Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [RFC patch 09/19] bpf: Use BPF_PROG_RUN_PIN_ON_CPU() at simple call sites. | Date | Wed, 19 Feb 2020 10:00:56 +0100 |
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Vinicius Costa Gomes <vinicius.gomes@intel.com> writes:
Cc+: seccomp folks
> Thomas Gleixner <tglx@linutronix.de> writes: > >> From: David Miller <davem@davemloft.net>
Leaving content for reference
>> 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); >> > > More a question really, isn't the behavior changing here? i.e. shouldn't > migrate_disable()/migrate_enable() be moved to outside the loop? Or is > running seccomp filters on different cpus not a problem?
In my understanding this is a list of filters and they are independent of each other.
Kees, Will. Andy?
Thanks,
tglx
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