[PATCH RFC POC 13/50] openrisc: commit fds on syscall exit

[Christian Brauner]

Add TIF_FD_SLOTS and test it together with TIF_SYSCALL_TRACE on the
way out of a system call. The check used to rely on the flags r30 had
been loaded with before the call. Reload them. The syscall may have set
the new bit. A task that reserved descriptors calls
do_syscall_trace_leave() which commits them before audit and the ptrace
exit stop.

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

diff --git a/arch/openrisc/include/asm/thread_info.h b/arch/openrisc/include/asm/thread_info.h
index e338fff7efb0..3d8a710a809d 100644
--- a/arch/openrisc/include/asm/thread_info.h
+++ b/arch/openrisc/include/asm/thread_info.h
@@ -92,6 +92,7 @@ register struct thread_info *current_thread_info_reg asm("r10");
 					 * mode
 					 */
 #define TIF_NOTIFY_SIGNAL	5	/* signal notifications exist */
+#define TIF_FD_SLOTS		6	/* syscall prepared descriptors */
 #define TIF_SYSCALL_TRACEPOINT  8       /* for ftrace syscall instrumentation */
 #define TIF_RESTORE_SIGMASK     9
 #define TIF_POLLING_NRFLAG	16	/* true if poll_idle() is polling						 * TIF_NEED_RESCHED
@@ -104,12 +105,14 @@ register struct thread_info *current_thread_info_reg asm("r10");
 #define _TIF_NEED_RESCHED	(1<<TIF_NEED_RESCHED)
 #define _TIF_SINGLESTEP		(1<<TIF_SINGLESTEP)
 #define _TIF_NOTIFY_SIGNAL	(1<<TIF_NOTIFY_SIGNAL)
+#define _TIF_FD_SLOTS		(1<<TIF_FD_SLOTS)
 #define _TIF_POLLING_NRFLAG	(1<<TIF_POLLING_NRFLAG)
 
 
 /* Work to do when returning from interrupt/exception */
 /* For OpenRISC, this is anything in the LSW other than syscall trace */
-#define _TIF_WORK_MASK (0xff & ~(_TIF_SYSCALL_TRACE|_TIF_SINGLESTEP))
+#define _TIF_WORK_MASK (0xff & ~(_TIF_SYSCALL_TRACE|_TIF_SINGLESTEP| \
+				 _TIF_FD_SLOTS))
 
 #endif /* __KERNEL__ */
 
diff --git a/arch/openrisc/kernel/entry.S b/arch/openrisc/kernel/entry.S
index 18e68680471e..c70265c4fe55 100644
--- a/arch/openrisc/kernel/entry.S
+++ b/arch/openrisc/kernel/entry.S
@@ -701,10 +701,11 @@ _syscall_show_regs:
 #endif
 
 _syscall_check_trace_leave:
-	/* r30 is a callee-saved register so this should still hold the
-	 * _TIF_SYSCALL_TRACE flag from _syscall_check_trace_enter above...
+	/* Reload the flags, the syscall may have set TIF_FD_SLOTS.
 	 * _syscall_trace_leave expects syscall result to be in pt_regs->r11.
 	 */
+	l.lwz	r30,TI_FLAGS(r10)
+	l.andi	r30,r30,(_TIF_SYSCALL_TRACE|_TIF_FD_SLOTS)
 	l.sfne	r30,r0
 	l.bf	_syscall_trace_leave
 	 l.nop
diff --git a/arch/openrisc/kernel/ptrace.c b/arch/openrisc/kernel/ptrace.c
index 287a9718f0c6..71614b36e516 100644
--- a/arch/openrisc/kernel/ptrace.c
+++ b/arch/openrisc/kernel/ptrace.c
@@ -13,6 +13,7 @@
  */
 
 #include <linux/kernel.h>
+#include <linux/file.h>
 #include <linux/sched.h>
 #include <linux/sched/task_stack.h>
 #include <linux/string.h>
@@ -311,6 +312,9 @@ asmlinkage 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);
 
 	step = test_thread_flag(TIF_SINGLESTEP);

-- 
2.53.0