perf probe: Fix to get declared file name from clang DWARF5

Fix to get the declared file name even if it uses file index 0
in DWARF5, using custom die_get_decl_file() function.

Actually, the DWARF5 standard says file index 0 of the DW_AT_decl_file
is invalid(1), but there is a discussion and maybe this will be updated
[2].

Anyway, clang generates such DWARF5 file for the linux kernel. Thus it
must be handled.

Without this, 'perf probe' returns an error:

   $ ./perf probe -k $BIN_PATH/vmlinux -s $SRC_PATH -L vfs_read:10
   Debuginfo analysis failed.
     Error: Failed to show lines.

With this, it can handle the case correctly:

  $ ./perf probe -k $BIN_PATH/vmlinux -s $SRC_PATH -L vfs_read:10
  <vfs_read@$SRC_PATH/fs/read_write.c:10>

       11         ret = rw_verify_area(READ, file, pos, count);
       12         if (ret)
                           return ret;

[1] DWARF5 specification 2.14 says "The value 0 indicates that no source file has been specified.")
[2] http://wiki.dwarfstd.org/index.php?title=DWARF5_Line_Table_File_Numbers)

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/166731052936.2100653.13380621874859467731.stgit@devnote3
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 216fc3d..30b36b5 100644 (file)
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -123,7 +123,7 @@ int cu_find_lineinfo(Dwarf_Die *cu_die, Dwarf_Addr addr,
        if (die_find_realfunc(cu_die, addr, &die_mem)
            && die_entrypc(&die_mem, &faddr) == 0 &&
            faddr == addr) {
-               *fname = dwarf_decl_file(&die_mem);
+               *fname = die_get_decl_file(&die_mem);
                dwarf_decl_line(&die_mem, lineno);
                goto out;
        }
@@ -486,6 +486,19 @@ static int die_get_decl_fileno(Dwarf_Die *pdie)
                return -ENOENT;
 }
 
+/* Return the file name by index */
+static const char *die_get_file_name(Dwarf_Die *dw_die, int idx)
+{
+       Dwarf_Die cu_die;
+       Dwarf_Files *files;
+
+       if (idx < 0 || !dwarf_diecu(dw_die, &cu_die, NULL, NULL) ||
+           dwarf_getsrcfiles(&cu_die, &files, NULL) != 0)
+               return NULL;
+
+       return dwarf_filesrc(files, idx, NULL, NULL);
+}
+
 /**
  * die_get_call_file - Get callsite file name of inlined function instance
  * @in_die: a DIE of an inlined function instance
@@ -495,18 +508,22 @@ static int die_get_decl_fileno(Dwarf_Die *pdie)
  */
 const char *die_get_call_file(Dwarf_Die *in_die)
 {
-       Dwarf_Die cu_die;
-       Dwarf_Files *files;
-       int idx;
-
-       idx = die_get_call_fileno(in_die);
-       if (idx < 0 || !dwarf_diecu(in_die, &cu_die, NULL, NULL) ||
-           dwarf_getsrcfiles(&cu_die, &files, NULL) != 0)
-               return NULL;
-
-       return dwarf_filesrc(files, idx, NULL, NULL);
+       return die_get_file_name(in_die, die_get_call_fileno(in_die));
 }
 
+/**
+ * die_get_decl_file - Find the declared file name of this DIE
+ * @dw_die: a DIE for something declared.
+ *
+ * Get declared file name of @dw_die.
+ * NOTE: Since some version of clang DWARF5 implementation incorrectly uses
+ * file index 0 for DW_AT_decl_file, die_get_decl_file() will return NULL for
+ * such cases. Use this function instead.
+ */
+const char *die_get_decl_file(Dwarf_Die *dw_die)
+{
+       return die_get_file_name(dw_die, die_get_decl_fileno(dw_die));
+}
 
 /**
  * die_find_child - Generic DIE search function in DIE tree
@@ -790,7 +807,7 @@ static int __die_walk_funclines_cb(Dwarf_Die *in_die, void *data)
        }
 
        if (addr) {
-               fname = dwarf_decl_file(in_die);
+               fname = die_get_decl_file(in_die);
                if (fname && dwarf_decl_line(in_die, &lineno) == 0) {
                        lw->retval = lw->callback(fname, lineno, addr, lw->data);
                        if (lw->retval != 0)
@@ -818,7 +835,7 @@ static int __die_walk_funclines(Dwarf_Die *sp_die, bool recursive,
        int lineno;
 
