GDB调试实践
调试实例
huhan@HuHan ~/cpp/coredump ls
test.cpp
huhan@HuHan ~/cpp/coredump
huhan@HuHan ~/cpp/coredump g++ -o test test.cpp -g
huhan@HuHan ~/cpp/coredump ulimit
unlimited
huhan@HuHan ~/cpp/coredump ulimit- c unlimited
zsh: command not found: ulimit-
✘ huhan@HuHan ~/cpp/coredump ulimit -c unlimied
ulimit: invalid number: unlimied
✘ huhan@HuHan ~/cpp/coredump ulimit -c unlimited
huhan@HuHan ~/cpp/coredump
huhan@HuHan ~/cpp/coredump g++ -o test test.cpp -g
huhan@HuHan ~/cpp/coredump ulimit -c unlimited
huhan@HuHan ~/cpp/coredump ls
test test.cpp
huhan@HuHan ~/cpp/coredump ./test
10
[1] 290 segmentation fault (core dumped) ./test
✘ huhan@HuHan ~/cpp/coredump gdb test core
GNU gdb (Ubuntu 9.2-0ubuntu1~20.04.1) 9.2
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Reading symbols from test...
[New LWP 290]
Core was generated by `./test'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00005586369c71f9 in func (p=0x0) at test.cpp:6
6 int y = *p;
(gdb) where
#0 0x00005586369c71f9 in func (p=0x0) at test.cpp:6
#1 0x00005586369c7296 in main () at test.cpp:19
(gdb) l
1 #include <iostream>
2 using namespace std;
3
4 int func(int *p)
5 {
6 int y = *p;
7 return y;
8 }
9
10 int add(int const& a, int const& b)
(gdb) l
11 {
12 return a + b;
13 }
14
15 int main()
16 {
17 cout<< add(4, 6) <<endl;
18 int *p = NULL;
19 return func(p);
20 }
(gdb) b 5
Breakpoint 1 at 0x5586369c71e9: file test.cpp, line 5.
(gdb) b 13
Breakpoint 2 at 0x5586369c7221: file test.cpp, line 13.
(gdb) b 17
Breakpoint 3 at 0x5586369c723e: file test.cpp, line 17.
(gdb) b main
Breakpoint 4 at 0x5586369c7223: file test.cpp, line 16.
(gdb) info b
Num Type Disp Enb Address What
1 breakpoint keep y 0x00005586369c71e9 in func(int*) at test.cpp:5
2 breakpoint keep y 0x00005586369c7221 in add(int const&, int const&) at test.cpp:13
3 breakpoint keep y 0x00005586369c723e in main() at test.cpp:17
4 breakpoint keep y 0x00005586369c7223 in main() at test.cpp:16
(gdb) r
Starting program: /home/huhan/cpp/coredump/test
Breakpoint 4, main () at test.cpp:16
16 {
(gdb) s
Breakpoint 3, main () at test.cpp:17
17 cout<< add(4, 6) <<endl;
(gdb) s
add (a=@0x55555555537d: 29590344, b=<error reading variable>) at test.cpp:11
11 {
(gdb) s
12 return a + b;
(gdb) p a
$1 = (const int &) @0x7fffffffdae8: 4
(gdb) n
Breakpoint 2, add (a=@0x7fffffffdae8: 4, b=@0x7fffffffdaec: 6) at test.cpp:13
13 }
(gdb) n
10
main () at test.cpp:18
18 int *p = NULL;
(gdb) n
19 return func(p);
(gdb) disassemble
Dump of assembler code for function main():
0x0000555555555223 <+0>: endbr64
0x0000555555555227 <+4>: push %rbp
0x0000555555555228 <+5>: mov %rsp,%rbp
0x000055555555522b <+8>: sub $0x20,%rsp
0x000055555555522f <+12>: mov %fs:0x28,%rax
0x0000555555555238 <+21>: mov %rax,-0x8(%rbp)
0x000055555555523c <+25>: xor %eax,%eax
0x000055555555523e <+27>: movl $0x6,-0x14(%rbp)
0x0000555555555245 <+34>: movl $0x4,-0x18(%rbp)
0x000055555555524c <+41>: lea -0x14(%rbp),%rdx
0x0000555555555250 <+45>: lea -0x18(%rbp),%rax
0x0000555555555254 <+49>: mov %rdx,%rsi
0x0000555555555257 <+52>: mov %rax,%rdi
0x000055555555525a <+55>: callq 0x555555555203 <add(int const&, int const&)>
0x000055555555525f <+60>: mov %eax,%esi
0x0000555555555261 <+62>: lea 0x2dd8(%rip),%rdi # 0x555555558040 <_ZSt4cout@@GLIBCXX_3.4>
0x0000555555555268 <+69>: callq 0x5555555550e0 <_ZNSolsEi@plt>
0x000055555555526d <+74>: mov %rax,%rdx
0x0000555555555270 <+77>: mov 0x2d59(%rip),%rax # 0x555555557fd0
0x0000555555555277 <+84>: mov %rax,%rsi
0x000055555555527a <+87>: mov %rdx,%rdi
0x000055555555527d <+90>: callq 0x5555555550b0 <_ZNSolsEPFRSoS_E@plt>
