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Message-ID: <20221126094530.226629-2-yangjihong1@huawei.com>
Date: Sat, 26 Nov 2022 17:45:27 +0800
From: Yang Jihong <yangjihong1@...wei.com>
To: <ast@...nel.org>, <daniel@...earbox.net>, <andrii@...nel.org>,
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CC: <yangjihong1@...wei.com>
Subject: [PATCH bpf-next v3 1/4] bpf: Adapt 32-bit return value kfunc for 32-bit ARM when zext extension
For ARM32 architecture, if data width of kfunc return value is 32 bits,
need to do explicit zero extension for high 32-bit, insn_def_regno should
return dst_reg for BPF_JMP type of BPF_PSEUDO_KFUNC_CALL. Otherwise,
opt_subreg_zext_lo32_rnd_hi32 returns -EFAULT, resulting in BPF failure.
Signed-off-by: Yang Jihong <yangjihong1@...wei.com>
---
kernel/bpf/verifier.c | 44 ++++++++++++++++++++++++++++++++++++++++---
1 file changed, 41 insertions(+), 3 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 264b3dc714cc..193ea927aa69 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1927,6 +1927,21 @@ find_kfunc_desc(const struct bpf_prog *prog, u32 func_id, u16 offset)
sizeof(tab->descs[0]), kfunc_desc_cmp_by_id_off);
}
+static int kfunc_desc_cmp_by_imm(const void *a, const void *b);
+
+static const struct bpf_kfunc_desc *
+find_kfunc_desc_by_imm(const struct bpf_prog *prog, s32 imm)
+{
+ struct bpf_kfunc_desc desc = {
+ .imm = imm,
+ };
+ struct bpf_kfunc_desc_tab *tab;
+
+ tab = prog->aux->kfunc_tab;
+ return bsearch(&desc, tab->descs, tab->nr_descs,
+ sizeof(tab->descs[0]), kfunc_desc_cmp_by_imm);
+}
+
static struct btf *__find_kfunc_desc_btf(struct bpf_verifier_env *env,
s16 offset)
{
@@ -2342,6 +2357,13 @@ static bool is_reg64(struct bpf_verifier_env *env, struct bpf_insn *insn,
*/
if (insn->src_reg == BPF_PSEUDO_CALL)
return false;
+
+ /* Kfunc call will reach here because of insn_has_def32,
+ * conservatively return TRUE.
+ */
+ if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL)
+ return true;
+
/* Helper call will reach here because of arg type
* check, conservatively return TRUE.
*/
@@ -2405,10 +2427,26 @@ static bool is_reg64(struct bpf_verifier_env *env, struct bpf_insn *insn,
}
/* Return the regno defined by the insn, or -1. */
-static int insn_def_regno(const struct bpf_insn *insn)
+static int insn_def_regno(struct bpf_verifier_env *env, const struct bpf_insn *insn)
{
switch (BPF_CLASS(insn->code)) {
case BPF_JMP:
+ if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) {
+ const struct bpf_kfunc_desc *desc;
+
+ /* The value of desc cannot be NULL */
+ desc = find_kfunc_desc_by_imm(env->prog, insn->imm);
+
+ /* A kfunc can return void.
+ * The btf type of the kfunc's return value needs
+ * to be checked against "void" first
+ */
+ if (desc->func_model.ret_size == 0)
+ return -1;
+ else
+ return insn->dst_reg;
+ }
+ fallthrough;
case BPF_JMP32:
case BPF_ST:
return -1;
@@ -2430,7 +2468,7 @@ static int insn_def_regno(const struct bpf_insn *insn)
/* Return TRUE if INSN has defined any 32-bit value explicitly. */
static bool insn_has_def32(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
- int dst_reg = insn_def_regno(insn);
+ int dst_reg = insn_def_regno(env, insn);
if (dst_reg == -1)
return false;
@@ -13335,7 +13373,7 @@ static int opt_subreg_zext_lo32_rnd_hi32(struct bpf_verifier_env *env,
int load_reg;
insn = insns[adj_idx];
- load_reg = insn_def_regno(&insn);
+ load_reg = insn_def_regno(env, &insn);
if (!aux[adj_idx].zext_dst) {
u8 code, class;
u32 imm_rnd;
--
2.30.GIT
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