[root@centos7 aarch64-bare-metal-qemu]# gcc -c test64.c -o test64.o [root@centos7 aarch64-bare-metal-qemu]# as -c startup64.s -o startup64.o [root@centos7 aarch64-bare-metal-qemu]# ld -Ttest64.ld test64.o startup64.o -o test64.elf [root@centos7
[root@centos7 aarch64-bare-metal-qemu]# qemu-system-aarch64 -M virt -cpu cortex-a57 -nographic -kernel test64.elf
Hello world!
[root@centos7 aarch64-bare-metal-qemu]# objdump -s -d test64.o > test64.txt [root@centos7 aarch64-bare-metal-qemu]# objdump -s -d startup64.o > startup64.txt [root@centos7 aarch64-bare-metal-qemu]# objdump -s -d test64.elf > test64.elf.txt [root@centos7 aarch64-bare-metal-qemu]# cat test64.txt test64.o: file format elf64-littleaarch64 Contents of section .text: 0000 ff4300d1 e00700f9 08000014 0020a1d2 .C........... .. 0010 e10740f9 21004039 010000b9 e00740f9 ..@.!.@9......@. 0020 00040091 e00700f9 e00740f9 00004039 ..........@...@9 0030 1f001f6b c1feff54 ff430091 c0035fd6 ...k...T.C...._. 0040 fd7bbfa9 fd030091 00000090 00000091 .{.............. 0050 00000094 fd7bc1a8 c0035fd6 .....{...._. Contents of section .rodata: 0000 00000009 00000000 48656c6c 6f20776f ........Hello wo 0010 726c6421 0a00 rld!.. Contents of section .comment: 0000 00474343 3a202847 4e552920 342e382e .GCC: (GNU) 4.8. 0010 35203230 31353036 32332028 52656420 5 20150623 (Red 0020 48617420 342e382e 352d3434 2900 Hat 4.8.5-44). Contents of section .eh_frame: 0000 10000000 00000000 017a5200 04781e01 .........zR..x.. 0010 1b0c1f00 14000000 18000000 00000000 ................ 0020 40000000 00410e10 4e0e0000 20000000 @....A..N... ... 0030 30000000 00000000 1c000000 00410e10 0............A.. 0040 9d029e01 410d1d44 dedd0c1f 00000000 ....A..D........ Disassembly of section .text: 0000000000000000 <print_uart0>: 0: d10043ff sub sp, sp, #0x10 4: f90007e0 str x0, [sp,#8] 8: 14000008 b 28 <print_uart0+0x28> c: d2a12000 mov x0, #0x9000000 // #150994944 10: f94007e1 ldr x1, [sp,#8] 14: 39400021 ldrb w1, [x1] 18: b9000001 str w1, [x0] 1c: f94007e0 ldr x0, [sp,#8] 20: 91000400 add x0, x0, #0x1 24: f90007e0 str x0, [sp,#8] 28: f94007e0 ldr x0, [sp,#8] 2c: 39400000 ldrb w0, [x0] 30: 6b1f001f cmp w0, wzr 34: 54fffec1 b.ne c <print_uart0+0xc> 38: 910043ff add sp, sp, #0x10 3c: d65f03c0 ret 0000000000000040 <c_entry>: 40: a9bf7bfd stp x29, x30, [sp,#-16]! 44: 910003fd mov x29, sp 48: 90000000 adrp x0, 0 <print_uart0> 4c: 91000000 add x0, x0, #0x0 50: 94000000 bl 0 <print_uart0> 54: a8c17bfd ldp x29, x30, [sp],#16 58: d65f03c0 ret [root@centos7 aarch64-bare-metal-qemu]# cat startup64.txt startup64.o: file format elf64-littleaarch64 Contents of section .text: 0000 9e000058 df030091 00000094 00000014 ...X............ 0010 00000000 00000000 ........ Disassembly of section .text: 0000000000000000 <_Reset>: 0: 5800009e ldr x30, 10 <_Reset+0x10> 4: 910003df mov sp, x30 8: 94000000 bl 0 <c_entry> c: 14000000 b c <_Reset+0xc> ... [root@centos7 aarch64-bare-metal-qemu]# cat test64.elf.txt test64.elf: file format elf64-littleaarch64 Contents of section .startup: 40000000 9e000058 df030091 14000094 00000014 ...X............ 40000010 e8100040 00000000 ...@.... Contents of section .text: 40000018 ff4300d1 e00700f9 08000014 0020a1d2 .C........... .. 40000028 e10740f9 21004039 010000b9 e00740f9 ..@.!.@9......@. 40000038 00040091 e00700f9 e00740f9 00004039 ..........@...@9 40000048 1f001f6b c1feff54 ff430091 c0035fd6 ...k...T.C...._. 40000058 fd7bbfa9 fd030091 00000090 00000291 .{.............. 40000068 ecffff97 fd7bc1a8 c0035fd6 .....