[PATCH v1 0/9] perf: Refactor/add fallbacks for reading build-id and debuglink

Ian Rogers
2025-11-23T02:32:29Z

This cleans up some tech debt mentioned in the thread:
https://lore.kernel.org/lkml/aQt66zhfxSA80xwt@gentoo.org/

The perf tool has fallbacks for objdump but not in the case of
build-id and debuglink reading. Refactor the code so that in the case
of read_build_id it now looks like:

```
int filename__read_build_id(const char *filename, struct build_id *bid, bool block)
{
struct kmod_path m = { .name = NULL, };
char path[PATH_MAX];
int err, fd;

if (!filename)
return -EFAULT;

err = kmod_path__parse(&m, filename);
if (err)
return -1;

if (m.comp) {
int error = 0;

fd = filename__decompress(filename, path, sizeof(path), m.comp, &error);
if (fd < 0) {
pr_debug("Failed to decompress (error %d) %s\n",
error, filename);
return -1;
}
lseek(fd, 0, SEEK_SET);
filename = path;
block = true;
} else {
fd = open(filename, block ? O_RDONLY : (O_RDONLY | O_NONBLOCK));
if (fd < 0) {
pr_debug("Failed to open %s\n", filename);
return -1;
}
}

err = libbfd__read_build_id(fd, filename, bid);
if (err == 0)
goto out;

err = libelf__read_build_id(fd, filename, bid);
if (err == 0)
goto out;

err = sym_min__read_build_id(fd, filename, bid);
...
```

That is what was previously symbol-elf decompression code is now made
common for all cases of reading. The handling of the block argument is
now common. There is a clear fallback from libbfd to libelf to the
symbol-minimal (sym_min) versions of the functions.

To support this there is refactoring of code into a perf-libelf.c
file, to follow patterns established for the capstone, LLVM and libbfd
code.

These changes conflict with James' removal of the block argument:
https://lore.kernel.org/lkml/20251121-james-perf-non-block-v1-1-6ab2702ab573@linaro.org/
I think we should do that change. It would be easy to apply that
change on these changes as rather than updating 3 functions, only 1
function needs updating.

Ian Rogers (9):
perf symbol: Reduce scope of elf__needs_adjust_symbols
perf symbol: Reduce scope of arch__sym_update
perf symbol: Move libelf code to its own file/header
perf symbol: Remove unused includes
perf symbol: Move dso__load_bfd_symbols out of symbol.h
perf symbol: Use fallbacks with filename__read_build_id
perf symbol: Use fallbacks for filename__read_debuglink
perf symbol: Use fallbacks for sysfs__read_build_id
perf dso: Move type helpers out of symbol and use fallbacks

tools/perf/arch/powerpc/util/sym-handling.c | 7 -
tools/perf/builtin-annotate.c | 47 +--
tools/perf/builtin-c2c.c | 58 +--
tools/perf/builtin-diff.c | 22 +-
tools/perf/builtin-inject.c | 19 +-
tools/perf/builtin-kmem.c | 41 ++-
tools/perf/builtin-kwork.c | 9 +-
tools/perf/builtin-mem.c | 16 +-
tools/perf/builtin-report.c | 76 ++--
tools/perf/builtin-sched.c | 50 ++-
tools/perf/builtin-script.c | 89 ++---
tools/perf/builtin-timechart.c | 34 +-
tools/perf/builtin-top.c | 85 +++--
tools/perf/builtin-trace.c | 82 ++---
.../scripts/python/Perf-Trace-Util/Context.c | 11 +-
tools/perf/tests/code-reading.c | 1 +
tools/perf/tests/hists_cumulate.c | 1 +
tools/perf/tests/hists_filter.c | 1 +
tools/perf/tests/hists_link.c | 1 +
tools/perf/tests/hists_output.c | 1 +
tools/perf/tests/mmap-thread-lookup.c | 1 +
tools/perf/tests/pe-file-parsing.c | 5 +-
tools/perf/util/Build | 6 +-
tools/perf/util/annotate-data.c | 7 +-
tools/perf/util/auxtrace.h | 1 +
tools/perf/util/block-info.c | 11 +-
tools/perf/util/build-id.c | 28 +-
tools/perf/util/callchain.c | 1 +
tools/perf/util/cs-etm.c | 1 +
tools/perf/util/data-convert-json.c | 30 +-
tools/perf/util/db-export.c | 16 +-
tools/perf/util/dlfilter.c | 11 +-
tools/perf/util/dlfilter.h | 1 +
tools/perf/util/dso.c | 57 +--
tools/perf/util/event.c | 41 ++-
tools/perf/util/evsel_fprintf.c | 14 +-
tools/perf/util/hist.c | 29 +-
tools/perf/util/intel-pt.c | 35 +-
tools/perf/util/kvm-stat.h | 5 +-
tools/perf/util/libbfd.c | 4 +-
tools/perf/util/libbfd.h | 15 +-
tools/perf/util/machine.c | 34 +-
tools/perf/util/perf-libelf.c | 286 +++++++++++++++
tools/perf/util/perf-libelf.h | 65 ++++
tools/perf/util/print_insn.c | 14 +-
tools/perf/util/probe-event.c | 1 +
tools/perf/util/probe-finder.c | 1 +
.../util/scripting-engines/trace-event-perl.c | 1 +
.../scripting-engines/trace-event-python.c | 1 +
tools/perf/util/symbol-elf.c | 337 +-----------------
tools/perf/util/symbol-minimal.c | 95 +++--
tools/perf/util/symbol-minimal.h | 13 +
tools/perf/util/symbol.c | 108 +++++-
tools/perf/util/symbol.h | 44 +--
tools/perf/util/symbol_fprintf.c | 1 +
tools/perf/util/thread-stack.c | 12 +-
tools/perf/util/thread.c | 18 +-
tools/perf/util/unwind-libdw.c | 15 +-
58 files changed, 1085 insertions(+), 931 deletions(-)
create mode 100644 tools/perf/util/perf-libelf.c
create mode 100644 tools/perf/util/perf-libelf.h
create mode 100644 tools/perf/util/symbol-minimal.h

--
2.52.0.rc2.455.g230fcf2819-goog