Re: [PATCH v1 bpf-next 10/11] libbpf: support llvm-generated indirect jumps

[Anton Protopopov <a.s.protopopov@gmail.com>]

On 25/08/25 05:06PM, Eduard Zingerman wrote:
> On Sat, 2025-08-16 at 18:06 +0000, Anton Protopopov wrote:
> 
> [...]
> 
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index fe4fc5438678..a5f04544c09c 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> 
> [...]
> 
> > @@ -6101,6 +6124,60 @@ static void poison_kfunc_call(struct bpf_program *prog, int relo_idx,
> >  	insn->imm = POISON_CALL_KFUNC_BASE + ext_idx;
> >  }
> >  
> > +static int create_jt_map(struct bpf_object *obj, int off, int size, int adjust_off)
> > +{
> > +	static union bpf_attr attr = {
> > +		.map_type = BPF_MAP_TYPE_INSN_ARRAY,
> > +		.key_size = 4,
> > +		.value_size = sizeof(struct bpf_insn_array_value),
> > +		.max_entries = 0,
> > +	};
> > +	struct bpf_insn_array_value val = {};
> > +	int map_fd;
> > +	int err;
> > +	__u32 i;
> > +	__u32 *jt;
> > +
> > +	attr.max_entries = size / 8;
> > +
> > +	map_fd = syscall(__NR_bpf, BPF_MAP_CREATE, &attr, sizeof(attr));
> > +	if (map_fd < 0)
> > +		return map_fd;
> > +
> > +	jt = (__u32 *)(obj->efile.jumptables_data.d_buf + off);
>   	     ^^^^^^^^^
>     Jump table entries are u64 now, e.g. see test case:
>     https://github.com/llvm/llvm-project/blob/39dc3c41e459e6c847c1e45e7e93c53aaf74c1de/llvm/test/CodeGen/BPF/jump_table_swith_stmt.ll#L68
> 
> [...]

Yes, thanks, I will change it to u64. (Just in case, it works now
because the code happens to work properly on little-endian: it uses
jt[2*i] for i-th element.)

> > @@ -6389,36 +6481,58 @@ static int append_subprog_relos(struct bpf_program *main_prog, struct bpf_progra
> 
> [...]
> 
> >  static int
> >  bpf_object__append_subprog_code(struct bpf_object *obj, struct bpf_program *main_prog,
> > -				struct bpf_program *subprog)
> > +		struct bpf_program *subprog)
> >  {
> > -       struct bpf_insn *insns;
> > -       size_t new_cnt;
> > -       int err;
> > +	struct bpf_insn *insns;
> > +	size_t new_cnt;
> > +	int err;
> 
> Could you please extract spaces vs tabs fix for this function as a separate commit?
> Just to make diff easier to read.
> 
> [...]

Sure, sorry, I haven't noticed it.