The dso_id previously contained the major, minor, inode and inode
generation information from a mmap2 event - the inode generation would
be zero when reading from /proc/pid/maps. The build_id was in the
dso. With build ID mmap2 events these fields wouldn't be initialized
which would largely mean the special empty case where any dso would
match for equality. This isn't desirable as if a dso is replaced we
want the comparison to yield a difference.
To support detecting the difference between DSOs based on build_id,
move the build_id out of the DSO and into the dso_id. The dso_id is
also stored in the DSO so nothing is lost. Capture in the dso_id what
parts have been initialized and rename dso_id__inject to
dso_id__improve_id so that it is clear the dso_id is being improved
upon with additional information. With the build_id in the dso_id, use
memcmp to compare for equality.
Signed-off-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250724163302.596743-7-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
The test needs a struct machine and creates one for the current host,
but a side-effect is that struct machine has set up kernel maps
including module maps.
If the 'Symbols' test --dso option specifies a current kernel module,
it will already be present as a kernel dso, and a map with kmaps needs
to be used otherwise there will be a segfault - see below.
For that case, find the existing map and use that. In that case also,
the dso is split by section into multiple dsos, so test those dsos
also. That in turn, shows up that those dsos have not had overlapping
symbols removed, so the test fails.
Example:
Before:
$ perf test -F -v Symbols --dso /lib/modules/$(uname -r)/kernel/arch/x86/kvm/kvm-intel.ko
70: Symbols :
--- start ---
Testing /lib/modules/6.7.2-local/kernel/arch/x86/kvm/kvm-intel.ko
Segmentation fault (core dumped)
After:
$ perf test -F -v Symbols --dso /lib/modules/$(uname -r)/kernel/arch/x86/kvm/kvm-intel.ko
70: Symbols :
--- start ---
Testing /lib/modules/6.7.2-local/kernel/arch/x86/kvm/kvm-intel.ko
Overlapping symbols:
41d30-41fbb l vmx_init
41d30-41fbb g init_module
---- end ----
Symbols: FAILED!
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240131192416.16387-1-adrian.hunter@intel.com
Add a test to check function symbols do not overlap and are not zero
length.
The main motivation for the test is to make it easier to review changes
to PLT symbol synthesis i.e. changes to dso__synthesize_plt_symbols().
By default the test uses the perf executable as a test DSO, but a
specific DSO can be specified via a new perf test option "--dso".
The test is useful in the following ways:
- Any DSO can be tested, even ones that do not run on the current
architecture. For example, using cross-compiled DSOs to see how
well perf handles different architectures.
- With verbose > 1 (e.g. -vv), all the symbols are printed, which
makes it easier to see issues.
- perf removes duplicate symbols and expands zero-length symbols
to reach the next symbol, however that is done before adding
synthesized symbols, so the test is checking those also.
Example:
$ perf test -v Symbols
74: Symbols :
--- start ---
test child forked, pid 154918
Testing /home/user/bin/perf
Overlapping symbols:
7d000-7f3a0 g _init
7d030-7d040 g __printf_chk@plt
test child finished with -1
---- end ----
Symbols: FAILED!
Note the test fails because perf expands the _init symbol over the PLT
because there are no PLT symbols at that point, but then
dso__synthesize_plt_symbols() creates them.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20230120123456.12449-2-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Ian Rogers
Colin Ian King
Adrian Hunter