[PATCH RFC POC 15/50] sh: commit fds on syscall exit

[Christian Brauner]

Add TIF_FD_SLOTS to the syscall work mask. syscall_exit rereads the
flags after the system call and goes to syscall_exit_work for any bit
in the all-work mask, but hands over a copy shifted right by eight
when the bit was in the upper byte. Reload the flags there and test
the full mask, so that the bit reaches do_syscall_trace_leave().

Signed-off-by: Christian Brauner (Amutable) <brauner at kernel.org>
---
 arch/sh/include/asm/thread_info.h | 10 +++++++---
 arch/sh/kernel/entry-common.S     |  8 ++++++--
 arch/sh/kernel/ptrace_32.c        |  4 ++++
 3 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/arch/sh/include/asm/thread_info.h b/arch/sh/include/asm/thread_info.h
index 471db5173036..d976cf21f346 100644
--- a/arch/sh/include/asm/thread_info.h
+++ b/arch/sh/include/asm/thread_info.h
@@ -106,6 +106,7 @@ extern void init_thread_xstate(void);
 #define TIF_SECCOMP		6	/* secure computing */
 #define TIF_NOTIFY_RESUME	7	/* callback before returning to user */
 #define TIF_SYSCALL_TRACEPOINT	8	/* for ftrace syscall instrumentation */
+#define TIF_FD_SLOTS		9	/* syscall prepared descriptors */
 #define TIF_POLLING_NRFLAG	17	/* true if poll_idle() is polling TIF_NEED_RESCHED */
 #define TIF_MEMDIE		18	/* is terminating due to OOM killer */
 
@@ -118,22 +119,25 @@ extern void init_thread_xstate(void);
 #define _TIF_SECCOMP		(1 << TIF_SECCOMP)
 #define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
 #define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
+#define _TIF_FD_SLOTS		(1 << TIF_FD_SLOTS)
 #define _TIF_POLLING_NRFLAG	(1 << TIF_POLLING_NRFLAG)
 
 /* work to do in syscall trace */
 #define _TIF_WORK_SYSCALL_MASK	(_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP | \
 				 _TIF_SYSCALL_AUDIT | _TIF_SECCOMP    | \
-				 _TIF_SYSCALL_TRACEPOINT)
+				 _TIF_SYSCALL_TRACEPOINT | _TIF_FD_SLOTS)
 
 /* work to do on any return to u-space */
 #define _TIF_ALLWORK_MASK	(_TIF_SYSCALL_TRACE | _TIF_SIGPENDING      | \
 				 _TIF_NEED_RESCHED  | _TIF_SYSCALL_AUDIT   | \
 				 _TIF_SINGLESTEP    | _TIF_NOTIFY_RESUME   | \
-				 _TIF_SYSCALL_TRACEPOINT | _TIF_NOTIFY_SIGNAL)
+				 _TIF_SYSCALL_TRACEPOINT | _TIF_NOTIFY_SIGNAL | \
+				 _TIF_FD_SLOTS)
 
 /* work to do on interrupt/exception return */
 #define _TIF_WORK_MASK		(_TIF_ALLWORK_MASK & ~(_TIF_SYSCALL_TRACE | \
-				 _TIF_SYSCALL_AUDIT | _TIF_SINGLESTEP))
+				 _TIF_SYSCALL_AUDIT | _TIF_SINGLESTEP | \
+				 _TIF_FD_SLOTS))
 
 /*
  * Thread-synchronous status.
diff --git a/arch/sh/kernel/entry-common.S b/arch/sh/kernel/entry-common.S
index 91ab2607a1ff..593a482e85f5 100644
--- a/arch/sh/kernel/entry-common.S
+++ b/arch/sh/kernel/entry-common.S
@@ -164,9 +164,13 @@ work_resched:
 
 	.align	2
 syscall_exit_work:
-	! r0: current_thread_info->flags
 	! r8: current_thread_info
-	tst	#(_TIF_WORK_SYSCALL_MASK & 0xff), r0
+	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
+	mov	#(_TIF_WORK_SYSCALL_MASK & 0xff), r1
+	mov	#(_TIF_WORK_SYSCALL_MASK >> 8), r2
+	shll8	r2
+	or	r2, r1
+	tst	r1, r0
 	bt/s	work_pending
 	 tst	#_TIF_NEED_RESCHED, r0
 	TRACE_IRQS_ON
diff --git a/arch/sh/kernel/ptrace_32.c b/arch/sh/kernel/ptrace_32.c
index 8794081483fb..3deadd71f464 100644
--- a/arch/sh/kernel/ptrace_32.c
+++ b/arch/sh/kernel/ptrace_32.c
@@ -8,6 +8,7 @@
  * Audit support by Yuichi Nakamura <ynakam at hitachisoft.jp>
  */
 #include <linux/kernel.h>
+#include <linux/file.h>
 #include <linux/sched.h>
 #include <linux/sched/task_stack.h>
 #include <linux/mm.h>
@@ -476,6 +477,9 @@ 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);
 
 	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))

-- 
2.53.0