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authorYonghong Song <yhs@fb.com>2017-10-24 09:53:08 +0300
committerDavid S. Miller <davem@davemloft.net>2017-10-25 04:47:47 +0300
commite87c6bc3852b981e71c757be20771546ce9f76f3 (patch)
treebad3be630137d8e873f4ad5a1ea77b4aa1853184 /kernel/trace
parent0b4c6841fee03e096b735074a0c4aab3a8e92986 (diff)
downloadlinux-e87c6bc3852b981e71c757be20771546ce9f76f3.tar.xz
bpf: permit multiple bpf attachments for a single perf event
This patch enables multiple bpf attachments for a kprobe/uprobe/tracepoint single trace event. Each trace_event keeps a list of attached perf events. When an event happens, all attached bpf programs will be executed based on the order of attachment. A global bpf_event_mutex lock is introduced to protect prog_array attaching and detaching. An alternative will be introduce a mutex lock in every trace_event_call structure, but it takes a lot of extra memory. So a global bpf_event_mutex lock is a good compromise. The bpf prog detachment involves allocation of memory. If the allocation fails, a dummy do-nothing program will replace to-be-detached program in-place. Signed-off-by: Yonghong Song <yhs@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/trace')
-rw-r--r--kernel/trace/bpf_trace.c82
-rw-r--r--kernel/trace/trace_kprobe.c6
-rw-r--r--kernel/trace/trace_syscalls.c34
-rw-r--r--kernel/trace/trace_uprobe.c3
4 files changed, 99 insertions, 26 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 3126da2f468a..b65011d320e3 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -17,7 +17,7 @@
/**
* trace_call_bpf - invoke BPF program
- * @prog: BPF program
+ * @call: tracepoint event
* @ctx: opaque context pointer
*
* kprobe handlers execute BPF programs via this helper.
@@ -29,7 +29,7 @@
* 1 - store kprobe event into ring buffer
* Other values are reserved and currently alias to 1
*/
-unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx)
+unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx)
{
unsigned int ret;
@@ -49,9 +49,22 @@ unsigned int trace_call_bpf(struct bpf_prog *prog, void *ctx)
goto out;
}
- rcu_read_lock();
- ret = BPF_PROG_RUN(prog, ctx);
- rcu_read_unlock();
+ /*
+ * Instead of moving rcu_read_lock/rcu_dereference/rcu_read_unlock
+ * to all call sites, we did a bpf_prog_array_valid() there to check
+ * whether call->prog_array is empty or not, which is
+ * a heurisitc to speed up execution.
+ *
+ * If bpf_prog_array_valid() fetched prog_array was
+ * non-NULL, we go into trace_call_bpf() and do the actual
+ * proper rcu_dereference() under RCU lock.
+ * If it turns out that prog_array is NULL then, we bail out.
+ * For the opposite, if the bpf_prog_array_valid() fetched pointer
+ * was NULL, you'll skip the prog_array with the risk of missing
+ * out of events when it was updated in between this and the
+ * rcu_dereference() which is accepted risk.
+ */
+ ret = BPF_PROG_RUN_ARRAY_CHECK(call->prog_array, ctx, BPF_PROG_RUN);
out:
__this_cpu_dec(bpf_prog_active);
@@ -741,3 +754,62 @@ const struct bpf_verifier_ops perf_event_verifier_ops = {
const struct bpf_prog_ops perf_event_prog_ops = {
};
+
+static DEFINE_MUTEX(bpf_event_mutex);
+
+int perf_event_attach_bpf_prog(struct perf_event *event,
+ struct bpf_prog *prog)
+{
+ struct bpf_prog_array __rcu *old_array;
+ struct bpf_prog_array *new_array;
+ int ret = -EEXIST;
+
+ mutex_lock(&bpf_event_mutex);
+
+ if (event->prog)
+ goto out;
+
+ old_array = rcu_dereference_protected(event->tp_event->prog_array,
+ lockdep_is_held(&bpf_event_mutex));
+ ret = bpf_prog_array_copy(old_array, NULL, prog, &new_array);
+ if (ret < 0)
+ goto out;
+
+ /* set the new array to event->tp_event and set event->prog */
+ event->prog = prog;
+ rcu_assign_pointer(event->tp_event->prog_array, new_array);
+ bpf_prog_array_free(old_array);
+
+out:
+ mutex_unlock(&bpf_event_mutex);
+ return ret;
+}
+
+void perf_event_detach_bpf_prog(struct perf_event *event)
+{
+ struct bpf_prog_array __rcu *old_array;
+ struct bpf_prog_array *new_array;
+ int ret;
+
+ mutex_lock(&bpf_event_mutex);
+
+ if (!event->prog)
+ goto out;
+
+ old_array = rcu_dereference_protected(event->tp_event->prog_array,
+ lockdep_is_held(&bpf_event_mutex));
+
+ ret = bpf_prog_array_copy(old_array, event->prog, NULL, &new_array);
+ if (ret < 0) {
+ bpf_prog_array_delete_safe(old_array, event->prog);
+ } else {
+ rcu_assign_pointer(event->tp_event->prog_array, new_array);
+ bpf_prog_array_free(old_array);
+ }
+
+ bpf_prog_put(event->prog);
+ event->prog = NULL;
+
+out:
+ mutex_unlock(&bpf_event_mutex);
+}
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 8a907e12b6b9..abf92e478cfb 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1174,13 +1174,12 @@ static void
kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs)
{
struct trace_event_call *call = &tk->tp.call;
- struct bpf_prog *prog = call->prog;
struct kprobe_trace_entry_head *entry;
struct hlist_head *head;
int size, __size, dsize;
int rctx;
- if (prog && !trace_call_bpf(prog, regs))
