Add TIF_FD_SLOTS and test it after the untraced system call has
stored its return value. A task that reserved descriptors joins the
traced path, where syscall_trace_exit() commits them before audit and
the ptrace exit stop.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 arch/csky/include/asm/thread_info.h | 2 ++
 arch/csky/kernel/entry.S            | 9 +++++++++
 arch/csky/kernel/ptrace.c           | 4 ++++
 3 files changed, 15 insertions(+)

diff --git a/arch/csky/include/asm/thread_info.h b/arch/csky/include/asm/thread_info.h
index fdd4f8ad45ac..59109ce64695 100644
--- a/arch/csky/include/asm/thread_info.h
+++ b/arch/csky/include/asm/thread_info.h
@@ -61,6 +61,7 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_SYSCALL_TRACEPOINT	5       /* syscall tracepoint instrumentation */
 #define TIF_SYSCALL_AUDIT	6	/* syscall auditing */
 #define TIF_NOTIFY_SIGNAL	7	/* signal notifications exist */
+#define TIF_FD_SLOTS		8	/* syscall prepared descriptors */
 #define TIF_POLLING_NRFLAG	16	/* poll_idle() is TIF_NEED_RESCHED */
 #define TIF_MEMDIE		18      /* is terminating due to OOM killer */
 #define TIF_RESTORE_SIGMASK	20	/* restore signal mask in do_signal() */
@@ -73,6 +74,7 @@ static inline struct thread_info *current_thread_info(void)
 #define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
 #define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
 #define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
+#define _TIF_FD_SLOTS		(1 << TIF_FD_SLOTS)
 #define _TIF_UPROBE		(1 << TIF_UPROBE)
 #define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)
 #define _TIF_MEMDIE		(1 << TIF_MEMDIE)
diff --git a/arch/csky/kernel/entry.S b/arch/csky/kernel/entry.S
index 3261f46f2244..6ff3074b9787 100644
--- a/arch/csky/kernel/entry.S
+++ b/arch/csky/kernel/entry.S
@@ -80,6 +80,15 @@ ENTRY(csky_systemcall)
 	jsr     syscallid
 #endif
 	stw     a0, (sp, LSAVE_A0)      /* Save return value */
+	/* descriptors reserved by the syscall are committed in syscall_trace_exit() */
+	mov     r9, sp
+	bmaski  r10, THREAD_SHIFT
+	andn    r9, r10
+	ldw     r10, (r9, TINFO_FLAGS)
+	lrw	r9, _TIF_FD_SLOTS
+	and	r10, r9
+	cmpnei	r10, 0
+	bt      1f
 	jmpi    ret_from_exception
 
 csky_syscall_trace:
diff --git a/arch/csky/kernel/ptrace.c b/arch/csky/kernel/ptrace.c
index ee2867a1576e..b19fef9d396d 100644
--- a/arch/csky/kernel/ptrace.c
+++ b/arch/csky/kernel/ptrace.c
@@ -4,6 +4,7 @@
 #include <linux/audit.h>
 #include <linux/elf.h>
 #include <linux/errno.h>
+#include <linux/file.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/ptrace.h>
@@ -335,6 +336,9 @@ asmlinkage int syscall_trace_enter(struct pt_regs *regs)
 
 asmlinkage void syscall_trace_exit(struct pt_regs *regs)
 {
+	if (test_thread_flag(TIF_FD_SLOTS))
+		fd_slots_commit(regs);
+
 	audit_syscall_exit(regs);
 
 	if (test_thread_flag(TIF_SYSCALL_TRACE))

-- 
2.53.0