linux-kernel - [PATCH] perf headers: fix processing of pmu

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Date:   Mon,  8 Jun 2020 09:18:05 -0700
From:   Stephane Eranian <eranian@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     acme@...hat.com, jolsa@...hat.com, peterz@...radead.org,
        mingo@...e.hu, irogers@...gle.com
Subject: [PATCH] perf headers: fix processing of pmu_mappings

This patch fixes a bug in process_pmu_mappings() where the code
would not produce an env->pmu_mappings string that was easily parsable.
The function parses the PMU_MAPPING header information into a string
consisting of value:name pairs where value is the PMU type identifier
and name is the PMU name, e.g., 10:ibs_fetch. As it was, the code
was producing a truncated string with only the first pair showing
even though the rest was there but after the \0.
This patch fixes the problem byt adding a proper white space between
pairs and moving the \0 termination to the end. With this patch applied,
all pairs appear and are easily parsed.

Before:
14:amd_iommu_1

After:
14:amd_iommu_1 7:uprobe 5:breakpoint 10:amd_l3 19:amd_iommu_6 8:power 4:cpu 17:amd_iommu_4 15:amd_iommu_2 1:software 6:kprobe 13:amd_iommu_0 9:amd_df 20:amd_iommu_7 18:amd_iommu_5 2:tracepoint 21:msr 12:ibs_op 16:amd_iommu_3 11:ibs_fetch

Signed-off-by: Stephane Eranian <eranian@...gle.com>
---
 tools/perf/util/header.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index 7a67d017d72c3..cf72124da9350 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -2462,13 +2462,15 @@ static int process_numa_topology(struct feat_fd *ff, void *data __maybe_unused)
 static int process_pmu_mappings(struct feat_fd *ff, void *data __maybe_unused)
 {
 	char *name;
-	u32 pmu_num;
+	u32 pmu_num, o_num;
 	u32 type;
 	struct strbuf sb;
 
 	if (do_read_u32(ff, &pmu_num))
 		return -1;
 
+	o_num = pmu_num;
+
 	if (!pmu_num) {
 		pr_debug("pmu mappings not available\n");
 		return 0;
@@ -2486,10 +2488,11 @@ static int process_pmu_mappings(struct feat_fd *ff, void *data __maybe_unused)
 		if (!name)
 			goto error;
 
-		if (strbuf_addf(&sb, "%u:%s", type, name) < 0)
+		/* add proper spacing between entries */
+		if (pmu_num < o_num && strbuf_add(&sb, " ", 1) < 0)
 			goto error;
-		/* include a NULL character at the end */
-		if (strbuf_add(&sb, "", 1) < 0)
+
+		if (strbuf_addf(&sb, "%u:%s", type, name) < 0)
 			goto error;
 
 		if (!strcmp(name, "msr"))
@@ -2498,6 +2501,9 @@ static int process_pmu_mappings(struct feat_fd *ff, void *data __maybe_unused)
 		free(name);
 		pmu_num--;
 	}
+	/* include a NULL character at the end */
+	if (strbuf_add(&sb, "", 1) < 0)
+		goto error;
 	ff->ph->env.pmu_mappings = strbuf_detach(&sb, NULL);
 	return 0;
 
-- 
2.27.0.278.ge193c7cf3a9-goog