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  • 如何制作裸机ARM程序并在QEMU上运行它们？

如何制作裸机ARM程序并在QEMU上运行它们？

arm embedded

如何制作裸机ARM程序并在QEMU上运行它们？,arm,embedded,qemu,bare-metal,Arm,Embedded,Qemu,Bare Metal,我正试图让它按预期工作，但没有成功（在bl main指令后出现故障）。 根据教程，该命令 (qemu) xp /1dw 0xa0000018 结果应该是打印33（但我得到的是0x00） 这是主调用后寄存器的内容（参见startup.s） 我有以下文件 main.c startup.s lscript.ld Makefile 我正在使用以下工具链 arm-2013.11-24-arm-none-eabi-i686-pc-linux-gnu 生成文件： SR

我正试图让它按预期工作，但没有成功（在bl main指令后出现故障）。 根据教程，该命令

(qemu) xp /1dw 0xa0000018
结果应该是打印33（但我得到的是0x00）

这是主调用后寄存器的内容（参见startup.s）

我有以下文件

  main.c
  startup.s
  lscript.ld
  Makefile
我正在使用以下工具链

arm-2013.11-24-arm-none-eabi-i686-pc-linux-gnu
生成文件：

SRCS := main.c startup.s

LINKER_NAME := lscript.ld
ELF_NAME := program.elf
BIN_NAME := program.bin
FLASH_NAME := flash.bin

CC := arm-none-eabi
CFLAGS := -nostdlib
OBJFLAGS ?= -DS
QEMUFLAGS := -M connex -pflash $(FLASH_NAME) -nographic -serial /dev/null

# Allocate 16MB to use as a virtual flash for th qemu
# bs = blocksize -> 4KB
# count = number of block -> 4096
# totalsize = 16MB
setup:
    dd if=/dev/zero of=$(FLASH_NAME) bs=4096 count=4096

# Compile srcs and write to virtual flash
all: clean setup
    $(CC)-gcc $(CFLAGS) -o $(ELF_NAME) -T $(LINKER_NAME) $(SRCS)
    $(CC)-objcopy -O binary $(ELF_NAME) $(BIN_NAME)
    dd if=$(BIN_NAME) of=$(FLASH_NAME) bs=4096 conv=notrunc

objdump:
    $(CC)-objdump $(OBJFLAGS) $(ELF_NAME)

mem-placement:
    $(CC)-nm -n $(ELF_NAME)

qemu:
    qemu-system-arm $(QEMUFLAGS) 

clean:
    rm -rf *.bin
    rm -rf *.elf

static int arr[] = { 1, 10, 4, 5, 6, 7 };
static int sum;
static const int n = sizeof(arr) / sizeof(arr[0]);

int main()
{
    int i;

    for (i = 0; i < n; i++){
        sum += arr[i];
    }
    return 0;
}

.section "vectors"
reset:  b     _start
undef:  b     undef
swi:    b     swi
pabt:   b     pabt
dabt:   b     dabt
    nop
irq:    b     irq
fiq:    b     fiq

    .text
_start:
init:
    @@ Copy data to RAM.
    ldr   r0, =flash_sdata
    ldr   r1, =ram_sdata
    ldr   r2, =data_size

    @@ Handle data_size == 0
    cmp   r2, #0
    beq   init_bss

copy:
    ldrb   r4, [r0], #1
    strb   r4, [r1], #1
    subs   r2, r2, #1
    bne    copy

init_bss:
    @@ Initialize .bss
    ldr   r0, =sbss
    ldr   r1, =ebss
    ldr   r2, =bss_size

    @@ Handle bss_size == 0
    cmp   r2, #0
    beq   init_stack
    mov   r4, #0

zero:
    strb  r4, [r0], #1
    subs  r2, r2, #1
    bne   zero

init_stack:
    @@ Initialize the stack pointer
    ldr   sp, =0xA4000000

    @@ **this call dosent work as expected.. (r13/sp contains 0xA4000000)**
    bl    main

    @@ Dosent return from main
    @@ r0 should now contain 33 
stop:
    b     stop

/*
 * Linker for testing purposes 
 * (using 16 MB virtual flash = 0x0100_0000)
 */

MEMORY {
    rom (rx)  : ORIGIN = 0x00000000, LENGTH = 0x01000000
    ram (rwx) : ORIGIN = 0xA0000000, LENGTH = 0x04000000
}


SECTIONS {
    .text : {
          * (vectors);
          * (.text);
    } > rom

    .rodata : {
          * (.rodata);
    } > rom

    flash_sdata = .;
    ram_sdata = ORIGIN(ram);

    .data : AT (flash_sdata) {
          * (.data);
    } > ram

    ram_edata = .;
    data_size = ram_edata - ram_sdata;

    sbss = .;
    .bss : {
         * (.bss);
    } > ram
    ebss = .;
    bss_size = ebss - sbss;

