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removed bootloader-specific; bootloader now also uses std crt0.S

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stnolting 2020-08-19 21:12:57 +02:00
parent 9bb75774f8
commit 3613029249
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sw/common/bootloader_crt0.S
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/* ################################################################################################# */
/* # << NEORV32 - bootloader_crt0.S - Bootloader Start-Up Code >> # */
/* # ********************************************************************************************* # */
/* # Minimal hardware setup (STACK + Trap handler). The rest is done by the bootloader itself. # */
/* # ********************************************************************************************* # */
/* # BSD 3-Clause License # */
/* # # */
/* # Copyright (c) 2020, Stephan Nolting. All rights reserved. # */
/* # # */
/* # 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. # */
/* # # */
/* # 3. Neither the name of the copyright holder nor the names of its contributors may be used to # */
/* # endorse or promote products derived from this software without specific prior written # */
/* # permission. # */
/* # # */
/* # 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 HOLDER 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. # */
/* # ********************************************************************************************* # */
/* # The NEORV32 Processor - https://github.com/stnolting/neorv32 (c) Stephan Nolting # */
/* ################################################################################################# */
.file "bootloader_crt0.S"
.section .text
.balign 4
.global _start
// SYSINFO
.equ SYSINFO_DSPACE_BASE, 0xFFFFFFF4
.equ SYSINFO_DSPACE_SIZE, 0xFFFFFFFC
_start:
.cfi_startproc
.cfi_undefined ra
// *********************************************************
// Setup stack pointer
// *********************************************************
__crt0_stack_pointer_init:
lw x11, SYSINFO_DSPACE_BASE(zero) // data memory space base address
lw x12, SYSINFO_DSPACE_SIZE(zero) // data memory space size
add sp, x11, x12
addi sp, sp, -4 // stack pointer = last entry
// *********************************************************
// Init exception vector base with dummy handler
// *********************************************************
la x13, __crt0_dummy_trap_handler
csrw mtvec, x13
// *********************************************************
// Init register file
// *********************************************************
__crt0_clear_reg_file:
addi zero, zero, 0
addi x1, zero, 0
//addi x2, zero, 0 # keep x2 = sp
addi x3, zero, 0
addi x4, zero, 0
addi x5, zero, 0
addi x6, zero, 0
addi x7, zero, 0
addi x8, zero, 0
addi x9, zero, 0
addi x10, zero, 0
//addi x11, zero, 0 # allready initialized
//addi x12, zero, 0 # allready initialized
//addi x13, zero, 0 # allready initialized
addi x14, zero, 0
addi x15, zero, 0
// *********************************************************
// Call main function
// *********************************************************
__crt0_main_entry:
jal ra, main
// if main returns: stall
__crt0_the_end:
j __crt0_the_end # restart if main returns
// *********************************************************
// dummy trap handler (for exceptions & IRQs)
// tries to move on to next instruction
// *********************************************************
.global __crt0_dummy_trap_handler
.balign 4
__crt0_dummy_trap_handler:
addi sp, sp, -8
sw x8, 0(sp)
sw x9, 4(sp)
csrr x8, mcause
blt x8, zero, __crt0_dummy_trap_handler_irq // skip mepc modification if interrupt
__crt0_dummy_trap_handler_compute_return:
csrr x8, mepc
// is compressed instruction?
lh x9, 0(x8) // get compressed instruction or lower 16 bits of uncompressed instruction that caused exception
andi x9, x9, 3 // mask: isolate lowest 2 opcode bits (= 11 for uncompressed instructions)
addi x8, x8, +2 // only this for compressed instructions
csrw mepc, x8 // set return address when compressed instruction
addi x8, zero, 3
bne x8, x9, __crt0_dummy_trap_handler_irq // jump if compressed instruction
// is uncompressed instruction
csrr x8, mepc
addi x8, x8, +2 // add another 2 (making +4) for uncompressed instructions
csrw mepc, x8
__crt0_dummy_trap_handler_irq:
lw x9, 0(sp)
lw x8, 4(sp)
addi sp, sp, +8
mret
.cfi_endproc
.end