ANDROID: ARM: fiq_glue: Add custom fiq return handler api.

Change-Id: I5ff2764e85151ca0a88576542fda07c2d33dd065
Signed-off-by: Arve Hjønnevåg <arve@android.com>

arch/arm/common/fiq_glue.S

@@ -22,13 +22,14 @@
 		/* fiq stack: r0-r15,cpsr,spsr of interrupted mode */
 
 ENTRY(fiq_glue)
-		/* store pc, cpsr from previous mode */
+		/* store pc, cpsr from previous mode, reserve space for spsr */
 		mrs	r12, spsr
-		sub	r11, lr, #4
+		sub	lr, lr, #4
 		subs	r10, #1
 		bne	nested_fiq
 
-		stmfd	sp!, {r11-r12, lr}
+		str	r12, [sp, #-8]!
+		str	lr, [sp, #-4]!
 
 		/* store r8-r14 from previous mode */
 		sub	sp, sp, #(7 * 4)
@@ -85,12 +86,15 @@ fiq_from_usr_mode_exit:
 		msr	cpsr_c, #(FIQ_MODE | PSR_I_BIT | PSR_F_BIT)
 
 		ldmfd	sp!, {r0-r7}
-		add	sp, sp, #(7 * 4)
-		ldmfd	sp!, {r11-r12, lr}
+		ldr	lr, [sp, #(4 * 7)]
+		ldr	r12, [sp, #(4 * 8)]
+		add	sp, sp, #(10 * 4)
 exit_fiq:
 		msr	spsr_cxsf, r12
 		add	r10, #1
-		movs	pc, r11
+		cmp	r11, #0
+		moveqs	pc, lr
+		bx	r11 /* jump to custom fiq return function */
 
 nested_fiq:
 		orr	r12, r12, #(PSR_F_BIT)
@@ -98,14 +102,17 @@ nested_fiq:
 
 fiq_glue_end:
 
-ENTRY(fiq_glue_setup) /* func, data, sp */
-		mrs		r3, cpsr
+ENTRY(fiq_glue_setup) /* func, data, sp, smc call number */
+		stmfd		sp!, {r4}
+		mrs		r4, cpsr
 		msr		cpsr_c, #(FIQ_MODE | PSR_I_BIT | PSR_F_BIT)
 		movs		r8, r0
 		mov		r9, r1
 		mov		sp, r2
+		mov		r11, r3
 		moveq		r10, #0
 		movne		r10, #1
-		msr		cpsr_c, r3
+		msr		cpsr_c, r4
+		ldmfd		sp!, {r4}
 		bx		lr
 

arch/arm/common/fiq_glue_setup.c

@@ -18,20 +18,23 @@
 #include <asm/fiq_glue.h>
 
 extern unsigned char fiq_glue, fiq_glue_end;
-extern void fiq_glue_setup(void *func, void *data, void *sp);
+extern void fiq_glue_setup(void *func, void *data, void *sp,
+			   fiq_return_handler_t fiq_return_handler);
 
 static struct fiq_handler fiq_debbuger_fiq_handler = {
 	.name = "fiq_glue",
 };
 DEFINE_PER_CPU(void *, fiq_stack);
 static struct fiq_glue_handler *current_handler;
+static fiq_return_handler_t fiq_return_handler;
 static DEFINE_MUTEX(fiq_glue_lock);
 
 static void fiq_glue_setup_helper(void *info)
 {
 	struct fiq_glue_handler *handler = info;
 	fiq_glue_setup(handler->fiq, handler,
-		__get_cpu_var(fiq_stack) + THREAD_START_SP);
+		__get_cpu_var(fiq_stack) + THREAD_START_SP,
+		fiq_return_handler);
 }
 
 int fiq_glue_register_handler(struct fiq_glue_handler *handler)
@@ -80,6 +83,49 @@ err_busy:
 	return ret;
 }
 
+static void fiq_glue_update_return_handler(void (*fiq_return)(void))
+{
+	fiq_return_handler = fiq_return;
+	if (current_handler)
+		on_each_cpu(fiq_glue_setup_helper, current_handler, true);
+}
+
+int fiq_glue_set_return_handler(void (*fiq_return)(void))
+{
+	int ret;
+
+	mutex_lock(&fiq_glue_lock);
+	if (fiq_return_handler) {
+		ret = -EBUSY;
+		goto err_busy;
+	}
+	fiq_glue_update_return_handler(fiq_return);
+	ret = 0;
+err_busy:
+	mutex_unlock(&fiq_glue_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL(fiq_glue_set_return_handler);
+
+int fiq_glue_clear_return_handler(void (*fiq_return)(void))
+{
+	int ret;
+
+	mutex_lock(&fiq_glue_lock);
+	if (WARN_ON(fiq_return_handler != fiq_return)) {
+		ret = -EINVAL;
+		goto err_inval;
+	}
+	fiq_glue_update_return_handler(NULL);
+	ret = 0;
+err_inval:
+	mutex_unlock(&fiq_glue_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL(fiq_glue_clear_return_handler);
+
 /**
  * fiq_glue_resume - Restore fiqs after suspend or low power idle states
  *
@@ -93,7 +139,8 @@ void fiq_glue_resume(void)
 	if (!current_handler)
 		return;
 	fiq_glue_setup(current_handler->fiq, current_handler,
-		__get_cpu_var(fiq_stack) + THREAD_START_SP);
+		__get_cpu_var(fiq_stack) + THREAD_START_SP,
+		fiq_return_handler);
 	if (current_handler->resume)
 		current_handler->resume(current_handler);
 }

arch/arm/include/asm/fiq_glue.h

@@ -18,8 +18,11 @@ struct fiq_glue_handler {
 	void (*fiq)(struct fiq_glue_handler *h, void *regs, void *svc_sp);
 	void (*resume)(struct fiq_glue_handler *h);
 };
+typedef void (*fiq_return_handler_t)(void);
 
 int fiq_glue_register_handler(struct fiq_glue_handler *handler);
+int fiq_glue_set_return_handler(fiq_return_handler_t fiq_return);
+int fiq_glue_clear_return_handler(fiq_return_handler_t fiq_return);
 
 #ifdef CONFIG_FIQ_GLUE
 void fiq_glue_resume(void);