[PATCH v2 2/6] perf dwarf-aux: Fix libdw API contract violations

[Ian Rogers <irogers@google.com>]

Check return values of `dwarf_decl_line`, `dwarf_getfuncs`, and
`dwarf_lineaddr` to prevent using uninitialized stack variables or
incorrectly reporting success on failure.

Fixes: 57f95bf5f882 ("perf probe: Show correct statement line number by perf probe -l")
Fixes: 3f4460a28fb2 ("perf probe: Filter out redundant inline-instances")
Fixes: 75186a9b09e4 ("perf probe: Fix to show lines of sys_ functions correctly")
Fixes: e0d153c69040 ("perf-probe: Move dwarf library routines to dwarf-aux.{c, h}")
Fixes: 6243b9dc4c99 ("perf probe: Move dwarf specific functions to dwarf-aux.c")
Assisted-by: Gemini-CLI:Google Gemini 3
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/dwarf-aux.c | 34 ++++++++++++++++++++++------------
 1 file changed, 22 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 6752adca8ee8..0b75b4af2b47 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -125,7 +125,8 @@ int cu_find_lineinfo(Dwarf_Die *cu_die, Dwarf_Addr addr,
 	    && die_entrypc(&die_mem, &faddr) == 0 &&
 	    faddr == addr) {
 		*fname = die_get_decl_file(&die_mem);
-		dwarf_decl_line(&die_mem, lineno);
+		if (dwarf_decl_line(&die_mem, lineno) != 0)
+			return -ENOENT;
 		goto out;
 	}
 
@@ -797,8 +798,8 @@ static int __die_walk_instances_cb(Dwarf_Die *inst, void *data)
 
 	/* Ignore redundant instances */
 	if (dwarf_tag(inst) == DW_TAG_inlined_subroutine) {
-		dwarf_decl_line(origin, &tmp);
-		if (die_get_call_lineno(inst) == tmp) {
+		if (dwarf_decl_line(origin, &tmp) == 0 &&
+		    die_get_call_lineno(inst) == tmp) {
 			tmp = die_get_decl_fileno(origin);
 			if (die_get_call_fileno(inst) == tmp)
 				return DIE_FIND_CB_CONTINUE;
@@ -950,7 +951,11 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
 	/* Get the CU die */
 	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);
+		if (dwarf_decl_line(rt_die, &decl) != 0) {
+			pr_debug2("Failed to get the declared line number of %s\n",
+				  dwarf_diename(rt_die));
+			return -EINVAL;
+		}
 		decf = die_get_decl_file(rt_die);
 		if (!decf) {
 			pr_debug2("Failed to get the declared file name of %s\n",
@@ -1004,8 +1009,8 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
 				    die_get_call_lineno(&die_mem) == lineno)
 					goto found;
 
-				dwarf_decl_line(&die_mem, &inl);
-				if (inl != decl ||
+				if (dwarf_decl_line(&die_mem, &inl) != 0 ||
+				    inl != decl ||
 				    decf != die_get_decl_file(&die_mem))
 					continue;
 			}
@@ -1036,8 +1041,10 @@ int die_walk_lines(Dwarf_Die *rt_die, line_walk_callback_t callback, void *data)
 			.data = data,
 			.retval = 0,
 		};
-		dwarf_getfuncs(cu_die, __die_walk_culines_cb, &param, 0);
-		ret = param.retval;
+		if (dwarf_getfuncs(cu_die, __die_walk_culines_cb, &param, 0) < 0)
+			ret = -EINVAL;
+		else
+			ret = param.retval;
 	}
 
 	return ret;
@@ -1941,10 +1948,13 @@ static bool die_get_postprologue_addr(unsigned long entrypc_idx,
 			break;
 	}
 
-	dwarf_lineaddr(line, postprologue_addr);
-	if (*postprologue_addr >= highpc)
-		dwarf_lineaddr(dwarf_onesrcline(lines, i - 1),
-			       postprologue_addr);
+	if (dwarf_lineaddr(line, postprologue_addr) != 0)
+		return false;
+	if (*postprologue_addr >= highpc) {
+		if (dwarf_lineaddr(dwarf_onesrcline(lines, i - 1),
+				   postprologue_addr) != 0)
+			return false;
+	}
 
 	return true;
 }
-- 
2.54.0.545.g6539524ca2-goog