perf annotate: Don't return -1 for error when doing BPF disassembly

Return errno when open_memstream() fails and add two new speciall error
codes for when an invalid, non BPF file or one without BTF is passed to
symbol__disassemble_bpf(), so that its callers can rely on
symbol__strerror_disassemble() to convert that to a human readable error
message that can help figure out what is wrong, with hints even.

Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Song Liu <songliubraving@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Cc: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/n/tip-usevw9r2gcipfcrbpaueurw0@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/annotate.c

@@ -1637,6 +1637,13 @@ int symbol__strerror_disassemble(struct symbol *sym __maybe_unused, struct map *
 	case SYMBOL_ANNOTATE_ERRNO__ARCH_INIT_CPUID_PARSING:
 		scnprintf(buf, buflen, "Problems while parsing the CPUID in the arch specific initialization.");
 		break;
+	case SYMBOL_ANNOTATE_ERRNO__BPF_INVALID_FILE:
+		scnprintf(buf, buflen, "Invalid BPF file: %s.", dso->long_name);
+		break;
+	case SYMBOL_ANNOTATE_ERRNO__BPF_MISSING_BTF:
+		scnprintf(buf, buflen, "The %s BPF file has no BTF section, compile with -g or use pahole -J.",
+			  dso->long_name);
+		break;
 	default:
 		scnprintf(buf, buflen, "Internal error: Invalid %d error code\n", errnum);
 		break;
@@ -1719,13 +1726,13 @@ static int symbol__disassemble_bpf(struct symbol *sym,
 	char tpath[PATH_MAX];
 	size_t buf_size;
 	int nr_skip = 0;
-	int ret = -1;
 	char *buf;
 	bfd *bfdf;
+	int ret;
 	FILE *s;
 
 	if (dso->binary_type != DSO_BINARY_TYPE__BPF_PROG_INFO)
-		return -1;
+		return SYMBOL_ANNOTATE_ERRNO__BPF_INVALID_FILE;
 
 	pr_debug("%s: handling sym %s addr %" PRIx64 " len %" PRIx64 "\n", __func__,
 		  sym->name, sym->start, sym->end - sym->start);
@@ -1738,8 +1745,10 @@ static int symbol__disassemble_bpf(struct symbol *sym,
 	assert(bfd_check_format(bfdf, bfd_object));
 
 	s = open_memstream(&buf, &buf_size);
-	if (!s)
+	if (!s) {
+		ret = errno;
 		goto out;
+	}
 	init_disassemble_info(&info, s,
 			      (fprintf_ftype) fprintf);
 
@@ -1748,8 +1757,10 @@ static int symbol__disassemble_bpf(struct symbol *sym,
 
 	info_node = perf_env__find_bpf_prog_info(dso->bpf_prog.env,
 						 dso->bpf_prog.id);
-	if (!info_node)
+	if (!info_node) {
+		return SYMBOL_ANNOTATE_ERRNO__BPF_MISSING_BTF;
 		goto out;
+	}
 	info_linear = info_node->info_linear;
 	sub_id = dso->bpf_prog.sub_id;
 

tools/perf/util/annotate.h

@@ -372,6 +372,8 @@ enum symbol_disassemble_errno {
 	SYMBOL_ANNOTATE_ERRNO__NO_LIBOPCODES_FOR_BPF,
 	SYMBOL_ANNOTATE_ERRNO__ARCH_INIT_CPUID_PARSING,
 	SYMBOL_ANNOTATE_ERRNO__ARCH_INIT_REGEXP,
+	SYMBOL_ANNOTATE_ERRNO__BPF_INVALID_FILE,
+	SYMBOL_ANNOTATE_ERRNO__BPF_MISSING_BTF,
 
 	__SYMBOL_ANNOTATE_ERRNO__END,
 };