perf dwarf-aux: Use signed variable types in match_var_offset

match_var_offset() compares address offsets to determine if an access
falls within a variable's bounds. The offsets involved for those
relative to base registers from DW_OP_breg can be negative.

The current implementation uses unsigned types (u64) for these offsets,
which rejects almost all negative values.

Change the signature of match_var_offset() to use signed types (s64).

This ensures correct behavior when addr_offset or addr_type are
negative.

Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Zecheng Li <zecheng@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Xu Liu <xliuprof@google.com>
Link: https://lore.kernel.org/r/20250825195412.223077-2-zecheng@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 559c953ca172..920054425578 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -1388,18 +1388,19 @@ struct find_var_data {
 #define DWARF_OP_DIRECT_REGS  32
 
 static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *data,
-			     u64 addr_offset, u64 addr_type, bool is_pointer)
+			     s64 addr_offset, s64 addr_type, bool is_pointer)
 {
 	Dwarf_Die type_die;
 	Dwarf_Word size;
+	s64 offset = addr_offset - addr_type;
 
-	if (addr_offset == addr_type) {
+	if (offset == 0) {
 		/* Update offset relative to the start of the variable */
 		data->offset = 0;
 		return true;
 	}
 
-	if (addr_offset < addr_type)
+	if (offset < 0)
 		return false;
 
 	if (die_get_real_type(die_mem, &type_die) == NULL)
@@ -1414,11 +1415,11 @@ static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *data,
 	if (dwarf_aggregate_size(&type_die, &size) < 0)
 		return false;
 
-	if (addr_offset >= addr_type + size)
+	if ((u64)offset >= size)
 		return false;
 
 	/* Update offset relative to the start of the variable */
-	data->offset = addr_offset - addr_type;
+	data->offset = offset;
 	return true;
 }