{...._. Contents of section .rodata: 40000078 00000009 00000000 48656c6c 6f20776f ........Hello wo 40000088 726c6421 0a00 rld!.. Contents of section .eh_frame: 40000090 14000000 00000000 017a5200 04781e01 .........zR..x.. 400000a0 1b0c1f00 00000000 14000000 1c000000 ................ 400000b0 68ffffff 40000000 00410e10 4e0e0000 h...@....A..N... 400000c0 24000000 34000000 90ffffff 1c000000 $...4........... 400000d0 00410e10 9d029e01 410d1d44 dedd0c1f .A......A..D.... 400000e0 00000000 00000000 ........ Contents of section .comment: 0000 4743433a 2028474e 55292034 2e382e35 GCC: (GNU) 4.8.5 0010 20323031 35303632 33202852 65642048 20150623 (Red H 0020 61742034 2e382e35 2d343429 00 at 4.8.5-44). Disassembly of section .startup: 0000000040000000 <_Reset>: 40000000: 5800009e ldr x30, 40000010 <_Reset+0x10> 40000004: 910003df mov sp, x30 40000008: 94000014 bl 40000058 <c_entry> 4000000c: 14000000 b 4000000c <_Reset+0xc> 40000010: 400010e8 .word 0x400010e8 40000014: 00000000 .word 0x00000000 Disassembly of section .text: 0000000040000018 <print_uart0>: 40000018: d10043ff sub sp, sp, #0x10 4000001c: f90007e0 str x0, [sp,#8] 40000020: 14000008 b 40000040 <print_uart0+0x28> 40000024: d2a12000 mov x0, #0x9000000 // #150994944 40000028: f94007e1 ldr x1, [sp,#8] 4000002c: 39400021 ldrb w1, [x1] 40000030: b9000001 str w1, [x0] 40000034: f94007e0 ldr x0, [sp,#8] 40000038: 91000400 add x0, x0, #0x1 4000003c: f90007e0 str x0, [sp,#8] 40000040: f94007e0 ldr x0, [sp,#8] 40000044: 39400000 ldrb w0, [x0] 40000048: 6b1f001f cmp w0, wzr 4000004c: 54fffec1 b.ne 40000024 <print_uart0+0xc> 40000050: 910043ff add sp, sp, #0x10 40000054: d65f03c0 ret 0000000040000058 <c_entry>: 40000058: a9bf7bfd stp x29, x30, [sp,#-16]! 4000005c: 910003fd mov x29, sp 40000060: 90000000 adrp x0, 40000000 <_Reset> 40000064: 91020000 add x0, x0, #0x80 40000068: 97ffffec bl 40000018 <print_uart0> 4000006c: a8c17bfd ldp x29, x30, [sp],#16 40000070: d65f03c0 ret
链接脚本和栈指针
C函数栈指针
链接地址
- The address to load the program to should be changed too. '0x10000' is not valid RAM or ROM address for -M virt. According to virt.c, '0x40000000' is OK to use. So my linker script is modified and named test64.ld
0x40000000
[root@centos7 aarch64-bare-metal-qemu]# cat test64.ld ENTRY(_Reset) SECTIONS { . = 0x40000000; .startup . : { startup64.o(.text) } .text : { *(.text) } .data : { *(.data) } .bss : { *(.bss COMMON) } . = ALIGN(8); . = . + 0x1000; /* 4kB of stack memory */ stack_top = .; }
Disassembly of section .startup: 0000000040000000 <_Reset>: 40000000: 5800009e ldr x30, 40000010 <_Reset+0x10> 40000004: 910003df mov sp, x30 40000008: 94000014 bl 40000058 <c_entry> 4000000c: 14000000 b 4000000c <_Reset+0xc> 40000010: 400010e8 .word 0x400010e8 40000014: 00000000 .word 0x00000000 Disassembly of section .text: 0000000040000018 <print_uart0>: 40000018: d10043ff sub sp, sp, #0x10 4000001c: f90007e0 str x0, [sp,#8] 40000020: 14000008 b 40000040 <print_uart0+0x28> 40000024: d2a12000 mov x0, #0x9000000 // #150994944 40000028: f94007e1 ldr x1, [sp,#8] 4000002c: 39400021 ldrb w1, [x1] 40000030: b9000001 str w1, [x0] 40000034: f94007e0 ldr x0, [sp,#8] 40000038: 91000400 add x0, x0, #0x1 4000003c: f90007e0 str x0, [sp,#8] 40000040: f94007e0 ldr x0, [sp,#8] 40000044: 39400000 ldrb w0, [x0] 40000048: 6b1f001f cmp w0, wzr 4000004c: 54fffec1 b.ne 40000024 <print_uart0+0xc> 40000050: 910043ff add sp, sp, #0x10 40000054: d65f03c0 ret 0000000040000058 <c_entry>: 40000058: a9bf7bfd stp x29, x30, [sp,#-16]! 4000005c: 910003fd mov x29, sp 40000060: 90000000 adrp x0, 40000000 <_Reset> 40000064: 91020000 add x0, x0, #0x80 40000068: 97ffffec bl 40000018 <print_uart0> 4000006c: a8c17bfd ldp x29, x30, [sp],#16 40000070: d65f03c0 ret
