[PATCH v2 10/17] perf dso: Support BPF programs in dso__read_symbol

Ian Rogers
2025-01-22T06:25:11Z

Set the buffer to the code in the BPF linear info. This enables BPF
JIT code disassembly by LLVM and capstone. Move the disassmble_bpf
calls to disassemble_objdump so that they are only called after
falling back to the objdump option.

Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/util/disasm.c | 12 +++---
tools/perf/util/dso.c | 85 +++++++++++++++++++++++++---------------
2 files changed, 60 insertions(+), 37 deletions(-)

diff --git a/tools/perf/util/disasm.c b/tools/perf/util/disasm.c
index a9cc588a3006..99b9c21e02b0 100644
--- a/tools/perf/util/disasm.c
+++ b/tools/perf/util/disasm.c
@@ -1500,6 +1500,12 @@ 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(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
@@ -1681,11 +1687,7 @@ 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 0285904ed26d..a90799bed230 100644
--- a/tools/perf/util/dso.c
+++ b/tools/perf/util/dso.c
@@ -1686,48 +1686,69 @@ 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)
{
- 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;
- struct find_file_offset_data data = {
- .ip = start,
- };
+ const u8 *buf;
+ size_t len = end - start;

*out_buf = NULL;
*out_buf_len = 0;
*is_64bit = false;

- nsinfo__mountns_enter(dso__nsinfo(dso), &nsc);
- fd = open(symfs_filename, O_RDONLY);
- nsinfo__mountns_exit(&nsc);
- if (fd < 0)
+ if (dso__binary_type(dso) == DSO_BINARY_TYPE__BPF_IMAGE) {
+ pr_debug("No BPF image disassembly support\n");
return NULL;
+ } else 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;
+ buf = (const u8 *)(uintptr_t)(info_linear->info.jited_prog_insns);
+ assert(len <= info_linear->info.jited_prog_len);
+#else
+ pr_debug("No BPF program disassembly support\n");
+ return NULL;
+#endif
+ } else {
+ struct nscookie nsc;
+ int fd;
+ ssize_t count;
+ struct find_file_offset_data data = {
+ .ip = start,
+ };
+ u8 *code_buf = 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);
- close(fd);
- fd = -1;
-
- if ((u64)count != len)
- goto err;
+ nsinfo__mountns_enter(dso__nsinfo(dso), &nsc);
+ fd = open(symfs_filename, O_RDONLY);
+ nsinfo__mountns_exit(&nsc);
+ if (fd < 0)
+ return NULL;

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