    /DISCARD/ : {
      *(.note*)
      *(.comment)
      *(.ARM*)
      /*
      *(.debug*)
      */
    }
} 

program.elf:     file format elf32-littlearm

Disassembly of section .text:
00000000 <reset>:
0:  ea000023    b   94 <_start>

00000004 <undef>:
4:  eafffffe    b   4 <undef>

00000008 <swi>:
8:  eafffffe    b   8 <swi>

0000000c <pabt>:
c:  eafffffe    b   c <pabt>

00000010 <dabt>:
10: eafffffe    b   10 <dabt>
14: e320f000    nop {0} 

00000018 <irq>:
18: eafffffe    b   18 <irq>

0000001c <fiq>:
1c: eafffffe    b   1c <fiq>

00000020 <main>:
20: e52db004    push    {fp}        ; (str fp, [sp, #-4]!)
24: e28db000    add fp, sp, #0
28: e24dd00c    sub sp, sp, #12
2c: e3a03000    mov r3, #0
30: e50b3008    str r3, [fp, #-8]
34: ea00000d    b   70 <main+0x50>
38: e3003000    movw    r3, #0
3c: e34a3000    movt    r3, #40960  ; 0xa000
40: e51b2008    ldr r2, [fp, #-8]
44: e7932102    ldr r2, [r3, r2, lsl #2]
48: e3003018    movw    r3, #24
4c: e34a3000    movt    r3, #40960  ; 0xa000
50: e5933000    ldr r3, [r3]
54: e0822003    add r2, r2, r3
58: e3003018    movw    r3, #24
5c: e34a3000    movt    r3, #40960  ; 0xa000
60: e5832000    str r2, [r3]
64: e51b3008    ldr r3, [fp, #-8]
68: e2833001    add r3, r3, #1
6c: e50b3008    str r3, [fp, #-8]
70: e3a02006    mov r2, #6
74: e51b3008    ldr r3, [fp, #-8]
78: e1530002    cmp r3, r2
7c: baffffed    blt 38 <main+0x18>
80: e3a03000    mov r3, #0
84: e1a00003    mov r0, r3
88: e24bd000    sub sp, fp, #0
8c: e49db004    pop {fp}        ; (ldr fp, [sp], #4)
90: e12fff1e    bx  lr 

00000094 <_start>:
94: e59f004c    ldr r0, [pc, #76]   ; e8 <stop+0x4>
98: e59f104c    ldr r1, [pc, #76]   ; ec <stop+0x8>
9c: e59f204c    ldr r2, [pc, #76]   ; f0 <stop+0xc>
a0: e3520000    cmp r2, #0
a4: 0a000003    beq b8 <init_bss> 

000000a8 <copy>:
a8: e4d04001    ldrb    r4, [r0], #1
ac: e4c14001    strb    r4, [r1], #1
b0: e2522001    subs    r2, r2, #1
b4: 1afffffb    bne a8 <copy> 

000000b8 <init_bss>:
b8: e59f0034    ldr r0, [pc, #52]   ; f4 <stop+0x10>
bc: e59f1034    ldr r1, [pc, #52]   ; f8 <stop+0x14>
c0: e59f2034    ldr r2, [pc, #52]   ; fc <stop+0x18>
c4: e3520000    cmp r2, #0
c8: 0a000003    beq dc <init_stack>
cc: e3a04000    mov r4, #0

000000d0 <zero>:
d0: e4c04001    strb    r4, [r0], #1
d4: e2522001    subs    r2, r2, #1
d8: 1afffffc    bne d0 <zero>  

000000dc <init_stack>:
dc: e3a0d329    mov sp, #-1543503872    ; 0xa4000000
e0: ebffffce    bl  20 <main> 

000000e4 <stop>:
e4: eafffffe    b   e4 <stop>
e8: 00000104    andeq   r0, r0, r4, lsl #2
ec: a0000000    andge   r0, r0, r0
f0: 00000018    andeq   r0, r0, r8, lsl r0
f4: a0000018    andge   r0, r0, r8, lsl r0
f8: a000001c    andge   r0, r0, ip, lsl r0
fc: 00000004    andeq   r0, r0, r4

Disassembly of section .rodata:
00000100 <n>:
100:    00000006    andeq   r0, r0, r6

Disassembly of section .data:
a0000000 <arr>:
a0000000:   00000001    andeq   r0, r0, r1
a0000004:   0000000a    andeq   r0, r0, sl
a0000008:   00000004    andeq   r0, r0, r4
a000000c:   00000005    andeq   r0, r0, r5
a0000010:   00000006    andeq   r0, r0, r6
a0000014:   00000007    andeq   r0, r0, r7

Disassembly of section .bss: 
a0000018 <sum>:
a0000018:   00000000    andeq   r0, r0, r0
main.c：

SRCS := main.c startup.s

LINKER_NAME := lscript.ld
ELF_NAME := program.elf
BIN_NAME := program.bin
FLASH_NAME := flash.bin

CC := arm-none-eabi
CFLAGS := -nostdlib
OBJFLAGS ?= -DS
QEMUFLAGS := -M connex -pflash $(FLASH_NAME) -nographic -serial /dev/null

# Allocate 16MB to use as a virtual flash for th qemu
# bs = blocksize -> 4KB
# count = number of block -> 4096
# totalsize = 16MB
setup:
    dd if=/dev/zero of=$(FLASH_NAME) bs=4096 count=4096