链接地址0x10000
[root@centos7 aarch64-bare-metal-qemu]# cat test64.ld ENTRY(_Reset) SECTIONS { . = 0x10000; .startup . : { startup64.o(.text) } .text : { *(.text) } .data : { *(.data) } .bss : { *(.bss COMMON) } . = ALIGN(8); . = . + 0x1000; /* 4kB of stack memory */ stack_top = .; }
[root@centos7 aarch64-bare-metal-qemu]# ld -Ttest64.ld test64.o startup64.o -o test64.elf [root@centos7 aarch64-bare-metal-qemu]# objdump -s -d test64.elf > test64.elf.txt2 [root@centos7 aarch64-bare-metal-qemu]# cat test64.elf.txt2
[root@centos7 aarch64-bare-metal-qemu]# cat test64.elf.txt2 test64.elf: file format elf64-littleaarch64 Contents of section .startup: 10000 9e000058 df030091 14000094 00000014 ...X............ 10010 e8100100 00000000 ........ Contents of section .text: 10018 ff4300d1 e00700f9 08000014 0020a1d2 .C........... .. 10028 e10740f9 21004039 010000b9 e00740f9 ..@.!.@9......@. 10038 00040091 e00700f9 e00740f9 00004039 ..........@...@9 10048 1f001f6b c1feff54 ff430091 c0035fd6 ...k...T.C...._. 10058 fd7bbfa9 fd030091 00000090 00000291 .{.............. 10068 ecffff97 fd7bc1a8 c0035fd6 .....{...._. Contents of section .rodata: 10078 00000009 00000000 48656c6c 6f20776f ........Hello wo 10088 726c6421 0a00 rld!.. Contents of section .eh_frame: 10090 14000000 00000000 017a5200 04781e01 .........zR..x.. 100a0 1b0c1f00 00000000 14000000 1c000000 ................ 100b0 68ffffff 40000000 00410e10 4e0e0000 h...@....A..N... 100c0 24000000 34000000 90ffffff 1c000000 $...4........... 100d0 00410e10 9d029e01 410d1d44 dedd0c1f .A......A..D.... 100e0 00000000 00000000 ........ Contents of section .comment: 0000 4743433a 2028474e 55292034 2e382e35 GCC: (GNU) 4.8.5 0010 20323031 35303632 33202852 65642048 20150623 (Red H 0020 61742034 2e382e35 2d343429 00 at 4.8.5-44). Disassembly of section .startup: 0000000000010000 <_Reset>: 10000: 5800009e ldr x30, 10010 <_Reset+0x10> 10004: 910003df mov sp, x30 10008: 94000014 bl 10058 <c_entry> 1000c: 14000000 b 1000c <_Reset+0xc> 10010: 000110e8 .word 0x000110e8 10014: 00000000 .word 0x00000000 Disassembly of section .text: 0000000000010018 <print_uart0>: 10018: d10043ff sub sp, sp, #0x10 1001c: f90007e0 str x0, [sp,#8] 10020: 14000008 b 10040 <print_uart0+0x28> 10024: d2a12000 mov x0, #0x9000000 // #150994944 10028: f94007e1 ldr x1, [sp,#8] 1002c: 39400021 ldrb w1, [x1] 10030: b9000001 str w1, [x0] 10034: f94007e0 ldr x0, [sp,#8] 10038: 91000400 add x0, x0, #0x1 1003c: f90007e0 str x0, [sp,#8] 10040: f94007e0 ldr x0, [sp,#8] 10044: 39400000 ldrb w0, [x0] 10048: 6b1f001f cmp w0, wzr 1004c: 54fffec1 b.ne 10024 <print_uart0+0xc> 10050: 910043ff add sp, sp, #0x10 10054: d65f03c0 ret 0000000000010058 <c_entry>: 10058: a9bf7bfd stp x29, x30, [sp,#-16]! 1005c: 910003fd mov x29, sp 10060: 90000000 adrp x0, 10000 <_Reset> 10064: 91020000 add x0, x0, #0x80 10068: 97ffffec bl 10018 <print_uart0> 1006c: a8c17bfd ldp x29, x30, [sp],#16 10070: d65f03c0 ret
没有helloworld 输出
[root@centos7 aarch64-bare-metal-qemu]# qemu-system-aarch64 -M virt -cpu cortex-a57 -nographic -kernel test64.elf
Killed
heap
[root@centos7 aarch64-bare-metal-qemu]# cat test64.ld ENTRY(_Reset) SECTIONS { . = 0x40000000; .startup . : { startup64.o(.text) } .text : { *(.text) } .data : { *(.data) } .bss : { *(.bss COMMON) } . = ALIGN(8); heap_low = .; /* for _sbrk */ . = . + 0x10000; /* 64kB of heap memory */ heap_top = .; /* for _sbrk */ . = . + 0x1000; /* 4kB of stack memory */ stack_top = .; }
