#include "nios2.h"
#include "system.h"
/* Setup header files to work with assembler code. */
#define ALT_ASM_SRC
/* Debug logging facility */
#include "sys/alt_log_printf.h"
/*************************************************************************\
| MACROS |
\*************************************************************************/
/*
* The new build tools explicitly define macros when alt_load()
* must be called. The define ALT_LOAD_EXPLICITLY_CONTROLLED tells us that
* those macros are controlling if alt_load() needs to be called.
*/
#ifdef ALT_LOAD_EXPLICITLY_CONTROLLED
/* Need to call alt_load() if any of these sections are being copied. */
#if defined(ALT_LOAD_COPY_RODATA) || defined(ALT_LOAD_COPY_RWDATA) || defined(ALT_LOAD_COPY_EXCEPTIONS)
#define CALL_ALT_LOAD
#endif
#else /* !ALT_LOAD_EXPLICITLY_CONTROLLED */
/*
* The legacy build tools use the following macros to detect when alt_load()
* needs to be called.
*/
#define __ALT_LOAD_SECTIONS(res, text, rodata, exc) \
((res##_BASE != rodata##_BASE) || \
(res##_BASE != rwdata##_BASE) || \
(res##_BASE != exc##_BASE))
#define _ALT_LOAD_SECTIONS(res, text, rodata, exc) \
__ALT_LOAD_SECTIONS(res, text, rodata, exc)
#define ALT_LOAD_SECTIONS _ALT_LOAD_SECTIONS(ALT_RESET_DEVICE, \
ALT_RODATA_DEVICE, \
ALT_RWDATA_DEVICE, \
ALT_EXCEPTIONS_DEVICE)
/* Call alt_load() if there is no bootloader and ALT_LOAD_SECTIONS isn't 0. */
#if defined(ALT_NO_BOOTLOADER) && ALT_LOAD_SECTIONS
#define CALL_ALT_LOAD
#endif
#endif /* !ALT_LOAD_EXPLICITLY_CONTROLLED */
/*
* When the legacy build tools define a macro called ALT_NO_BOOTLOADER,
* it indicates that initialization code is allowed at the reset address.
* The new build tools define a macro called ALT_ALLOW_CODE_AT_RESET for
* the same purpose.
*/
#ifdef ALT_NO_BOOTLOADER
#define ALT_ALLOW_CODE_AT_RESET
#endif
/*************************************************************************\
| EXTERNAL REFERENCES |
\*************************************************************************/
/*
* The entry point for user code is either "main" in hosted mode, or
* "alt_main" in standalone mode. These are explicitly referenced here,
* to ensure they are built into the executable. This allows the user
* to build them into libraries, rather than supplying them in object
* files at link time.
*/
.globl main
.globl alt_main
/*
* Create a reference to the software multiply/divide and trap handers,
* so that if they are provided, they will appear in the executable.
*/
#ifndef ALT_NO_INSTRUCTION_EMULATION
.globl alt_exception_muldiv
#endif
#ifdef ALT_TRAP_HANDLER
.globl alt_exception_trap
#endif
/*
* Linker defined symbols used to initialize bss.
*/
.globl __bss_start
.globl __bss_end
/*************************************************************************\
| RESET SECTION (.entry) |
\*************************************************************************/
/*
* This is the reset entry point for Nios II.
*
* At reset, only the cache line which contain the reset vector is
* initialized by the hardware. The code within the first cache line
* initializes the remainder of the instruction cache.
*/
.section .entry, "xa"
.align 5
/*
* Explicitly allow the use of r1 (the assembler temporary register)
* within this code. This register is normally reserved for the use of
* the assembler.
*/
.set noat
/*
* Some tools want to know where the reset vector is.
* Code isn't always provided at the reset vector but at least the
* __reset label always contains the reset vector address because
* it is defined at the start of the .entry section.
*/
.globl __reset
.type __reset, @function
__reset:
/*
* Initialize the instruction cache if present (i.e. size > 0) and
* reset code is allowed unless optimizing for RTL simulation.
* RTL simulations can ensure the instruction cache is already initialized
* so skipping this loop speeds up RTL simulation.
*/
#if NIOS2_ICACHE_SIZE > 0 && defined(ALT_ALLOW_CODE_AT_RESET) && !defined(ALT_SIM_OPTIMIZE)
/* Assume the instruction cache size is always a power of two. */
#if NIOS2_ICACHE_SIZE > 0x8000
movhi r2, %hi(NIOS2_ICACHE_SIZE)
#else
movui r2, NIOS2_ICACHE_SIZE
#endif
0:
initi r2
addi r2, r2, -NIOS2_ICACHE_LINE_SIZE
bgt r2, zero, 0b
1:
/*
* The following debug information tells the ISS not to run the loop above
* but to perform its actions using faster internal code.
*/
.pushsection .debug_alt_sim_info
.int 1, 1, 0b, 1b
.popsection
#endif /* Initialize Instruction Cache */
/*
* Jump to the _start entry point in the .text section if reset code
* is allowed or if optimizing for RTL simulation.