# Compile srcs and write to virtual flash
all: clean setup
    $(CC)-gcc $(CFLAGS) -o $(ELF_NAME) -T $(LINKER_NAME) $(SRCS)
    $(CC)-objcopy -O binary $(ELF_NAME) $(BIN_NAME)
    dd if=$(BIN_NAME) of=$(FLASH_NAME) bs=4096 conv=notrunc

objdump:
    $(CC)-objdump $(OBJFLAGS) $(ELF_NAME)

mem-placement:
    $(CC)-nm -n $(ELF_NAME)

qemu:
    qemu-system-arm $(QEMUFLAGS) 

clean:
    rm -rf *.bin
    rm -rf *.elf

static int arr[] = { 1, 10, 4, 5, 6, 7 };
static int sum;
static const int n = sizeof(arr) / sizeof(arr[0]);

int main()
{
    int i;

    for (i = 0; i < n; i++){
        sum += arr[i];
    }
    return 0;
}

.section "vectors"
reset:  b     _start
undef:  b     undef
swi:    b     swi
pabt:   b     pabt
dabt:   b     dabt
    nop
irq:    b     irq
fiq:    b     fiq

    .text
_start:
init:
    @@ Copy data to RAM.
    ldr   r0, =flash_sdata
    ldr   r1, =ram_sdata
    ldr   r2, =data_size

    @@ Handle data_size == 0
    cmp   r2, #0
    beq   init_bss

copy:
    ldrb   r4, [r0], #1
    strb   r4, [r1], #1
    subs   r2, r2, #1
    bne    copy

init_bss:
    @@ Initialize .bss
    ldr   r0, =sbss
    ldr   r1, =ebss
    ldr   r2, =bss_size

    @@ Handle bss_size == 0
    cmp   r2, #0
    beq   init_stack
    mov   r4, #0

zero:
    strb  r4, [r0], #1
    subs  r2, r2, #1
    bne   zero

init_stack:
    @@ Initialize the stack pointer
    ldr   sp, =0xA4000000

    @@ **this call dosent work as expected.. (r13/sp contains 0xA4000000)**
    bl    main

    @@ Dosent return from main
    @@ r0 should now contain 33 
stop:
    b     stop

/*
 * Linker for testing purposes 
 * (using 16 MB virtual flash = 0x0100_0000)
 */

MEMORY {
    rom (rx)  : ORIGIN = 0x00000000, LENGTH = 0x01000000
    ram (rwx) : ORIGIN = 0xA0000000, LENGTH = 0x04000000
}


SECTIONS {
    .text : {
          * (vectors);
          * (.text);
    } > rom

    .rodata : {
          * (.rodata);
    } > rom

    flash_sdata = .;
    ram_sdata = ORIGIN(ram);

    .data : AT (flash_sdata) {
          * (.data);
    } > ram

    ram_edata = .;
    data_size = ram_edata - ram_sdata;

    sbss = .;
    .bss : {
         * (.bss);
    } > ram
    ebss = .;
    bss_size = ebss - sbss;

    /DISCARD/ : {
      *(.note*)
      *(.comment)
      *(.ARM*)
      /*
      *(.debug*)
      */
    }
} 

program.elf:     file format elf32-littlearm

Disassembly of section .text:
00000000 <reset>:
0:  ea000023    b   94 <_start>

00000004 <undef>:
4:  eafffffe    b   4 <undef>

00000008 <swi>:
8:  eafffffe    b   8 <swi>

0000000c <pabt>:
c:  eafffffe    b   c <pabt>

00000010 <dabt>:
10: eafffffe    b   10 <dabt>
14: e320f000    nop {0} 

00000018 <irq>:
18: eafffffe    b   18 <irq>

0000001c <fiq>:
1c: eafffffe    b   1c <fiq>

00000020 <main>:
20: e52db004    push    {fp}        ; (str fp, [sp, #-4]!)
24: e28db000    add fp, sp, #0
28: e24dd00c    sub sp, sp, #12
2c: e3a03000    mov r3, #0
30: e50b3008    str r3, [fp, #-8]
34: ea00000d    b   70 <main+0x50>
38: e3003000    movw    r3, #0
3c: e34a3000    movt    r3, #40960  ; 0xa000
40: e51b2008    ldr r2, [fp, #-8]
44: e7932102    ldr r2, [r3, r2, lsl #2]
48: e3003018    movw    r3, #24
4c: e34a3000    movt    r3, #40960  ; 0xa000
50: e5933000    ldr r3, [r3]
54: e0822003    add r2, r2, r3
58: e3003018    movw    r3, #24
5c: e34a3000    movt    r3, #40960  ; 0xa000
60: e5832000    str r2, [r3]
64: e51b3008    ldr r3, [fp, #-8]
68: e2833001    add r3, r3, #1
6c: e50b3008    str r3, [fp, #-8]
70: e3a02006    mov r2, #6
74: e51b3008    ldr r3, [fp, #-8]
78: e1530002    cmp r3, r2
7c: baffffed    blt 38 <main+0x18>
80: e3a03000    mov r3, #0
84: e1a00003    mov r0, r3
88: e24bd000    sub sp, fp, #0
8c: e49db004    pop {fp}        ; (ldr fp, [sp], #4)
90: e12fff1e    bx  lr 