[root@centos7 aarch64-bare-metal-qemu]# ld -Ttest64.ld test64.o startup64.o -o test64.elf
[root@centos7 aarch64-bare-metal-qemu]# ld -Ttest64.ld test64.o startup64.o -o test64.elf [root@centos7 aarch64-bare-metal-qemu]# objdump -s -d test64.elf > test64.elf.txt3 [root@centos7 aarch64-bare-metal-qemu]# cat test64.elf.txt3 test64.elf: file format elf64-littleaarch64 Contents of section .startup: 40000000 9e000058 df030091 14000094 00000014 ...X............ 40000010 e8100140 00000000 ...@.... Contents of section .text: 40000018 ff4300d1 e00700f9 08000014 0020a1d2 .C........... .. 40000028 e10740f9 21004039 010000b9 e00740f9 ..@.!.@9......@. 40000038 00040091 e00700f9 e00740f9 00004039 ..........@...@9 40000048 1f001f6b c1feff54 ff430091 c0035fd6 ...k...T.C...._. 40000058 fd7bbfa9 fd030091 00000090 00000291 .{.............. 40000068 ecffff97 fd7bc1a8 c0035fd6 .....{...._. Contents of section .rodata: 40000078 00000009 00000000 48656c6c 6f20776f ........Hello wo 40000088 726c6421 0a00 rld!.. Contents of section .eh_frame: 40000090 14000000 00000000 017a5200 04781e01 .........zR..x.. 400000a0 1b0c1f00 00000000 14000000 1c000000 ................ 400000b0 68ffffff 40000000 00410e10 4e0e0000 h...@....A..N... 400000c0 24000000 34000000 90ffffff 1c000000 $...4........... 400000d0 00410e10 9d029e01 410d1d44 dedd0c1f .A......A..D.... 400000e0 00000000 00000000 ........ Contents of section .comment: 0000 4743433a 2028474e 55292034 2e382e35 GCC: (GNU) 4.8.5 0010 20323031 35303632 33202852 65642048 20150623 (Red H 0020 61742034 2e382e35 2d343429 00 at 4.8.5-44). Disassembly of section .startup: 0000000040000000 <_Reset>: 40000000: 5800009e ldr x30, 40000010 <_Reset+0x10> 40000004: 910003df mov sp, x30 40000008: 94000014 bl 40000058 <c_entry> 4000000c: 14000000 b 4000000c <_Reset+0xc> 40000010: 400110e8 .word 0x400110e8 40000014: 00000000 .word 0x00000000 Disassembly of section .text: 0000000040000018 <print_uart0>: 40000018: d10043ff sub sp, sp, #0x10 4000001c: f90007e0 str x0, [sp,#8] 40000020: 14000008 b 40000040 <print_uart0+0x28> 40000024: d2a12000 mov x0, #0x9000000 // #150994944 40000028: f94007e1 ldr x1, [sp,#8] 4000002c: 39400021 ldrb w1, [x1] 40000030: b9000001 str w1, [x0] 40000034: f94007e0 ldr x0, [sp,#8] 40000038: 91000400 add x0, x0, #0x1 4000003c: f90007e0 str x0, [sp,#8] 40000040: f94007e0 ldr x0, [sp,#8] 40000044: 39400000 ldrb w0, [x0] 40000048: 6b1f001f cmp w0, wzr 4000004c: 54fffec1 b.ne 40000024 <print_uart0+0xc> 40000050: 910043ff add sp, sp, #0x10 40000054: d65f03c0 ret 0000000040000058 <c_entry>: 40000058: a9bf7bfd stp x29, x30, [sp,#-16]! 4000005c: 910003fd mov x29, sp 40000060: 90000000 adrp x0, 40000000 <_Reset> 40000064: 91020000 add x0, x0, #0x80 40000068: 97ffffec bl 40000018 <print_uart0> 4000006c: a8c17bfd ldp x29, x30, [sp],#16 40000070: d65f03c0 ret
链接脚本定义堆
[root@centos7 aarch64-bare-metal-qemu]# gcc -c test64.c -o test64.o -nostdlib test64.c: In function ‘_sbrk’: test64.c:40:2: warning: passing argument 1 of ‘print_pointer’ makes pointer from integer without a cast [enabled by default] print_pointer(heap_low); ^ test64.c:12:6: note: expected ‘const char *’ but argument is of type ‘char’ void print_pointer(const char *s) { ^ test64.c:41:2: warning: passing argument 1 of ‘print_pointer’ makes pointer from integer without a cast [enabled by default] print_pointer(heap_top); ^ test64.c:12:6: note: expected ‘const char *’ but argument is of type ‘char’ void print_pointer(const char *s) { ^ test64.c:51:9: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] return (caddr_t) prev_heap_end; ^ [root@centos7 aarch64-bare-metal-qemu]# as -c startup64.s -o startup64.o [root@centos7 aarch64-bare-metal-qemu]# ld -Ttest64.ld test64.o startup64.o -o test64.elf [root@centos7 aarch64-bare-metal-qemu]# qemu-system-aarch64 -M virt -cpu cortex-a57 -nographic -kernel test64.elf Hello world! 