On Fri, Dec 01, 2023 at 11:06:52AM -0800, Song Liu wrote:
> +int arch_bpf_trampoline_size(const struct btf_func_model *m, u32 flags,
> + struct bpf_tramp_links *tlinks, void *func_addr)
> +{
> + struct bpf_tramp_image im;
> + void *image;
> + int ret;
> +
> + /* Allocate a temporary buffer for __arch_prepare_bpf_trampoline().
> + * This will NOT cause fragmentation in direct map, as we do not
> + * call set_memory_*() on this buffer.
> + */
> + image = bpf_jit_alloc_exec(PAGE_SIZE);
> + if (!image)
> + return -ENOMEM;
> +
> + ret = __arch_prepare_bpf_trampoline(&im, image, image + PAGE_SIZE, m, flags,
> + tlinks, func_addr);
> + bpf_jit_free_exec(image);
> + return ret;
> +}
There is no need to allocate an executable page just to compute the size, right?
Instead of bpf_jit_alloc_exec() it should work with alloc_page() ?
Similar in patch 7:
int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void
*image, void *image_end,
const struct btf_func_model *m, u32 flags,
struct bpf_tramp_links *tlinks,
void *func_addr)
{
- return __arch_prepare_bpf_trampoline(im, image, image_end, m,
flags, tlinks, func_addr);
+ void *rw_image, *tmp;
+ int ret;
+ u32 size = image_end - image;
+
+ rw_image = bpf_jit_alloc_exec(size);
+ if (!rw_image)
+ return -ENOMEM;
+
+ ret = __arch_prepare_bpf_trampoline(im, rw_image, rw_image +
size, image, m,
+ flags, tlinks, func_addr);
+ if (ret < 0)
+ goto out;
+
+ tmp = bpf_arch_text_copy(image, rw_image, size);
+ if (IS_ERR(tmp))
+ ret = PTR_ERR(tmp);
+out:
+ bpf_jit_free_exec(rw_image);
+ return ret;
}
In the above only 'image' has to be ROX. rw_image can be allocated
with kvmalloc().
Just like it's done in the main loop of JIT via
bpf_jit_binary_pack_alloc() -> kvmalloc() -> rw_header.
pw-bot: cr