*/
#if defined(ALT_ALLOW_CODE_AT_RESET) || defined(ALT_SIM_OPTIMIZE)
/* Jump to the _start entry point in the .text section. */
movhi r1, %hi(_start)
ori r1, r1, %lo(_start)
jmp r1
.size __reset, . - __reset
#endif /* Jump to _start */
/*
* When not using exit, provide an _exit symbol to prevent unresolved
* references to _exit from the linker script.
*/
#ifdef ALT_NO_EXIT
.globl _exit
_exit:
#endif
/*************************************************************************\
| TEXT SECTION (.text) |
\*************************************************************************/
/*
* Start of the .text section, and also the code entry point when
* the code is executed by a bootloader rather than directly from reset.
*/
.section .text
.align 2
.globl _start
.type _start, @function
_start:
/*
* Initialize the data cache if present (i.e. size > 0) and not
* optimizing for RTL simulation.
* RTL simulations can ensure the data cache is already initialized
* so skipping this loop speeds up RTL simulation.
*/
#if NIOS2_DCACHE_SIZE > 0 && !defined(ALT_SIM_OPTIMIZE)
/* Assume the data cache size is always a power of two. */
#if NIOS2_DCACHE_SIZE > 0x8000
movhi r2, %hi(NIOS2_DCACHE_SIZE)
#else
movui r2, NIOS2_DCACHE_SIZE
#endif
0:
initd 0(r2)
addi r2, r2, -NIOS2_DCACHE_LINE_SIZE
bgt r2, zero, 0b
1:
/*
* The following debug information tells the ISS not to run the loop above
* but to perform its actions using faster internal code.
*/
.pushsection .debug_alt_sim_info
.int 2, 1, 0b, 1b
.popsection
#endif /* Initialize Data Cache */
/* Log that caches have been initialized. */
ALT_LOG_PUTS(alt_log_msg_cache)
/* Log that the stack pointer is about to be setup. */
ALT_LOG_PUTS(alt_log_msg_stackpointer)
/*
* Now that the caches are initialized, set up the stack pointer.
* The value provided by the linker is assumed to be correctly aligned.
*/
movhi sp, %hi(__alt_stack_pointer)
ori sp, sp, %lo(__alt_stack_pointer)
/* Set up the global pointer. */
movhi gp, %hi(_gp)
ori gp, gp, %lo(_gp)
/*
* Clear the BSS if not optimizing for RTL simulation.
*
* This uses the symbols: __bss_start and __bss_end, which are defined
* by the linker script. They mark the begining and the end of the bss
* region. The linker script guarantees that these values are word aligned.
*/
#ifndef ALT_SIM_OPTIMIZE
/* Log that the BSS is about to be cleared. */
ALT_LOG_PUTS(alt_log_msg_bss)
movhi r2, %hi(__bss_start)
ori r2, r2, %lo(__bss_start)
movhi r3, %hi(__bss_end)
ori r3, r3, %lo(__bss_end)
beq r2, r3, 1f
0:
stw zero, (r2)
addi r2, r2, 4
bltu r2, r3, 0b
1:
/*
* The following debug information tells the ISS not to run the loop above
* but to perform its actions using faster internal code.
*/
.pushsection .debug_alt_sim_info
.int 3, 1, 0b, 1b
.popsection
#endif /* ALT_SIM_OPTIMIZE */
/*
* The alt_load() facility is normally used when there is no bootloader.
* It copies some sections into RAM so it acts like a mini-bootloader.
*/
#ifdef CALL_ALT_LOAD
#ifdef ALT_STACK_CHECK
/*
* If the user has selected stack checking then we need to set up a safe
* value in the stack limit register so that the relocation functions
* don't think the stack has overflowed (the contents of the rwdata
* section aren't defined until alt_load() has been called).
*/
mov et, zero
#endif
call alt_load
#endif /* CALL_ALT_LOAD */
#ifdef ALT_STACK_CHECK
/*
* Set up the stack limit (if required). The linker has set up the
* copy of the variable which is in memory.
*/
ldw et, %gprel(alt_stack_limit_value)(gp)
#endif
/* Log that alt_main is about to be called. */
ALT_LOG_PUTS(alt_log_msg_alt_main)
/* Call the C entry point. It should never return. */
call alt_main
/* Wait in infinite loop in case alt_main does return. */
alt_after_alt_main:
br alt_after_alt_main
.size _start, . - _start
/*
* Add information about the stack base if stack overflow checking is enabled.
*/
#ifdef ALT_STACK_CHECK
.globl alt_stack_limit_value
.section .sdata,"aws",@progbits
.align 2
.type alt_stack_limit_value, @object
.size alt_stack_limit_value, 4
alt_stack_limit_value:
.long __alt_stack_limit
#endif
Maintained by John Loomis, last updated 13 November 2008