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Subject[RFC patch 09/19] bpf: Use BPF_PROG_RUN_PIN_ON_CPU() at simple call sites.
From: David Miller <davem@davemloft.net>

All of these cases are strictly of the form:

preempt_disable();
BPF_PROG_RUN(...);
preempt_enable();

Replace this with BPF_PROG_RUN_PIN_ON_CPU() which wraps BPF_PROG_RUN()
with:

migrate_disable();
BPF_PROG_RUN(...);
migrate_enable();

On non RT enabled kernels this maps to preempt_disable/enable() and on RT
enabled kernels this solely prevents migration, which is sufficient as
there is no requirement to prevent reentrancy to any BPF program from a
preempting task. The only requirement is that the program stays on the same
CPU.

Therefore, this is a trivially correct transformation.

[ tglx: Converted to BPF_PROG_RUN_PIN_ON_CPU() ]

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

---
include/linux/filter.h | 4 +---
kernel/seccomp.c | 4 +---
net/core/flow_dissector.c | 4 +---
net/core/skmsg.c | 8 ++------
net/kcm/kcmsock.c | 4 +---
5 files changed, 6 insertions(+), 18 deletions(-)

--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -713,9 +713,7 @@ static inline u32 bpf_prog_run_clear_cb(
if (unlikely(prog->cb_access))
memset(cb_data, 0, BPF_SKB_CB_LEN);

- preempt_disable();
- res = BPF_PROG_RUN(prog, skb);
- preempt_enable();
+ res = BPF_PROG_RUN_PIN_ON_CPU(prog, skb);
return res;
}

--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -268,16 +268,14 @@ static u32 seccomp_run_filters(const str
* All filters in the list are evaluated and the lowest BPF return
* value always takes priority (ignoring the DATA).
*/
- preempt_disable();
for (; f; f = f->prev) {
- u32 cur_ret = BPF_PROG_RUN(f->prog, sd);
+ u32 cur_ret = BPF_PROG_RUN_PIN_ON_CPU(f->prog, sd);

if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) {
ret = cur_ret;
*match = f;
}
}
- preempt_enable();
return ret;
}
#endif /* CONFIG_SECCOMP_FILTER */
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -920,9 +920,7 @@ bool bpf_flow_dissect(struct bpf_prog *p
(int)FLOW_DISSECTOR_F_STOP_AT_ENCAP);
flow_keys->flags = flags;

- preempt_disable();
- result = BPF_PROG_RUN(prog, ctx);
- preempt_enable();
+ result = BPF_PROG_RUN_PIN_ON_CPU(prog, ctx);

flow_keys->nhoff = clamp_t(u16, flow_keys->nhoff, nhoff, hlen);
flow_keys->thoff = clamp_t(u16, flow_keys->thoff,
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -628,7 +628,6 @@ int sk_psock_msg_verdict(struct sock *sk
struct bpf_prog *prog;
int ret;

- preempt_disable();
rcu_read_lock();
prog = READ_ONCE(psock->progs.msg_parser);
if (unlikely(!prog)) {
@@ -638,7 +637,7 @@ int sk_psock_msg_verdict(struct sock *sk

sk_msg_compute_data_pointers(msg);
msg->sk = sk;
- ret = BPF_PROG_RUN(prog, msg);
+ ret = BPF_PROG_RUN_PIN_ON_CPU(prog, msg);
ret = sk_psock_map_verd(ret, msg->sk_redir);
psock->apply_bytes = msg->apply_bytes;
if (ret == __SK_REDIRECT) {
@@ -653,7 +652,6 @@ int sk_psock_msg_verdict(struct sock *sk
}
out:
rcu_read_unlock();
- preempt_enable();
return ret;
}
EXPORT_SYMBOL_GPL(sk_psock_msg_verdict);
@@ -665,9 +663,7 @@ static int sk_psock_bpf_run(struct sk_ps

skb->sk = psock->sk;
bpf_compute_data_end_sk_skb(skb);
- preempt_disable();
- ret = BPF_PROG_RUN(prog, skb);
- preempt_enable();
+ ret = BPF_PROG_RUN_PIN_ON_CPU(prog, skb);
/* strparser clones the skb before handing it to a upper layer,
* meaning skb_orphan has been called. We NULL sk on the way out
* to ensure we don't trigger a BUG_ON() in skb/sk operations
--- a/net/kcm/kcmsock.c
+++ b/net/kcm/kcmsock.c
@@ -380,9 +380,7 @@ static int kcm_parse_func_strparser(stru
struct bpf_prog *prog = psock->bpf_prog;
int res;

- preempt_disable();
- res = BPF_PROG_RUN(prog, skb);
- preempt_enable();
+ res = BPF_PROG_RUN_PIN_ON_CPU(prog, skb);
return res;
}

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