perf unwind-libdw: Handle JIT-generated DSOs properly

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>

diff --git a/tools/perf/util/unwind-libdw.c b/tools/perf/util/unwind-libdw.c
index 8554db3fc0d7c9fb6523032e6257e3d49abd64b7..6013335a8daea58a4fe19c0b4a5041e522f6707d 100644 (file)
--- a/tools/perf/util/unwind-libdw.c
+++ b/tools/perf/util/unwind-libdw.c
@@ -46,6 +46,7 @@ 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.
@@ -58,13 +59,25 @@ 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 into
+        * 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 = map__start(al->map);
+       else
+               base = map__start(al->map) - map__pgoff(al->map);
+
        mod = dwfl_addrmodule(ui->dwfl, ip);
        if (mod) {
                Dwarf_Addr s;
 
                dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL);
-               if (s != map__start(al->map) - map__pgoff(al->map))
-                       mod = 0;
+               if (s != base)
+                       mod = NULL;
        }
 
        if (!mod) {
@@ -72,14 +85,14 @@ static int __report_module(struct addr_location *al, u64 ip,
 
                __symbol__join_symfs(filename, sizeof(filename), dso->long_name);
                mod = dwfl_report_elf(ui->dwfl, dso->short_name, filename, -1,
-                                     map__start(al->map) - map__pgoff(al->map), 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,
-                                             map__start(al->map) - map__pgoff(al->map), false);
+                                             base, false);
        }
 
        if (mod) {