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x86/cfi,bpf: Fix bpf_struct_ops CFI

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BPF struct_ops uses __arch_prepare_bpf_trampoline() to write
trampolines for indirect function calls. These tramplines much have
matching CFI.

In order to obtain the correct CFI hash for the various methods, add a
matching structure that contains stub functions, the compiler will
generate correct CFI which we can pilfer for the trampolines.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20231215092707.566977112@infradead.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Peter Zijlstra
2023-12-15 10:12:20 +01:00
committed by Alexei Starovoitov
parent e72d88d18d
commit 2cd3e3772e
7 changed files with 191 additions and 32 deletions
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kernel/bpf/bpf_struct_ops.c
+8 -8
View File
@@ -352,17 +352,16 @@ const struct bpf_link_ops bpf_struct_ops_link_lops = {
int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
struct bpf_tramp_link *link,
const struct btf_func_model *model,
void *image, void *image_end)
void *stub_func, void *image, void *image_end)
{
u32 flags;
u32 flags = BPF_TRAMP_F_INDIRECT;
int size;
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;
if (model->ret_size > 0)
flags |= BPF_TRAMP_F_RET_FENTRY_RET;
size = arch_bpf_trampoline_size(model, flags, tlinks, NULL);
if (size < 0)
@@ -370,7 +369,7 @@ int bpf_struct_ops_prepare_trampoline(struct bpf_tramp_links *tlinks,
if (size > (unsigned long)image_end - (unsigned long)image)
return -E2BIG;
return arch_prepare_bpf_trampoline(NULL, image, image_end,
model, flags, tlinks, NULL);
model, flags, tlinks, stub_func);
}
static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
@@ -504,11 +503,12 @@ static long bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key,
err = bpf_struct_ops_prepare_trampoline(tlinks, link,
&st_ops->func_models[i],
*(void **)(st_ops->cfi_stubs + moff),
image, image_end);
if (err < 0)
goto reset_unlock;
*(void **)(kdata + moff) = image;
*(void **)(kdata + moff) = image + cfi_get_offset();
image += err;
/* put prog_id to udata */