Re: [PATCH bpf-next] arm64, bpf: Use bpf_prog_pack for arm64 bpf trampoline

[Pu Lehui <pulehui@huawei.com>]

On 2024/3/5 4:28, Puranjay Mohan wrote:
> We used bpf_prog_pack to aggregate bpf programs into huge page to
> relieve the iTLB pressure on the system. This was merged for ARM64[1]
> We can apply it to bpf trampoline as well. This would increase the
> preformance of fentry and struct_ops programs.
> 
> [1] https://lore.kernel.org/bpf/20240228141824.119877-1-puranjay12@gmail.com/
> 
> Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
> ---
>   arch/arm64/net/bpf_jit_comp.c | 55 +++++++++++++++++++++++++++++------
>   1 file changed, 46 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
> index 5afc7a525eca..c5b461dda438 100644
> --- a/arch/arm64/net/bpf_jit_comp.c
> +++ b/arch/arm64/net/bpf_jit_comp.c
> @@ -2076,7 +2076,7 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
>   		/* store return value */
>   		emit(A64_STR64I(A64_R(0), A64_SP, retval_off), ctx);
>   		/* reserve a nop for bpf_tramp_image_put */
> -		im->ip_after_call = ctx->image + ctx->idx;
> +		im->ip_after_call = ctx->ro_image + ctx->idx;
>   		emit(A64_NOP, ctx);
>   	}
>   
> @@ -2091,7 +2091,7 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
>   				run_ctx_off, false);
>   
>   	if (flags & BPF_TRAMP_F_CALL_ORIG) {
> -		im->ip_epilogue = ctx->image + ctx->idx;
> +		im->ip_epilogue = ctx->ro_image + ctx->idx;
>   		emit_addr_mov_i64(A64_R(0), (const u64)im, ctx);
>   		emit_call((const u64)__bpf_tramp_exit, ctx);
>   	}
> @@ -2124,9 +2124,6 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im,
>   		emit(A64_RET(A64_R(10)), ctx);
>   	}
>   
> -	if (ctx->image)
> -		bpf_flush_icache(ctx->image, ctx->image + ctx->idx);
> -
>   	kfree(branches);
>   
>   	return ctx->idx;
> @@ -2169,14 +2166,43 @@ int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
>   	return ret < 0 ? ret : ret * AARCH64_INSN_SIZE;
>   }
>   
> -int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image,
> -				void *image_end, const struct btf_func_model *m,
> +void *arch_alloc_bpf_trampoline(unsigned int size)
> +{
> +	return bpf_prog_pack_alloc(size, jit_fill_hole);
> +}
> +
> +void arch_free_bpf_trampoline(void *image, unsigned int size)
> +{
> +	bpf_prog_pack_free(image, size);
> +}
> +
> +void arch_protect_bpf_trampoline(void *image, unsigned int size)
> +{
> +}
> +
> +void arch_unprotect_bpf_trampoline(void *image, unsigned int size)
> +{
> +}
> +
> +int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *ro_image,
> +				void *ro_image_end, const struct btf_func_model *m,
>   				u32 flags, struct bpf_tramp_links *tlinks,
>   				void *func_addr)
>   {
>   	int ret, nregs;
> +	void *image, *tmp;
> +	u32 size = ro_image_end - ro_image;
> +
> +	/* image doesn't need to be in module memory range, so we can
> +	 * use kvmalloc.
> +	 */
> +	image = kvmalloc(size, GFP_KERNEL);
> +	if (!image)
> +		return -ENOMEM;
> +
>   	struct jit_ctx ctx = {
>   		.image = image,
> +		.ro_image = ro_image,
>   		.idx = 0,
>   	};
>   
> @@ -2185,15 +2211,26 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image,
>   	if (nregs > 8)
>   		return -ENOTSUPP;
>   
> -	jit_fill_hole(image, (unsigned int)(image_end - image));
> +	jit_fill_hole(image, (unsigned int)(ro_image_end - ro_image));
>   	ret = prepare_trampoline(&ctx, im, tlinks, func_addr, nregs, flags);
>   
> -	if (ret > 0 && validate_code(&ctx) < 0)
> +	if (ret > 0 && validate_code(&ctx) < 0) {
>   		ret = -EINVAL;
> +		goto out;
> +	}
>   
>   	if (ret > 0)
>   		ret *= AARCH64_INSN_SIZE;
>   
> +	tmp = bpf_arch_text_copy(ro_image, image, size);
> +	if (IS_ERR(tmp)) {
> +		ret = PTR_ERR(tmp);
> +		goto out;
> +	}
> +
> +	bpf_flush_icache(ro_image, ro_image + size);
> +out:
> +	kvfree(image);
>   	return ret;
>   }
>   

Reviewed-by: Pu Lehui <pulehui@huawei.com>