Re: [PATCHv2 bpf 1/2] bpf: Add checkip argument to bpf_arch_text_poke

[Ilya Leoshkevich <iii@linux.ibm.com>]

On Tue, 2023-11-28 at 10:28 +0100, Jiri Olsa wrote:
> We need to be able to skip ip address check for caller in following
> changes. Adding checkip argument to allow that.
> 
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  arch/arm64/net/bpf_jit_comp.c   |  3 ++-
>  arch/riscv/net/bpf_jit_comp64.c |  5 +++--
>  arch/s390/net/bpf_jit_comp.c    |  3 ++-
>  arch/x86/net/bpf_jit_comp.c     | 24 +++++++++++++-----------
>  include/linux/bpf.h             |  2 +-
>  kernel/bpf/arraymap.c           |  8 ++++----
>  kernel/bpf/core.c               |  2 +-
>  kernel/bpf/trampoline.c         | 12 ++++++------
>  8 files changed, 32 insertions(+), 27 deletions(-)

[...]

> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -435,19 +435,21 @@ static int __bpf_arch_text_poke(void *ip, enum
> bpf_text_poke_type t,
>  }
>  
>  int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
> -                      void *old_addr, void *new_addr)
> +                      void *old_addr, void *new_addr, bool checkip)
>  {
> -       if (!is_kernel_text((long)ip) &&
> -           !is_bpf_text_address((long)ip))
> -               /* BPF poking in modules is not supported */
> -               return -EINVAL;
> +       if (checkip) {
> +               if (!is_kernel_text((long)ip) &&
> +                   !is_bpf_text_address((long)ip))
> +                       /* BPF poking in modules is not supported */
> +                       return -EINVAL;
>  
> -       /*
> -        * See emit_prologue(), for IBT builds the trampoline hook is
> preceded
> -        * with an ENDBR instruction.
> -        */
> -       if (is_endbr(*(u32 *)ip))
> -               ip += ENDBR_INSN_SIZE;
> +               /*
> +                * See emit_prologue(), for IBT builds the trampoline
> hook is preceded
> +                * with an ENDBR instruction.
> +                */
> +               if (is_endbr(*(u32 *)ip))
> +                       ip += ENDBR_INSN_SIZE;

Do we really want to skip the IP adjustment too?

> +       }
>  
>         return __bpf_arch_text_poke(ip, t, old_addr, new_addr);
>  }

[...]