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bpf: core: introduce main_prog_aux for stream access

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BPF streams are only valid for the main programs, to make it easier to
access streams from subprogs, introduce main_prog_aux in struct
bpf_prog_aux.

prog->aux->main_prog_aux = prog->aux, for main programs and
prog->aux->main_prog_aux = main_prog->aux, for subprograms.

Make bpf_prog_find_from_stack() use the added main_prog_aux to return
the mainprog when a subprog is found on the stack.

Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250911145808.58042-3-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Puranjay Mohan 2025-09-11 14:58:01 +00:00 committed by Alexei Starovoitov
parent 0460484244
commit 70f23546d2
3 changed files with 5 additions and 3 deletions
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1
include/linux/bpf.h
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@ -1633,6 +1633,7 @@ struct bpf_prog_aux {
/* function name for valid attach_btf_id */
const char *attach_func_name;
struct bpf_prog **func;
struct bpf_prog_aux *main_prog_aux;
void *jit_data; /* JIT specific data. arch dependent */
struct bpf_jit_poke_descriptor *poke_tab;
struct bpf_kfunc_desc_tab *kfunc_tab;

6
kernel/bpf/core.c
View File

@ -120,6 +120,7 @@ struct bpf_prog *bpf_prog_alloc_no_stats(unsigned int size, gfp_t gfp_extra_flag
fp->pages = size / PAGE_SIZE;
fp->aux = aux;
fp->aux->main_prog_aux = aux;
fp->aux->prog = fp;
fp->jit_requested = ebpf_jit_enabled();
fp->blinding_requested = bpf_jit_blinding_enabled(fp);
@ -3297,9 +3298,8 @@ static bool find_from_stack_cb(void *cookie, u64 ip, u64 sp, u64 bp)
rcu_read_unlock();
if (!prog)
return true;
if (bpf_is_subprog(prog))
return true;
ctxp->prog = prog;
/* Make sure we return the main prog if we found a subprog */
ctxp->prog = prog->aux->main_prog_aux->prog;
return false;
}

1
kernel/bpf/verifier.c
View File

@ -21601,6 +21601,7 @@ static int jit_subprogs(struct bpf_verifier_env *env)
func[i]->aux->func_info_cnt = prog->aux->func_info_cnt;
func[i]->aux->poke_tab = prog->aux->poke_tab;
func[i]->aux->size_poke_tab = prog->aux->size_poke_tab;
func[i]->aux->main_prog_aux = prog->aux;
for (j = 0; j < prog->aux->size_poke_tab; j++) {
struct bpf_jit_poke_descriptor *poke;