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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>, <martin.lau@...ux.dev>, <song@...nel.org>, <yhs@...com>, <john.fastabend@...il.com>, <kpsingh@...nel.org>, <sdf@...gle.com>, <haoluo@...gle.com>, <jolsa@...nel.org>, <illusionist.neo@...il.com>, <linux@...linux.org.uk>, <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>, <mykolal@...com>, <shuah@...nel.org>, <benjamin.tissoires@...hat.com>, <memxor@...il.com>, <colin.i.king@...il.com>, <asavkov@...hat.com>, <delyank@...com>, <bpf@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>, <linux-kselftest@...r.kernel.org> 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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