| Message ID | 20241004145818.1726671-6-mathieu.desnoyers@efficios.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | tracing: Allow system call tracepoints to handle page faults | expand |
On Fri, 4 Oct 2024 10:58:15 -0400 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote: > Use Tasks Trace RCU to protect iteration of system call enter/exit > tracepoint probes to allow those probes to handle page faults. > > In preparation for this change, all tracers registering to system call > enter/exit tracepoints should expect those to be called with preemption > enabled. > > This allows tracers to fault-in userspace system call arguments such as > path strings within their probe callbacks. > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> > Cc: Michael Jeanson <mjeanson@efficios.com> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: Masami Hiramatsu <mhiramat@kernel.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: Alexei Starovoitov <ast@kernel.org> > Cc: Yonghong Song <yhs@fb.com> > Cc: Paul E. McKenney <paulmck@kernel.org> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Arnaldo Carvalho de Melo <acme@kernel.org> > Cc: Mark Rutland <mark.rutland@arm.com> > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> > Cc: Namhyung Kim <namhyung@kernel.org> > Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com> > Cc: bpf@vger.kernel.org > Cc: Joel Fernandes <joel@joelfernandes.org> > --- > include/linux/tracepoint.h | 12 ++++++++++-- > init/Kconfig | 1 + > 2 files changed, 11 insertions(+), 2 deletions(-) > > diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h > index 014790495ad8..cefd44b7c91f 100644 > --- a/include/linux/tracepoint.h > +++ b/include/linux/tracepoint.h > @@ -17,6 +17,7 @@ > #include <linux/errno.h> > #include <linux/types.h> > #include <linux/rcupdate.h> > +#include <linux/rcupdate_trace.h> > #include <linux/tracepoint-defs.h> > #include <linux/static_call.h> > > @@ -107,6 +108,7 @@ void for_each_tracepoint_in_module(struct module *mod, > #ifdef CONFIG_TRACEPOINTS > static inline void tracepoint_synchronize_unregister(void) > { > + synchronize_rcu_tasks_trace(); > synchronize_rcu(); > } > #else > @@ -204,11 +206,17 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) > if (!(cond)) \ > return; \ > \ > - preempt_disable_notrace(); \ Should add a comment somewhere stating that the syscall version is to allow faults. -- Steve > + if (syscall) \ > + rcu_read_lock_trace(); \ > + else \ > + preempt_disable_notrace(); \ > \ > __DO_TRACE_CALL(name, TP_ARGS(args)); \ > \ > - preempt_enable_notrace(); \ > + if (syscall) \ > + rcu_read_unlock_trace(); \ > + else \ > + preempt_enable_notrace(); \ > } while (0) > > /* > diff --git a/init/Kconfig b/init/Kconfig > index fbd0cb06a50a..eedd0064fb36 100644 > --- a/init/Kconfig > +++ b/init/Kconfig > @@ -1984,6 +1984,7 @@ config BINDGEN_VERSION_TEXT > # > config TRACEPOINTS > bool > + select TASKS_TRACE_RCU > > source "kernel/Kconfig.kexec" >
On 2024-10-09 01:23, Steven Rostedt wrote: > On Fri, 4 Oct 2024 10:58:15 -0400 > Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote: > >> Use Tasks Trace RCU to protect iteration of system call enter/exit >> tracepoint probes to allow those probes to handle page faults. >> >> In preparation for this change, all tracers registering to system call >> enter/exit tracepoints should expect those to be called with preemption >> enabled. >> >> This allows tracers to fault-in userspace system call arguments such as >> path strings within their probe callbacks. >> >> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> >> Cc: Michael Jeanson <mjeanson@efficios.com> >> Cc: Steven Rostedt <rostedt@goodmis.org> >> Cc: Masami Hiramatsu <mhiramat@kernel.org> >> Cc: Peter Zijlstra <peterz@infradead.org> >> Cc: Alexei Starovoitov <ast@kernel.org> >> Cc: Yonghong Song <yhs@fb.com> >> Cc: Paul E. McKenney <paulmck@kernel.org> >> Cc: Ingo Molnar <mingo@redhat.com> >> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> >> Cc: Mark Rutland <mark.rutland@arm.com> >> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> >> Cc: