perf annotate: Use an array for the disassembler preference

Prior to this change a string was used which could cause issues with
an unrecognized disassembler in symbol__disassembler. Change to
initializing an array of perf_disassembler enum values. If a value
already exists then adding it a second time is ignored to avoid array
out of bounds problems present in the previous code, it also allows a
statically sized array and removes memory allocation needs. Errors in
the disassembler string are reported when the config is parsed during
perf annotate or perf top start up. If the array is uninitialized
after processing the config file the default llvm, capstone then
objdump values are added but without a need to parse a string.

Fixes: a6e8a58de629 ("perf disasm: Allow configuring what disassemblers to use")
Closes: https://lore.kernel.org/lkml/CAP-5=fUdfCyxmEiTpzS2uumUp3-SyQOseX2xZo81-dQtWXj6vA@mail.gmail.com/
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20250124043856.1177264-1-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

1 files changed, 71 insertions, 5 deletions

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index 0d2ea22bd9e4..31bb326b07a6 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -2100,6 +2100,57 @@ int symbol__annotate2(struct map_symbol *ms, struct evsel *evsel,
 	return 0;
 }
 
+const char * const perf_disassembler__strs[] = {
+	[PERF_DISASM_UNKNOWN]  = "unknown",
+	[PERF_DISASM_LLVM]     = "llvm",
+	[PERF_DISASM_CAPSTONE] = "capstone",
+	[PERF_DISASM_OBJDUMP]  = "objdump",
+};
+
+
+static void annotation_options__add_disassembler(struct annotation_options *options,
+						 enum perf_disassembler dis)
+{
+	for (u8 i = 0; i < ARRAY_SIZE(options->disassemblers); i++) {
+		if (options->disassemblers[i] == dis) {
+			/* Disassembler is already present then don't add again. */
+			return;
+		}
+		if (options->disassemblers[i] == PERF_DISASM_UNKNOWN) {
+			/* Found a free slot. */
+			options->disassemblers[i] = dis;
+			return;
+		}
+	}
+	pr_err("Failed to add disassembler %d\n", dis);
+}
+
+static int annotation_options__add_disassemblers_str(struct annotation_options *options,
+						const char *str)
+{
+	while (str && *str != '\0') {
+		const char *comma = strchr(str, ',');
+		int len = comma ? comma - str : (int)strlen(str);
+		bool match = false;
+
+		for (u8 i = 0; i < ARRAY_SIZE(perf_disassembler__strs); i++) {
+			const char *dis_str = perf_disassembler__strs[i];
+
+			if (len == (int)strlen(dis_str) && !strncmp(str, dis_str, len)) {
+				annotation_options__add_disassembler(options, i);
+				match = true;
+				break;
+			}
+		}
+		if (!match) {
+			pr_err("Invalid disassembler '%.*s'\n", len, str);
+			return -1;
+		}
+		str = comma ? comma + 1 : NULL;
+	}
+	return 0;
+}
+
 static int annotation__config(const char *var, const char *value, void *data)
 {
 	struct annotation_options *opt = data;
@@ -2115,11 +2166,10 @@ static int annotation__config(const char *var, const char *value, void *data)
 		else if (opt->offset_level < ANNOTATION__MIN_OFFSET_LEVEL)
 			opt->offset_level = ANNOTATION__MIN_OFFSET_LEVEL;
 	} else if (!strcmp(var, "annotate.disassemblers")) {
-		opt->disassemblers_str = strdup(value);
-		if (!opt->disassemblers_str) {
-			pr_err("Not enough memory for annotate.disassemblers\n");
-			return -1;
-		}
+		int err = annotation_options__add_disassemblers_str(opt, value);
+
+		if (err)
+			return err;
 	} else if (!strcmp(var, "annotate.hide_src_code")) {
 		opt->hide_src_code = perf_config_bool("hide_src_code", value);
 	} else if (!strcmp(var, "annotate.jump_arrows")) {
@@ -2185,9 +2235,25 @@ void annotation_options__exit(void)
 	zfree(&annotate_opts.objdump_path);
 }
 
+static void annotation_options__default_init_disassemblers(struct annotation_options *options)
+{
+	if (options->disassemblers[0] != PERF_DISASM_UNKNOWN) {
+		/* Already initialized. */
+		return;
+	}
+#ifdef HAVE_LIBLLVM_SUPPORT
+	annotation_options__add_disassembler(options, PERF_DISASM_LLVM);
+#endif
+#ifdef HAVE_LIBCAPSTONE_SUPPORT
+	annotation_options__add_disassembler(options, PERF_DISASM_CAPSTONE);
+#endif
+	annotation_options__add_disassembler(options, PERF_DISASM_OBJDUMP);
+}
+
 void annotation_config__init(void)
 {
 	perf_config(annotation__config, &annotate_opts);
+	annotation_options__default_init_disassemblers(&annotate_opts);
 }
 
 static unsigned int parse_percent_type(char *str1, char *str2)