我正在尝试为raspberry pi 2编译freeRTOS。这些是我到目前为止尝试的命令：
arm-none-eabi-gcc -march = armv7-a -mcpu = cortex-a7 -mfpu = neon-vfpv4 -mfloat-abi = hard test.c -o test.o
arm-none-eabi-as -march = armv7-a -mcpu = cortex-a7 -mfpu = neon-vfpv4 -mfloat-abi = hard startup.s -o startup.o
arm-none-eabi-ld test.o startup.o -static -Map kernel7.map -o target.elf -T raspberrypi.ld
两个上层工作正常。然而，最后一个没有，它给了我以下错误：
startup.o：在功能_start':
(.init+0x0): multiple definition of _ start＆＃39;
test.o ::（。text + 0x6c）：首先在这里定义
startup.o：在函数swi_handler':
(.init+0x28): undefined reference to vPortYieldProcessor＆＃39;
startup.o：在函数irq_handler':
(.init+0x38): undefined reference to vFreeRTOS_ISR＆＃39;
startup.o：在函数zero_loop':
(.init+0xcc): undefined reference to rpi_cpu_irq_disable＆＃39;
这是相应的代码：
test.c：
#include <stdio.h>
void exit(int code)
{
while(1)
;
}
int main(void)
{
return 0;
}
startup.s：
.extern system_init
.extern __bss_start
.extern __bss_end
.extern vFreeRTOS_ISR
.extern vPortYieldProcessor
.extern rpi_cpu_irq_disable
.extern main
.section .init
.globl _start
;;
_start:
;@ All the following instruction should be read as:
;@ Load the address at symbol into the program counter.
ldr pc,reset_handler ;@ Processor Reset handler -- we will have to force this on the raspi!
;@ Because this is the first instruction executed, of cause it causes an immediate branch into reset!
ldr pc,undefined_handler ;@ Undefined instruction handler -- processors that don't have thumb can emulate thumb!
ldr pc,swi_handler ;@ Software interrupt / TRAP (SVC) -- system SVC handler for switching to kernel mode.
ldr pc,prefetch_handler ;@ Prefetch/abort handler.
ldr pc,data_handler ;@ Data abort handler/
ldr pc,unused_handler ;@ -- Historical from 26-bit addressing ARMs -- was invalid address handler.
ldr pc,irq_handler ;@ IRQ handler
ldr pc,fiq_handler ;@ Fast interrupt handler.
;@ Here we create an exception address table! This means that reset/hang/irq can be absolute addresses
reset_handler: .word reset
undefined_handler: .word undefined_instruction
swi_handler: .word vPortYieldProcessor
prefetch_handler: .word prefetch_abort
data_handler: .word data_abort
unused_handler: .word unused
irq_handler: .word vFreeRTOS_ISR
fiq_handler: .word fiq
reset:
/* Disable IRQ & FIQ */
cpsid if
/* Check for HYP mode */
mrs r0, cpsr_all
and r0, r0, #0x1F
mov r8, #0x1A
cmp r0, r8
beq overHyped
b continueBoot
overHyped: /* Get out of HYP mode */
ldr r1, =continueBoot
msr ELR_hyp, r1
mrs r1, cpsr_all
and r1, r1, #0x1f ;@ CPSR_MODE_MASK
orr r1, r1, #0x13 ;@ CPSR_MODE_SUPERVISOR
msr SPSR_hyp, r1
eret
continueBoot:
;@ In the reset handler, we need to copy our interrupt vector table to 0x0000, its currently at 0x8000
mov r0,#0x8000 ;@ Store the source pointer
mov r1,#0x0000 ;@ Store the destination pointer.
