From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Hao Luo <haoluo@google.com>
Cc: Networking <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
open list <linux-kernel@vger.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>, Shuah Khan <shuah@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andriin@fb.com>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@chromium.org>,
Quentin Monnet <quentin@isovalent.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>, Andrey Ignatov <rdna@fb.com>,
Jakub Sitnicki <jakub@cloudflare.com>
Subject: Re: [PATCH bpf-next v2 5/6] bpf: Introduce bpf_this_cpu_ptr()
Date: Fri, 4 Sep 2020 13:09:06 -0700 [thread overview]
Message-ID: <CAEf4Bza2W9jO3FRCf_y44SwhUHr=WoCLigqLh3pUMMOaUBF64w@mail.gmail.com> (raw)
In-Reply-To: <20200903223332.881541-6-haoluo@google.com>
On Thu, Sep 3, 2020 at 3:35 PM Hao Luo <haoluo@google.com> wrote:
>
> Add bpf_this_cpu_ptr() to help access percpu var on this cpu. This
> helper always returns a valid pointer, therefore no need to check
> returned value for NULL. Also note that all programs run with
> preemption disabled, which means that the returned pointer is stable
> during all the execution of the program.
>
> Signed-off-by: Hao Luo <haoluo@google.com>
> ---
looks good, few small things, but otherwise:
Acked-by: Andrii Nakryiko <andriin@fb.com>
> include/linux/bpf.h | 1 +
> include/uapi/linux/bpf.h | 14 ++++++++++++++
> kernel/bpf/verifier.c | 10 +++++++---
> kernel/trace/bpf_trace.c | 14 ++++++++++++++
> tools/include/uapi/linux/bpf.h | 14 ++++++++++++++
> 5 files changed, 50 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 6b2034f7665e..506fdd5d0463 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -307,6 +307,7 @@ enum bpf_return_type {
> RET_PTR_TO_ALLOC_MEM_OR_NULL, /* returns a pointer to dynamically allocated memory or NULL */
> RET_PTR_TO_BTF_ID_OR_NULL, /* returns a pointer to a btf_id or NULL */
> RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL, /* returns a pointer to a valid memory or a btf_id or NULL */
> + RET_PTR_TO_MEM_OR_BTF_ID, /* returns a pointer to a valid memory or a btf_id */
> };
>
> /* eBPF function prototype used by verifier to allow BPF_CALLs from eBPF programs
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index d0ec94d5bdbf..e7ca91c697ed 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3612,6 +3612,19 @@ union bpf_attr {
> * bpf_per_cpu_ptr() must check the returned value.
> * Return
> * A generic pointer pointing to the kernel percpu variable on *cpu*.
> + *
> + * void *bpf_this_cpu_ptr(const void *percpu_ptr)
> + * Description
> + * Take a pointer to a percpu ksym, *percpu_ptr*, and return a
> + * pointer to the percpu kernel variable on this cpu. See the
> + * description of 'ksym' in **bpf_per_cpu_ptr**\ ().
> + *
> + * bpf_this_cpu_ptr() has the same semantic as this_cpu_ptr() in
> + * the kernel. Different from **bpf_per_cpu_ptr**\ (), it would
> + * never return NULL.
> + * Return
> + * A generic pointer pointing to the kernel percpu variable on
what's "a generic pointer"? is it as opposed to sk_buff pointer or something?
> + * this cpu.
