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authorYonghong Song <yhs@fb.com>2017-08-04 16:00:09 -0700
committerDavid S. Miller <davem@davemloft.net>2017-08-07 14:09:48 -0700
commitcf5f5cea270655dd49370760576c64b228583b79 (patch)
tree5758e9d56b94542d082d40ed66f8d8effa6287f9 /kernel/trace/trace_syscalls.c
parentd226a2b84d0528da7e35e7e19e052293889cdd21 (diff)
bpf: add support for sys_enter_* and sys_exit_* tracepoints
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 The legality of bpf program ctx access is also checked. Function trace_event_get_offsets returns correct max offset for each specific syscall tracepoint, which is compared against the maximum offset access in bpf program. Signed-off-by: Yonghong Song <yhs@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/trace/trace_syscalls.c')
-rw-r--r--kernel/trace/trace_syscalls.c53
1 files changed, 51 insertions, 2 deletions
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 5e10395da88e..7a1a92036563 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[sys_data->nb_args];
+ } param;
+ int i;
+
+ *(struct pt_regs **)&param = 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);
+}
+
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 **)&param = regs;
+ param.syscall_nr = rec->nr;
+ param.ret = rec->ret;
+ return trace_call_bpf(prog, &param);
+}
+
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);
}