;@ Here we copy the branching instructions
ldmia r0!,{r2,r3,r4,r5,r6,r7,r8,r9} ;@ Load multiple values from indexed address. ; Auto-increment R0
stmia r1!,{r2,r3,r4,r5,r6,r7,r8,r9} ;@ Store multiple values from the indexed address. ; Auto-increment R1
;@ So the branches get the correct address we also need to copy our vector table!
ldmia r0!,{r2,r3,r4,r5,r6,r7,r8,r9} ;@ Load from 4*n of regs (8) as R0 is now incremented.
stmia r1!,{r2,r3,r4,r5,r6,r7,r8,r9} ;@ Store this extra set of data.
;@ Set up the various STACK pointers for different CPU modes
;@ (PSR_IRQ_MODE|PSR_FIQ_DIS|PSR_IRQ_DIS)
mov r0,#0xD2
msr cpsr_c,r0
mov sp,#0x8000
;@ (PSR_FIQ_MODE|PSR_FIQ_DIS|PSR_IRQ_DIS)
mov r0,#0xD1
msr cpsr_c,r0
mov sp,#0x4000
;@ (PSR_SVC_MODE|PSR_FIQ_DIS|PSR_IRQ_DIS)
mov r0,#0xD3
msr cpsr_c,r0
mov sp,#0x8000000
ldr r0, =__bss_start
ldr r1, =__bss_end
mov r2, #0
zero_loop:
cmp r0,r1
it lt
strlt r2,[r0], #4
blt zero_loop
bl rpi_cpu_irq_disable
;@ mov sp,#0x1000000
b main ;@ We're ready?? Lets start main execution!
.section .text
undefined_instruction:
b undefined_instruction
prefetch_abort:
b prefetch_abort
data_abort:
b data_abort
unused:
b unused
fiq:
b fiq
hang:
b hang
.globl PUT32
PUT32:
str r1,[r0]
bx lr
.globl GET32
GET32:
ldr r0,[r0]
bx lr
.globl dummy
dummy:
bx lr
raspberrypi.ld：
/**
* BlueThunder Linker Script for the raspberry Pi!
*
*
*
**/
MEMORY
{
RESERVED (r) : ORIGIN = 0x00000000, LENGTH = 32K
INIT_RAM (rwx) : ORIGIN = 0x00008000, LENGTH = 32K
RAM (rwx) : ORIGIN = 0x00010000, LENGTH = 128M
}
ENTRY(_start)
SECTIONS {
/*
* Our init section allows us to place the bootstrap code at address 0x8000
*
* This is where the Graphics processor forces the ARM to start execution.
* However the interrupt vector code remains at 0x0000, and so we must copy the correct
* branch instructions to 0x0000 - 0x001C in order to get the processor to handle interrupts.
*
*/
.init : {
KEEP(*(.init))
} > INIT_RAM = 0
.module_entries : {
__module_entries_start = .;
KEEP(*(.module_entries))
KEEP(*(.module_entries.*))
__module_entries_end = .;
__module_entries_size = SIZEOF(.module_entries);
} > INIT_RAM
/**
* This is the main code section, it is essentially of unlimited size. (128Mb).
*
**/
.text : {
*(.text)
} > RAM
/*
* Next we put the data.
*/
.data : {
*(.data)
} > RAM
.bss :
{
__bss_start = .;
*(.bss)
*(.bss.*)
__bss_end = .;
} > RAM
/*
__exidx_start = .;
.ARM.exidx :
{
*(.ARM.exidx* .gnu.linkonce.armexidx.*)
} > RAM
__exidx_end = .;
*/
/**
* Place HEAP here???
**/
PROVIDE(__HEAP_START = __bss_end );
/**
* Stack starts at the top of the RAM, and moves down!
**/
_estack = ORIGIN(RAM) + LENGTH(RAM);
}
正如您所看到的，test.c不包含名为_start的入口点，它的汇编编译形式也没有。只有startup.s确实。
关于如何解决当前问题的任何想法？
编辑：如果需要，可以在此处找到所有代码：https://github.com/jameswalmsley/RaspberryPi-FreeRTOS