On Thu, Feb 25, 2021 at 1:35 AM Yonghong Song <yhs@xxxxxx> wrote:
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 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 <yhs@xxxxxx>
---
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,
+ 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
