On Wed, May 18, 2022 at 09:16:35AM -0400, Xu Kuohai wrote:
> BPF_TRAM_F_XXX flags are not used by user code and are almost constant
> at compile time, so run time validation is a bit overkill. Remove
> is_valid_bpf_tramp_flags() and add some usage comments.
>
> Signed-off-by: Xu Kuohai <xukuohai@xxxxxxxxxx>
> Acked-by: Song Liu <songliubraving@xxxxxx>
Am I right in thinking this is independent of the arm64-specific bits, and
could be taken on its own now?
Mark.
> ---
> arch/x86/net/bpf_jit_comp.c | 20 --------------------
> kernel/bpf/bpf_struct_ops.c | 3 +++
> kernel/bpf/trampoline.c | 3 +++
> 3 files changed, 6 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index a2b6d197c226..7698ef3b4821 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -1922,23 +1922,6 @@ static int invoke_bpf_mod_ret(const struct btf_func_model *m, u8 **pprog,
> return 0;
> }
>
> -static bool is_valid_bpf_tramp_flags(unsigned int flags)
> -{
> - if ((flags & BPF_TRAMP_F_RESTORE_REGS) &&
> - (flags & BPF_TRAMP_F_SKIP_FRAME))
> - return false;
> -
> - /*
> - * BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops,
> - * and it must be used alone.
> - */
> - if ((flags & BPF_TRAMP_F_RET_FENTRY_RET) &&
> - (flags & ~BPF_TRAMP_F_RET_FENTRY_RET))
> - return false;
> -
> - return true;
> -}
> -
> /* Example:
> * __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev);
> * its 'struct btf_func_model' will be nr_args=2
> @@ -2017,9 +2000,6 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
> if (nr_args > 6)
> return -ENOTSUPP;
>
> - if (!is_valid_bpf_tramp_flags(flags))
> - return -EINVAL;
> -
> /* Generated trampoline stack layout:
> *
> * RBP + 8 [ return address ]
> diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
> index d9a3c9207240..0572cc5aeb28 100644
> --- a/kernel/bpf/bpf_struct_ops.c
> +++ b/kernel/bpf/bpf_struct_ops.c
> @@ -341,6 +341,9 @@ int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
>
> tlinks[BPF_TRAMP_FENTRY].links[0] = link;
> tlinks[BPF_TRAMP_FENTRY].nr_links = 1;
> + /* BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops,
> + * and it must be used alone.
> + */
> flags = model->ret_size > 0 ? BPF_TRAMP_F_RET_FENTRY_RET : 0;
> return arch_prepare_bpf_trampoline(NULL, image, image_end,
> model, flags, tlinks, NULL);
> diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c
> index 93c7675f0c9e..bd3f2e673874 100644
> --- a/kernel/bpf/trampoline.c
> +++ b/kernel/bpf/trampoline.c
> @@ -358,6 +358,9 @@ static int bpf_trampoline_update(struct bpf_trampoline *tr)
>
> if (tlinks[BPF_TRAMP_FEXIT].nr_links ||
> tlinks[BPF_TRAMP_MODIFY_RETURN].nr_links)
> + /* NOTE: BPF_TRAMP_F_RESTORE_REGS and BPF_TRAMP_F_SKIP_FRAME
> + * should not be set together.
> + */
> flags = BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_SKIP_FRAME;
>
> if (ip_arg)
> --
> 2.30.2
>
