Add TIF_FD_SLOTS and test it once the system call has stored its
return value. A task that reserved descriptors uses the traced path.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 arch/xtensa/include/asm/thread_info.h | 2 ++
 arch/xtensa/kernel/entry.S            | 5 +++++
 arch/xtensa/kernel/ptrace.c           | 4 ++++
 3 files changed, 11 insertions(+)

diff --git a/arch/xtensa/include/asm/thread_info.h b/arch/xtensa/include/asm/thread_info.h
index 5b74dfc35ef9..0c8eb5dc8398 100644
--- a/arch/xtensa/include/asm/thread_info.h
+++ b/arch/xtensa/include/asm/thread_info.h
@@ -124,6 +124,7 @@ static __always_inline struct thread_info *current_thread_info(void)
 #define TIF_SYSCALL_AUDIT	9	/* syscall auditing active */
 #define TIF_SECCOMP		10	/* secure computing */
 #define TIF_MEMDIE		11	/* is terminating due to OOM killer */
+#define TIF_FD_SLOTS		12	/* syscall prepared descriptors */
 
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
 #define _TIF_SIGPENDING		(1<<TIF_SIGPENDING)
@@ -134,6 +135,7 @@ static __always_inline struct thread_info *current_thread_info(void)
 #define _TIF_NOTIFY_RESUME	(1<<TIF_NOTIFY_RESUME)
 #define _TIF_SYSCALL_AUDIT	(1<<TIF_SYSCALL_AUDIT)
 #define _TIF_SECCOMP		(1<<TIF_SECCOMP)
+#define _TIF_FD_SLOTS		(1<<TIF_FD_SLOTS)
 
 #define _TIF_WORK_MASK		(_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP | \
 				 _TIF_SYSCALL_TRACEPOINT | \
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index 272fff587907..4b95f48736e6 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -1976,6 +1976,11 @@ ENTRY(system_call)
 1:	/* regs->areg[2] = return_value */
 
 	s32i	abi_rv, abi_saved0, PT_AREG2
+
+	/* descriptors reserved by the syscall are committed in do_syscall_trace_leave */
+	GET_THREAD_INFO(a4, a1)
+	l32i	a4, a4, TI_FLAGS
+	bbsi.l	a4, TIF_FD_SLOTS, 1f
 	bnez	abi_saved1, 1f
 .Lsyscall_exit:
 #if defined(__XTENSA_WINDOWED_ABI__)
diff --git a/arch/xtensa/kernel/ptrace.c b/arch/xtensa/kernel/ptrace.c
index 364e4fdabb00..d44d62a56b85 100644
--- a/arch/xtensa/kernel/ptrace.c
+++ b/arch/xtensa/kernel/ptrace.c
@@ -13,6 +13,7 @@
  */
 
 #include <linux/audit.h>
+#include <linux/file.h>
 #include <linux/errno.h>
 #include <linux/hw_breakpoint.h>
 #include <linux/kernel.h>
@@ -571,6 +572,9 @@ void do_syscall_trace_leave(struct pt_regs *regs)
 {
 	int step;
 
+	if (test_thread_flag(TIF_FD_SLOTS))
+		fd_slots_commit(regs);
+
 	audit_syscall_exit(regs);
 
 	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))

-- 
2.53.0