callsite of dso__load_sym() uses the want_symtab functionality,
so place the logic at the callsite instead of within dso__load_sym().

This sets us up for removal of want_symtab completely once we keep
multiple elf handles (within symsrc's) around.

Setup for the later patch

"perf symbols: Use both runtime and debug images"
Signed-off-by: NCody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Hansen <dave@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matt Hellsley <matthltc@us.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1344637382-22789-15-git-send-email-cody@linux.vnet.ibm.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Previously dso__synthesize_plt_symbols() was reopening the elf file to
obtain dynsyms from it. Rather than reopen the file, use the already
opened reference within the symsrc to access it.

Setup for the later patch

"perf symbols: Use both runtime and debug images"
Signed-off-by: NCody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Hansen <dave@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matt Hellsley <matthltc@us.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1344637382-22789-14-git-send-email-cody@linux.vnet.ibm.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

In certain cases, dso__load requires dso->symbol_type to be set prior to
calling it. With the introduction of symsrc*, the symtab_type is now
stored in a symsrc which is then passed to dso__load_sym().

Change dso__load_sym() to use the symtab_type from them symsrc (setting
dso->symtab_type as well).

Setup for later patch

"perf symbols: Use both runtime and debug images"
Signed-off-by: NCody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Hansen <dave@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matt Hellsley <matthltc@us.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1344637382-22789-13-git-send-email-cody@linux.vnet.ibm.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Factors opening of certain sections & tracking certain elf info into an
external structure.

The goal here is to keep multiple elfs (and their looked up
sections/indexes) around during the symbol generation process (in
dso__load()).

We need this to properly resolve symbols on PPC due to the use of
function descriptors & the .opd section (ie: symbols which are functions
don't point to their actual location, they point to their function
descriptor in .opd which contains their actual location.

It would be possible to just keep the (Elf *) around, but then we'd end
up with duplicate code for looking up the same sections and checking for
the existence of an important section wouldn't be as clean (and we need
to keep the Elf stuff confined to symtab-elf.c).

Utilized by the later patch
"perf symbols: Use both runtime and debug images"
Signed-off-by: NCody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Hansen <dave@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matt Hellsley <matthltc@us.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1344637382-22789-12-git-send-email-cody@linux.vnet.ibm.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

If we call elf_section_by_name() with a truncated elf image (ie: the
file header indicates that the section headers are placed past the end
of the file), elf_strptr() causes a segfault within libelf.

Avoid this by checking that we can access the section string table
properly.

Should really be fixed in libelf/elfutils.
Signed-off-by: NCody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Hansen <dave@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matt Hellsley <matthltc@us.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1344637382-22789-10-git-send-email-cody@linux.vnet.ibm.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

If .dynsym exists but .dynstr is empty (NO_BITS or size==0), a segfault
occurs.  Avoid this by checking that .dynstr is not empty.
Signed-off-by: NCody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Hansen <dave@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matt Hellsley <matthltc@us.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1344637382-22789-6-git-send-email-cody@linux.vnet.ibm.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Prelink only adjusts the addresses of non-zero symbols. Do the same when we
reverse the adjustments.
Signed-off-by: NCody P Schafer <cody@linux.vnet.ibm.com>
Cc: David Hansen <dave@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matt Hellsley <matthltc@us.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1344637382-22789-4-git-send-email-cody@linux.vnet.ibm.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

Factor out the dependency of ELF handling into separate symbol-elf.c
file. It is a preparation of building a minimalistic version perf tools
which doesn't depend on the elfutils.
Signed-off-by: NNamhyung Kim <namhyung@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1344228082-15569-3-git-send-email-namhyung@kernel.org
[ committer note: removed blank line at symbol-elf.c EOF ]
Signed-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>