0x0000555555555282 <+95>: movq $0x0,-0x10(%rbp)
=> 0x000055555555528a <+103>: mov -0x10(%rbp),%rax
0x000055555555528e <+107>: mov %rax,%rdi
0x0000555555555291 <+110>: callq 0x5555555551e9 <func(int*)>
0x0000555555555296 <+115>: nop
0x0000555555555297 <+116>: mov -0x8(%rbp),%rcx
0x000055555555529b <+120>: xor %fs:0x28,%rcx
0x00005555555552a4 <+129>: je 0x5555555552b9 <main()+150>
0x00005555555552a6 <+131>: jmp 0x5555555552b4 <main()+145>
0x00005555555552a8 <+133>: endbr64
0x00005555555552ac <+137>: mov %rax,%rdi
0x00005555555552af <+140>: callq 0x5555555550f0 <_Unwind_Resume@plt>
0x00005555555552b4 <+145>: callq 0x5555555550c0 <__stack_chk_fail@plt>
0x00005555555552b9 <+150>: leaveq
0x00005555555552ba <+151>: retq
End of assembler dump.
(gdb) s
Breakpoint 1, func (p=0x555555555330 <__libc_csu_init>) at test.cpp:5
5 {
(gdb) s
6 int y = *p;
(gdb) s
Program received signal SIGSEGV, Segmentation fault.
0x00005555555551f9 in func (p=0x0) at test.cpp:6
6 int y = *p;
(gdb) q
A debugging session is active.
Inferior 1 [process 299] will be killed.
Quit anyway? (y or n) n
Not confirmed.
(gdb) info frame
Stack level 0, frame at 0x7fffffffdae0:
rip = 0x5555555551f9 in func (test.cpp:6); saved rip = 0x555555555296
called by frame at 0x7fffffffdb10
source language c++.
Arglist at 0x7fffffffdac8, args: p=0x0
Locals at 0x7fffffffdac8, Previous frame's sp is 0x7fffffffdae0
Saved registers:
rbp at 0x7fffffffdad0, rip at 0x7fffffffdad8
(gdb) n
Program terminated with signal SIGSEGV, Segmentation fault.
The program no longer exists.
(gdb) q
huhan@HuHan ~/cpp/coredump
命令速查
启动 GDB
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断点
break main
break 101
break basic.c:101
break basic.c:foo
break *0x00400448
info breakpoints
delete 1
delete
clear
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clear line
clear basic.c:101
clear basic.c:main
clear *0x00400448
disable 2
enable 2
rbreak {regexpr}
tbreak function|line
hbreak function|line
ignore {id} {count}
condition {id} {expr}
condition 2 i == 20
watch {expr}
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catch exec
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set args {args} ...
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代码浏览
list 101
list 1,10
list main
list basic.c:main
list -
list *0x22e4
cd dir
pwd
search {regexpr}
reverse-search {regexp}
dir {dirname}
dir
show directories
浏览数据
print {expression}
print /x {expression}
print array[i]@count
print $
print *$->next
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print ::gx
print 'basic.c'::gx
print /x &main
x *0x11223344
x /nfu {address}
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x/x &gx
x/4wx &main
x/gf &gd1
help x
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info functions {regexp}
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file {object}
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info threads
thread {id}
break {line} thread all
thread apply {id..} cmd
thread apply all cmd
set schedule-locking ?
set non-stop on/off
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进程调试
info inferiors
inferior {id}
kill inferior {id...}
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set follow-fork-mode parent/child
汇编调试
info registers
info all-registers
print/x $pc
stepi
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info line *0x2c4e
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其他命令
define command ... end
<return>
shell {command} [args]
source {file}
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参考资料
GDB命令 | ZDZN 文档教程
GDB 调试指南
如何通过gdb查看反汇编代码