0000 0000 Killed [root@centos7 aarch64-bare-metal-qemu]# ls ans ans.o ans.s hello hello.o hello.txt libc.s LICENSE Makefile README.md startup64.o startup64.s startup64.txt sys sys.o sys.s test64.c test64.elf test64.elf.txt test64.elf.txt2 test64.elf.txt3 test64.ld test64.o test64.txt [root@centos7 aarch64-bare-metal-qemu]# cat test64.ld ENTRY(_Reset) SECTIONS { . = 0x40000000; .startup . : { startup64.o(.text) } .text : { *(.text) } .data : { *(.data) } .bss : { *(.bss COMMON) } . = ALIGN(8); heap_low = .; /* for _sbrk */ . = . + 0x10000; /* 64kB of heap memory */ heap_top = .; /* for _sbrk */ . = . + 0x1000; /* 4kB of stack memory */ stack_top = .; }
volatile unsigned int * const UART0DR = (unsigned int *) 0x09000000; typedef unsigned int caddr_t; caddr_t _sbrk(int incr) ; void print_uart0(const char *s) { while(*s != '\0') { /* Loop until end of string */ *UART0DR = (unsigned int)(*s); /* Transmit char */ s++; /* Next char */ } } void print_pointer(const char *s) { int new_value[4]; char buf_temp[4]; int temp,x; for (x = 0; x < 4; x++) { new_value[x] = temp % 10; temp = temp / 10; buf_temp[x] = new_value[x] +48; *UART0DR = (unsigned int)(buf_temp[x]); /* Transmit char */ } *UART0DR = '\n'; /* Transmit char */ } void c_entry() { print_uart0("Hello world!\n"); _sbrk(16); } char *heap_end = 0; caddr_t _sbrk(int incr) { extern char heap_low; /* Defined by the linker */ extern char heap_top; /* Defined by the linker */ char *prev_heap_end; if (heap_end == 0) { heap_end = &heap_low; } print_pointer(heap_low); print_pointer(heap_top); prev_heap_end = heap_end; if (heap_end + incr > &heap_top) { /* Heap and stack collision */ return (caddr_t)0; } heap_end += incr; return (caddr_t) prev_heap_end; }
C代码中如何使用链接脚本中定义的变量
SECTIONS { ..... . = ALIGN(4); .rodata : { *(.rodata) } . = ALIGN(4); .data : { *(.data) } . = ALIGN(4); .got : { *(.got) } . = ALIGN(4); __bss_start = .; .bss : { *(.bss) } _end = .; }
其中__bss_start, _end 表示BSS段的起始、终止地址。
我们想对这段空间清零时，
1．在汇编代码中，可以直接引用__bss_start, _end，比如：
ldr r0, =__bss_start
ldr r1, =_end
在C代码中，我们不能直接引用它们，要这样做：
void clean_bss(void) { extern int __bss_start, _end; int *p = &__bss_start; for (; p < &_end; p++) *p = 0; }
_bss_start, _end不是表示某个值吗？在C代码中为什么要使用取址符号 & ?
原因：
在C代码中，这样的语句：
int foo = 1000;
会导致2件事情发生：
1. 在代码中，留出4字节的空间，保存数值1000
2．在C语言的symbole talbe，即符号表中，有一个名为foo的项，它里面存有那4字节空间的地址。
我们执行 foo = 1时，会先去符号表中找到foo对应的地址，然后把数值1填到那个地址对应的内存；
我们执行 int *a = &foo时，会直接把符号表中foo的地址，写给a。
在链接脚本中，假设
__bss_start = 1000
__bss_start并不是一个变量，它只是一个值，并不需要在内存中留出一段空间来保存它；
在C语言中，符号表中会有一个名为__bss_start的项，这个项目中的值（地址值）是1000；
注意，这个1000并没有实际存在的内存。
所以：在C语言中，要去使用链接脚本中定义的值时，应该这样做：
extern int __bss_start; int val = &__bss_start;
使用取址符号&去得到它在符号表中的值。
