Currently, bpf programs cannot be attached to sys_enter_* and sys_exit_*
style tracepoints. The iovisor/bcc issue #748
(https://github.com/iovisor/bcc/issues/748) documents this issue.
For example, if you try to attach a bpf program to tracepoints
syscalls/sys_enter_newfstat, you will get the following error:
# ./tools/trace.py t:syscalls:sys_enter_newfstat
Ioctl(PERF_EVENT_IOC_SET_BPF): Invalid argument
Failed to attach BPF to tracepoint
The main reason is that syscalls/sys_enter_* and syscalls/sys_exit_*
tracepoints are treated differently from other tracepoints and there
is no bpf hook to it.
This patch adds bpf support for these syscalls tracepoints by
. permitting bpf attachment in ioctl PERF_EVENT_IOC_SET_BPF
. calling bpf programs in perf_syscall_enter and perf_syscall_exit
Signed-off-by: Yonghong Song <y...@fb.com>
---
include/linux/syscalls.h | 6 +++++
kernel/events/core.c | 8 ++++---
kernel/trace/trace_syscalls.c | 53 +++++++++++++++++++++++++++++++++++++++++--
3 files changed, 62 insertions(+), 5 deletions(-)
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 3cb15ea..00fa3eb 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -117,6 +117,12 @@ extern struct trace_event_class event_class_syscall_exit;
extern struct trace_event_functions enter_syscall_print_funcs;
extern struct trace_event_functions exit_syscall_print_funcs;
+static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
+{
+ return tp_event->class == &event_class_syscall_enter ||
+ tp_event->class == &event_class_syscall_exit;
+}
+
#define SYSCALL_TRACE_ENTER_EVENT(sname) \
static struct syscall_metadata __syscall_meta_##sname; \
static struct trace_event_call __used \
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 426c2ff..750b8d3 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -8050,7 +8050,7 @@ static void perf_event_free_bpf_handler(struct perf_event
*event)
static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd)
{
- bool is_kprobe, is_tracepoint;
+ bool is_kprobe, is_tracepoint, is_syscall_tp;
struct bpf_prog *prog;
if (event->attr.type != PERF_TYPE_TRACEPOINT)
@@ -8061,7 +8061,8 @@ static int perf_event_set_bpf_prog(struct perf_event
*event, u32 prog_fd)
is_kprobe = event->tp_event->flags & TRACE_EVENT_FL_UKPROBE;
is_tracepoint = event->tp_event->flags & TRACE_EVENT_FL_TRACEPOINT;
- if (!is_kprobe && !is_tracepoint)
+ is_syscall_tp = is_syscall_trace_event(event->tp_event);
+ if (!is_kprobe && !is_tracepoint && !is_syscall_tp)
/* bpf programs can only be attached to u/kprobe or tracepoint
*/
return -EINVAL;
@@ -8070,7 +8071,8 @@ static int perf_event_set_bpf_prog(struct perf_event
*event, u32 prog_fd)
return PTR_ERR(prog);
if ((is_kprobe && prog->type != BPF_PROG_TYPE_KPROBE) ||
- (is_tracepoint && prog->type != BPF_PROG_TYPE_TRACEPOINT)) {
+ (is_tracepoint && prog->type != BPF_PROG_TYPE_TRACEPOINT) ||
+ (is_syscall_tp && prog->type != BPF_PROG_TYPE_TRACEPOINT)) {
/* valid fd, but invalid bpf program type */
bpf_prog_put(prog);
return -EINVAL;
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 5e10395..3bd9e1c 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -559,11 +559,29 @@ 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) {
+ struct syscall_tp_t {
+ unsigned long long regs;
+ unsigned long syscall_nr;
+ unsigned long args[6]; /* maximum 6 arguments */
+ } param;
+ int i;
+
+ *(struct pt_regs **)¶m = regs;
+ param.syscall_nr = rec->nr;
+ for (i = 0; i < sys_data->nb_args && i < 6; i++)
+ param.args[i] = rec->args[i];
+ return trace_call_bpf(prog, ¶m);
+}
+
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;
int syscall_nr;
int rctx;
int size;
@@ -578,8 +596,9 @@ 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 (hlist_empty(head))
+ if (!prog && hlist_empty(head))
return;
/* get the size after alignment with the u32 buffer size field */
@@ -594,6 +613,13 @@ static void perf_syscall_enter(void *ignore, struct
pt_regs *regs, long id)
rec->nr = syscall_nr;
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)) ||
+ hlist_empty(head)) {
+ perf_swevent_put_recursion_context(rctx);
+ return;
+ }
+
perf_trace_buf_submit(rec, size, rctx,
sys_data->enter_event->event.type, 1, regs,
head, NULL);
@@ -633,11 +659,26 @@ 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) {
+ struct syscall_tp_t {
+ unsigned long long regs;
+ unsigned long syscall_nr;
+ unsigned long ret;
+ } param;
+
+ *(struct pt_regs **)¶m = regs;
+ param.syscall_nr = rec->nr;
+ param.ret = rec->ret;
+ return trace_call_bpf(prog, ¶m);
+}
+
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;
int syscall_nr;
int rctx;
int size;
@@ -652,8 +693,9 @@ 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 (hlist_empty(head))
+ if (!prog && hlist_empty(head))
return;
/* We can probably do that at build time */
@@ -666,6 +708,13 @@ 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)) ||
+ hlist_empty(head)) {
+ perf_swevent_put_recursion_context(rctx);
+ return;
+ }
+
perf_trace_buf_submit(rec, size, rctx, sys_data->exit_event->event.type,
1, regs, head, NULL);
}
--
2.9.4