00000094 <_start>:
94: e59f004c    ldr r0, [pc, #76]   ; e8 <stop+0x4>
98: e59f104c    ldr r1, [pc, #76]   ; ec <stop+0x8>
9c: e59f204c    ldr r2, [pc, #76]   ; f0 <stop+0xc>
a0: e3520000    cmp r2, #0
a4: 0a000003    beq b8 <init_bss> 

000000a8 <copy>:
a8: e4d04001    ldrb    r4, [r0], #1
ac: e4c14001    strb    r4, [r1], #1
b0: e2522001    subs    r2, r2, #1
b4: 1afffffb    bne a8 <copy> 

000000b8 <init_bss>:
b8: e59f0034    ldr r0, [pc, #52]   ; f4 <stop+0x10>
bc: e59f1034    ldr r1, [pc, #52]   ; f8 <stop+0x14>
c0: e59f2034    ldr r2, [pc, #52]   ; fc <stop+0x18>
c4: e3520000    cmp r2, #0
c8: 0a000003    beq dc <init_stack>
cc: e3a04000    mov r4, #0

000000d0 <zero>:
d0: e4c04001    strb    r4, [r0], #1
d4: e2522001    subs    r2, r2, #1
d8: 1afffffc    bne d0 <zero>  

000000dc <init_stack>:
dc: e3a0d329    mov sp, #-1543503872    ; 0xa4000000
e0: ebffffce    bl  20 <main> 

000000e4 <stop>:
e4: eafffffe    b   e4 <stop>
e8: 00000104    andeq   r0, r0, r4, lsl #2
ec: a0000000    andge   r0, r0, r0
f0: 00000018    andeq   r0, r0, r8, lsl r0
f4: a0000018    andge   r0, r0, r8, lsl r0
f8: a000001c    andge   r0, r0, ip, lsl r0
fc: 00000004    andeq   r0, r0, r4

Disassembly of section .rodata:
00000100 <n>:
100:    00000006    andeq   r0, r0, r6

Disassembly of section .data:
a0000000 <arr>:
a0000000:   00000001    andeq   r0, r0, r1
a0000004:   0000000a    andeq   r0, r0, sl
a0000008:   00000004    andeq   r0, r0, r4
a000000c:   00000005    andeq   r0, r0, r5
a0000010:   00000006    andeq   r0, r0, r6
a0000014:   00000007    andeq   r0, r0, r7

Disassembly of section .bss: 
a0000018 <sum>:
a0000018:   00000000    andeq   r0, r0, r0
lscript.ld：

SRCS := main.c startup.s

LINKER_NAME := lscript.ld
ELF_NAME := program.elf
BIN_NAME := program.bin
FLASH_NAME := flash.bin

CC := arm-none-eabi
CFLAGS := -nostdlib
OBJFLAGS ?= -DS
QEMUFLAGS := -M connex -pflash $(FLASH_NAME) -nographic -serial /dev/null

# Allocate 16MB to use as a virtual flash for th qemu
# bs = blocksize -> 4KB
# count = number of block -> 4096
# totalsize = 16MB
setup:
    dd if=/dev/zero of=$(FLASH_NAME) bs=4096 count=4096

# Compile srcs and write to virtual flash
all: clean setup
    $(CC)-gcc $(CFLAGS) -o $(ELF_NAME) -T $(LINKER_NAME) $(SRCS)
    $(CC)-objcopy -O binary $(ELF_NAME) $(BIN_NAME)
    dd if=$(BIN_NAME) of=$(FLASH_NAME) bs=4096 conv=notrunc

objdump:
    $(CC)-objdump $(OBJFLAGS) $(ELF_NAME)

mem-placement:
    $(CC)-nm -n $(ELF_NAME)

qemu:
    qemu-system-arm $(QEMUFLAGS) 

clean:
    rm -rf *.bin
    rm -rf *.elf

static int arr[] = { 1, 10, 4, 5, 6, 7 };
static int sum;
static const int n = sizeof(arr) / sizeof(arr[0]);

int main()
{
    int i;

    for (i = 0; i < n; i++){
        sum += arr[i];
    }
    return 0;
}

.section "vectors"
reset:  b     _start
undef:  b     undef
swi:    b     swi
pabt:   b     pabt
dabt:   b     dabt
    nop
irq:    b     irq
fiq:    b     fiq

    .text
_start:
init:
    @@ Copy data to RAM.
    ldr   r0, =flash_sdata
    ldr   r1, =ram_sdata
    ldr   r2, =data_size

    @@ Handle data_size == 0
    cmp   r2, #0
    beq   init_bss

copy:
    ldrb   r4, [r0], #1
    strb   r4, [r1], #1
    subs   r2, r2, #1
    bne    copy

init_bss:
    @@ Initialize .bss
    ldr   r0, =sbss
    ldr   r1, =ebss
    ldr   r2, =bss_size

