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
50 lines
1007 B
C
50 lines
1007 B
C
// SPDX-License-Identifier: GPL-2.0
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#include <vmlinux.h>
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#include <bpf/bpf_tracing.h>
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#include <bpf/bpf_helpers.h>
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struct map_value {
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struct task_struct __kptr_untrusted *ptr;
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};
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struct {
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__uint(type, BPF_MAP_TYPE_LRU_HASH);
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__uint(max_entries, 1);
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__type(key, int);
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__type(value, struct map_value);
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} lru_map SEC(".maps");
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int pid = 0;
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int result = 1;
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SEC("fentry/bpf_ktime_get_ns")
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int printk(void *ctx)
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{
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struct map_value v = {};
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if (pid == bpf_get_current_task_btf()->pid)
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bpf_map_update_elem(&lru_map, &(int){0}, &v, 0);
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return 0;
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}
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SEC("fentry/do_nanosleep")
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int nanosleep(void *ctx)
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{
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struct map_value val = {}, *v;
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struct task_struct *current;
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bpf_map_update_elem(&lru_map, &(int){0}, &val, 0);
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v = bpf_map_lookup_elem(&lru_map, &(int){0});
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if (!v)
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return 0;
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bpf_map_delete_elem(&lru_map, &(int){0});
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current = bpf_get_current_task_btf();
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v->ptr = current;
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pid = current->pid;
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bpf_ktime_get_ns();
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result = !v->ptr;
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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