On Fri, 4 Oct 2024 10:58:15 -0400 Mathieu Desnoyers <[email protected]> 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 <[email protected]> > Cc: Michael Jeanson <[email protected]> > Cc: Steven Rostedt <[email protected]> > Cc: Masami Hiramatsu <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Alexei Starovoitov <[email protected]> > Cc: Yonghong Song <[email protected]> > Cc: Paul E. McKenney <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Arnaldo Carvalho de Melo <[email protected]> > Cc: Mark Rutland <[email protected]> > Cc: Alexander Shishkin <[email protected]> > Cc: Namhyung Kim <[email protected]> > Cc: Andrii Nakryiko <[email protected]> > Cc: [email protected] > Cc: Joel Fernandes <[email protected]> > --- > 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" >
