[PATCH v6 10/15] perf dso: Support BPF programs in dso__read_symbol

Ian Rogers
2025-09-29T19:09:07Z

Set the buffer to the code in the BPF linear info. This enables BPF
JIT code disassembly by LLVM and capstone. Move the common but minimal
disassmble_bpf_image call to disassemble_objdump so that it is only
called after falling back to the objdump option. Similarly move the
disassmble_bpf function to disassemble_objdump and rename to
disassmble_bpf_libbfd to make it clearer that this support relies on
libbfd.

Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/util/disasm.c | 12 +++--
tools/perf/util/dso.c | 100 ++++++++++++++++++++++++++-------------
tools/perf/util/libbfd.c | 4 +-
tools/perf/util/libbfd.h | 6 +--
4 files changed, 80 insertions(+), 42 deletions(-)

diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
index a1240543c89c..e64902e520ab 100644
--- a/tools/perf/util/disasm.c
+++ b/tools/perf/util/disasm.c
@@ -1521,6 +1521,12 @@ static int symbol__disassemble_objdump(const char *filename, struct symbol *sym,
struct child_process objdump_process;
int err;

+ if (dso__binary_type(dso) == DSO_BINARY_TYPE__BPF_PROG_INFO)
+ return symbol__disassemble_bpf_libbfd(sym, args);
+
+ if (dso__binary_type(dso) == DSO_BINARY_TYPE__BPF_IMAGE)
+ return symbol__disassemble_bpf_image(sym, args);
+
err = asprintf(&command,
"%s %s%s --start-address=0x%016" PRIx64
" --stop-address=0x%016" PRIx64
@@ -1655,11 +1661,7 @@ int symbol__disassemble(struct symbol *sym, struct annotate_args *args)

pr_debug("annotating [%p] %30s : [%p] %30s\n", dso, dso__long_name(dso), sym, sym->name);

- if (dso__binary_type(dso) == DSO_BINARY_TYPE__BPF_PROG_INFO) {
- return symbol__disassemble_bpf(sym, args);
- } else if (dso__binary_type(dso) == DSO_BINARY_TYPE__BPF_IMAGE) {
- return symbol__disassemble_bpf_image(sym, args);
- } else if (dso__binary_type(dso) == DSO_BINARY_TYPE__NOT_FOUND) {
+ if (dso__binary_type(dso) == DSO_BINARY_TYPE__NOT_FOUND) {
return SYMBOL_ANNOTATE_ERRNO__COULDNT_DETERMINE_FILE_TYPE;
} else if (dso__is_kcore(dso)) {
kce.addr = map__rip_2objdump(map, sym->start);
diff --git a/tools/perf/util/dso.c b/tools/perf/util/dso.c
index 87d075942de6..0aed5c8691bd 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -1816,23 +1816,17 @@ static int find_file_offset(u64 start, u64 len, u64 pgoff, void *arg)
return 0;
}

-const u8 *dso__read_symbol(struct dso *dso, const char *symfs_filename,
- const struct map *map, const struct symbol *sym,
- u8 **out_buf, u64 *out_buf_len, bool *is_64bit)
+static const u8 *__dso__read_symbol(struct dso *dso, const char *symfs_filename,
+ u64 start, size_t len,
+ u8 **out_buf, u64 *out_buf_len, bool *is_64bit)
{
struct nscookie nsc;
- u64 start = map__rip_2objdump(map, sym->start);
- u64 end = map__rip_2objdump(map, sym->end);
- int fd, count;
- u8 *buf = NULL;
- size_t len;
+ int fd;
+ ssize_t count;
struct find_file_offset_data data = {
.ip = start,
};
-
- *out_buf = NULL;
- *out_buf_len = 0;
- *is_64bit = false;
+ u8 *code_buf = NULL;

nsinfo__mountns_enter(dso__nsinfo(dso), &nsc);
fd = open(symfs_filename, O_RDONLY);
@@ -1840,28 +1834,70 @@ const u8 *dso__read_symbol(struct dso *dso, const char *symfs_filename,
if (fd < 0)
return NULL;

- if (file__read_maps(fd, /*exe=*/true, find_file_offset, &data, is_64bit) == 0)
- goto err;
-
- len = end - start;
- buf = malloc(len);
- if (buf == NULL)
- goto err;
-
- count = pread(fd, buf, len, data.offset);
+ if (file__read_maps(fd, /*exe=*/true, find_file_offset, &data, is_64bit) == 0) {
+ close(fd);
+ return NULL;
+ }
+ code_buf = malloc(len);
+ if (code_buf == NULL) {
+ close(fd);
+ return NULL;
+ }
+ count = pread(fd, code_buf, len, data.offset);
close(fd);
- fd = -1;
+ if ((u64)count != len) {
+ free(code_buf);
+ return NULL;
+ }
+ *out_buf = code_buf;
+ *out_buf_len = len;
+ return code_buf;
+}

