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 <[e-mail]>
Acked-by: Namhyung Kim <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Steven Rostedt (VMware) <[e-mail]>
Link: https://lore.kernel.org/r/166731052936.2100653.13380621874859467731.stgit@devnote3
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/util/dwarf-aux.c

···
 	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;
 	}
···
 		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
···
  */
 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
···
 	}
 
 	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)
···
 	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);
···
 	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));
···
 
 				dwarf_decl_line(&die_mem, &inl);
 				if (inl != decl ||
-				    decf != dwarf_decl_file(&die_mem))
+				    decf != die_get_decl_file(&die_mem))
 					continue;
 			}
 		}

tools/perf/util/dwarf-aux.h

···
 /* 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);
 

tools/perf/util/probe-finder.c

···
 
 	/* 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;
 	}
···
 		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;
···
 				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;
 			}
···
 			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;
···
 			}
 		}
 		/* 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;
 	}
···
 
 	/* 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;