[root@centos7 aarch64-bare-metal-qemu]# vim test64.c volatile unsigned int * const UART0DR = (unsigned int *) 0x09000000; typedef unsigned int caddr_t; caddr_t _sbrk(int incr) ; void print_uart0(const char *s) { while(*s != '\0') { /* Loop until end of string */ *UART0DR = (unsigned int)(*s); /* Transmit char */ s++; /* Next char */ } } void print_pointer(int pointer) { int new_value[4]; char buf_temp[4]; int temp,x; temp = pointer; for (x = 0; x < 4; x++) { new_value[x] = temp % 10; temp = temp / 10; buf_temp[x] = new_value[x] +48; *UART0DR = (unsigned int)(buf_temp[x]); /* Transmit char */ 从低到高输出，反了 } *UART0DR = '\n'; /* Transmit char */ } void c_entry() { print_uart0("Hello world!\n"); _sbrk(16); } char *heap_end = 0; caddr_t _sbrk(int incr) { extern int heap_low; /* Defined by the linker */ extern int heap_top; /* Defined by the linker */ char *prev_heap_end; if (heap_end == 0) { heap_end = &heap_low; } print_pointer(&heap_low); print_pointer(&heap_top); prev_heap_end = heap_end; if (heap_end + incr > &heap_top) { /* Heap and stack collision */ return (caddr_t)0; } heap_end += incr; return (caddr_t) prev_heap_end; }
[root@centos7 aarch64-bare-metal-qemu]# qemu-system-aarch64 -M virt -cpu cortex-a57 -nographic -kernel test64.elf Hello world! 4452 0808 Killed
[root@centos7 aarch64-bare-metal-qemu]# objdump -s -d test64.elf > test64.elf.txt3 [root@centos7 aarch64-bare-metal-qemu]# cat test64.elf.txt3 test64.elf: file format elf64-littleaarch64 Contents of section .startup: 40000000 9e000058 df030091 4d000094 00000014 ...X....M....... 40000010 d0120140 00000000 ...@.... Contents of section .text: 40000018 ff4300d1 e00700f9 08000014 0020a1d2 .C........... .. 40000028 e10740f9 21004039 010000b9 e00740f9 ..@.!.@9......@. 40000038 00040091 e00700f9 e00740f9 00004039 ..........@...@9 40000048 1f001f6b c1feff54 ff430091 c0035fd6 ...k...T.C...._. 40000058 ff0301d1 e00700f9 e00740f9 e03f00b9 ..........@..?.. 40000068 ff3b00b9 2c000014 e13f40b9 40018052 .;..,....?@.@..R 40000078 220cc01a e003022a 00741e53 0000020b "......*.t.S.... 40000088 00781f53 2100004b e2630091 e03b80b9 .x.S!..K.c...;.. 40000098 00f47ed3 4000008b 010000b9 e13f40b9 ..~.@........?@. 400000a8 e0cc8c52 c0ccac72 207c209b 00fc60d3 ...R...r | ...`. 400000b8 027c0213 207c1f13 4000004b e03f00b9 .|.. |..@..K.?.. 400000c8 e1630091 e03b80b9 00f47ed3 2000008b .c...;....~. ... 400000d8 000040b9 001c0053 00c00011 011c0053 ..@....S.......S 400000e8 e03b80b9 e2030191 4000008b 01001d38 .;......@......8 400000f8 0020a1d2 e13b80b9 e2030191 4100018b . ...;......A... 40000108 21005d38 010000b9 e03b40b9 00040011 !.]8.....;@..... 40000118 e03b00b9 e03b40b9 1f1c0071 6dfaff54 .;...;@....qm..T 40000128 0020a1d2 41018052 010000b9 ff030191 . ..A..R........ 40000138 c0035fd6 fd7bbfa9 fd030091 00000090 .._..{.......... 40000148 00800891 b3ffff97 00028052 03000094 ...........R.... 40000158 fd7bc1a8 c0035fd6 fd7bbda9 fd030091 .{...._..{...... 40000168 a01f00b9 00000090 00200b91 000040f9 ......... ....@. 40000178 1f001feb c1000054 00000090 00200b91 .......T..... .. 40000188 01000090 21400b91 010000f9 00000090 ....!@.......... 40000198 00400b91 afffff97 80000090 00400b91 .@...........@.. 400001a8 acffff97 00000090 00200b91 000040f9 ......... ....@. 400001b8 a01700f9 00000090 00200b91 010040f9 ......... ....@. 400001c8 a01f80b9 2100008b 80000090 00400b91 ....!........@.. 400001d8 3f0000eb 69000054 00008052 0a000014 ?...i..T...R.... 400001e8 00000090 00200b91 010040f9 a01f80b9 ..... ....@..... 400001f8 2100008b 00000090 00200b91 010000f9 !........ ...... 40000208 a01740f9 fd7bc3a8 c0035fd6 ..@..{...._. Contents of section .rodata: 40000218 00000009 00000000 48656c6c 6f20776f ........Hello wo 40000228 726c6421 0a00 rld!.. Contents of section .eh_frame: 40000230 14000000 00000000 017a5200 04781e01 .........zR..x.. 40000240 1b0c1f00 00000000 14000000 1c000000 ................ 40000250 c8fdffff 40000000 00410e10 4e0e0000 ....@....A..N... 40000260 14000000 34000000 f0fdffff e4000000 ....4........... 