Commit 0a542a86 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller

bpf: handle pseudo BPF_CALL insn

in native eBPF programs userspace is using pseudo BPF_CALL instructions
which encode one of 'enum bpf_func_id' inside insn->imm field.
Verifier checks that program using correct function arguments to given func_id.
If all checks passed, kernel needs to fixup BPF_CALL->imm fields by
replacing func_id with in-kernel function pointer.
eBPF interpreter just calls the function.

In-kernel eBPF users continue to use generic BPF_CALL.
Signed-off-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 09756af4
...@@ -357,6 +357,40 @@ void bpf_register_prog_type(struct bpf_prog_type_list *tl) ...@@ -357,6 +357,40 @@ void bpf_register_prog_type(struct bpf_prog_type_list *tl)
list_add(&tl->list_node, &bpf_prog_types); list_add(&tl->list_node, &bpf_prog_types);
} }
/* fixup insn->imm field of bpf_call instructions:
* if (insn->imm == BPF_FUNC_map_lookup_elem)
* insn->imm = bpf_map_lookup_elem - __bpf_call_base;
* else if (insn->imm == BPF_FUNC_map_update_elem)
* insn->imm = bpf_map_update_elem - __bpf_call_base;
* else ...
*
* this function is called after eBPF program passed verification
*/
static void fixup_bpf_calls(struct bpf_prog *prog)
{
const struct bpf_func_proto *fn;
int i;
for (i = 0; i < prog->len; i++) {
struct bpf_insn *insn = &prog->insnsi[i];
if (insn->code == (BPF_JMP | BPF_CALL)) {
/* we reach here when program has bpf_call instructions
* and it passed bpf_check(), means that
* ops->get_func_proto must have been supplied, check it
*/
BUG_ON(!prog->aux->ops->get_func_proto);
fn = prog->aux->ops->get_func_proto(insn->imm);
/* all functions that have prototype and verifier allowed
* programs to call them, must be real in-kernel functions
*/
BUG_ON(!fn->func);
insn->imm = fn->func - __bpf_call_base;
}
}
}
/* drop refcnt on maps used by eBPF program and free auxilary data */ /* drop refcnt on maps used by eBPF program and free auxilary data */
static void free_used_maps(struct bpf_prog_aux *aux) static void free_used_maps(struct bpf_prog_aux *aux)
{ {
...@@ -478,6 +512,9 @@ static int bpf_prog_load(union bpf_attr *attr) ...@@ -478,6 +512,9 @@ static int bpf_prog_load(union bpf_attr *attr)
if (err < 0) if (err < 0)
goto free_used_maps; goto free_used_maps;
/* fixup BPF_CALL->imm field */
fixup_bpf_calls(prog);
/* eBPF program is ready to be JITed */ /* eBPF program is ready to be JITed */
bpf_prog_select_runtime(prog); bpf_prog_select_runtime(prog);
......
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