[bpf-next,1/3] bpf: Use precise image size for struct_ops trampoline

Commit Message

Pu Lehui Jan. 23, 2024, 10:32 a.m. UTC

From: Pu Lehui <[e-mail]>

For trampoline using bpf_prog_pack, we need to generate a rw_image
buffer with size of (image_end - image). For regular trampoline, we use
the precise image size generated by arch_bpf_trampoline_size to allocate
rw_image. But for struct_ops trampoline, we allocate rw_image directly
using close to PAGE_SIZE size. We do not need to allocate for that much,
as the patch size is usually much smaller than PAGE_SIZE. Let's use
precise image size for it too.

Signed-off-by: Pu Lehui <[e-mail]>
---
 kernel/bpf/bpf_struct_ops.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Song Liu Jan. 29, 2024, 5:21 p.m. UTC | #1

On Tue, Jan 23, 2024 at 2:32 AM Pu Lehui <[e-mail]> wrote:
>
> From: Pu Lehui <[e-mail]>
>
> For trampoline using bpf_prog_pack, we need to generate a rw_image
> buffer with size of (image_end - image). For regular trampoline, we use
> the precise image size generated by arch_bpf_trampoline_size to allocate
> rw_image. But for struct_ops trampoline, we allocate rw_image directly
> using close to PAGE_SIZE size. We do not need to allocate for that much,
> as the patch size is usually much smaller than PAGE_SIZE. Let's use
> precise image size for it too.
>
> Signed-off-by: Pu Lehui <[e-mail]>

Acked-by: Song Liu <[e-mail]>

Patch

diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 02068bd0e4d9..e2e1bf3c69a3 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -368,7 +368,7 @@  int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
 		return size;
 	if (size > (unsigned long)image_end - (unsigned long)image)
 		return -E2BIG;
-	return arch_prepare_bpf_trampoline(NULL, image, image_end,
+	return arch_prepare_bpf_trampoline(NULL, image, image + size,
 					   model, flags, tlinks, stub_func);
 }