diff options
Diffstat (limited to 'nuttx/arch/arm/src/armv7-m/exc_return.h')
| -rw-r--r-- | nuttx/arch/arm/src/armv7-m/exc_return.h | 51 |
1 files changed, 39 insertions, 12 deletions
diff --git a/nuttx/arch/arm/src/armv7-m/exc_return.h b/nuttx/arch/arm/src/armv7-m/exc_return.h index f32fd7a06..cffbd3e2e 100644 --- a/nuttx/arch/arm/src/armv7-m/exc_return.h +++ b/nuttx/arch/arm/src/armv7-m/exc_return.h @@ -1,8 +1,8 @@ /************************************************************************************ * arch/arm/src/armv7-m/exc_return.h * - * Copyright (C) 2011 Gregory Nutt. All rights reserved. - * Author: Gregory Nutt <spudmonkey@racsa.co.cr> + * Copyright (C) 2011-2012 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <gnutt@nuttx.org> * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions @@ -48,38 +48,65 @@ /* The processor saves an EXC_RETURN value to the LR on exception entry. The * exception mechanism relies on this value to detect when the processor has - * completed an exception handler. Bits[31:4] of an EXC_RETURN value are - * 0xfffffffX. When the processor loads a value matching this pattern to the - * PC it detects that the operation is a not a normal branch operation and, - * instead, that the exception is complete. Therefore, it starts the exception - * return sequence. Bits[3:0] of the EXC_RETURN value indicate the required - * return stack and processor mode: + * completed an exception handler. + * + * Bits [31:28] of an EXC_RETURN value are always 1. When the processor loads a + * value matching this pattern to the PC it detects that the operation is a not + * a normal branch operation and instead, that the exception is complete. + * Therefore, it starts the exception return sequence. + * + * Bits[4:0] of the EXC_RETURN value indicate the required return stack and eventual + * processor mode. The remaining bits of the EXC_RETURN value should be set to 1. + */ + +/* EXC_RETURN_BASE: Bits that are always set in an EXC_RETURN value. */ + +#define EXC_RETURN_BASE 0xffffffe1 + +/* EXC_RETURN_PROCESS_STACK: The exception saved (and will restore) the hardware + * context using the process stack pointer (if not set, the context was saved + * using the main stack pointer) + */ + +#define EXC_RETURN_PROCESS_STACK (1 << 2) + +/* EXC_RETURN_THREAD_MODE: The exception will return to thread mode (if not set, + * return stays in handler mode) + */ + +#define EXC_RETURN_THREAD_MODE (1 << 3) + +/* EXC_RETURN_STD_CONTEXT: The state saved on the stack does not include the + * volatile FP registers and FPSCR. If this bit is clear, the state does include + * these registers. */ + +#define EXC_RETURN_STD_CONTEXT (1 << 4) /* EXC_RETURN_HANDLER: Return to handler mode. Exception return gets state from * the main stack. Execution uses MSP after return. */ -#define EXC_RETURN_HANDLER 0xfffffff1 +#define EXC_RETURN_HANDLER 0xfffffff1 /* EXC_RETURN_PRIVTHR: Return to privileged thread mode. Exception return gets * state from the main stack. Execution uses MSP after return. */ -#define EXC_RETURN_PRIVTHR 0xfffffff9 +#define EXC_RETURN_PRIVTHR 0xfffffff9 /* EXC_RETURN_UNPRIVTHR: Return to unprivileged thread mode. Exception return gets * state from the process stack. Execution uses PSP after return. */ -#define EXC_RETURN_UNPRIVTHR 0xfffffffd +#define EXC_RETURN_UNPRIVTHR 0xfffffffd /* In the kernel build is not selected, then all threads run in privileged thread * mode. */ #ifdef CONFIG_NUTTX_KERNEL -# define EXC_RETURN 0xfffffff9 +# define EXC_RETURN 0xfffffff9 #endif /************************Th************************************************************ |