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Message-Id: <20190627003616.20767-49-sashal@kernel.org>
Date: Wed, 26 Jun 2019 20:36:04 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: Matt Mullins <mmullins@...com>, Andrii Nakryiko <andriin@...com>,
Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...nel.org>,
Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org,
bpf@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 49/60] bpf: fix nested bpf tracepoints with per-cpu data
From: Matt Mullins <mmullins@...com>
[ Upstream commit 9594dc3c7e71b9f52bee1d7852eb3d4e3aea9e99 ]
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@...com>
Acked-by: Andrii Nakryiko <andriin@...com>
Acked-by: Daniel Borkmann <daniel@...earbox.net>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
kernel/trace/bpf_trace.c | 100 ++++++++++++++++++++++++++++++++-------
1 file changed, 84 insertions(+), 16 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 6c28d519447d..83c4e76f513a 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -365,8 +365,6 @@ static const struct bpf_func_proto bpf_perf_event_read_value_proto = {
.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)
@@ -398,24 +396,50 @@ __bpf_perf_event_output(struct pt_regs *regs, struct bpf_map *map,
return 0;
}
+/*
+ * 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 = {
@@ -772,16 +796,48 @@ pe_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
/*
* 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 = {
@@ -798,12 +854,18 @@ static const struct bpf_func_proto bpf_perf_event_output_proto_raw_tp = {
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 = {
@@ -818,11 +880,17 @@ static const struct bpf_func_proto bpf_get_stackid_proto_raw_tp = {
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 = {
--
2.20.1
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