+ if (bpf_prog_array_valid(call) && !trace_call_bpf(call, regs))
return;
head = this_cpu_ptr(call->perf_events);
@@ -1210,13 +1209,12 @@ kretprobe_perf_func(struct trace_kprobe *tk, struct kretprobe_instance *ri,
struct pt_regs *regs)
{
struct trace_event_call *call = &tk->tp.call;
- struct bpf_prog *prog = call->prog;
struct kretprobe_trace_entry_head *entry;
struct hlist_head *head;
int size, __size, dsize;
int rctx;
- if (prog && !trace_call_bpf(prog, regs))
+ if (bpf_prog_array_valid(call) && !trace_call_bpf(call, regs))
return;
head = this_cpu_ptr(call->perf_events);
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 696afe72d3b1..71a6af34d7a9 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -559,9 +559,10 @@ static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
static int sys_perf_refcount_enter;
static int sys_perf_refcount_exit;
-static int perf_call_bpf_enter(struct bpf_prog *prog, struct pt_regs *regs,
- struct syscall_metadata *sys_data,
- struct syscall_trace_enter *rec) {
+static int perf_call_bpf_enter(struct trace_event_call *call, struct pt_regs *regs,
+ struct syscall_metadata *sys_data,
+ struct syscall_trace_enter *rec)
+{
struct syscall_tp_t {
unsigned long long regs;
unsigned long syscall_nr;
@@ -573,7 +574,7 @@ static int perf_call_bpf_enter(struct bpf_prog *prog, struct pt_regs *regs,
param.syscall_nr = rec->nr;
for (i = 0; i < sys_data->nb_args; i++)
param.args[i] = rec->args[i];
- return trace_call_bpf(prog, &param);
+ return trace_call_bpf(call, &param);
}
static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
@@ -581,7 +582,7 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
struct syscall_metadata *sys_data;
struct syscall_trace_enter *rec;
struct hlist_head *head;
- struct bpf_prog *prog;
+ bool valid_prog_array;
int syscall_nr;
int rctx;
int size;
@@ -596,9 +597,9 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
if (!sys_data)
return;
- prog = READ_ONCE(sys_data->enter_event->prog);
head = this_cpu_ptr(sys_data->enter_event->perf_events);
- if (!prog && hlist_empty(head))
+ valid_prog_array = bpf_prog_array_valid(sys_data->enter_event);
+ if (!valid_prog_array && hlist_empty(head))
return;
/* get the size after alignment with the u32 buffer size field */
@@ -614,7 +615,8 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
syscall_get_arguments(current, regs, 0, sys_data->nb_args,
(unsigned long *)&rec->args);
- if ((prog && !perf_call_bpf_enter(prog, regs, sys_data, rec)) ||
+ if ((valid_prog_array &&
+ !perf_call_bpf_enter(sys_data->enter_event, regs, sys_data, rec)) ||
hlist_empty(head)) {
perf_swevent_put_recursion_context(rctx);
return;
@@ -659,8 +661,9 @@ static void perf_sysenter_disable(struct trace_event_call *call)
mutex_unlock(&syscall_trace_lock);
}
-static int perf_call_bpf_exit(struct bpf_prog *prog, struct pt_regs *regs,
- struct syscall_trace_exit *rec) {
+static int perf_call_bpf_exit(struct trace_event_call *call, struct pt_regs *regs,
+ struct syscall_trace_exit *rec)
+{
struct syscall_tp_t {
unsigned long long regs;
unsigned long syscall_nr;
@@ -670,7 +673,7 @@ static int perf_call_bpf_exit(struct bpf_prog *prog, struct pt_regs *regs,
*(struct pt_regs **)&param = regs;
param.syscall_nr = rec->nr;
param.ret = rec->ret;
- return trace_call_bpf(prog, &param);
+ return trace_call_bpf(call, &param);
}
static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
@@ -678,7 +681,7 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
struct syscall_metadata *sys_data;
struct syscall_trace_exit *rec;
struct hlist_head *head;
- struct bpf_prog *prog;
+ bool valid_prog_array;
int syscall_nr;
int rctx;
int size;
@@ -693,9 +696,9 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
if (!sys_data)
return;
- prog = READ_ONCE(sys_data->exit_event->prog);
head = this_cpu_ptr(sys_data->exit_event->perf_events);
- if (!prog && hlist_empty(head))
+ valid_prog_array = bpf_prog_array_valid(sys_data->exit_event);
+ if (!valid_prog_array && hlist_empty(head))
return;
/* We can probably do that at build time */
@@ -709,7 +712,8 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
rec->nr = syscall_nr;
rec->ret = syscall_get_return_value(current, regs);
- if ((prog && !perf_call_bpf_exit(prog, regs, rec)) ||
+ if ((valid_prog_array &&
+ !perf_call_bpf_exit(sys_data->exit_event, regs, rec)) ||
hlist_empty(head)) {
perf_swevent_put_recursion_context(rctx);
return;
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index 4525e0271a53..153c0e411461 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -1113,13 +1113,12 @@ static void __uprobe_perf_func(struct trace_uprobe *tu,
{
struct trace_event_call *call = &tu->tp.call;
struct uprobe_trace_entry_head *entry;
- struct bpf_prog *prog = call->prog;
struct hlist_head *head;
void *data;
int size, esize;
int rctx;
- if (prog && !trace_call_bpf(prog, regs))
+ if (bpf_prog_array_valid(call) && !trace_call_bpf(call, regs))
return;
esize = SIZEOF_TRACE_ENTRY(is_ret_probe(tu));