diff options
| author | Yonghong Song <yhs@fb.com> | 2022-11-23 21:32:17 -0800 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2022-11-24 12:54:13 -0800 |
| commit | 9bb00b2895cbfe0ad410457b605d0a72524168c1 (patch) | |
| tree | f8bf5198e886f0620fe99007f92914146ddc356f /include | |
| parent | 01685c5bddaa6df3d662c8afed5e5289fcc68e5a (diff) | |
bpf: Add kfunc bpf_rcu_read_lock/unlock()
Add two kfunc's bpf_rcu_read_lock() and bpf_rcu_read_unlock(). These two kfunc's
can be used for all program types. The following is an example about how
rcu pointer are used w.r.t. bpf_rcu_read_lock()/bpf_rcu_read_unlock().
struct task_struct {
...
struct task_struct *last_wakee;
struct task_struct __rcu *real_parent;
...
};
Let us say prog does 'task = bpf_get_current_task_btf()' to get a
'task' pointer. The basic rules are:
- 'real_parent = task->real_parent' should be inside bpf_rcu_read_lock
region. This is to simulate rcu_dereference() operation. The
'real_parent' is marked as MEM_RCU only if (1). task->real_parent is
inside bpf_rcu_read_lock region, and (2). task is a trusted ptr. So
MEM_RCU marked ptr can be 'trusted' inside the bpf_rcu_read_lock region.
- 'last_wakee = real_parent->last_wakee' should be inside bpf_rcu_read_lock
region since it tries to access rcu protected memory.
- the ptr 'last_wakee' will be marked as PTR_UNTRUSTED since in general
it is not clear whether the object pointed by 'last_wakee' is valid or
not even inside bpf_rcu_read_lock region.
The verifier will reset all rcu pointer register states to untrusted
at bpf_rcu_read_unlock() kfunc call site, so any such rcu pointer
won't be trusted any more outside the bpf_rcu_read_lock() region.
The current implementation does not support nested rcu read lock
region in the prog.
Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/20221124053217.2373910-1-yhs@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/bpf.h | 3 | ||||
| -rw-r--r-- | include/linux/bpf_verifier.h | 5 |
2 files changed, 7 insertions, 1 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 43fd7eeeeabb..c6aa6912ea16 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -572,6 +572,9 @@ enum bpf_type_flag { */ PTR_TRUSTED = BIT(12 + BPF_BASE_TYPE_BITS), + /* MEM is tagged with rcu and memory access needs rcu_read_lock protection. */ + MEM_RCU = BIT(13 + BPF_BASE_TYPE_BITS), + __BPF_TYPE_FLAG_MAX, __BPF_TYPE_LAST_FLAG = __BPF_TYPE_FLAG_MAX - 1, }; diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 545152ac136c..c05aa6e1f6f5 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -344,6 +344,7 @@ struct bpf_verifier_state { u32 id; } active_lock; bool speculative; + bool active_rcu_lock; /* first and last insn idx of this verifier state */ u32 first_insn_idx; @@ -445,6 +446,7 @@ struct bpf_insn_aux_data { u32 seen; /* this insn was processed by the verifier at env->pass_cnt */ bool sanitize_stack_spill; /* subject to Spectre v4 sanitation */ bool zext_dst; /* this insn zero extends dst reg */ + bool storage_get_func_atomic; /* bpf_*_storage_get() with atomic memory alloc */ u8 alu_state; /* used in combination with alu_limit */ /* below fields are initialized once */ @@ -534,6 +536,7 @@ struct bpf_verifier_env { bool bypass_spec_v1; bool bypass_spec_v4; bool seen_direct_write; + bool rcu_tag_supported; struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */ const struct bpf_line_info *prev_linfo; struct bpf_verifier_log log; @@ -680,7 +683,7 @@ static inline bool bpf_prog_check_recur(const struct bpf_prog *prog) } } -#define BPF_REG_TRUSTED_MODIFIERS (MEM_ALLOC | PTR_TRUSTED) +#define BPF_REG_TRUSTED_MODIFIERS (MEM_ALLOC | MEM_RCU | PTR_TRUSTED) static inline bool bpf_type_has_unsafe_modifiers(u32 type) { |