40000270 00410e40 770e0000 24000000 4c000000 .A.@w...$...L... 40000280 bcfeffff 24000000 00410e10 9d029e01 ....$....A...... 40000290 410d1d46 dedd0c1f 00000000 00000000 A..F............ 400002a0 24000000 74000000 b8feffff b4000000 $...t........... 400002b0 00410e30 9d069e05 410d1d6a dedd0c1f .A.0....A..j.... 400002c0 00000000 00000000 ........ Contents of section .comment: 0000 4743433a 2028474e 55292034 2e382e35 GCC: (GNU) 4.8.5 0010 20323031 35303632 33202852 65642048 20150623 (Red H 0020 61742034 2e382e35 2d343429 00 at 4.8.5-44). Disassembly of section .startup: 0000000040000000 <_Reset>: 40000000: 5800009e ldr x30, 40000010 <_Reset+0x10> 40000004: 910003df mov sp, x30 40000008: 9400004d bl 4000013c <c_entry> 4000000c: 14000000 b 4000000c <_Reset+0xc> 40000010: 400112d0 .word 0x400112d0 40000014: 00000000 .word 0x00000000 Disassembly of section .text: 0000000040000018 <print_uart0>: 40000018: d10043ff sub sp, sp, #0x10 4000001c: f90007e0 str x0, [sp,#8] 40000020: 14000008 b 40000040 <print_uart0+0x28> 40000024: d2a12000 mov x0, #0x9000000 // #150994944 40000028: f94007e1 ldr x1, [sp,#8] 4000002c: 39400021 ldrb w1, [x1] 40000030: b9000001 str w1, [x0] 40000034: f94007e0 ldr x0, [sp,#8] 40000038: 91000400 add x0, x0, #0x1 4000003c: f90007e0 str x0, [sp,#8] 40000040: f94007e0 ldr x0, [sp,#8] 40000044: 39400000 ldrb w0, [x0] 40000048: 6b1f001f cmp w0, wzr 4000004c: 54fffec1 b.ne 40000024 <print_uart0+0xc> 40000050: 910043ff add sp, sp, #0x10 40000054: d65f03c0 ret 0000000040000058 <print_pointer>: 40000058: d10103ff sub sp, sp, #0x40 4000005c: f90007e0 str x0, [sp,#8] 40000060: f94007e0 ldr x0, [sp,#8] 40000064: b9003fe0 str w0, [sp,#60] 40000068: b9003bff str wzr, [sp,#56] 4000006c: 1400002c b 4000011c <print_pointer+0xc4> 40000070: b9403fe1 ldr w1, [sp,#60] 40000074: 52800140 mov w0, #0xa // #10 40000078: 1ac00c22 sdiv w2, w1, w0 4000007c: 2a0203e0 mov w0, w2 40000080: 531e7400 lsl w0, w0, #2 40000084: 0b020000 add w0, w0, w2 40000088: 531f7800 lsl w0, w0, #1 4000008c: 4b000021 sub w1, w1, w0 40000090: 910063e2 add x2, sp, #0x18 40000094: b9803be0 ldrsw x0, [sp,#56] 40000098: d37ef400 lsl x0, x0, #2 4000009c: 8b000040 add x0, x2, x0 400000a0: b9000001 str w1, [x0] 400000a4: b9403fe1 ldr w1, [sp,#60] 400000a8: 528ccce0 mov w0, #0x6667 // #26215 400000ac: 72acccc0 movk w0, #0x6666, lsl #16 400000b0: 9b207c20 smull x0, w1, w0 400000b4: d360fc00 lsr x0, x0, #32 400000b8: 13027c02 asr w2, w0, #2 400000bc: 131f7c20 asr w0, w1, #31 400000c0: 4b000040 sub w0, w2, w0 400000c4: b9003fe0 str w0, [sp,#60] 400000c8: 910063e1 add x1, sp, #0x18 400000cc: b9803be0 ldrsw x0, [sp,#56] 400000d0: d37ef400 lsl x0, x0, #2 400000d4: 8b000020 add x0, x1, x0 400000d8: b9400000 ldr w0, [x0] 400000dc: 53001c00 uxtb w0, w0 400000e0: 1100c000 add w0, w0, #0x30 400000e4: 53001c01 uxtb w1, w0 400000e8: b9803be0 ldrsw x0, [sp,#56] 400000ec: 910103e2 add x2, sp, #0x40 400000f0: 8b000040 add x0, x2, x0 400000f4: 381d0001 sturb w1, [x0,#-48] 400000f8: d2a12000 mov x0, #0x9000000 // #150994944 400000fc: b9803be1 ldrsw x1, [sp,#56] 40000100: 910103e2 add x2, sp, #0x40 40000104: 8b010041 add x1, x2, x1 40000108: 385d0021 ldurb w1, [x1,#-48] 4000010c: b9000001 str w1, [x0] 40000110: b9403be0 ldr w0, [sp,#56] 40000114: 11000400 add w0, w0, #0x1 40000118: b9003be0 str w0, [sp,#56] 4000011c: b9403be0 ldr w0, [sp,#56] 40000120: 71001c1f cmp w0, #0x7 40000124: 54fffa6d b.le 40000070 <print_pointer+0x18> 40000128: d2a12000 mov x0, #0x9000000 // #150994944 4000012c: 52800141 mov w1, #0xa // #10 40000130: b9000001 str w1, [x0] 40000134: 910103ff add sp, sp, #0x40 40000138: d65f03c0 ret 000000004000013c <c_entry>: 4000013c: a9bf7bfd stp x29, x30, [sp,#-16]! 