        /* Handle function declaration line */
-       fname = dwarf_decl_file(sp_die);
+       fname = die_get_decl_file(sp_die);
        if (fname && dwarf_decl_line(sp_die, &lineno) == 0 &&
            die_entrypc(sp_die, &addr) == 0) {
                lw.retval = callback(fname, lineno, addr, data);
@@ -873,7 +890,7 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
        if (dwarf_tag(rt_die) != DW_TAG_compile_unit) {
                cu_die = dwarf_diecu(rt_die, &die_mem, NULL, NULL);
                dwarf_decl_line(rt_die, &decl);
-               decf = dwarf_decl_file(rt_die);
+               decf = die_get_decl_file(rt_die);
                if (!decf) {
                        pr_debug2("Failed to get the declared file name of %s\n",
                                  dwarf_diename(rt_die));
@@ -928,7 +945,7 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
 
                                dwarf_decl_line(&die_mem, &inl);
                                if (inl != decl ||
-                                   decf != dwarf_decl_file(&die_mem))
+                                   decf != die_get_decl_file(&die_mem))
                                        continue;
                        }
                }

diff --git a/tools/perf/util/dwarf-aux.h b/tools/perf/util/dwarf-aux.h
index 7ee0fa1..7ec8bc1 100644 (file)
--- a/tools/perf/util/dwarf-aux.h
+++ b/tools/perf/util/dwarf-aux.h
@@ -50,6 +50,9 @@ int die_get_call_lineno(Dwarf_Die *in_die);
 /* Get callsite file name of inlined function instance */
 const char *die_get_call_file(Dwarf_Die *in_die);
 
+/* Get declared file name of a DIE */
+const char *die_get_decl_file(Dwarf_Die *dw_die);
+
 /* Get type die */
 Dwarf_Die *die_get_type(Dwarf_Die *vr_die, Dwarf_Die *die_mem);
 

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 1aa8fcc..54b49ce 100644 (file)
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -763,7 +763,7 @@ static int find_best_scope_cb(Dwarf_Die *fn_die, void *data)
 
        /* Skip if declared file name does not match */
        if (fsp->file) {
-               file = dwarf_decl_file(fn_die);
+               file = die_get_decl_file(fn_die);
                if (!file || strcmp(fsp->file, file) != 0)
                        return 0;
        }
@@ -1071,7 +1071,7 @@ static int probe_point_search_cb(Dwarf_Die *sp_die, void *data)
                return DWARF_CB_OK;
 
        /* Check declared file */
-       fname = dwarf_decl_file(sp_die);
+       fname = die_get_decl_file(sp_die);
        if (!fname) {
                pr_warning("A function DIE doesn't have decl_line. Maybe broken DWARF?\n");
                return DWARF_CB_OK;
@@ -1151,7 +1151,7 @@ static int pubname_search_cb(Dwarf *dbg, Dwarf_Global *gl, void *data)
                                return DWARF_CB_OK;
 
                        if (param->file) {
-                               fname = dwarf_decl_file(param->sp_die);
+                               fname = die_get_decl_file(param->sp_die);
                                if (!fname || strtailcmp(param->file, fname))
                                        return DWARF_CB_OK;
                        }
@@ -1750,7 +1750,7 @@ int debuginfo__find_probe_point(struct debuginfo *dbg, u64 addr,
                        goto post;
                }
 
-               fname = dwarf_decl_file(&spdie);
+               fname = die_get_decl_file(&spdie);
                if (addr == baseaddr) {
                        /* Function entry - Relative line number is 0 */
                        lineno = baseline;
@@ -1787,7 +1787,7 @@ int debuginfo__find_probe_point(struct debuginfo *dbg, u64 addr,
                        }
                }
                /* Verify the lineno and baseline are in a same file */
-               tmp = dwarf_decl_file(&spdie);
+               tmp = die_get_decl_file(&spdie);
                if (!tmp || (fname && strcmp(tmp, fname) != 0))
                        lineno = 0;
        }
@@ -1902,13 +1902,13 @@ static int line_range_search_cb(Dwarf_Die *sp_die, void *data)
 
        /* Check declared file */
        if (lr->file) {
-               fname = dwarf_decl_file(sp_die);
+               fname = die_get_decl_file(sp_die);
                if (!fname || strtailcmp(lr->file, fname))
                        return DWARF_CB_OK;
        }
 
        if (die_match_name(sp_die, lr->function) && die_is_func_def(sp_die)) {
-               lf->fname = dwarf_decl_file(sp_die);
+               lf->fname = die_get_decl_file(sp_die);
                dwarf_decl_line(sp_die, &lr->offset);
                pr_debug("fname: %s, lineno:%d\n", lf->fname, lr->offset);
                lf->lno_s = lr->offset + lr->start;