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03b77e17ae
__kptr meant to store PTR_UNTRUSTED kernel pointers inside bpf maps. The concept felt useful, but didn't get much traction, since bpf_rdonly_cast() was added soon after and bpf programs received a simpler way to access PTR_UNTRUSTED kernel pointers without going through restrictive __kptr usage. Rename __kptr_ref -> __kptr and __kptr -> __kptr_untrusted to indicate its intended usage. The main goal of __kptr_untrusted was to read/write such pointers directly while bpf_kptr_xchg was a mechanism to access refcnted kernel pointers. The next patch will allow RCU protected __kptr access with direct read. At that point __kptr_untrusted will be deprecated. Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: David Vernet <void@manifault.com> Link: https://lore.kernel.org/bpf/20230303041446.3630-2-alexei.starovoitov@gmail.com
72 lines
1.7 KiB
C
72 lines
1.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
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#ifndef _TASK_KFUNC_COMMON_H
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#define _TASK_KFUNC_COMMON_H
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#include <errno.h>
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#include <vmlinux.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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struct __tasks_kfunc_map_value {
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struct task_struct __kptr * task;
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};
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struct hash_map {
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__uint(type, BPF_MAP_TYPE_HASH);
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__type(key, int);
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__type(value, struct __tasks_kfunc_map_value);
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__uint(max_entries, 1);
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} __tasks_kfunc_map SEC(".maps");
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struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym;
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struct task_struct *bpf_task_kptr_get(struct task_struct **pp) __ksym;
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void bpf_task_release(struct task_struct *p) __ksym;
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struct task_struct *bpf_task_from_pid(s32 pid) __ksym;
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static inline struct __tasks_kfunc_map_value *tasks_kfunc_map_value_lookup(struct task_struct *p)
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{
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s32 pid;
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long status;
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status = bpf_probe_read_kernel(&pid, sizeof(pid), &p->pid);
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if (status)
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return NULL;
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return bpf_map_lookup_elem(&__tasks_kfunc_map, &pid);
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}
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static inline int tasks_kfunc_map_insert(struct task_struct *p)
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{
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struct __tasks_kfunc_map_value local, *v;
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long status;
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struct task_struct *acquired, *old;
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s32 pid;
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status = bpf_probe_read_kernel(&pid, sizeof(pid), &p->pid);
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if (status)
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return status;
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local.task = NULL;
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status = bpf_map_update_elem(&__tasks_kfunc_map, &pid, &local, BPF_NOEXIST);
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if (status)
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return status;
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v = bpf_map_lookup_elem(&__tasks_kfunc_map, &pid);
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if (!v) {
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bpf_map_delete_elem(&__tasks_kfunc_map, &pid);
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return -ENOENT;
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}
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acquired = bpf_task_acquire(p);
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old = bpf_kptr_xchg(&v->task, acquired);
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if (old) {
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bpf_task_release(old);
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return -EEXIST;
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}
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return 0;
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}
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#endif /* _TASK_KFUNC_COMMON_H */
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