[PATCH 6.1 143/236] perf unwind-libdw: Handle JIT-generated DSOs properly

Greg Kroah-Hartman
2024-05-14T11:34:16Z

From: Namhyung Kim <namhyung@kernel.org>

[ Upstream commit c966d23a351a33f8a977fd7efbb6f467132f7383 ]

Usually DSOs are mapped from the beginning of the file, so the base
address of the DSO can be calculated by map->start - map->pgoff.

However, JIT DSOs which are generated by `perf inject -j`, are mapped
only the code segment. This makes unwind-libdw code confusing and
rejects processing unwinds in the JIT DSOs. It should use the map
start address as base for them to fix the confusion.

Fixes: 1fe627da30331024 ("perf unwind: Take pgoff into account when reporting elf to libdwfl")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Fangrui Song <maskray@google.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Pablo Galindo <pablogsal@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20231212070547.612536-3-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/perf/util/unwind-libdw.c | 21 +++++++++++++++++----
1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c
index 94aa40f6e3482..9a7bdc0e14cc2 100644
--- a/tools/perf/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw.c
@@ -45,6 +45,7 @@ static int __report_module(struct addr_location *al, u64 ip,
{
Dwfl_Module *mod;
struct dso *dso = NULL;
+ Dwarf_Addr base;
/*
* Some callers will use al->sym, so we can't just use the
* cheaper thread__find_map() here.
@@ -57,24 +58,36 @@ static int __report_module(struct addr_location *al, u64 ip,
if (!dso)
return 0;

+ /*
+ * The generated JIT DSO files only map the code segment without
+ * ELF headers. Since JIT codes used to be packed in a memory
+ * segment, calculating the base address using pgoff falls info
+ * a different code in another DSO. So just use the map->start
+ * directly to pick the correct one.
+ */
+ if (!strncmp(dso->long_name, "/tmp/jitted-", 12))
+ base = al->map->start;
+ else
+ base = al->map->start - al->map->pgoff;
+
mod = dwfl_addrmodule(ui->dwfl, ip);
if (mod) {
Dwarf_Addr s;

dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL);
- if (s != al->map->start - al->map->pgoff)
- mod = 0;
+ if (s != base)
+ mod = NULL;
}

if (!mod)
mod = dwfl_report_elf(ui->dwfl, dso->short_name, dso->long_name, -1,
- al->map->start - al->map->pgoff, false);
+ base, false);
if (!mod) {
char filename[PATH_MAX];

if (dso__build_id_filename(dso, filename, sizeof(filename), false))
mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
- al->map->start - al->map->pgoff, false);
+ base, false);
}

if (mod) {
--
2.43.0