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> @@ -3764,6 +3777,7 @@ union bpf_attr {
> FN(d_path), \
> FN(copy_from_user), \
> FN(bpf_per_cpu_ptr), \
> + FN(bpf_this_cpu_ptr), \
> /* */
>
> /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index a702600ff581..e070d2abc405 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -5016,8 +5016,10 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
> regs[BPF_REG_0].type = PTR_TO_MEM_OR_NULL;
> regs[BPF_REG_0].id = ++env->id_gen;
> regs[BPF_REG_0].mem_size = meta.mem_size;
> - } else if (fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL) {
> + } else if (fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL ||
> + fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID) {
> const struct btf_type *t;
> + bool not_null = fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID;
nit: this is fine, but I'd inline it below
>
> mark_reg_known_zero(env, regs, BPF_REG_0);
> t = btf_type_skip_modifiers(btf_vmlinux, meta.ret_btf_id, NULL);
> @@ -5034,10 +5036,12 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
> tname, PTR_ERR(ret));
> return -EINVAL;
> }
> - regs[BPF_REG_0].type = PTR_TO_MEM_OR_NULL;
> + regs[BPF_REG_0].type = not_null ?
> + PTR_TO_MEM : PTR_TO_MEM_OR_NULL;
> regs[BPF_REG_0].mem_size = tsize;
> } else {
> - regs[BPF_REG_0].type = PTR_TO_BTF_ID_OR_NULL;
> + regs[BPF_REG_0].type = not_null ?
> + PTR_TO_BTF_ID : PTR_TO_BTF_ID_OR_NULL;
> regs[BPF_REG_0].btf_id = meta.ret_btf_id;
> }
> } else if (fn->ret_type == RET_PTR_TO_BTF_ID_OR_NULL) {
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index d474c1530f87..466acf82a9c7 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -1160,6 +1160,18 @@ static const struct bpf_func_proto bpf_per_cpu_ptr_proto = {
> .arg2_type = ARG_ANYTHING,
> };
>
> +BPF_CALL_1(bpf_this_cpu_ptr, const void *, percpu_ptr)
> +{
> + return (u64)this_cpu_ptr(percpu_ptr);
see previous comment, this might trigger unnecessary compilation
warnings on 32-bit arches
> +}
> +
> +static const struct bpf_func_proto bpf_this_cpu_ptr_proto = {
> + .func = bpf_this_cpu_ptr,
> + .gpl_only = false,
> + .ret_type = RET_PTR_TO_MEM_OR_BTF_ID,
> + .arg1_type = ARG_PTR_TO_PERCPU_BTF_ID,
> +};
> +
[...]
next prev parent reply other threads:[~2020-09-04 20:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-03 22:33 [PATCH bpf-next v2 0/6] bpf: BTF support for ksyms Hao Luo
2020-09-03 22:33 ` [PATCH bpf-next v2 1/6] bpf: Introduce pseudo_btf_id Hao Luo
2020-09-04 19:05 ` Andrii Nakryiko
2020-09-14 4:55 ` Hao Luo
2020-09-03 22:33 ` [PATCH bpf-next v2 2/6] bpf/libbpf: BTF support for typed ksyms Hao Luo
2020-09-04 19:34 ` Andrii Nakryiko
2020-09-14 4:56 ` Hao Luo
2020-09-03 22:33 ` [PATCH bpf-next v2 3/6] bpf/selftests: ksyms_btf to test " Hao Luo
2020-09-04 19:49 ` Andrii Nakryiko
2020-09-14 4:58 ` Hao Luo
2020-09-14 22:06 ` Andrii Nakryiko
2020-09-03 22:33 ` [PATCH bpf-next v2 4/6] bpf: Introduce bpf_per_cpu_ptr() Hao Luo
2020-09-04 20:04 ` Andrii Nakryiko
2020-09-14 5:01 ` Hao Luo
2020-09-14 18:09 ` Andrii Nakryiko
2020-09-03 22:33 ` [PATCH bpf-next v2 5/6] bpf: Introduce bpf_this_cpu_ptr() Hao Luo
2020-09-04 20:09 ` Andrii Nakryiko [this message]
2020-09-14 5:04 ` Hao Luo
2020-09-03 22:33 ` [PATCH bpf-next v2 6/6] bpf/selftests: Test for bpf_per_cpu_ptr() and bpf_this_cpu_ptr() Hao Luo
2020-09-04 20:15 ` Andrii Nakryiko
2020-09-14 16:59 ` Hao Luo
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