40000140: 910003fd mov x29, sp 40000144: 90000000 adrp x0, 40000000 <_Reset> 40000148: 91088000 add x0, x0, #0x220 4000014c: 97ffffb3 bl 40000018 <print_uart0> 40000150: 52800200 mov w0, #0x10 // #16 40000154: 94000003 bl 40000160 <_sbrk> 40000158: a8c17bfd ldp x29, x30, [sp],#16 4000015c: d65f03c0 ret 0000000040000160 <_sbrk>: 40000160: a9bd7bfd stp x29, x30, [sp,#-48]! 40000164: 910003fd mov x29, sp 40000168: b9001fa0 str w0, [x29,#28] 4000016c: 90000000 adrp x0, 40000000 <_Reset> 40000170: 910b2000 add x0, x0, #0x2c8 40000174: f9400000 ldr x0, [x0] 40000178: eb1f001f cmp x0, xzr 4000017c: 540000c1 b.ne 40000194 <_sbrk+0x34> 40000180: 90000000 adrp x0, 40000000 <_Reset> 40000184: 910b2000 add x0, x0, #0x2c8 40000188: 90000001 adrp x1, 40000000 <_Reset> 4000018c: 910b4021 add x1, x1, #0x2d0 40000190: f9000001 str x1, [x0] 40000194: 90000000 adrp x0, 40000000 <_Reset> 40000198: 910b4000 add x0, x0, #0x2d0 4000019c: 97ffffaf bl 40000058 <print_pointer> 400001a0: 90000080 adrp x0, 40010000 <heap_low+0xfd30> 400001a4: 910b4000 add x0, x0, #0x2d0 400001a8: 97ffffac bl 40000058 <print_pointer> 400001ac: 90000000 adrp x0, 40000000 <_Reset> 400001b0: 910b2000 add x0, x0, #0x2c8 400001b4: f9400000 ldr x0, [x0] 400001b8: f90017a0 str x0, [x29,#40] 400001bc: 90000000 adrp x0, 40000000 <_Reset> 400001c0: 910b2000 add x0, x0, #0x2c8 400001c4: f9400001 ldr x1, [x0] 400001c8: b9801fa0 ldrsw x0, [x29,#28] 400001cc: 8b000021 add x1, x1, x0 400001d0: 90000080 adrp x0, 40010000 <heap_low+0xfd30> 400001d4: 910b4000 add x0, x0, #0x2d0 400001d8: eb00003f cmp x1, x0 400001dc: 54000069 b.ls 400001e8 <_sbrk+0x88> 400001e0: 52800000 mov w0, #0x0 // #0 400001e4: 1400000a b 4000020c <_sbrk+0xac> 400001e8: 90000000 adrp x0, 40000000 <_Reset> 400001ec: 910b2000 add x0, x0, #0x2c8 400001f0: f9400001 ldr x1, [x0] 400001f4: b9801fa0 ldrsw x0, [x29,#28] 400001f8: 8b000021 add x1, x1, x0 400001fc: 90000000 adrp x0, 40000000 <_Reset> 40000200: 910b2000 add x0, x0, #0x2c8 40000204: f9000001 str x1, [x0] 40000208: f94017a0 ldr x0, [x29,#40] 4000020c: a8c37bfd ldp x29, x30, [sp],#48 40000210: d65f03c0 ret [root@centos7 aarch64-bare-metal-qemu]#
volatile unsigned int * const UART0DR = (unsigned int *) 0x09000000; typedef unsigned int caddr_t; caddr_t _sbrk(int incr) ; void print_uart0(const char *s) { while(*s != '\0') { /* Loop until end of string */ *UART0DR = (unsigned int)(*s); /* Transmit char */ s++; /* Next char */ } } void print_pointer(int pointer) { int new_value[8]; char buf_temp[8]; int temp,x; temp = pointer; for (x = 0; x < 8; x++) { new_value[x] = temp % 10; temp = temp / 10; buf_temp[x] = new_value[x] +48; //*UART0DR = (unsigned int)(buf_temp[x]); /* Transmit char */ if (0 == temp) { break; } } for (x; x > 0; --x) { *UART0DR = (unsigned int)(buf_temp[x-1]); /* Transmit char */ } *UART0DR = '\n'; /* Transmit char */ } void c_entry() { print_uart0("Hello world!\n"); _sbrk(16); } char *heap_end = 0; caddr_t _sbrk(int incr) { extern int heap_low; /* Defined by the linker */ extern int heap_top; /* Defined by the linker */ char *prev_heap_end; if (heap_end == 0) { heap_end = &heap_low; } print_pointer(&heap_low); print_pointer(&heap_top); prev_heap_end = heap_end; if (heap_end + incr > &heap_top) { /* Heap and stack collision */ return (caddr_t)0; } heap_end += incr; return (caddr_t) prev_heap_end; }