    @@ Handle bss_size == 0
    cmp   r2, #0
    beq   init_stack
    mov   r4, #0

zero:
    strb  r4, [r0], #1
    subs  r2, r2, #1
    bne   zero

init_stack:
    @@ Initialize the stack pointer
    ldr   sp, =0xA4000000

    @@ **this call dosent work as expected.. (r13/sp contains 0xA4000000)**
    bl    main

    @@ Dosent return from main
    @@ r0 should now contain 33 
stop:
    b     stop

/*
 * Linker for testing purposes 
 * (using 16 MB virtual flash = 0x0100_0000)
 */

MEMORY {
    rom (rx)  : ORIGIN = 0x00000000, LENGTH = 0x01000000
    ram (rwx) : ORIGIN = 0xA0000000, LENGTH = 0x04000000
}


SECTIONS {
    .text : {
          * (vectors);
          * (.text);
    } > rom

    .rodata : {
          * (.rodata);
    } > rom

    flash_sdata = .;
    ram_sdata = ORIGIN(ram);

    .data : AT (flash_sdata) {
          * (.data);
    } > ram

    ram_edata = .;
    data_size = ram_edata - ram_sdata;

    sbss = .;
    .bss : {
         * (.bss);
    } > ram
    ebss = .;
    bss_size = ebss - sbss;

    /DISCARD/ : {
      *(.note*)
      *(.comment)
      *(.ARM*)
      /*
      *(.debug*)
      */
    }
} 

program.elf:     file format elf32-littlearm

Disassembly of section .text:
00000000 <reset>:
0:  ea000023    b   94 <_start>

00000004 <undef>:
4:  eafffffe    b   4 <undef>

00000008 <swi>:
8:  eafffffe    b   8 <swi>

0000000c <pabt>:
c:  eafffffe    b   c <pabt>

00000010 <dabt>:
10: eafffffe    b   10 <dabt>
14: e320f000    nop {0} 

00000018 <irq>:
18: eafffffe    b   18 <irq>

0000001c <fiq>:
1c: eafffffe    b   1c <fiq>

00000020 <main>:
20: e52db004    push    {fp}        ; (str fp, [sp, #-4]!)
24: e28db000    add fp, sp, #0
28: e24dd00c    sub sp, sp, #12
2c: e3a03000    mov r3, #0
30: e50b3008    str r3, [fp, #-8]
34: ea00000d    b   70 <main+0x50>
38: e3003000    movw    r3, #0
3c: e34a3000    movt    r3, #40960  ; 0xa000
40: e51b2008    ldr r2, [fp, #-8]
44: e7932102    ldr r2, [r3, r2, lsl #2]
48: e3003018    movw    r3, #24
4c: e34a3000    movt    r3, #40960  ; 0xa000
50: e5933000    ldr r3, [r3]
54: e0822003    add r2, r2, r3
58: e3003018    movw    r3, #24
5c: e34a3000    movt    r3, #40960  ; 0xa000
60: e5832000    str r2, [r3]
64: e51b3008    ldr r3, [fp, #-8]
68: e2833001    add r3, r3, #1
6c: e50b3008    str r3, [fp, #-8]
70: e3a02006    mov r2, #6
74: e51b3008    ldr r3, [fp, #-8]
78: e1530002    cmp r3, r2
7c: baffffed    blt 38 <main+0x18>
80: e3a03000    mov r3, #0
84: e1a00003    mov r0, r3
88: e24bd000    sub sp, fp, #0
8c: e49db004    pop {fp}        ; (ldr fp, [sp], #4)
90: e12fff1e    bx  lr 

00000094 <_start>:
94: e59f004c    ldr r0, [pc, #76]   ; e8 <stop+0x4>
98: e59f104c    ldr r1, [pc, #76]   ; ec <stop+0x8>
9c: e59f204c    ldr r2, [pc, #76]   ; f0 <stop+0xc>
a0: e3520000    cmp r2, #0
a4: 0a000003    beq b8 <init_bss> 

000000a8 <copy>:
a8: e4d04001    ldrb    r4, [r0], #1
ac: e4c14001    strb    r4, [r1], #1
b0: e2522001    subs    r2, r2, #1
b4: 1afffffb    bne a8 <copy> 

000000b8 <init_bss>:
b8: e59f0034    ldr r0, [pc, #52]   ; f4 <stop+0x10>
bc: e59f1034    ldr r1, [pc, #52]   ; f8 <stop+0x14>
c0: e59f2034    ldr r2, [pc, #52]   ; fc <stop+0x18>
c4: e3520000    cmp r2, #0
c8: 0a000003    beq dc <init_stack>
cc: e3a04000    mov r4, #0

000000d0 <zero>:
d0: e4c04001    strb    r4, [r0], #1
d4: e2522001    subs    r2, r2, #1
d8: 1afffffc    bne d0 <zero>  

000000dc <init_stack>:
dc: e3a0d329    mov sp, #-1543503872    ; 0xa4000000
e0: ebffffce    bl  20 <main> 

000000e4 <stop>:
e4: eafffffe    b   e4 <stop>
e8: 00000104    andeq   r0, r0, r4, lsl #2
ec: a0000000    andge   r0, r0, r0
f0: 00000018    andeq   r0, r0, r8, lsl r0
f4: a0000018    andge   r0, r0, r8, lsl r0
f8: a000001c    andge   r0, r0, ip, lsl r0
fc: 00000004    andeq   r0, r0, r4

