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tracing: Allow system call tracepoints to handle page faults

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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.

Cc: Michael Jeanson <mjeanson@efficios.com>
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>
Link: https://lore.kernel.org/20241009010718.2050182-6-mathieu.desnoyers@efficios.com
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Mathieu Desnoyers 2024-10-08 21:07:15 -04:00 committed by Steven Rostedt (Google)
parent 4aadde89d8
commit a363d27cdb
2 changed files with 17 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

18
include/linux/tracepoint.h
View file

@ -17,6 +17,7 @@
#include <linux/errno.h> #include <linux/errno.h>
#include <linux/types.h> #include <linux/types.h>
#include <linux/rcupdate.h> #include <linux/rcupdate.h>
#include <linux/rcupdate_trace.h>
#include <linux/tracepoint-defs.h> #include <linux/tracepoint-defs.h>
#include <linux/static_call.h> #include <linux/static_call.h>
@ -107,6 +108,7 @@ void for_each_tracepoint_in_module(struct module *mod,
#ifdef CONFIG_TRACEPOINTS #ifdef CONFIG_TRACEPOINTS
static inline void tracepoint_synchronize_unregister(void) static inline void tracepoint_synchronize_unregister(void)
{ {
synchronize_rcu_tasks_trace();
synchronize_rcu(); synchronize_rcu();
} }
#else #else
@ -196,6 +198,12 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
/* /*
* it_func[0] is never NULL because there is at least one element in the array * it_func[0] is never NULL because there is at least one element in the array
* when the array itself is non NULL. * when the array itself is non NULL.
*
* 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.
*/ */
#define __DO_TRACE(name, args, cond, syscall) \ #define __DO_TRACE(name, args, cond, syscall) \
do { \ do { \
@ -204,11 +212,17 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
if (!(cond)) \ if (!(cond)) \
return; \ return; \
\ \
preempt_disable_notrace(); \ if (syscall) \
rcu_read_lock_trace(); \
else \
preempt_disable_notrace(); \
\ \
__DO_TRACE_CALL(name, TP_ARGS(args)); \ __DO_TRACE_CALL(name, TP_ARGS(args)); \
\ \
preempt_enable_notrace(); \ if (syscall) \
rcu_read_unlock_trace(); \
else \
preempt_enable_notrace(); \
} while (0) } while (0)
/* /*

1
init/Kconfig
View file

@ -1985,6 +1985,7 @@ config BINDGEN_VERSION_TEXT
# #
config TRACEPOINTS config TRACEPOINTS
bool bool
select TASKS_TRACE_RCU
source "kernel/Kconfig.kexec" source "kernel/Kconfig.kexec"