From: Matt Mullins mmullins@fb.com
commit 9594dc3c7e71b9f52bee1d7852eb3d4e3aea9e99 upstream.
BPF_PROG_TYPE_RAW_TRACEPOINTs can be executed nested on the same CPU, as they do not increment bpf_prog_active while executing.
This enables three levels of nesting, to support - a kprobe or raw tp or perf event, - another one of the above that irq context happens to call, and - another one in nmi context (at most one of which may be a kprobe or perf event).
Fixes: 20b9d7ac4852 ("bpf: avoid excessive stack usage for perf_sample_data") Signed-off-by: Matt Mullins mmullins@fb.com Acked-by: Andrii Nakryiko andriin@fb.com Acked-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/trace/bpf_trace.c | 100 +++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 84 insertions(+), 16 deletions(-)
--- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -402,8 +402,6 @@ static const struct bpf_func_proto bpf_p .arg4_type = ARG_CONST_SIZE, };
-static DEFINE_PER_CPU(struct perf_sample_data, bpf_trace_sd); - static __always_inline u64 __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map, u64 flags, struct perf_sample_data *sd) @@ -434,24 +432,50 @@ __bpf_perf_event_output(struct pt_regs * return perf_event_output(event, sd, regs); }
+/* + * Support executing tracepoints in normal, irq, and nmi context that each call + * bpf_perf_event_output + */ +struct bpf_trace_sample_data { + struct perf_sample_data sds[3]; +}; + +static DEFINE_PER_CPU(struct bpf_trace_sample_data, bpf_trace_sds); +static DEFINE_PER_CPU(int, bpf_trace_nest_level); BPF_CALL_5(bpf_perf_event_output, struct pt_regs *, regs, struct bpf_map *, map, u64, flags, void *, data, u64, size) { - struct perf_sample_data *sd = this_cpu_ptr(&bpf_trace_sd); + struct bpf_trace_sample_data *sds = this_cpu_ptr(&bpf_trace_sds); + int nest_level = this_cpu_inc_return(bpf_trace_nest_level); struct perf_raw_record raw = { .frag = { .size = size, .data = data, }, }; + struct perf_sample_data *sd; + int err;
- if (unlikely(flags & ~(BPF_F_INDEX_MASK))) - return -EINVAL; + if (WARN_ON_ONCE(nest_level > ARRAY_SIZE(sds->sds))) { + err = -EBUSY; + goto out; + } + + sd = &sds->sds[nest_level - 1]; + + if (unlikely(flags & ~(BPF_F_INDEX_MASK))) { + err = -EINVAL; + goto out; + }
perf_sample_data_init(sd, 0, 0); sd->raw = &raw;
- return __bpf_perf_event_output(regs, map, flags, sd); + err = __bpf_perf_event_output(regs, map, flags, sd); + +out: + this_cpu_dec(bpf_trace_nest_level); + return err; }
static const struct bpf_func_proto bpf_perf_event_output_proto = { @@ -808,16 +832,48 @@ pe_prog_func_proto(enum bpf_func_id func /* * bpf_raw_tp_regs are separate from bpf_pt_regs used from skb/xdp * to avoid potential recursive reuse issue when/if tracepoints are added - * inside bpf_*_event_output, bpf_get_stackid and/or bpf_get_stack + * inside bpf_*_event_output, bpf_get_stackid and/or bpf_get_stack. + * + * Since raw tracepoints run despite bpf_prog_active, support concurrent usage + * in normal, irq, and nmi context. */ -static DEFINE_PER_CPU(struct pt_regs, bpf_raw_tp_regs); +struct bpf_raw_tp_regs { + struct pt_regs regs[3]; +}; +static DEFINE_PER_CPU(struct bpf_raw_tp_regs, bpf_raw_tp_regs); +static DEFINE_PER_CPU(int, bpf_raw_tp_nest_level); +static struct pt_regs *get_bpf_raw_tp_regs(void) +{ + struct bpf_raw_tp_regs *tp_regs = this_cpu_ptr(&bpf_raw_tp_regs); + int nest_level = this_cpu_inc_return(bpf_raw_tp_nest_level); + + if (WARN_ON_ONCE(nest_level > ARRAY_SIZE(tp_regs->regs))) { + this_cpu_dec(bpf_raw_tp_nest_level); + return ERR_PTR(-EBUSY); + } + + return &tp_regs->regs[nest_level - 1]; +} + +static void put_bpf_raw_tp_regs(void) +{ + this_cpu_dec(bpf_raw_tp_nest_level); +} + BPF_CALL_5(bpf_perf_event_output_raw_tp, struct bpf_raw_tracepoint_args *, args, struct bpf_map *, map, u64, flags, void *, data, u64, size) { - struct pt_regs *regs = this_cpu_ptr(&bpf_raw_tp_regs); + struct pt_regs *regs = get_bpf_raw_tp_regs(); + int ret; + + if (IS_ERR(regs)) + return PTR_ERR(regs);
perf_fetch_caller_regs(regs); - return ____bpf_perf_event_output(regs, map, flags, data, size); + ret = ____bpf_perf_event_output(regs, map, flags, data, size); + + put_bpf_raw_tp_regs(); + return ret; }
static const struct bpf_func_proto bpf_perf_event_output_proto_raw_tp = { @@ -834,12 +890,18 @@ static const struct bpf_func_proto bpf_p BPF_CALL_3(bpf_get_stackid_raw_tp, struct bpf_raw_tracepoint_args *, args, struct bpf_map *, map, u64, flags) { - struct pt_regs *regs = this_cpu_ptr(&bpf_raw_tp_regs); + struct pt_regs *regs = get_bpf_raw_tp_regs(); + int ret; + + if (IS_ERR(regs)) + return PTR_ERR(regs);
perf_fetch_caller_regs(regs); /* similar to bpf_perf_event_output_tp, but pt_regs fetched differently */ - return bpf_get_stackid((unsigned long) regs, (unsigned long) map, - flags, 0, 0); + ret = bpf_get_stackid((unsigned long) regs, (unsigned long) map, + flags, 0, 0); + put_bpf_raw_tp_regs(); + return ret; }
static const struct bpf_func_proto bpf_get_stackid_proto_raw_tp = { @@ -854,11 +916,17 @@ static const struct bpf_func_proto bpf_g BPF_CALL_4(bpf_get_stack_raw_tp, struct bpf_raw_tracepoint_args *, args, void *, buf, u32, size, u64, flags) { - struct pt_regs *regs = this_cpu_ptr(&bpf_raw_tp_regs); + struct pt_regs *regs = get_bpf_raw_tp_regs(); + int ret; + + if (IS_ERR(regs)) + return PTR_ERR(regs);
perf_fetch_caller_regs(regs); - return bpf_get_stack((unsigned long) regs, (unsigned long) buf, - (unsigned long) size, flags, 0); + ret = bpf_get_stack((unsigned long) regs, (unsigned long) buf, + (unsigned long) size, flags, 0); + put_bpf_raw_tp_regs(); + return ret; }
static const struct bpf_func_proto bpf_get_stack_proto_raw_tp = {