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[62.202.191.212]) by smtp.gmail.com with ESMTPSA id ca8-20020aa7cd68000000b0043d7b19abd0sm531988edb.39.2022.09.04.13.41.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 04 Sep 2022 13:41:56 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Dave Marchevsky , Delyan Kratunov Subject: [PATCH RFC bpf-next v1 07/32] bpf: Allow specifying volatile type modifier for kptrs Date: Sun, 4 Sep 2022 22:41:20 +0200 Message-Id: <20220904204145.3089-8-memxor@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220904204145.3089-1-memxor@gmail.com> References: <20220904204145.3089-1-memxor@gmail.com> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1457; i=memxor@gmail.com; h=from:subject; bh=EAJh0euJO1zfWYt0lcTRwXNayT97xfctSqXX1QFhvhY=; b=owEBbQKS/ZANAwAKAUzgyIZIvxHKAcsmYgBjFQ1wurIaJQy2LdIrCOuZhZAMqhHjoCA2ijoanJDs Ql2Bp2+JAjMEAAEKAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCYxUNcAAKCRBM4MiGSL8RytVSD/ 0R15CMzUxhdJVoDLrZf40nyyb5uDCQJVoI3NZqA2N7tG2qNKZyfTQHQBj9O+kssb47GNB2pzUR7xlX mT9CyXz7Tu/011s715tR4hH8fIfu8l5ymJ5kHdf0vvpRtI3LlA+ew/qScuT2BuD+jbyMDMSEATyAF6 yPLTZeVFw/wat4YOA3P8tWAzyDOFZy0hXAH+TLBFK7DDCNHlQJDVaTTqdya+c0KRPm28J/j37TrwDc jVZlD+gpM1knKkFS43/lp/Sy3awhcxoOje3pTzQcpjtWpUA/TU9lsYSX/leGpNI5kVfpR/2tE5B31K AqIbjvO2UNBe64j25Szz4/Yt/UIIFGjl3urW3OXu6+y5D1/kCQR8bjQgofuZqbAPDvNmgpABxl2mgT HqAn9pJmtNYLS1w9YRBYK4+DlNWAXaa5+N2pJirYtm/g7JCdnqD1ag0qEHtzf7WiyX8OId7Jzj1YCk OtcVnOx4yZuXSDNKwH1QYgmeeSWQWNiGw8qz3ySIvtAamCxSo8KjDEeFQwjZTo3vh2B94M7RjacFvi JA6RjzuvtVqb/MqVcT+VZqXS3FwoC3/tzbxu+lQmfKbuprvaqjpRGRLtoZ7XnDqIcnbiMvrV4O26vN lLTiK8kKl6PryqrT/ePBckjuJLRPrSmO+El1R3Spx9NtgFAF0TAavX6gABMw== X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=4BBE2A7E06ECF9D5823C61114CE0C88648BF11CA Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org This is useful in particular to mark the pointer as volatile, so that compiler treats each load and store to the field as a volatile access. The alternative is having to define and use READ_ONCE and WRITE_ONCE in the BPF program. Signed-off-by: Kumar Kartikeya Dwivedi --- include/linux/btf.h | 5 +++++ kernel/bpf/btf.c | 3 +++ 2 files changed, 8 insertions(+) diff --git a/include/linux/btf.h b/include/linux/btf.h index ad93c2d9cc1c..b3d47e9b9d5c 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -279,6 +279,11 @@ static inline bool btf_type_is_typedef(const struct btf_type *t) return BTF_INFO_KIND(t->info) == BTF_KIND_TYPEDEF; } +static inline bool btf_type_is_volatile(const struct btf_type *t) +{ + return BTF_INFO_KIND(t->info) == BTF_KIND_VOLATILE; +} + static inline bool btf_type_is_func(const struct btf_type *t) { return BTF_INFO_KIND(t->info) == BTF_KIND_FUNC; diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 903719b89238..5e860f76595c 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -3225,6 +3225,9 @@ static int btf_find_kptr(const struct btf *btf, const struct btf_type *t, enum bpf_kptr_type type; u32 res_id; + /* Permit modifiers on the pointer itself */ + if (btf_type_is_volatile(t)) + t = btf_type_by_id(btf, t->type); /* For PTR, sz is always == 8 */ if (!btf_type_is_ptr(t)) return BTF_FIELD_IGNORE; -- 2.34.1