perf jit: Fix inaccurate DWARF line table

Fix an issue where addresses in the DWARF line table are offset by -0x40
(GEN_ELF_TEXT_OFFSET). This can be seen with `objdump -S` on the ELF
files after perf inject.

Committer notes:

Ian added this in his Acked-by reply:

 ---
Without too much knowledge this looks good to me. The original code came
from oprofile's jit support:

  https://sourceforge.net/p/oprofile/oprofile/ci/master/tree/opjitconv/debug_line.c#l325
 ---

Signed-off-by: Nick Gasson <nick.gasson@arm.com>
Acked-by: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20200528051916.6722-1-nick.gasson@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/genelf_debug.c b/tools/perf/util/genelf_debug.c
index 30e9f61..dd40683 100644 (file)
--- a/tools/perf/util/genelf_debug.c
+++ b/tools/perf/util/genelf_debug.c
@@ -342,7 +342,7 @@ static void emit_lineno_info(struct buffer_ext *be,
         */
 
        /* start state of the state machine we take care of */
-       unsigned long last_vma = code_addr;
+       unsigned long last_vma = 0;
        char const  *cur_filename = NULL;
        unsigned long cur_file_idx = 0;
        int last_line = 1;
@@ -473,7 +473,7 @@ jit_process_debug_info(uint64_t code_addr,
                ent = debug_entry_next(ent);
        }
        add_compilation_unit(di, buffer_ext_size(dl));
-       add_debug_line(dl, debug, nr_debug_entries, 0);
+       add_debug_line(dl, debug, nr_debug_entries, GEN_ELF_TEXT_OFFSET);
        add_debug_abbrev(da);
        if (0) buffer_ext_dump(da, "abbrev");