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Message-Id: <20241217-perf_fix_riscv_obj_reading-v2-1-58f81b7b4c7d@rivosinc.com>
Date: Tue, 17 Dec 2024 15:52:08 -0800
From: Charlie Jenkins <charlie@...osinc.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>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>
Cc: linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-riscv@...ts.infradead.org, Charlie Jenkins <charlie@...osinc.com>
Subject: [PATCH v2] tools: perf: tests: Fix code reading for riscv
After binutils commit e43d876 which was first included in binutils 2.41,
riscv no longer supports dumping in the middle of instructions. Increase
the objdump window by 2-bytes to ensure that any instruction that sits
on the boundary of the specified stop-address is not cut in half.
Signed-off-by: Charlie Jenkins <charlie@...osinc.com>
---
A binutils patch has been sent as well to fix this in objdump [1].
Link:
https://sourceware.org/pipermail/binutils/2024-December/138139.html [1]
---
Changes in v2:
- Do objdump version detection at runtime (Ian)
- Link to v1: https://lore.kernel.org/r/20241216-perf_fix_riscv_obj_reading-v1-0-b75962660a9b@rivosinc.com
---
tools/perf/tests/code-reading.c | 84 ++++++++++++++++++++++++++++++++++++++++-
1 file changed, 83 insertions(+), 1 deletion(-)
diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c
index 27c82cfb7e7de42284bf5af9cf7594a3a963052e..7e24d10a543ac18ac2be70b829d088874e0edfd5 100644
--- a/tools/perf/tests/code-reading.c
+++ b/tools/perf/tests/code-reading.c
@@ -1,5 +1,6 @@
// SPDX-License-Identifier: GPL-2.0
#include <errno.h>
+#include <linux/kconfig.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <inttypes.h>
@@ -176,6 +177,66 @@ static int read_objdump_output(FILE *f, void *buf, size_t *len, u64 start_addr)
return err;
}
+/*
+ * Only gets GNU objdump version. Returns 0 for llvm-objdump.
+ */
+static int objdump_version(void)
+{
+ size_t line_len;
+ char cmd[PATH_MAX * 2];
+ char *line = NULL;
+ const char *fmt;
+ FILE *f;
+ int ret;
+
+ int version_tmp, version_num = 0;
+ char *version = 0, *token;
+
+ fmt = "%s --version";
+ ret = snprintf(cmd, sizeof(cmd), fmt, test_objdump_path);
+ if (ret <= 0 || (size_t)ret >= sizeof(cmd))
+ return -1;
+ /* Ignore objdump errors */
+ strcat(cmd, " 2>/dev/null");
+ f = popen(cmd, "r");
+ if (!f) {
+ pr_debug("popen failed\n");
+ return -1;
+ }
+ /* Get first line of objdump --version output */
+ ret = getline(&line, &line_len, f);
+ pclose(f);
+ if (ret < 0) {
+ pr_debug("getline failed\n");
+ return -1;
+ }
+
+ token = strsep(&line, " ");
+ if (token != NULL && !strcmp(token, "GNU")) {
+ // version is last part of first line of objdump --version output.
+ while ((token = strsep(&line, " ")))
+ version = token;
+
+ // Convert version into a format we can compare with
+ token = strsep(&version, ".");
+ version_num = atoi(token);
+ if (version_num)
+ version_num *= 10000;
+
+ token = strsep(&version, ".");
+ version_tmp = atoi(token);
+ if (token)
+ version_num += version_tmp * 100;
+
+ token = strsep(&version, ".");
+ version_tmp = atoi(token);
+ if (token)
+ version_num += version_tmp;
+ }
+
+ return version_num;
+}
+
static int read_via_objdump(const char *filename, u64 addr, void *buf,
size_t len)
{
@@ -183,9 +244,30 @@ static int read_via_objdump(const char *filename, u64 addr, void *buf,
const char *fmt;
FILE *f;
int ret;
+ u64 stop_address = addr + len;
+
+ if (IS_ENABLED(__riscv)) {
+ int version = objdump_version();
+
+ /* Default to this workaround if version parsing fails */
+ if (version < 0 || version > 24100) {
+ /*
+ * Starting at riscv objdump version 2.41, dumping in
+ * the middle of an instruction is not supported. riscv
+ * instructions are aligned along 2-byte intervals and
+ * can be either 2-bytes or 4-bytes. This makes it
+ * possible that the stop-address lands in the middle of
+ * a 4-byte instruction. Increase the stop_address by
+ * two to ensure an instruction is not cut in half, but
+ * leave the len as-is so only the expected number of
+ * bytes are collected.
+ */
+ stop_address += 2;
+ }
+ }
fmt = "%s -z -d --start-address=0x%"PRIx64" --stop-address=0x%"PRIx64" %s";
- ret = snprintf(cmd, sizeof(cmd), fmt, test_objdump_path, addr, addr + len,
+ ret = snprintf(cmd, sizeof(cmd), fmt, test_objdump_path, addr, stop_address,
filename);
if (ret <= 0 || (size_t)ret >= sizeof(cmd))
return -1;
---
base-commit: fac04efc5c793dccbd07e2d59af9f90b7fc0dca4
change-id: 20241213-perf_fix_riscv_obj_reading-cabf02be3c85
--
- Charlie
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