linux-kernel - [PATCH v1 1/6] perf dwarf-aux: Use signed comparison in match_var

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Message-ID: <20250725202809.1230085-2-zecheng@google.com>
Date: Fri, 25 Jul 2025 20:28:04 +0000
From: Zecheng Li <zecheng@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	"Liang, Kan" <kan.liang@...ux.intel.com>, Masami Hiramatsu <mhiramat@...nel.org>
Cc: Zecheng Li <zli94@...u.edu>, Xu Liu <xliuprof@...gle.com>, 
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Zecheng Li <zecheng@...gle.com>
Subject: [PATCH v1 1/6] perf dwarf-aux: Use signed comparison 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.

This commit changes the local variables within match_var_offset to
signed types (s64) before performing comparisons. This ensures correct
behavior when addr_offset_ or addr_type_ are negative.

Signed-off-by: Zecheng Li <zecheng@...gle.com>
---
 tools/perf/util/dwarf-aux.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 559c953ca172..bf906dff9ef0 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -1388,10 +1388,12 @@ 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)
+			     u64 addr_offset_, u64 addr_type_, bool is_pointer)
 {
 	Dwarf_Die type_die;
 	Dwarf_Word size;
+	s64 addr_offset = (s64)addr_offset_;
+	s64 addr_type = (s64)addr_type_;
 
 	if (addr_offset == addr_type) {
 		/* Update offset relative to the start of the variable */
@@ -1414,7 +1416,7 @@ 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 (addr_offset_ - addr_type_ >= size)
 		return false;
 
 	/* Update offset relative to the start of the variable */
-- 
2.50.1.470.g6ba607880d-goog