On 2024-10-04 00:38, Steven Rostedt wrote:
On Thu, 3 Oct 2024 11:16:38 -0400
Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote:
Add a might_fault() check to validate that the bpf sys_enter/sys_exit
probe callbacks are indeed called from a context where page faults can
be handled.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Tested-by: Andrii Nakryiko <andrii@xxxxxxxxxx> # BPF parts
Cc: Michael Jeanson <mjeanson@xxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Yonghong Song <yhs@xxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
Cc: bpf@xxxxxxxxxxxxxxx
Cc: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
---
include/trace/bpf_probe.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/include/trace/bpf_probe.h b/include/trace/bpf_probe.h
index 211b98d45fc6..099df5c3e38a 100644
--- a/include/trace/bpf_probe.h
+++ b/include/trace/bpf_probe.h
@@ -57,6 +57,7 @@ __bpf_trace_##call(void *__data, proto) \
static notrace void \
__bpf_trace_##call(void *__data, proto) \
{ \
+ might_fault(); \
And I think this gets called at places that do not allow faults.
Context matters:
#undef DECLARE_EVENT_SYSCALL_CLASS
#define DECLARE_EVENT_SYSCALL_CLASS(call, proto, args, tstruct, assign, print) \
__DECLARE_EVENT_CLASS(call, PARAMS(proto), PARAMS(args), PARAMS(tstruct), \
PARAMS(assign), PARAMS(print)) \
static notrace void \
perf_trace_##call(void *__data, proto) \
{ \
u64 __count __attribute__((unused)); \
struct task_struct *__task __attribute__((unused)); \
\
might_fault(); \
guard(preempt_notrace)(); \
do_perf_trace_##call(__data, args); \
}
Not an issue.
Thanks,
Mathieu
-- Steve
guard(preempt_notrace)(); \
CONCATENATE(bpf_trace_run, COUNT_ARGS(args))(__data, CAST_TO_U64(args)); \
}
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
