linux基础36——调试coredump的两种方法

一段程序示例:

#include <stdio.h>

int main()
{
	int *p = NULL;

	*p = 0;

	printf("core dump\n");

	return 0;
}

编译生成可执行程序，执行可执行程序段错误。

[email protected] coredump]# cat test1.cpp 
#include <stdio.h>

int main()
{
	int *p = NULL;

	*p = 0;

	printf("core dump\n");

	return 0;
}
[[email protected] coredump]# g++ -g test1.cpp 
[[email protected] coredump]# ls
a.out  test1.cpp
[[email protected] coredump]# ./a.out 
段错误

1. dmesg+addr2line调试

dmesg ，一种程序，用于检测和控制内核缓冲。程序用来帮助用户，了解系统的启动信息，可以获得出错堆栈地址。

addr2line ，可以将指令的地址和可执行映像转换成文件名，函数名或源代码的工具。这种功能将跟踪地址转换成更有意义的内容来说很有用。

在调用 addr2line 工具时，要使用 -e 选项来指定可执行映像，使用 -f 选项可以告诉工具输出函数名。

[[email protected] coredump]# dmesg | grep a.out 
[    4.593497] iTCO_wdt: initialized. heartbeat=30 sec (nowayout=0)
[  273.301104] a.out[1841]: segfault at 0 ip 0000000000400536 sp 00007ffc056508d0 error 6 in a.out[400000+1000]
[  455.796400] a.out[1860]: segfault at 0 ip 0000000000400536 sp 00007fff62fdf580 error 6 in a.out[400000+1000]
[[email protected] coredump]# addr2line -e a.out 0000000000400536
/home/coredump/test1.cpp:7

先通过dmesg找到对应出错的地址，再用 addr2line -e 将地址解析到对应的代码行。

2. strace+addr2line调试

strace 是一个集诊断、调试、统计与一体的工具，我们可以使用strace，对应用的系统调用和信号传递的跟踪结果，来对应用进行分析，以达到解决问题，或者是了解应用工作过程的目的。

strace 的简单的用法就是，执行一个指定的命令，在指定的命令结束之后，它也就退出了。
在命令执行的过程中，strace 会记录和解析命令进程的所有系统调用，以及这个进程所接收到的，所有的信号值。

• -c ，统计每一系统调用的所执行的时间,次数和出错的次数等
• -p ，指定进程pid
• -i  ，输出系统调用的入口指针

[[email protected] coredump]# strace -i ./a.out 
[00007f031a295cc7] execve("./a.out", ["./a.out"], 0x7ffe7ac63618 /* 25 vars */) = 0
[00007f1e86f67aac] brk(NULL)            = 0x1455000
[00007f1e86f687da] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1e8716f000
[00007f1e86f686d7] access("/etc/ld.so.preload", R_OK) = -1 ENOENT (没有那个文件或目录)
[00007f1e86f68677] open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
[00007f1e86f68604] fstat(3, {st_mode=S_IFREG|0644, st_size=36474, ...}) = 0
[00007f1e86f687da] mmap(NULL, 36474, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f1e87166000
[00007f1e86f68787] close(3)             = 0
[00007f1e86f68677] open("/lib/libstdc++.so.6", O_RDONLY|O_CLOEXEC) = 3
[00007f1e86f68697] read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\[email protected]\217\t\0\0\0\0\0"..., 832) = 832
[00007f1e86f68604] fstat(3, {st_mode=S_IFREG|0755, st_size=16646312, ...}) = 0
[00007f1e86f687da] mmap(NULL, 3983616, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1e86b82000
[00007f1e86f68877] mprotect(0x7f1e86d3f000, 2093056, PROT_NONE) = 0
[00007f1e86f687da] mmap(0x7f1e86f3e000, 57344, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1bc000) = 0x7f1e86f3e000
[00007f1e86f687da] mmap(0x7f1e86f4c000, 10496, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f1e86f4c000
[00007f1e86f68787] close(3)             = 0
[00007f1e86f68677] open("/lib64/libm.so.6", O_RDONLY|O_CLOEXEC) = 3
[00007f1e86f68697] read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0PS\0\0\0\0\0\0"..., 832) = 832
[00007f1e86f68604] fstat(3, {st_mode=S_IFREG|0755, st_size=1136944, ...}) = 0
[00007f1e86f687da] mmap(NULL, 3150136, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1e86880000
[00007f1e86f68877] mprotect(0x7f1e86981000, 2093056, PROT_NONE) = 0
[00007f1e86f687da] mmap(0x7f1e86b80000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x100000) = 0x7f1e86b80000
[00007f1e86f68787] close(3)             = 0
[00007f1e86f68677] open("/lib64/libgcc_s.so.1", O_RDONLY|O_CLOEXEC) = 3
[00007f1e86f68697] read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\320*\0\0\0\0\0\0"..., 832) = 832
[00007f1e86f68604] fstat(3, {st_mode=S_IFREG|0755, st_size=88720, ...}) = 0
[00007f1e86f687da] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1e87165000
[00007f1e86f687da] mmap(NULL, 2184192, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1e8666a000
[00007f1e86f68877] mprotect(0x7f1e8667f000, 2093056, PROT_NONE) = 0
[00007f1e86f687da] mmap(0x7f1e8687e000, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x14000) = 0x7f1e8687e000
[00007f1e86f68787] close(3)             = 0
[00007f1e86f68677] open("/lib64/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
[00007f1e86f68697] read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0`&\2\0\0\0\0\0"..., 832) = 832
[00007f1e86f68604] fstat(3, {st_mode=S_IFREG|0755, st_size=2156344, ...}) = 0
[00007f1e86f687da] mmap(NULL, 3985920, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f1e8629c000
[00007f1e86f68877] mprotect(0x7f1e86460000, 2093056, PROT_NONE) = 0
[00007f1e86f687da] mmap(0x7f1e8665f000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1c3000) = 0x7f1e8665f000
[00007f1e86f687da] mmap(0x7f1e86665000, 16896, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f1e86665000
[00007f1e86f68787] close(3)             = 0
[00007f1e86f687da] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1e87164000
[00007f1e86f687da] mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1e87162000
[00007f1e86f4fefd] arch_prctl(ARCH_SET_FS, 0x7f1e87162740) = 0
[00007f1e86f68877] mprotect(0x7f1e8665f000, 16384, PROT_READ) = 0
[00007f1e86f68877] mprotect(0x7f1e8687e000, 4096, PROT_READ) = 0
[00007f1e86f68877] mprotect(0x7f1e86b80000, 4096, PROT_READ) = 0
[00007f1e86f687da] mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f1e87161000
[00007f1e86f68877] mprotect(0x7f1e86f3e000, 45056, PROT_READ) = 0
[00007f1e86f68877] mprotect(0x600000, 4096, PROT_READ) = 0
[00007f1e86f68877] mprotect(0x7f1e87170000, 4096, PROT_READ) = 0
[00007f1e86f68857] munmap(0x7f1e87166000, 36474) = 0
[00007f1e8639127c] brk(NULL)            = 0x1455000
[00007f1e8639127c] brk(0x1487000)       = 0x1487000
[0000000000400536] --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=NULL} ---
[????????????????] +++ killed by SIGSEGV +++
段错误
[[email protected] coredump]# addr2line -e a.out 0000000000400536
/home/coredump/test1.cpp:7
[[email protected] coredump]#