Ensure errno is set and return to caller for error handling. Unusually
for perf the value isn't negated as expected by
symbol__strerror_disassemble.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/capstone.c |  3 ++-
 tools/perf/util/dso.c      | 14 ++++++++++++--
 tools/perf/util/llvm.c     |  3 ++-
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/capstone.c b/tools/perf/util/capstone.c
index f103988184c8..032548828925 100644
--- a/tools/perf/util/capstone.c
+++ b/tools/perf/util/capstone.c
@@ -12,6 +12,7 @@
 #include "symbol.h"
 #include "thread.h"
 #include <dlfcn.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <inttypes.h>
 #include <string.h>
@@ -463,7 +464,7 @@ int symbol__disassemble_capstone(const char *filename __maybe_unused,
 	buf = dso__read_symbol(dso, filename, map, sym,
 			       &code_buf, &buf_len, &is_64bit);
 	if (buf == NULL)
-		return -1;
+		return errno;
 
 	/* add the function address and name */
 	scnprintf(disasm_buf, sizeof(disasm_buf), "%#"PRIx64" <%s>:",
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index a90799bed230..247e59605f26 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -1697,6 +1697,7 @@ const u8 *dso__read_symbol(struct dso *dso, const char *symfs_filename,
 
 	if (dso__binary_type(dso) == DSO_BINARY_TYPE__BPF_IMAGE) {
 		pr_debug("No BPF image disassembly support\n");
+		errno = EOPNOTSUPP;
 		return NULL;
 	} else if (dso__binary_type(dso) == DSO_BINARY_TYPE__BPF_PROG_INFO) {
 #ifdef HAVE_LIBBPF_SUPPORT
@@ -1715,6 +1716,7 @@ const u8 *dso__read_symbol(struct dso *dso, const char *symfs_filename,
 		assert(len <= info_linear->info.jited_prog_len);
 #else
 		pr_debug("No BPF program disassembly support\n");
+		errno = EOPNOTSUPP;
 		return NULL;
 #endif
 	} else {
@@ -1725,26 +1727,34 @@ const u8 *dso__read_symbol(struct dso *dso, const char *symfs_filename,
 			.ip = start,
 		};
 		u8 *code_buf = NULL;
+		int saved_errno;
 
 		nsinfo__mountns_enter(dso__nsinfo(dso), &nsc);
 		fd = open(symfs_filename, O_RDONLY);
+		saved_errno = errno;
 		nsinfo__mountns_exit(&nsc);
-		if (fd < 0)
+		if (fd < 0) {
+			errno = saved_errno;
 			return NULL;
+		}
 
-		if (file__read_maps(fd, /*exe=*/true, find_file_offset, &data, is_64bit) == 0) {
+		if (file__read_maps(fd, /*exe=*/true, find_file_offset, &data, is_64bit) <= 0) {
 			close(fd);
+			errno = ENOENT;
 			return NULL;
 		}
 		buf = code_buf = malloc(len);
 		if (buf == NULL) {
 			close(fd);
+			errno = ENOMEM;
 			return NULL;
 		}
 		count = pread(fd, code_buf, len, data.offset);
+		saved_errno = errno;
 		close(fd);
 		if ((u64)count != len) {
 			free(code_buf);
+			errno = saved_errno;
 			return NULL;
 		}
 		*out_buf = code_buf;
diff --git a/tools/perf/util/llvm.c b/tools/perf/util/llvm.c
index a28f130c8951..1607364ee736 100644
--- a/tools/perf/util/llvm.c
+++ b/tools/perf/util/llvm.c
@@ -9,6 +9,7 @@
 #include "srcline.h"
 #include "symbol.h"
 #include <dlfcn.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <inttypes.h>
 #include <unistd.h>
@@ -365,7 +366,7 @@ int symbol__disassemble_llvm(const char *filename, struct symbol *sym,
 	buf = dso__read_symbol(dso, filename, map, sym,
 			       &code_buf, &buf_len, &is_64bit);
 	if (buf == NULL)
-		return -1;
+		return errno;
 
 	init_llvm();
 	if (arch__is(args->arch, "x86")) {
-- 
2.48.0.rc2.279.g1de40edade-goog