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Message-Id: <20240627152340.82413-9-mathieu.desnoyers@efficios.com>
Date: Thu, 27 Jun 2024 11:23:40 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Steven Rostedt <rostedt@...dmis.org>,
Masami Hiramatsu <mhiramat@...nel.org>
Cc: linux-trace-kernel@...r.kernel.org,
linux-kernel@...r.kernel.org,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Peter Zijlstra <peterz@...radead.org>,
Alexei Starovoitov <ast@...nel.org>,
Yonghong Song <yhs@...com>,
"Paul E . McKenney" <paulmck@...nel.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
bpf@...r.kernel.org,
Joel Fernandes <joel@...lfernandes.org>,
Michael Jeanson <mjeanson@...icios.com>
Subject: [PATCH v5 8/8] tracing: Convert sys_enter/exit to faultable tracepoints
Convert the definition of the system call enter/exit tracepoints to
faultable tracepoints now that all upstream tracers handle it.
This allows tracers to fault-in userspace system call arguments such as
path strings within their probe callbacks.
Link: https://lore.kernel.org/lkml/20231002202531.3160-1-mathieu.desnoyers@efficios.com/
Co-developed-by: Michael Jeanson <mjeanson@...icios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Signed-off-by: Michael Jeanson <mjeanson@...icios.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Alexei Starovoitov <ast@...nel.org>
Cc: Yonghong Song <yhs@...com>
Cc: Paul E. McKenney <paulmck@...nel.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: bpf@...r.kernel.org
Cc: Joel Fernandes <joel@...lfernandes.org>
---
Since v4:
- Use 'guard(preempt_notrace)'.
- Add brackets to multiline 'if' statements.
---
include/trace/events/syscalls.h | 4 +--
kernel/trace/trace_syscalls.c | 52 ++++++++++++++++++++++++++++-----
2 files changed, 46 insertions(+), 10 deletions(-)
diff --git a/include/trace/events/syscalls.h b/include/trace/events/syscalls.h
index b6e0cbc2c71f..dc30e3004818 100644
--- a/include/trace/events/syscalls.h
+++ b/include/trace/events/syscalls.h
@@ -15,7 +15,7 @@
#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
-TRACE_EVENT_FN(sys_enter,
+TRACE_EVENT_FN_MAY_FAULT(sys_enter,
TP_PROTO(struct pt_regs *regs, long id),
@@ -41,7 +41,7 @@ TRACE_EVENT_FN(sys_enter,
TRACE_EVENT_FLAGS(sys_enter, TRACE_EVENT_FL_CAP_ANY)
-TRACE_EVENT_FN(sys_exit,
+TRACE_EVENT_FN_MAY_FAULT(sys_exit,
TP_PROTO(struct pt_regs *regs, long ret),
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index 9c581d6da843..314666d663b6 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -299,6 +299,12 @@ static void ftrace_syscall_enter(void *data, struct pt_regs *regs, long id)
int syscall_nr;
int size;
+ /*
+ * Probe called with preemption enabled (may_fault), but ring buffer and
+ * per-cpu data require preemption to be disabled.
+ */
+ guard(preempt_notrace)();
+
syscall_nr = trace_get_syscall_nr(current, regs);
if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
return;
@@ -338,6 +344,12 @@ static void ftrace_syscall_exit(void *data, struct pt_regs *regs, long ret)
struct trace_event_buffer fbuffer;
int syscall_nr;
+ /*
+ * Probe called with preemption enabled (may_fault), but ring buffer and
+ * per-cpu data require preemption to be disabled.
+ */
+ guard(preempt_notrace)();
+
syscall_nr = trace_get_syscall_nr(current, regs);
if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
return;
@@ -376,8 +388,11 @@ static int reg_event_syscall_enter(struct trace_event_file *file,
if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
return -ENOSYS;
mutex_lock(&syscall_trace_lock);
- if (!tr->sys_refcount_enter)
- ret = register_trace_sys_enter(ftrace_syscall_enter, tr);
+ if (!tr->sys_refcount_enter) {
+ ret = register_trace_prio_flags_sys_enter(ftrace_syscall_enter, tr,
+ TRACEPOINT_DEFAULT_PRIO,
+ TRACEPOINT_MAY_FAULT);
+ }
if (!ret) {
rcu_assign_pointer(tr->enter_syscall_files[num], file);
tr->sys_refcount_enter++;
@@ -414,8 +429,11 @@ static int reg_event_syscall_exit(struct trace_event_file *file,
if (WARN_ON_ONCE(num < 0 || num >= NR_syscalls))
return -ENOSYS;
mutex_lock(&syscall_trace_lock);
- if (!tr->sys_refcount_exit)
- ret = register_trace_sys_exit(ftrace_syscall_exit, tr);
+ if (!tr->sys_refcount_exit) {
+ ret = register_trace_prio_flags_sys_exit(ftrace_syscall_exit, tr,
+ TRACEPOINT_DEFAULT_PRIO,
+ TRACEPOINT_MAY_FAULT);
+ }
if (!ret) {
rcu_assign_pointer(tr->exit_syscall_files[num], file);
tr->sys_refcount_exit++;
@@ -582,6 +600,12 @@ static void perf_syscall_enter(void *ignore, struct pt_regs *regs, long id)
int rctx;
int size;
+ /*
+ * Probe called with preemption enabled (may_fault), but ring buffer and
+ * per-cpu data require preemption to be disabled.
+ */
+ guard(preempt_notrace)();
+
syscall_nr = trace_get_syscall_nr(current, regs);
if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
return;
@@ -630,8 +654,11 @@ static int perf_sysenter_enable(struct trace_event_call *call)
num = ((struct syscall_metadata *)call->data)->syscall_nr;
mutex_lock(&syscall_trace_lock);
- if (!sys_perf_refcount_enter)
- ret = register_trace_sys_enter(perf_syscall_enter, NULL);
+ if (!sys_perf_refcount_enter) {
+ ret = register_trace_prio_flags_sys_enter(perf_syscall_enter, NULL,
+ TRACEPOINT_DEFAULT_PRIO,
+ TRACEPOINT_MAY_FAULT);
+ }
if (ret) {
pr_info("event trace: Could not activate syscall entry trace point");
} else {
@@ -682,6 +709,12 @@ static void perf_syscall_exit(void *ignore, struct pt_regs *regs, long ret)
int rctx;
int size;
+ /*
+ * Probe called with preemption enabled (may_fault), but ring buffer and
+ * per-cpu data require preemption to be disabled.
+ */
+ guard(preempt_notrace)();
+
syscall_nr = trace_get_syscall_nr(current, regs);
if (syscall_nr < 0 || syscall_nr >= NR_syscalls)
return;
@@ -727,8 +760,11 @@ static int perf_sysexit_enable(struct trace_event_call *call)
num = ((struct syscall_metadata *)call->data)->syscall_nr;
mutex_lock(&syscall_trace_lock);
- if (!sys_perf_refcount_exit)
- ret = register_trace_sys_exit(perf_syscall_exit, NULL);
+ if (!sys_perf_refcount_exit) {
+ ret = register_trace_prio_flags_sys_exit(perf_syscall_exit, NULL,
+ TRACEPOINT_DEFAULT_PRIO,
+ TRACEPOINT_MAY_FAULT);
+ }
if (ret) {
pr_info("event trace: Could not activate syscall exit trace point");
} else {
--
2.39.2
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