On Wed, 2025-07-02 at 10:11 -0700, Yonghong Song wrote:
> Add a 'struct bpf_scc_callchain callchain' field in bpf_verifier_env.
> This way, the previous bpf_scc_callchain local variables can be
> replaced by taking address of env->callchain. This can reduce stack
> usage and fix the following error:
> kernel/bpf/verifier.c:19921:12: error: stack frame size (1368) exceeds limit (1280) in 'do_check'
> [-Werror,-Wframe-larger-than]
>
> Reported-by: Arnd Bergmann <arnd@xxxxxxxxxx>
> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
> ---
Oh, well.
I liked stack allocation for callchain object, because it emphasized
its ephemeral by-value status.
The changes lgtm, all places with callchain stack allocation replaced.
Acked-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
[...]
> include/linux/bpf_verifier.h | 1 +
> kernel/bpf/verifier.c | 36 ++++++++++++++++++------------------
> 2 files changed, 19 insertions(+), 18 deletions(-)
>
> diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
> index 7e459e839f8b..e2c175d608bb 100644
> --- a/include/linux/bpf_verifier.h
> +++ b/include/linux/bpf_verifier.h
> @@ -841,6 +841,7 @@ struct bpf_verifier_env {
> char tmp_str_buf[TMP_STR_BUF_LEN];
> struct bpf_insn insn_buf[INSN_BUF_SIZE];
> struct bpf_insn epilogue_buf[INSN_BUF_SIZE];
> + struct bpf_scc_callchain callchain;
Nit: maybe a comment here about this being a scratch buffer?
> /* array of pointers to bpf_scc_info indexed by SCC id */
> struct bpf_scc_info **scc_info;
> u32 scc_cnt;
[...]
