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[176.36.0.241]) by smtp.gmail.com with ESMTPSA id si26-20020a170906ceda00b00a3d2fe84ff9sm8085ejb.36.2024.02.13.08.40.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Feb 2024 08:40:07 -0800 (PST) Message-ID: Subject: Re: [PATCH v2 bpf-next 2/4] bpf: handle bpf_user_pt_regs_t typedef explicitly for PTR_TO_CTX global arg From: Eduard Zingerman To: Andrii Nakryiko , bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, martin.lau@kernel.org Cc: kernel-team@meta.com Date: Tue, 13 Feb 2024 18:40:06 +0200 In-Reply-To: <20240212233221.2575350-3-andrii@kernel.org> References: <20240212233221.2575350-1-andrii@kernel.org> <20240212233221.2575350-3-andrii@kernel.org> Autocrypt: addr=eddyz87@gmail.com; prefer-encrypt=mutual; keydata=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 nYzhLWGcczc6J71q1Dje0l5vIPaSFOgwmWD4DA+WvuxM/shH4rtWeodbv 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 t1iq+gsfnXbPz5AnS598ScZI1oP7OrPSFJkt/z4acEbOQDQs8aUqrd46PV jsdqGvKnXZxzylux29UTNby4jTlz9pNJM+wPrDRmGfchLDUmf6CffaUYCbu4FiId+9+dcTCDvxbABRy1C3OJ8QY7cxfJ+pEZW18fRJ0XCl/fiV/ecAOfB3HsqgTzAn555h0rkFgay0hAvMU/mAW/CFNSIxV397zm749ZNLA0L2dMy1AKuOqH+/B+/ImBfJMDjmdyJQ8WU/OFRuGLdqOd2oZrA1iuPIa+yUYyZkaZfz/emQwpIL1+Q4p1R/OplA4yc301AqruXXUcVDbEB+joHW3hy5FwK5t5OwTKatrSJBkydSF9zdXy98fYzGniRyRA65P0Ix/8J3BYB4edY2/w0Ip/mdYsYQljBY0A== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2024-02-12 at 15:32 -0800, Andrii Nakryiko wrote: > Expected canonical argument type for global function arguments > representing PTR_TO_CTX is `bpf_user_pt_regs_t *ctx`. This currently > works on s390x by accident because kernel resolves such typedef to > underlying struct (which is anonymous on s390x), and erroneously > accepting it as expected context type. We are fixing this problem next, > which would break s390x arch, so we need to handle `bpf_user_pt_regs_t` > case explicitly for KPROBE programs. >=20 > Fixes: 91cc1a99740e ("bpf: Annotate context types") > Signed-off-by: Andrii Nakryiko > --- Nit: same could be achieved w/o special casing kprobes by looking if typedef's type is named before skipping, e.g. as below. But I do not insist, probably good as it is as well. --- diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index f0ce384aa73e..830635b37fa1 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -907,11 +907,9 @@ bool btf_member_is_reg_int(const struct btf *btf, cons= t struct btf_type *s, } =20 /* Similar to btf_type_skip_modifiers() but does not skip typedefs. */ -static const struct btf_type *btf_type_skip_qualifiers(const struct btf *b= tf, - u32 id) +static const struct btf_type *__btf_type_skip_qualifiers(const struct btf = *btf, + const struct btf_type *t) { - const struct btf_type *t =3D btf_type_by_id(btf, id); - while (btf_type_is_modifier(t) && BTF_INFO_KIND(t->info) !=3D BTF_KIND_TYPEDEF) { t =3D btf_type_by_id(btf, t->type); @@ -920,6 +918,12 @@ static const struct btf_type *btf_type_skip_qualifiers= (const struct btf *btf, return t; } =20 +static const struct btf_type *btf_type_skip_qualifiers(const struct btf *b= tf, + u32 id) +{ + return __btf_type_skip_qualifiers(btf, btf_type_by_id(btf, id)); +} + #define BTF_SHOW_MAX_ITER 10 =20 #define BTF_KIND_BIT(kind) (1ULL << kind) @@ -5695,9 +5699,25 @@ bool btf_is_prog_ctx_type(struct bpf_verifier_log *l= og, const struct btf *btf, const char *tname, *ctx_tname; =20 t =3D btf_type_by_id(btf, t->type); - while (btf_type_is_modifier(t)) - t =3D btf_type_by_id(btf, t->type); - if (!btf_type_is_struct(t)) { + + /* Skip modifiers, but stop if skipping of typedef would + * lead an anonymous type, e.g. like for s390: + * + * typedef struct { ... } user_pt_regs; + * typedef user_pt_regs bpf_user_pt_regs_t; + */ + t =3D __btf_type_skip_qualifiers(btf, t); + while (btf_type_is_typedef(t)) { + const struct btf_type *t1; + + t1 =3D btf_type_by_id(btf, t->type); + t1 =3D __btf_type_skip_qualifiers(btf, t1); + tname =3D btf_name_by_offset(btf, t1->name_off); + if (!tname || tname[0] =3D=3D '\0') + break; + t =3D t1; + } + if (!btf_type_is_struct(t) && !btf_type_is_typedef(t)) { /* Only pointer to struct is supported for now. * That means that BPF_PROG_TYPE_TRACEPOINT with BTF * is not supported yet.