arm: Add _CPU_Exception_resume()

cpukit/score/cpu/arm/armv4-exception-resume.S

@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+
+/*
+ * Copyright (c) 2024 embedded brains GmbH & Co. KG
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <rtems/asm.h>
+
+#ifdef ARM_MULTILIB_ARCH_V4
+
+.section ".text"
+
+.arm
+
+FUNCTION_ENTRY(_CPU_Exception_resume)
+
+#ifdef ARM_MULTILIB_VFP
+	ldr	r1, [r0, #ARM_EXCEPTION_FRAME_VFP_CONTEXT_OFFSET]
+	cmp	r1, #0
+	beq	.Lvfp_restore_done
+
+	/* Restore FPEXC, FPSCR, and D0-D31 */
+	ldmia	r1!, {r2-r3}
+	vmsr	FPEXC, r2
+	vmsr	FPSCR, r3
+	vstmia	r1!, {d0-d15}
+#ifdef ARM_MULTILIB_VFP_D32
+	vstmia	r1!, {d16-d31}
+#endif
+
+.Lvfp_restore_done:
+#endif /* ARM_MULTILIB_VFP */
+
+	/*
+	 * Restore the original stack pointer of the exception mode.  Assume
+	 * that the exception frame was produced by a default exception
+	 * handler.
+	 */
+	mov	sp, r0
+
+	ldr	r1, [r0, #ARM_EXCEPTION_FRAME_REGISTER_PC_OFFSET]
+	ldr	r2, [r0, #ARM_EXCEPTION_FRAME_REGISTER_CPSR_OFFSET]
+	mov	lr, r1
+	msr	spsr, r2
+	mrs	r3, cpsr
+	bic	r4, r2, #(ARM_PSR_I | ARM_PSR_F)
+	and	r5, r3, #(ARM_PSR_I | ARM_PSR_F)
+	orr	r4, r4, r5
+
+	/* We assume that we do not resume to user mode */
+	msr	cpsr, r4
+
+	/* Restore potentially banked registers in the mode to resume */
+	add	r1, r0, #ARM_EXCEPTION_FRAME_REGISTER_R8_OFFSET
+	ldm	r1, {r8-r13}
+
+	msr	cpsr, r3
+	ldm	r0, {r0-r7}
+	movs	pc, lr
+
+FUNCTION_END(_CPU_Exception_resume)
+
+#endif /* ARM_MULTILIB_ARCH_V4 */

cpukit/score/cpu/arm/cpu.c

@@ -91,12 +91,38 @@ RTEMS_STATIC_ASSERT(
   CPU_Exception_frame_alignment
 );
 
+RTEMS_STATIC_ASSERT(
+  offsetof( CPU_Exception_frame, register_r8 )
+    == ARM_EXCEPTION_FRAME_REGISTER_R8_OFFSET,
+  ARM_EXCEPTION_FRAME_REGISTER_R8_OFFSET
+);
+
 RTEMS_STATIC_ASSERT(
   offsetof( CPU_Exception_frame, register_sp )
     == ARM_EXCEPTION_FRAME_REGISTER_SP_OFFSET,
   ARM_EXCEPTION_FRAME_REGISTER_SP_OFFSET
 );
 
+RTEMS_STATIC_ASSERT(
+  offsetof( CPU_Exception_frame, register_pc )
+    == ARM_EXCEPTION_FRAME_REGISTER_PC_OFFSET,
+  ARM_EXCEPTION_FRAME_REGISTER_PC_OFFSET
+);
+
+#if defined(ARM_MULTILIB_ARCH_V4)
+  RTEMS_STATIC_ASSERT(
+    offsetof( CPU_Exception_frame, register_cpsr )
+      == ARM_EXCEPTION_FRAME_REGISTER_CPSR_OFFSET,
+    ARM_EXCEPTION_FRAME_REGISTER_CPSR_OFFSET
+  );
+#elif defined(ARM_MULTILIB_ARCH_V6M) || defined(ARM_MULTILIB_ARCH_V7M)
+  RTEMS_STATIC_ASSERT(
+    offsetof( CPU_Exception_frame, register_xpsr )
+      == ARM_EXCEPTION_FRAME_REGISTER_XPSR_OFFSET,
+    ARM_EXCEPTION_FRAME_REGISTER_XPSR_OFFSET
+  );
+#endif
+
 RTEMS_STATIC_ASSERT(
   sizeof( ARM_VFP_context ) == ARM_VFP_CONTEXT_SIZE,
   ARM_VFP_CONTEXT_SIZE

cpukit/score/cpu/arm/include/rtems/score/cpu.h

@@ -199,8 +199,18 @@
 
 #define ARM_EXCEPTION_FRAME_SIZE 80
 
+#define ARM_EXCEPTION_FRAME_REGISTER_R8_OFFSET 32
+
 #define ARM_EXCEPTION_FRAME_REGISTER_SP_OFFSET 52
 
+#define ARM_EXCEPTION_FRAME_REGISTER_PC_OFFSET 60
+
+#if defined(ARM_MULTILIB_ARCH_V4)
+  #define ARM_EXCEPTION_FRAME_REGISTER_CPSR_OFFSET 64
+#elif defined(ARM_MULTILIB_ARCH_V6M) || defined(ARM_MULTILIB_ARCH_V7M)
+  #define ARM_EXCEPTION_FRAME_REGISTER_XPSR_OFFSET 64
+#endif
+
 #define ARM_EXCEPTION_FRAME_VFP_CONTEXT_OFFSET 72
 
 #define ARM_VFP_CONTEXT_SIZE 264

cpukit/score/cpu/arm/include/rtems/score/cpuimpl.h

@@ -183,6 +183,8 @@ static inline void *_CPU_Get_TLS_thread_pointer(
   return (void *) context->thread_id;
 }
 
+RTEMS_NO_RETURN void _CPU_Exception_resume( const CPU_Exception_frame *frame );
+
 #ifdef __cplusplus
 }
 #endif

spec/build/cpukit/cpuarm.yml

@@ -40,6 +40,7 @@ source:
 - cpukit/score/cpu/arm/arm_exc_abort.S
 - cpukit/score/cpu/arm/arm_exc_interrupt.S
 - cpukit/score/cpu/arm/armv4-exception-default.S
+- cpukit/score/cpu/arm/armv4-exception-resume.S
 - cpukit/score/cpu/arm/armv4-sync-synchronize.c
 - cpukit/score/cpu/arm/armv4-isr-install-vector.c
 - cpukit/score/cpu/arm/armv7-thread-idle.c