On Fri, Dec 30, 2022 at 3:38 AM <xiangxia.m.yue@xxxxxxxxx> wrote:
>
> From: Tonghao Zhang <xiangxia.m.yue@xxxxxxxxx>
>
> With bpf_jit_binary_pack_finalize invoked, we copy
> rw_header to header and then image/insn is valid.
>
> Write a test BPF prog which include subprog:
>
> $ llvm-objdump -d subprog.o
> Disassembly of section .text:
> 0000000000000000 <subprog>:
> 0: 18 01 00 00 73 75 62 70 00 00 00 00 72 6f 67 00 r1 = 29114459903653235 ll
> 2: 7b 1a f8 ff 00 00 00 00 *(u64 *)(r10 - 8) = r1
> 3: bf a1 00 00 00 00 00 00 r1 = r10
> 4: 07 01 00 00 f8 ff ff ff r1 += -8
> 5: b7 02 00 00 08 00 00 00 r2 = 8
> 6: 85 00 00 00 06 00 00 00 call 6
> 7: 95 00 00 00 00 00 00 00 exit
> Disassembly of section raw_tp/sys_enter:
> 0000000000000000 <entry>:
> 0: 85 10 00 00 ff ff ff ff call -1
> 1: b7 00 00 00 00 00 00 00 r0 = 0
> 2: 95 00 00 00 00 00 00 00 exit
>
> Without this patch, kernel print message:
> [ 580.775387] flen=8 proglen=51 pass=3 image=ffffffffa000c20c from=kprobe-load pid=1643
> [ 580.777236] JIT code: 00000000: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc
> [ 580.779037] JIT code: 00000010: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc
> [ 580.780767] JIT code: 00000020: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc
> [ 580.782568] JIT code: 00000030: cc cc cc
>
> $ bpf_jit_disasm
> 51 bytes emitted from JIT compiler (pass:3, flen:8)
> ffffffffa000c20c + <x>:
> 0: int3
> 1: int3
> 2: int3
> 3: int3
> 4: int3
> 5: int3
> ...
>
> To fix this issue:
> [ 260.016071] flen=3 proglen=20 pass=1 image=ffffffffa000c11c from=kprobe-load pid=1568
> [ 260.018094] JIT code: 00000000: 0f 1f 44 00 00 66 90 55 48 89 e5 e8 38 00 00 00
> [ 260.020124] JIT code: 00000010: 31 c0 c9 c3
> [ 260.021229] flen=8 proglen=51 pass=1 image=ffffffffa000c164 from=kprobe-load pid=1568
> [ 260.023132] JIT code: 00000000: 0f 1f 44 00 00 66 90 55 48 89 e5 48 81 ec 08 00
> [ 260.025129] JIT code: 00000010: 00 00 48 bf 73 75 62 70 72 6f 67 00 48 89 7d f8
> [ 260.027199] JIT code: 00000020: 48 89 ef 48 83 c7 f8 be 08 00 00 00 e8 9e 19 1d
> [ 260.029226] JIT code: 00000030: e1 c9 c3
>
> $ bpf_jit_disasm
> 51 bytes emitted from JIT compiler (pass:1, flen:8)
> ffffffffa000c164 + <x>:
> 0: nopl 0x0(%rax,%rax,1)
> 5: xchg %ax,%ax
> 7: push %rbp
> 8: mov %rsp,%rbp
> b: sub $0x8,%rsp
> 12: movabs $0x676f7270627573,%rdi
> 1c: mov %rdi,-0x8(%rbp)
> 20: mov %rbp,%rdi
> 23: add $0xfffffffffffffff8,%rdi
> 27: mov $0x8,%esi
> 2c: callq 0xffffffffe11d19cf
> 31: leaveq
> 32: retq
>
> $ bpf_jit_disasm
> 20 bytes emitted from JIT compiler (pass:1, flen:3)
> ffffffffa000c11c + <x>:
> 0: nopl 0x0(%rax,%rax,1)
> 5: xchg %ax,%ax
> 7: push %rbp
> 8: mov %rsp,%rbp
> b: callq 0x0000000000000048
> 10: xor %eax,%eax
> 12: leaveq
> 13: retq
>
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@xxxxxxxxx>
> Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
> Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
> Cc: Martin KaFai Lau <martin.lau@xxxxxxxxx>
> Cc: Song Liu <song@xxxxxxxxxx>
> Cc: Yonghong Song <yhs@xxxxxx>
> Cc: John Fastabend <john.fastabend@xxxxxxxxx>
> Cc: KP Singh <kpsingh@xxxxxxxxxx>
> Cc: Stanislav Fomichev <sdf@xxxxxxxxxx>
> Cc: Hao Luo <haoluo@xxxxxxxxxx>
> Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
> Cc: Hou Tao <houtao1@xxxxxxxxxx>
> ---
> arch/x86/net/bpf_jit_comp.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index 36ffe67ad6e5..4e017102cc16 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -2543,9 +2543,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> cond_resched();
> }
>
> - if (bpf_jit_enable > 1)
> - bpf_jit_dump(prog->len, proglen, pass + 1, image);
> -
> if (image) {
> if (!prog->is_func || extra_pass) {
> /*
> @@ -2561,6 +2558,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
> goto out_image;
> }
>
> + if (bpf_jit_enable > 1)
> + bpf_jit_dump(prog->len, proglen, pass + 1, image);
> +
bpf_jit_enable==2 is broken.
Please delete it from everywhere including docs.
Use bpftool prog dump instead.