Disassembly of section .rodata:
00000100 <n>:
100:    00000006    andeq   r0, r0, r6

Disassembly of section .data:
a0000000 <arr>:
a0000000:   00000001    andeq   r0, r0, r1
a0000004:   0000000a    andeq   r0, r0, sl
a0000008:   00000004    andeq   r0, r0, r4
a000000c:   00000005    andeq   r0, r0, r5
a0000010:   00000006    andeq   r0, r0, r6
a0000014:   00000007    andeq   r0, r0, r7

Disassembly of section .bss: 
a0000018 <sum>:
a0000018:   00000000    andeq   r0, r0, r0
可执行文件的反汇编（objdump）：

SRCS := main.c startup.s

LINKER_NAME := lscript.ld
ELF_NAME := program.elf
BIN_NAME := program.bin
FLASH_NAME := flash.bin

CC := arm-none-eabi
CFLAGS := -nostdlib
OBJFLAGS ?= -DS
QEMUFLAGS := -M connex -pflash $(FLASH_NAME) -nographic -serial /dev/null

# Allocate 16MB to use as a virtual flash for th qemu
# bs = blocksize -> 4KB
# count = number of block -> 4096
# totalsize = 16MB
setup:
    dd if=/dev/zero of=$(FLASH_NAME) bs=4096 count=4096

# Compile srcs and write to virtual flash
all: clean setup
    $(CC)-gcc $(CFLAGS) -o $(ELF_NAME) -T $(LINKER_NAME) $(SRCS)
    $(CC)-objcopy -O binary $(ELF_NAME) $(BIN_NAME)
    dd if=$(BIN_NAME) of=$(FLASH_NAME) bs=4096 conv=notrunc

objdump:
    $(CC)-objdump $(OBJFLAGS) $(ELF_NAME)

mem-placement:
    $(CC)-nm -n $(ELF_NAME)

qemu:
    qemu-system-arm $(QEMUFLAGS) 

clean:
    rm -rf *.bin
    rm -rf *.elf

static int arr[] = { 1, 10, 4, 5, 6, 7 };
static int sum;
static const int n = sizeof(arr) / sizeof(arr[0]);

int main()
{
    int i;

    for (i = 0; i < n; i++){
        sum += arr[i];
    }
    return 0;
}

.section "vectors"
reset:  b     _start
undef:  b     undef
swi:    b     swi
pabt:   b     pabt
dabt:   b     dabt
    nop
irq:    b     irq
fiq:    b     fiq

    .text
_start:
init:
    @@ Copy data to RAM.
    ldr   r0, =flash_sdata
    ldr   r1, =ram_sdata
    ldr   r2, =data_size

    @@ Handle data_size == 0
    cmp   r2, #0
    beq   init_bss

copy:
    ldrb   r4, [r0], #1
    strb   r4, [r1], #1
    subs   r2, r2, #1
    bne    copy

init_bss:
    @@ Initialize .bss
    ldr   r0, =sbss
    ldr   r1, =ebss
    ldr   r2, =bss_size

    @@ Handle bss_size == 0
    cmp   r2, #0
    beq   init_stack
    mov   r4, #0

zero:
    strb  r4, [r0], #1
    subs  r2, r2, #1
    bne   zero

init_stack:
    @@ Initialize the stack pointer
    ldr   sp, =0xA4000000

    @@ **this call dosent work as expected.. (r13/sp contains 0xA4000000)**
    bl    main

    @@ Dosent return from main
    @@ r0 should now contain 33 
stop:
    b     stop

/*
 * Linker for testing purposes 
 * (using 16 MB virtual flash = 0x0100_0000)
 */

MEMORY {
    rom (rx)  : ORIGIN = 0x00000000, LENGTH = 0x01000000
    ram (rwx) : ORIGIN = 0xA0000000, LENGTH = 0x04000000
}


SECTIONS {
    .text : {
          * (vectors);
          * (.text);
    } > rom

    .rodata : {
          * (.rodata);
    } > rom

    flash_sdata = .;
    ram_sdata = ORIGIN(ram);

    .data : AT (flash_sdata) {
          * (.data);
    } > ram

    ram_edata = .;
    data_size = ram_edata - ram_sdata;

    sbss = .;
    .bss : {
         * (.bss);
    } > ram
    ebss = .;
    bss_size = ebss - sbss;

