> diff --git a/tools/testing/selftests/bpf/jit_disasm_helpers.c
> b/tools/testing/selftests/bpf/jit_disasm_helpers.c
> index 364c557c5115..9e6613479145 100644
> --- a/tools/testing/selftests/bpf/jit_disasm_helpers.c
> +++ b/tools/testing/selftests/bpf/jit_disasm_helpers.c
> @@ -170,9 +170,11 @@ int get_jited_program_text(int fd, char *text, size_t
> text_sz)
> struct bpf_prog_info info = {};
> __u32 info_len = sizeof(info);
> __u32 jited_funcs, len, pc;
> + __u32 trunc_len = 0;
> __u32 *func_lens = NULL;
> FILE *text_out = NULL;
> uint8_t *image = NULL;
> + char *triple = NULL;
> int i, err = 0;
>
> if (!llvm_initialized) {
> @@ -216,9 +218,21 @@ int get_jited_program_text(int fd, char *text, size_t
> text_sz)
> if (!ASSERT_OK(err, "bpf_prog_get_info_by_fd #2"))
> goto out;
>
> + /*
> + * last 8 bytes contains dummy_trampoline address in JIT
> + * output for 64-bit and 32-bit powerpc, which can't
> + * disassemble a to valid instruction.
> + */
This isn't a bug, but there's a grammar error here: "disassemble a to
valid instruction" should be "disassemble to a valid instruction".
> + triple = LLVMGetDefaultTargetTriple();
> + if (triple) {
> + if (strstr(triple, "powerpc"))
> + trunc_len = 8;
Will this remove a valid instruction on 32-bit PowerPC targets?
The dummy trampoline address is stored as an unsigned long, which
occupies 8 bytes on 64-bit PowerPC, but only 4 bytes on 32-bit
PowerPC.
Because the long branch stub ends with a 4-byte bctr instruction
followed by the dummy address, unconditionally truncating 8 bytes on
32-bit PowerPC would remove both the 4-byte dummy address and the
valid 4-byte bctr instruction from the disassembly.
Does the truncation length need to be determined dynamically based on
whether the target is 32-bit or 64-bit?
(Note: This concern was raised by [email protected] in v4:
https://lore.kernel.org/bpf/[email protected])
> + LLVMDisposeMessage(triple);
> + }
> +
> for (pc = 0, i = 0; i < jited_funcs; ++i) {
> fprintf(text_out, "func #%d:\n", i);
> - disasm_one_func(text_out, image + pc, func_lens[i]);
> + disasm_one_func(text_out, image + pc, func_lens[i] - trunc_len);
> fprintf(text_out, "\n");
> pc += func_lens[i];
> }
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/26121409898
