yonghong-song added a comment.
In D74668#2019558 <https://reviews.llvm.org/D74668#2019558>, @anakryiko wrote:
> what's the use case for flag==0 (no relocation)? why using built-in at all in
> such case? Also flag==1 means relocate to local BTF ID or remote (kernel) BTF
> ID? Do you plan to add flag=2 as well to cover both cases? Or am I
> misunderstanding the meaning of this flag?
Originally, I thought flag = 0 for the following use case:
e.g., they just want to know the type of a particular local structure for
pretty print purpose.
Note that currently only types for global/extern variables, function
parameters are recorded in btf.
int test() {
struct { int a; int b; ...} ctx;
btf_id = __builtin_btf_type_id(ctx, 0);
bpf_seq_write(seq, &btf_id, sizeof(btf_id));
bpf_seq_write(seq, &ctx, sizeof(ctx));
...
}
But obviously without relocation, this will not work with btf deduplication,
future static linking etc.
flag 1: for relocation. My original thinking is for vmlinux relocation.
I think you brought a good point about local relocation, so will need
to change the flag to:
flag 0 : local relocation
flag 1: vmlinux relocation
Two more relocation types will be generated:
BTF_TYPE_ID_LOCAL
BTF_TYPE_ID_REMOTE
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D74668/new/
https://reviews.llvm.org/D74668
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