On 5/17/2022 11:53 PM, Alexei Starovoitov wrote:
On Tue, May 17, 2022 at 03:18:35AM -0400, Xu Kuohai wrote:
+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;
+}
+int bpf_prepare_trampoline(struct bpf_tramp_image *tr, void *image,
void *image_end, const struct btf_func_model *m,u32 flags, struct bpf_tramp_links *tlinks,void *orig_call)+{
- if (!is_valid_bpf_tramp_flags(flags))
return -EINVAL;- return arch_prepare_bpf_trampoline(tr, image, image_end, m, flags,
tlinks, orig_call);+}
It's an overkill to introduce a new helper function just to validate flags that almost compile time constants. The flags are not user supplied. Please move /* BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops ... */ comment to bpf_struct_ops.c right before it calls arch_prepare_bpf_trampoline() And add a comment to trampoline.c saying that BPF_TRAMP_F_RESTORE_REGS and BPF_TRAMP_F_SKIP_FRAME should not be set together. We could add a warn_on there or in arch code, but feels like overkill. .
OK, will fix in next version.