    /DISCARD/ : {
      *(.note*)
      *(.comment)
      *(.ARM*)
      /*
      *(.debug*)
      */
    }
} 

program.elf:     file format elf32-littlearm

Disassembly of section .text:
00000000 <reset>:
0:  ea000023    b   94 <_start>

00000004 <undef>:
4:  eafffffe    b   4 <undef>

00000008 <swi>:
8:  eafffffe    b   8 <swi>

0000000c <pabt>:
c:  eafffffe    b   c <pabt>

00000010 <dabt>:
10: eafffffe    b   10 <dabt>
14: e320f000    nop {0} 

00000018 <irq>:
18: eafffffe    b   18 <irq>

0000001c <fiq>:
1c: eafffffe    b   1c <fiq>

00000020 <main>:
20: e52db004    push    {fp}        ; (str fp, [sp, #-4]!)
24: e28db000    add fp, sp, #0
28: e24dd00c    sub sp, sp, #12
2c: e3a03000    mov r3, #0
30: e50b3008    str r3, [fp, #-8]
34: ea00000d    b   70 <main+0x50>
38: e3003000    movw    r3, #0
3c: e34a3000    movt    r3, #40960  ; 0xa000
40: e51b2008    ldr r2, [fp, #-8]
44: e7932102    ldr r2, [r3, r2, lsl #2]
48: e3003018    movw    r3, #24
4c: e34a3000    movt    r3, #40960  ; 0xa000
50: e5933000    ldr r3, [r3]
54: e0822003    add r2, r2, r3
58: e3003018    movw    r3, #24
5c: e34a3000    movt    r3, #40960  ; 0xa000
60: e5832000    str r2, [r3]
64: e51b3008    ldr r3, [fp, #-8]
68: e2833001    add r3, r3, #1
6c: e50b3008    str r3, [fp, #-8]
70: e3a02006    mov r2, #6
74: e51b3008    ldr r3, [fp, #-8]
78: e1530002    cmp r3, r2
7c: baffffed    blt 38 <main+0x18>
80: e3a03000    mov r3, #0
84: e1a00003    mov r0, r3
88: e24bd000    sub sp, fp, #0
8c: e49db004    pop {fp}        ; (ldr fp, [sp], #4)
90: e12fff1e    bx  lr 

00000094 <_start>:
94: e59f004c    ldr r0, [pc, #76]   ; e8 <stop+0x4>
98: e59f104c    ldr r1, [pc, #76]   ; ec <stop+0x8>
9c: e59f204c    ldr r2, [pc, #76]   ; f0 <stop+0xc>
a0: e3520000    cmp r2, #0
a4: 0a000003    beq b8 <init_bss> 

000000a8 <copy>:
a8: e4d04001    ldrb    r4, [r0], #1
ac: e4c14001    strb    r4, [r1], #1
b0: e2522001    subs    r2, r2, #1
b4: 1afffffb    bne a8 <copy> 

000000b8 <init_bss>:
b8: e59f0034    ldr r0, [pc, #52]   ; f4 <stop+0x10>
bc: e59f1034    ldr r1, [pc, #52]   ; f8 <stop+0x14>
c0: e59f2034    ldr r2, [pc, #52]   ; fc <stop+0x18>
c4: e3520000    cmp r2, #0
c8: 0a000003    beq dc <init_stack>
cc: e3a04000    mov r4, #0

000000d0 <zero>:
d0: e4c04001    strb    r4, [r0], #1
d4: e2522001    subs    r2, r2, #1
d8: 1afffffc    bne d0 <zero>  

000000dc <init_stack>:
dc: e3a0d329    mov sp, #-1543503872    ; 0xa4000000
e0: ebffffce    bl  20 <main> 

000000e4 <stop>:
e4: eafffffe    b   e4 <stop>
e8: 00000104    andeq   r0, r0, r4, lsl #2
ec: a0000000    andge   r0, r0, r0
f0: 00000018    andeq   r0, r0, r8, lsl r0
f4: a0000018    andge   r0, r0, r8, lsl r0
f8: a000001c    andge   r0, r0, ip, lsl r0
fc: 00000004    andeq   r0, r0, r4

Disassembly of section .rodata:
00000100 <n>:
100:    00000006    andeq   r0, r0, r6

Disassembly of section .data:
a0000000 <arr>:
a0000000:   00000001    andeq   r0, r0, r1
a0000004:   0000000a    andeq   r0, r0, sl
a0000008:   00000004    andeq   r0, r0, r4
a000000c:   00000005    andeq   r0, r0, r5
a0000010:   00000006    andeq   r0, r0, r6
a0000014:   00000007    andeq   r0, r0, r7

Disassembly of section .bss: 
a0000018 <sum>:
a0000018:   00000000    andeq   r0, r0, r0