Namhyung Kim <namhyung@kernel.org> >> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com> >> Cc: bpf@vger.kernel.org >> Cc: Joel Fernandes <joel@joelfernandes.org> >> --- >> include/linux/tracepoint.h | 12 ++++++++++-- >> init/Kconfig | 1 + >> 2 files changed, 11 insertions(+), 2 deletions(-) >> >> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h >> index 014790495ad8..cefd44b7c91f 100644 >> --- a/include/linux/tracepoint.h >> +++ b/include/linux/tracepoint.h >> @@ -17,6 +17,7 @@ >> #include <linux/errno.h> >> #include <linux/types.h> >> #include <linux/rcupdate.h> >> +#include <linux/rcupdate_trace.h> >> #include <linux/tracepoint-defs.h> >> #include <linux/static_call.h> >> >> @@ -107,6 +108,7 @@ void for_each_tracepoint_in_module(struct module *mod, >> #ifdef CONFIG_TRACEPOINTS >> static inline void tracepoint_synchronize_unregister(void) >> { >> + synchronize_rcu_tasks_trace(); >> synchronize_rcu(); >> } >> #else >> @@ -204,11 +206,17 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) >> if (!(cond)) \ >> return; \ >> \ >> - preempt_disable_notrace(); \ > > Should add a comment somewhere stating that the syscall version is to allow faults. I plan to add this comment on top of __TO_TRACE: + * + * With @syscall=0, the tracepoint callback array dereference is + * protected by disabling preemption. + * With @syscall=1, the tracepoint callback array dereference is + * protected by Tasks Trace RCU, which allows probes to handle page + * faults. Thanks, Mathieu > > -- Steve > >> + if (syscall) \ >> + rcu_read_lock_trace(); \ >> + else \ >> + preempt_disable_notrace(); \ >> \ >> __DO_TRACE_CALL(name, TP_ARGS(args)); \ >> \ >> - preempt_enable_notrace(); \ >> + if (syscall) \ >> + rcu_read_unlock_trace(); \ >> + else \ >> + preempt_enable_notrace(); \ >> } while (0) >> >> /* >> diff --git a/init/Kconfig b/init/Kconfig >> index fbd0cb06a50a..eedd0064fb36 100644 >> --- a/init/Kconfig >> +++ b/init/Kconfig >> @@ -1984,6 +1984,7 @@ config BINDGEN_VERSION_TEXT >> # >> config TRACEPOINTS >> bool >> + select TASKS_TRACE_RCU >> >> source "kernel/Kconfig.kexec" >> >
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index 014790495ad8..cefd44b7c91f 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -17,6 +17,7 @@ #include <linux/errno.h> #include <linux/types.h> #include <linux/rcupdate.h> +#include <linux/rcupdate_trace.h> #include <linux/tracepoint-defs.h> #include <linux/static_call.h> @@ -107,6 +108,7 @@ void for_each_tracepoint_in_module(struct module *mod, #ifdef CONFIG_TRACEPOINTS static inline void tracepoint_synchronize_unregister(void) { + synchronize_rcu_tasks_trace(); synchronize_rcu(); } #else @@ -204,11 +206,17 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p) if (!(cond)) \ return; \ \ - preempt_disable_notrace(); \ + if (syscall) \ + rcu_read_lock_trace(); \ + else \ + preempt_disable_notrace(); \ \ __DO_TRACE_CALL(name, TP_ARGS(args)); \ \ - preempt_enable_notrace(); \ + if (syscall) \ + rcu_read_unlock_trace(); \ + else \ + preempt_enable_notrace(); \ } while (0) /* diff --git a/init/Kconfig b/init/Kconfig index fbd0cb06a50a..eedd0064fb36 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1984,6 +1984,7 @@ config BINDGEN_VERSION_TEXT # config TRACEPOINTS bool + select TASKS_TRACE_RCU source "kernel/Kconfig.kexec"
Use Tasks Trace RCU to protect iteration of system call enter/exit tracepoint probes to allow those probes to handle page faults. In preparation for this change, all tracers registering to system call enter/exit tracepoints should expect those to be called with preemption enabled. This allows tracers to fault-in userspace system call arguments such as path strings within their probe callbacks. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Michael Jeanson <mjeanson@efficios.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Yonghong Song <yhs@fb.com> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com> Cc: bpf@vger.kernel.org Cc: Joel Fernandes <joel@joelfernandes.org> --- include/linux/tracepoint.h | 12 ++++++++++-- init/Kconfig | 1 + 2 files changed, 11 insertions(+), 2 deletions(-)