Re: [PATCH v5 17/17] powerpc64/bpf: Add support for bpf trampolines
From: Alexei Starovoitov <hidden>
Date: 2024-09-17 07:50:46
Also in:
bpf, linux-kbuild, linuxppc-dev, lkml
On Sun, Sep 15, 2024 at 10:58 PM Hari Bathini [off-list ref] wrote:
+ + /* + * Generated stack layout: + * + * func prev back chain [ back chain ] + * [ ] + * bpf prog redzone/tailcallcnt [ ... ] 64 bytes (64-bit powerpc) + * [ ] --
...
+ + /* Dummy frame size for proper unwind - includes 64-bytes red zone for 64-bit powerpc */ + bpf_dummy_frame_size = STACK_FRAME_MIN_SIZE + 64;
What is the goal of such a large "red zone" ? The kernel stack is a limited resource. Why reserve 64 bytes ? tail call cnt can probably be optional as well.