program.elf：文件格式elf32 littlearm
第节的分解。正文：
00000000 :
0:ea000023 b 94
00000004 :
4:eafffffe b 4
00000008 :
8:eafffffe b 8
0000000c:
c:eafffffe b c
00000010 :
10:eafffffe b 10
14:e320f000 nop{0}
00000018 :
18:eafffffe b 18
0000001c：
1c:eafffffe b 1c
00000020 :
20:e52db004推送{fp}；（str fp，[sp，#-4]！）
24:e28db000添加fp，sp，#0
28:e24dd00c子sp，sp，#12
2c:e3a03000 mov r3，#0
30:e50b3008 str r3[fp，#-8]
34:ea00000d b 70
38:e3003000 movw r3，#0
3c:e34a3000移动r3，#40960；0xa000
40:e51b2008 ldr r2[fp，#-8]
44:e7932102 ldr r2[r3，r2，lsl#2]
48:e3003018 movw r3，#24
4c:e34a3000移动r3，#40960；0xa000
50:e5933000 ldr r3[r3]
54:e0822003添加r2、r2、r3
58:e3003018 movw r3，#24
5c:e34a3000移动r3，#40960；0xa000
60:E583200 str r2[r3]
64:e51b3008 ldr r3[fp，#-8]
68:e2833001添加r3，r3，#1
6c:e50b3008 str r3[fp，#-8]
70:e3a02006 mov r2#6
74:e51b3008 ldr r3[fp，#-8]
78:e1530002凸轮轴位置r3，r2
7c:baffffed blt 38
80:e3a03000 mov r3，#0
84:e1a00003 mov r0，r3
88:e24bd000子sp，fp，#0
8c:e49db004 pop{fp}；（ldr fp，[sp]，#4）
90:E12FF1E bx lr
00000094 :
94:e59f004c ldr r0，[pc，#76]；e8
98:e59f104c ldr r1，[pc，#76]；欧共体
9c:e59f204c ldr r2，[pc，#76]；f0
a0:e3520000 cmp r2，#0
a4:0a000003贝基b8
000000 A8：
a8:e4d04001 ldrb r4，[r0]，#1
ac:e4c14001 strb r4，[r1]，#1
b0:e2522001潜艇r2，r2，#1
b4:1afffffb bne a8
000000b8：
b8:e59f0034 ldr r0，[pc，#52]；f4
bc:e59f1034 ldr r1，[pc，#52]；f8
c0:e59f2034 ldr r2，[pc，#52]；足球俱乐部
c4:e3520000 cmp r2，#0
c8:0a000003 beq dc
抄送：e3a04000 mov r4，#0
000000d0：
d0:e4c04001 strb r4，[r0]，#1
d4:e2522001潜艇r2、r2、1
d8:1afffffc bne d0
000000 DC:
dc:e3a0d329 mov sp#-1543503872；0xa4000000
e0:ebffffce bl 20
000000e4：
e4:eafffffe b e4
e8:00000104安第克r0、r0、r4、lsl#2
ec:a0000000和GE r0、r0、r0
f0:00000018安第克r0、r0、r8、lsl r0
f4:a0000018和GE r0、r0、r8、lsl r0
f8:a000001c和GE r0、r0、ip、lsl r0
fc:00000004和r0、r0、r4
节段的拆卸。rodata：
00000100 :
100:00000006andeq r0，r0，r6
分解截面。数据：
a0000000：
a0000000:00000001 andeq r0、r0、r1
a0000004:0000000a和r0，r0，sl
a0000008:00000004和r0、r0、r4
a000000c:00000005 andeq r0、r0、r5
a0000010:00000006和r0、r0、r6
a0000014:00000007andeq r0，r0，r7
bss部分的拆卸：
a0000018：
a0000018:00000000安第克r0，r0，r0
有人能给我指出一个正确的方向来解释为什么这不能按照我的期望工作吗

感谢Henrik调试

首先，看看PC和PSR：您处于未定义模式，在未定义的指令处理程序中

好的，在异常模式下，LR会告诉您在哪里执行异常。PC偏移量和首选返回地址之间有一些稍微复杂的规则，确定它到底指向什么，但只要看一下它，它显然就在
movw
/
movt
对附近

movw
指令实际上只存在于ARMv7 ISA以后的版本中。一个简短的调查告诉我，您正在模拟的机器是一些旧的PXA255东西，其CPU只实现ARMv5 ISA。因此，它在一个早于多年的指令上出错也就不足为奇了

显然，您的编译器在默认情况下被配置为以ARMv7为目标（这并不少见），因此您需要将至少
-march=armv5te
添加到您的CFLAGS中，以针对适当的体系结构版本。“高级”的挑战是切换到一台不同的、更新的机器，但这将涉及将链接器脚本调整到新的内存映射，并为新的外围设备重写任何与硬件相关的代码，因此我会将这一想法保留更长的时间，一旦你熟悉了裸机代码的基本知识，并认真阅读了硬件参考手册。

对于我的ubuntu上的相同代码，我得到了

arm none eabi gcc-NOSDLIB-o sum.elf sum.lds startup.s-w /usr/lib/gcc/arm-none-eabi/4.9.3/../../../../arm-none-eabi/bin/ld:警告：找不到输入符号_start；默认为00000000 /tmp/ccBthV7t.o:在函数
init_stack'中：
（.text+0x4c）：未定义对
main'
collect2:错误：ld返回了1个退出状态

仅起作用的最小示例

  • 从主机终端获取输入，并通过模拟UART返回输出：

    enter a character
got: a
new alloc of 1 bytes at address 0x0x4000a1c0
enter a character
got: b
new alloc of 2 bytes at address 0x0x4000a1c0
enter a character
    它使用Newlib公开C标准库的一个子集。这允许您运行用C编写的现有程序，如果用户只使用C标准库的受限子集

    有关Newlib的更多详细信息，请访问：

  • 对于
    -M virt
    ，只有回购协议上的hello world。编译时使用：

    sudo apt-get install gcc-aarch64-linux-gnu
make CROSS_PREFIX=aarch64-linux-gnu-
    以下是从程序集打印单个字符的示例：

  • 对于
    -M raspi3
    。快速入门：关于回购的其他几个例子将涉及更高级的主题

    也d