On 8/8/24 6:05 PM, Eduard Zingerman wrote:
int get_jited_program_text(int fd, char *text, size_t text_sz)
Loads and disassembles jited instructions for program pointed to by fd.
Much like 'bpftool prog dump jited ...'.
The code and makefile changes are inspired by jit_disasm.c from bpftool.
Use llvm libraries to disassemble BPF program instead of libbfd to avoid
issues with disassembly output stability pointed out in [1].
Selftests makefile uses Makefile.feature to detect if LLVM libraries
are available. If that is not the case selftests build proceeds but
the function returns -ENOTSUP at runtime.
[1] commit eb9d1acf634b ("bpftool: Add LLVM as default library for disassembling JIT-ed programs")
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
---
tools/testing/selftests/bpf/.gitignore | 1 +
tools/testing/selftests/bpf/Makefile | 51 +++-
.../selftests/bpf/jit_disasm_helpers.c | 228 ++++++++++++++++++
.../selftests/bpf/jit_disasm_helpers.h | 10 +
4 files changed, 288 insertions(+), 2 deletions(-)
create mode 100644 tools/testing/selftests/bpf/jit_disasm_helpers.c
create mode 100644 tools/testing/selftests/bpf/jit_disasm_helpers.h
[...]
+static int disasm_one_func(FILE *text_out, uint8_t *image, __u32 len)
+{
+ char *label, *colon, *triple = NULL;
+ LLVMDisasmContextRef ctx = NULL;
+ struct local_labels labels = {};
+ __u32 *label_pc, pc;
+ int i, cnt, err = 0;
+ char buf[256];
+
+ triple = LLVMGetDefaultTargetTriple();
+ ctx = LLVMCreateDisasm(triple, &labels, 0, NULL, lookup_symbol);
+ if (!ASSERT_OK_PTR(ctx, "LLVMCreateDisasm")) {
+ err = -EINVAL;
+ goto out;
+ }
+
+ cnt = LLVMSetDisasmOptions(ctx, LLVMDisassembler_Option_PrintImmHex);
+ if (!ASSERT_EQ(cnt, 1, "LLVMSetDisasmOptions")) {
+ err = -EINVAL;
+ goto out;
+ }
+
+ /* discover labels */
+ labels.prog_len = len;
+ pc = 0;
+ while (pc < len) {
+ cnt = disasm_insn(ctx, image, len, pc, buf, 1);
+ if (cnt < 0) {
+ err = cnt;
+ goto out;
+ }
+ pc += cnt;
+ }
+ qsort(labels.pcs, labels.cnt, sizeof(*labels.pcs), cmp_u32);
+ /* GCC can't figure max bound for i and thus reports possible truncation */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wformat-truncation"
+ for (i = 0; i < labels.cnt; ++i)
+ snprintf(labels.names[i], sizeof(labels.names[i]), "L%d", i);
+#pragma GCC diagnostic pop
"-Wformat-truncation" is only available for llvm >= 18. One of my build with llvm15
has the following warning/error:
jit_disasm_helpers.c:113:32: error: unknown warning group '-Wformat-truncation', ignored [-Werror,-Wunknown-warning-option]
#pragma GCC diagnostic ignored "-Wformat-truncation"
Maybe you want to guard with proper clang version?
Not sure on gcc side when "-Wformat-truncation" is supported.
+
+ /* now print with labels */
+ labels.print_phase = true;
+ pc = 0;
+ while (pc < len) {
+ cnt = disasm_insn(ctx, image, len, pc, buf, sizeof(buf));
+ if (cnt < 0) {
+ err = cnt;
+ goto out;
+ }
+ label_pc = bsearch(&pc, labels.pcs, labels.cnt, sizeof(*labels.pcs), cmp_u32);
+ label = "";
+ colon = "";
+ if (label_pc) {
+ label = labels.names[label_pc - labels.pcs];
+ colon = ":";
+ }
+ fprintf(text_out, "%x:\t", pc);
+ for (i = 0; i < cnt; ++i)
+ fprintf(text_out, "%02x ", image[pc + i]);
+ for (i = cnt * 3; i < 12 * 3; ++i)
+ fputc(' ', text_out);
+ fprintf(text_out, "%s%s%s\n", label, colon, buf);
+ pc += cnt;
+ }
+
+out:
+ if (triple)
+ LLVMDisposeMessage(triple);
+ if (ctx)
+ LLVMDisasmDispose(ctx);
+ return err;
+}
+
[...]
