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bpf: Introducte bpf_this_cpu_ptr()

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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>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200929235049.2533242-6-haoluo@google.com
This commit is contained in:
Hao Luo 2020-09-29 16:50:48 -07:00 • committed by Alexei Starovoitov
parent eaa6bcb71e
commit 63d9b80dcf
6 changed files with 52 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

14
kernel/bpf/helpers.c
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@ -639,6 +639,18 @@ 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 (unsigned long)this_cpu_ptr((const void __percpu *)percpu_ptr);
}
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,
};
const struct bpf_func_proto bpf_get_current_task_proto __weak;
const struct bpf_func_proto bpf_probe_read_user_proto __weak;
const struct bpf_func_proto bpf_probe_read_user_str_proto __weak;
@ -707,6 +719,8 @@ bpf_base_func_proto(enum bpf_func_id func_id)
return &bpf_jiffies64_proto;
case BPF_FUNC_bpf_per_cpu_ptr:
return &bpf_per_cpu_ptr_proto;
case BPF_FUNC_bpf_this_cpu_ptr:
return &bpf_this_cpu_ptr_proto;
default:
break;
}