On Mon, 2023-08-07 at 16:11 +0300, Eduard Zingerman wrote:
[...]
> $ bpftool prog dump jited id <some-id>
> bpf_prog_ebeed182d92b487f:
> 0: nopl (%rax,%rax)
> 5: nop
> 7: pushq %rbp
> 8: movq %rsp, %rbp
> b: subq $8, %rsp
> 12: movl $553656332, -8(%rbp)
> 19: movswq %bp, %rdi ; <---- Note movswq %bp !
> 1d: addq $-8, %rdi
> 21: movl $3, %esi
> 26: cmpq %rdi, %rsi
> 29: jbe 0x2b
> 2b: callq 0xffffffffe11c484c
> 30: xorl %eax, %eax
> 32: leave
> 33: retq
>
> Note jit instruction #19 corresponding to BPF instruction #1, which
> loads truncated and sign-extended value of %rbp's first byte as an
> address of format string.
Correction: sign-extended value of %rbp's first *two* bytes,
disassembly with opcodes:
19: movswq %bp, %rdi
48 0f bf fd
[...]
