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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 except >>> it added a case to handle where subprog number is known >>> and there is no need to do find_subprog(). This case >>> is used later by implementing bpf_for_each_map() helper. >>> >>> Signed-off-by: Yonghong Song >>> --- >>> kernel/bpf/verifier.c | 54 ++++++++++++++++++++++++++++++++----------- >>> 1 file changed, 41 insertions(+), 13 deletions(-) >>> >>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >>> index a657860ecba5..092d2c734dd8 100644 >>> --- a/kernel/bpf/verifier.c >>> +++ b/kernel/bpf/verifier.c >>> @@ -5250,13 +5250,19 @@ 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, > > ok, patch #4 confused me because of this `int *insn_idx`. You don't > seem to be ever updating it, so why pass it by pointer?... What did I > miss? We do have something later: /* and go analyze first insn of the callee */ *insn_idx = target_insn; which is the old code and probably did not show up in the diff. The above statement changed insn_idx such that when done with examining the func call, the control will jump (*insn_idx)++ instruction. > >>> + set_callee_state_fn set_callee_st) >> >> nit: s/set_callee_st/set_callee_state_cb|set_calle_state_fn/ >> >> _st is quite an unusual suffix >> >>> { >>> 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, target_insn; >>> bool is_global = false; >>> >>> if (state->curframe + 1 >= MAX_CALL_FRAMES) { >>> @@ -5265,12 +5271,16 @@ 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; >>> + 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; >>> + } >>> + } else { >>> + target_insn = env->subprog_info[subprog].start - 1; >>> } >>> >>> caller = state->frame[state->curframe]; >>> @@ -5327,11 +5337,9 @@ 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_st(env, caller, callee, *insn_idx); >>> + if (err) >>> + return err; >>> >>> clear_caller_saved_regs(env, caller->regs); >>> >>> @@ -5350,6 +5358,26 @@ 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) >>> +{ >>> + return __check_func_call(env, insn, insn_idx, -1, set_callee_state); >> >> I think it would be much cleaner to not have this -1 special case in >> __check_func_call and instead search for the right subprog right here >> in check_func_call(). Related question, is meta.subprogno (in patch >> #4) expected to sometimes be < 0? If not, then I think >> __check_func_call() definitely shouldn't support -1 case at all. >> >> >>> +} >>> + >>> static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) >>> { >>> struct bpf_verifier_state *state = env->cur_state; >>> -- >>> 2.24.1 >>>