x86: fix UML and -regparm=3

introduce the "asmregparm" calling convention: for functions
implemented in assembly with a fixed regparm input parameters
calling convention.

mark the semaphore and rwsem slowpath functions with that.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/asm-x86/linkage.h

@@ -9,6 +9,11 @@
 #ifdef CONFIG_X86_32
 #define asmlinkage CPP_ASMLINKAGE __attribute__((regparm(0)))
 #define prevent_tail_call(ret) __asm__ ("" : "=r" (ret) : "0" (ret))
+/*
+ * For 32-bit UML - mark functions implemented in assembly that use
+ * regparm input parameters:
+ */
+#define asmregparm __attribute__((regparm(3)))
 #endif
 
 #ifdef CONFIG_X86_ALIGNMENT_16

include/asm-x86/rwsem.h

@@ -44,10 +44,14 @@
 
 struct rwsem_waiter;
 
-extern struct rw_semaphore *FASTCALL(rwsem_down_read_failed(struct rw_semaphore *sem));
-extern struct rw_semaphore *FASTCALL(rwsem_down_write_failed(struct rw_semaphore *sem));
-extern struct rw_semaphore *FASTCALL(rwsem_wake(struct rw_semaphore *));
-extern struct rw_semaphore *FASTCALL(rwsem_downgrade_wake(struct rw_semaphore *sem));
+extern asmregparm struct rw_semaphore *
+ rwsem_down_read_failed(struct rw_semaphore *sem);
+extern asmregparm struct rw_semaphore *
+ rwsem_down_write_failed(struct rw_semaphore *sem);
+extern asmregparm struct rw_semaphore *
+ rwsem_wake(struct rw_semaphore *);
+extern asmregparm struct rw_semaphore *
+ rwsem_downgrade_wake(struct rw_semaphore *sem);
 
 /*
  * the semaphore definition

include/asm-x86/semaphore_32.h

@@ -83,10 +83,10 @@ static inline void init_MUTEX_LOCKED (struct semaphore *sem)
 	sema_init(sem, 0);
 }
 
-void __down_failed(void /* special register calling convention */);
-int  __down_failed_interruptible(void  /* params in registers */);
-int  __down_failed_trylock(void  /* params in registers */);
-void __up_wakeup(void /* special register calling convention */);
+extern asmregparm void __down_failed(atomic_t *count_ptr);
+extern asmregparm int  __down_failed_interruptible(atomic_t *count_ptr);
+extern asmregparm int  __down_failed_trylock(atomic_t *count_ptr);
+extern asmregparm void __up_wakeup(atomic_t *count_ptr);
 
 /*
  * This is ugly, but we want the default case to fall through.

include/linux/linkage.h

@@ -13,6 +13,10 @@
 #define asmlinkage CPP_ASMLINKAGE
 #endif
 
+#ifndef asmregparm
+# define asmregparm
+#endif
+
 #ifndef prevent_tail_call
 # define prevent_tail_call(ret) do { } while (0)
 #endif

lib/rwsem.c

@@ -187,7 +187,7 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
 /*
  * wait for the read lock to be granted
  */
-struct rw_semaphore fastcall __sched *
+asmregparm struct rw_semaphore __sched *
 rwsem_down_read_failed(struct rw_semaphore *sem)
 {
 	struct rwsem_waiter waiter;
@@ -201,7 +201,7 @@ rwsem_down_read_failed(struct rw_semaphore *sem)
 /*
  * wait for the write lock to be granted
  */
-struct rw_semaphore fastcall __sched *
+asmregparm struct rw_semaphore __sched *
 rwsem_down_write_failed(struct rw_semaphore *sem)
 {
 	struct rwsem_waiter waiter;
@@ -216,7 +216,7 @@ rwsem_down_write_failed(struct rw_semaphore *sem)
  * handle waking up a waiter on the semaphore
  * - up_read/up_write has decremented the active part of count if we come here
  */
-struct rw_semaphore fastcall *rwsem_wake(struct rw_semaphore *sem)
+asmregparm struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem)
 {
 	unsigned long flags;
 
@@ -236,7 +236,7 @@ struct rw_semaphore fastcall *rwsem_wake(struct rw_semaphore *sem)
  * - caller incremented waiting part of count and discovered it still negative
  * - just wake up any readers at the front of the queue
  */
-struct rw_semaphore fastcall *rwsem_downgrade_wake(struct rw_semaphore *sem)
+asmregparm struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem)
 {
 	unsigned long flags;