- if ((u64)count != len)
- goto err;
+/*
+ * Read a symbol into memory for disassembly by a library like capstone of
+ * libLLVM. If memory is allocated out_buf holds it.
+ */
+const u8 *dso__read_symbol(struct dso *dso, const char *symfs_filename,
+ const struct map *map, const struct symbol *sym,
+ u8 **out_buf, u64 *out_buf_len, bool *is_64bit)
+{
+ u64 start = map__rip_2objdump(map, sym->start);
+ u64 end = map__rip_2objdump(map, sym->end);
+ size_t len = end - start;

- *out_buf = buf;
- *out_buf_len = len;
- return buf;
+ *out_buf = NULL;
+ *out_buf_len = 0;
+ *is_64bit = false;

-err:
- if (fd >= 0)
- close(fd);
- free(buf);
- return NULL;
+ if (dso__binary_type(dso) == DSO_BINARY_TYPE__BPF_IMAGE) {
+ /*
+ * Note, there is fallback BPF image disassembly in the objdump
+ * version but it currently does nothing.
+ */
+ return NULL;
+ }
+ if (dso__binary_type(dso) == DSO_BINARY_TYPE__BPF_PROG_INFO) {
+#ifdef HAVE_LIBBPF_SUPPORT
+ struct bpf_prog_info_node *info_node;
+ struct perf_bpil *info_linear;
+
+ *is_64bit = sizeof(void *) == sizeof(u64);
+ info_node = perf_env__find_bpf_prog_info(dso__bpf_prog(dso)->env,
+ dso__bpf_prog(dso)->id);
+ if (!info_node) {
+ errno = SYMBOL_ANNOTATE_ERRNO__BPF_MISSING_BTF;
+ return NULL;
+ }
+ info_linear = info_node->info_linear;
+ assert(len <= info_linear->info.jited_prog_len);
+ *out_buf_len = len;
+ return (const u8 *)(uintptr_t)(info_linear->info.jited_prog_insns);
+#else
+ pr_debug("No BPF program disassembly support\n");
+ return NULL;
+#endif
+ }
+ return __dso__read_symbol(dso, symfs_filename, start, len,
+ out_buf, out_buf_len, is_64bit);
}
diff --git a/tools/perf/util/libbfd.c b/tools/perf/util/libbfd.c
index 09a0eeb78a1a..01147fbf73b3 100644
--- a/tools/perf/util/libbfd.c
+++ b/tools/perf/util/libbfd.c
@@ -448,8 +448,8 @@ int libbfd_filename__read_debuglink(const char *filename, char *debuglink,
return err;
}

-int symbol__disassemble_bpf(struct symbol *sym __maybe_unused,
- struct annotate_args *args __maybe_unused)
+int symbol__disassemble_bpf_libbfd(struct symbol *sym __maybe_unused,
+ struct annotate_args *args __maybe_unused)
{
#ifdef HAVE_LIBBPF_SUPPORT
struct annotation *notes = symbol__annotation(sym);
diff --git a/tools/perf/util/libbfd.h b/tools/perf/util/libbfd.h
index 7441e95f8ec0..e300f171d1bd 100644
--- a/tools/perf/util/libbfd.h
+++ b/tools/perf/util/libbfd.h
@@ -29,7 +29,7 @@ int libbfd__read_build_id(const char *filename, struct build_id *bid, bool block

int libbfd_filename__read_debuglink(const char *filename, char *debuglink, size_t size);

-int symbol__disassemble_bpf(struct symbol *sym, struct annotate_args *args);
+int symbol__disassemble_bpf_libbfd(struct symbol *sym, struct annotate_args *args);

#else // !defined(HAVE_LIBBFD_SUPPORT)
#include "annotate.h"
@@ -72,8 +72,8 @@ static inline int libbfd_filename__read_debuglink(const char *filename __always_
return -1;
}

-static inline int symbol__disassemble_bpf(struct symbol *sym __always_unused,
- struct annotate_args *args __always_unused)
+static inline int symbol__disassemble_bpf_libbfd(struct symbol *sym __always_unused,
+ struct annotate_args *args __always_unused)
{
return SYMBOL_ANNOTATE_ERRNO__NO_LIBOPCODES_FOR_BPF;
}
--
2.51.0.570.gb178f27e6d-goog