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Mon, 23 Jun 2025 20:12:54 -0700 (PDT) Received: from localhost ([2a03:2880:30ff:4::]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-60c2f4a61b8sm346393a12.75.2025.06.23.20.12.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Jun 2025 20:12:54 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , Eduard Zingerman , Emil Tsalapatis , Barret Rhoden , Matt Bobrowski , kkd@meta.com, kernel-team@meta.com Subject: [PATCH bpf-next v3 01/12] bpf: Refactor bprintf buffer support Date: Mon, 23 Jun 2025 20:12:41 -0700 Message-ID: <20250624031252.2966759-2-memxor@gmail.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250624031252.2966759-1-memxor@gmail.com> References: <20250624031252.2966759-1-memxor@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=4083; h=from:subject; bh=t2BRcr2+6gJr3KgAcNgxMy3UcbJhiQrwP9oBAKjG6WA=; b=owEBbQKS/ZANAwAIAUzgyIZIvxHKAcsmYgBoWhWdXAGZufG0sXf1qzhje+9cXBSx0KqK77OawF/6 x2mr+K2JAjMEAAEIAB0WIQRLvip+Buz51YI8YRFM4MiGSL8RygUCaFoVnQAKCRBM4MiGSL8Ryu+LD/ 9phmxyP0zhTda9S5hOAx9H7rozgMUZBfivYG9ARjEuAseUMg38kPexRdWoeg3WpE/x/Rhwl3+oqGXp o08C7WwleUqcOkcjQYh98P0zXcsOfP9ebnm/VoXGXc75bDQBvCLMe7IfgjU2AWAo2wXmwgOjz+Gqtb OXff/JYzgYRBkRBdSGl/diwoETliz2EVCRRIl+tkG/uk+2alK+0YdA8+AjCBm+9p9KaimJ4vtaTkYr RDzC2cGcnU7ugmV5cnGxM1LK6kquVOZF+BcXqjgH813CXgnascY1x6jigxumyaQBlk1m5bb16YR8JJ nXKh9ZBXLMpj08QsdtrVrC9MoCZeav+JjkYEmw70BietO4rrs8uPGiK3gNHYt2M+xzbiat+Ir9odOF Xd03bHEx4Jk2QSv4w+SNOVwvQ6hX9knSHIBwj/LEhlXeWgoGLjzsMVPn+oOC+nsZoPYtxCLny0Ief6 dcVt9uGWuiE58AEJAU67F0zbLPqaqkqrGGlm6gnL4E9CmhVwdgkvh+CyRN6cRGZ5JZ7BKCZYuPI2/p THDuVQ+cVOVFM26x9jNAOKHtHDnZXLhagZLmBo31b2b+XSmW3BxNVjBHySw58QBj/TRwlPYnVK9SyU 7QpdjoNkZo+247T6mQnYFG8zw6si99+WsX9rcLpFXphfwYS8CJGBVMhLcl1w== X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=4BBE2A7E06ECF9D5823C61114CE0C88648BF11CA Content-Transfer-Encoding: 8bit Refactor code to be able to get and put bprintf buffers and use bpf_printf_prepare independently. This will be used in the next patch to implement BPF streams support, particularly as a staging buffer for strings that need to be formatted and then allocated and pushed into a stream. Signed-off-by: Kumar Kartikeya Dwivedi --- include/linux/bpf.h | 15 ++++++++++++++- kernel/bpf/helpers.c | 26 +++++++++++--------------- 2 files changed, 25 insertions(+), 16 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 5dd556e89cce..4fff0cee8622 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -3550,6 +3550,16 @@ bool btf_id_set_contains(const struct btf_id_set *set, u32 id); #define MAX_BPRINTF_VARARGS 12 #define MAX_BPRINTF_BUF 1024 +/* Per-cpu temp buffers used by printf-like helpers to store the bprintf binary + * arguments representation. + */ +#define MAX_BPRINTF_BIN_ARGS 512 + +struct bpf_bprintf_buffers { + char bin_args[MAX_BPRINTF_BIN_ARGS]; + char buf[MAX_BPRINTF_BUF]; +}; + struct bpf_bprintf_data { u32 *bin_args; char *buf; @@ -3557,9 +3567,12 @@ struct bpf_bprintf_data { bool get_buf; }; -int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args, +int bpf_bprintf_prepare(const char *fmt, u32 fmt_size, const u64 *raw_args, u32 num_args, struct bpf_bprintf_data *data); void bpf_bprintf_cleanup(struct bpf_bprintf_data *data); +int bpf_try_get_buffers(struct bpf_bprintf_buffers **bufs); +void bpf_put_buffers(void); + #ifdef CONFIG_BPF_LSM void bpf_cgroup_atype_get(u32 attach_btf_id, int cgroup_atype); diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index b71e428ad936..67d48f9fb173 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -763,22 +763,13 @@ static int bpf_trace_copy_string(char *buf, void *unsafe_ptr, char fmt_ptype, return -EINVAL; } -/* Per-cpu temp buffers used by printf-like helpers to store the bprintf binary - * arguments representation. - */ -#define MAX_BPRINTF_BIN_ARGS 512 - /* Support executing three nested bprintf helper calls on a given CPU */ #define MAX_BPRINTF_NEST_LEVEL 3 -struct bpf_bprintf_buffers { - char bin_args[MAX_BPRINTF_BIN_ARGS]; - char buf[MAX_BPRINTF_BUF]; -}; static DEFINE_PER_CPU(struct bpf_bprintf_buffers[MAX_BPRINTF_NEST_LEVEL], bpf_bprintf_bufs); static DEFINE_PER_CPU(int, bpf_bprintf_nest_level); -static int try_get_buffers(struct bpf_bprintf_buffers **bufs) +int bpf_try_get_buffers(struct bpf_bprintf_buffers **bufs) { int nest_level; @@ -794,16 +785,21 @@ static int try_get_buffers(struct bpf_bprintf_buffers **bufs) return 0; } -void bpf_bprintf_cleanup(struct bpf_bprintf_data *data) +void bpf_put_buffers(void) { - if (!data->bin_args && !data->buf) - return; if (WARN_ON_ONCE(this_cpu_read(bpf_bprintf_nest_level) == 0)) return; this_cpu_dec(bpf_bprintf_nest_level); preempt_enable(); } +void bpf_bprintf_cleanup(struct bpf_bprintf_data *data) +{ + if (!data->bin_args && !data->buf) + return; + bpf_put_buffers(); +} + /* * bpf_bprintf_prepare - Generic pass on format strings for bprintf-like helpers * @@ -818,7 +814,7 @@ void bpf_bprintf_cleanup(struct bpf_bprintf_data *data) * In argument preparation mode, if 0 is returned, safe temporary buffers are * allocated and bpf_bprintf_cleanup should be called to free them after use. */ -int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args, +int bpf_bprintf_prepare(const char *fmt, u32 fmt_size, const u64 *raw_args, u32 num_args, struct bpf_bprintf_data *data) { bool get_buffers = (data->get_bin_args && num_args) || data->get_buf; @@ -834,7 +830,7 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args, return -EINVAL; fmt_size = fmt_end - fmt; - if (get_buffers && try_get_buffers(&buffers)) + if (get_buffers && bpf_try_get_buffers(&buffers)) return -EBUSY; if (data->get_bin_args) { -- 2.47.1