RISCV GDB debug调试

hello.c

#include <stdio.h>
int main(){
    long a = 0x876543210 ;
    float pi = 3.1415926 ;
    printf("Hello %s!\n","World");
    a = a*pi;
    return a ;
}

如何生成汇编代码

riscv64-unknown-elf-gcc -S hello.c 只会生成汇编代码hello.s 不会生成.out文件

    .file   "hello.c"
    .option nopic
    .text
    .section    .rodata
    .align  3
.LC2:
    .string "World"
    .align  3
.LC3:
    .string "Hello %s!\n"
    .text
    .align  1
    .globl  main
    .type   main, @function
main:
    addi    sp,sp,-32
    sd  ra,24(sp)
    sd  s0,16(sp)
    addi    s0,sp,32
    lui a5,%hi(.LC0)
    ld  a5,%lo(.LC0)(a5)
    sd  a5,-24(s0)
    lui a5,%hi(.LC1)
    flw fa5,%lo(.LC1)(a5)
    fsw fa5,-28(s0)
    lui a5,%hi(.LC2)
    addi    a1,a5,%lo(.LC2)
    lui a5,%hi(.LC3)
    addi    a0,a5,%lo(.LC3)
    call    printf
    ld  a5,-24(s0)
    fcvt.s.l    fa4,a5
    flw fa5,-28(s0)
    fmul.s  fa5,fa4,fa5
    fcvt.l.s a5,fa5,rtz
    sd  a5,-24(s0)
    ld  a5,-24(s0)
    sext.w  a5,a5
    mv  a0,a5
    ld  ra,24(sp)
    ld  s0,16(sp)
    addi    sp,sp,32
    jr  ra
    .size   main, .-main
    .section    .rodata
    .align  3
.LC0:
    .dword  36344967696
    .align  2
.LC1:
    .word   1078530010
    .ident  "GCC: (GNU) 8.1.0"

如何反汇编.out文件

首先生成.out文件riscv64-unknown-elf-gcc -o hello.out hello.c

然后反汇编 riscv64-unknown-elf-objdump -d hello.out > hello_disassemble.s

即可查看反汇编代码,搜索main函数如下，当然也包括其他内置函数

hello.out:     file format elf64-littleriscv
Disassembly of section .text:
00000000000100b0 <_start>:
   100b0:   0000d197            auipc   gp,0xd
   100b4:   fd818193            addi    gp,gp,-40 # 1d088 <__global_pointer$>
   100b8:   84818513            addi    a0,gp,-1976 # 1c8d0 <_edata>
   100bc:   8d818613            addi    a2,gp,-1832 # 1c960 <_end>           
   .....
   ...

000000000001038c <printf>:
   1038c:   711d                    addi    sp,sp,-96
   1038e:   f832                    sd  a2,48(sp)
   10390:   fc36                    sd  a3,56(sp)        
   ....
   ..

0000000000010198 <main>:
   10198:   1101         addi    sp,sp,-32
   1019a:   ec06         sd  ra,24(sp)
   1019c:   e822         sd  s0,16(sp)
   1019e:   1000         addi    s0,sp,32
   101a0:   67e9         lui a5,0x1a
   101a2:   a687b783     ld  a5,-1432(a5) # 19a68 <__clzdi2+0x54>
   101a6:   fef43423     sd  a5,-24(s0)
   101aa:   67e9         lui a5,0x1a
   101ac:   a707a787     flw fa5,-1424(a5) # 19a70 <__clzdi2+0x5c>
   101b0:   fef42227     fsw fa5,-28(s0)
   101b4:   67e9         lui a5,0x1a
   101b6:   a5078593     addi    a1,a5,-1456 # 19a50 <__clzdi2+0x3c>
   101ba:   67e9         lui a5,0x1a
   101bc:   a5878513     addi    a0,a5,-1448 # 19a58 <__clzdi2+0x44>
   101c0:   1cc000ef     jal ra,1038c <printf>
   101c4:   fe843783     ld  a5,-24(s0)
   101c8:   d027f753     fcvt.s.l    fa4,a5
   101cc:   fe442787     flw fa5,-28(s0)
   101d0:   10f777d3     fmul.s  fa5,fa4,fa5
   101d4:   c02797d3     fcvt.l.s    a5,fa5,rtz
   101d8:   fef43423     sd  a5,-24(s0)
   101dc:   fe843783     ld  a5,-24(s0)
   101e0:   2781         sext.w  a5,a5
   101e2:   853e         mv  a0,a5
   101e4:   60e2         ld  ra,24(sp)
   101e6:   6442         ld  s0,16(sp)
   101e8:   6105         addi    sp,sp,32
   101ea:   8082         ret         
   ....
   ...