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bpf: Refactor check_func_call() to allow callback function

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Later proposed bpf_for_each_map_elem() helper has callback
function as one of its arguments. This patch refactored
check_func_call() to permit callback function which sets
callee state. Different callback functions may have
different callee states.
There is no functionality change for this patch.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210226204923.3884627-1-yhs@fb.com
This commit is contained in:
Yonghong Song 2021-02-26 12:49:23 -08:00 • committed by Alexei Starovoitov
parent bc2591d63f
commit 1435137573
1 changed files with 43 additions and 17 deletions
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60
kernel/bpf/verifier.c
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@ -5249,13 +5249,19 @@ static void clear_caller_saved_regs(struct bpf_verifier_env *env,
}
}
static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
int *insn_idx)
typedef int (*set_callee_state_fn)(struct bpf_verifier_env *env,
struct bpf_func_state *caller,
struct bpf_func_state *callee,
int insn_idx);
static int __check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
int *insn_idx, int subprog,
set_callee_state_fn set_callee_state_cb)
{
struct bpf_verifier_state *state = env->cur_state;
struct bpf_func_info_aux *func_info_aux;
struct bpf_func_state *caller, *callee;
int i, err, subprog, target_insn;
int err;
bool is_global = false;
if (state->curframe + 1 >= MAX_CALL_FRAMES) {
@ -5264,14 +5270,6 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
return -E2BIG;
}
target_insn = *insn_idx + insn->imm;
subprog = find_subprog(env, target_insn + 1);
if (subprog < 0) {
verbose(env, "verifier bug. No program starts at insn %d\n",
target_insn + 1);
return -EFAULT;
}
caller = state->frame[state->curframe];
if (state->frame[state->curframe + 1]) {
verbose(env, "verifier bug. Frame %d already allocated\n",
@ -5326,11 +5324,9 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
if (err)
return err;
/* copy r1 - r5 args that callee can access. The copy includes parent
* pointers, which connects us up to the liveness chain
*/
for (i = BPF_REG_1; i <= BPF_REG_5; i++)
callee->regs[i] = caller->regs[i];
err = set_callee_state_cb(env, caller, callee, *insn_idx);
if (err)
return err;
clear_caller_saved_regs(env, caller->regs);
@ -5338,7 +5334,7 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
state->curframe++;
/* and go analyze first insn of the callee */
*insn_idx = target_insn;
*insn_idx = env->subprog_info[subprog].start - 1;
if (env->log.level & BPF_LOG_LEVEL) {
verbose(env, "caller:\n");
@ -5349,6 +5345,36 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
return 0;
}
static int set_callee_state(struct bpf_verifier_env *env,
struct bpf_func_state *caller,
struct bpf_func_state *callee, int insn_idx)
{
int i;
/* copy r1 - r5 args that callee can access. The copy includes parent
* pointers, which connects us up to the liveness chain
*/
for (i = BPF_REG_1; i <= BPF_REG_5; i++)
callee->regs[i] = caller->regs[i];
return 0;
}
static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
int *insn_idx)
{
int subprog, target_insn;
target_insn = *insn_idx + insn->imm + 1;
subprog = find_subprog(env, target_insn);
if (subprog < 0) {
verbose(env, "verifier bug. No program starts at insn %d\n",
target_insn);
return -EFAULT;
}
return __check_func_call(env, insn, insn_idx, subprog, set_callee_state);
}
static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx)
{
struct bpf_verifier_state *state = env->cur_state;