linux-kernel - [PATCH] perf jit: Fix inaccurate DWARF line table

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Message-Id: <20200528051916.6722-1-nick.gasson@arm.com>
Date:   Thu, 28 May 2020 13:19:16 +0800
From:   Nick Gasson <nick.gasson@....com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, Ian Rogers <irogers@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Stephane Eranian <eranian@...gle.com>
Cc:     Nick Gasson <nick.gasson@....com>, linux-kernel@...r.kernel.org
Subject: [PATCH] perf jit: Fix inaccurate DWARF line table

Fix an issue where addresses in the DWARF line table are offset by
-0x40 (GEN_ELF_TEXT_OFFSET). This can be seen with `objdump -S` on the
ELF files after perf inject.

Signed-off-by: Nick Gasson <nick.gasson@....com>
---
 tools/perf/util/genelf_debug.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/genelf_debug.c b/tools/perf/util/genelf_debug.c
index 30e9f618f6cd..dd40683bd4c0 100644
--- a/tools/perf/util/genelf_debug.c
+++ b/tools/perf/util/genelf_debug.c
@@ -342,7 +342,7 @@ static void emit_lineno_info(struct buffer_ext *be,
 	 */
 
 	/* start state of the state machine we take care of */
-	unsigned long last_vma = code_addr;
+	unsigned long last_vma = 0;
 	char const  *cur_filename = NULL;
 	unsigned long cur_file_idx = 0;
 	int last_line = 1;
@@ -473,7 +473,7 @@ jit_process_debug_info(uint64_t code_addr,
 		ent = debug_entry_next(ent);
 	}
 	add_compilation_unit(di, buffer_ext_size(dl));
-	add_debug_line(dl, debug, nr_debug_entries, 0);
+	add_debug_line(dl, debug, nr_debug_entries, GEN_ELF_TEXT_OFFSET);
 	add_debug_abbrev(da);
 	if (0) buffer_ext_dump(da, "abbrev");
 
-- 
2.26.2