Coredump练习
Coredump练习
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系统环境
[root@localhost crash]# cat /proc/version Linux version 4.18.0-147.el8.x86_64 (mockbuild@kbuilder.bsys.centos.org) (gcc version 8.3.1 20190507 (Red Hat 8.3.1-4) (GCC)) #1 SMP Wed Dec 4 21:51:45 UTC 2019 [root@localhost crash]# uname -a Linux localhost.localdomain 4.18.0-147.el8.x86_64 #1 SMP Wed Dec 4 21:51:45 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux [root@localhost crash]# uname -r 4.18.0-147.el8.x86_64
设定ulimit -c
可设定core文件的大小为unlimited或者指定的最大Size
[root@localhost crash]# ulimit -c
unlimited
[root@localhost crash]# ulimit -c 1024
[root@localhost crash]# ulimit -c
1024
[root@localhost crash]# ulimit -c 4096
[root@localhost crash]# ulimit -c
4096
ulimit -a 可以列出所有的资源限制
[root@localhost crash]# ulimit -a
core file size (blocks, -c) 4096
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 7083
max locked memory (kbytes, -l) 16384
max memory size (kbytes, -m) unlimited
open files (-n) 1024
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 7083
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
设定core文件的保存路径
proc/sys/kernel/core_pattern可以控制core文件保存位置和文件名格式。
echo “/corefile/core-%e-%p-%t” > core_pattern，可以将core文件统一生成到/corefile目录下，产生的文件名为core-命令名-pid-时间戳
以下是参数列表:
%p - insert pid into filename 添加pid
%u - insert current uid into filename 添加当前uid
%g - insert current gid into filename 添加当前gid
%s - insert signal that caused the coredump into the filename 添加导致产生core的信号
%t - insert UNIX time that the coredump occurred into filename 添加core文件生成时的unix时间
%h - insert hostname where the coredump happened into filename 添加主机名
%e - insert coredumping executable name into filename 添加命令名
[root@localhost kernel]# ll |grep core
-rw-r--r--. 1 root root 0 Oct 19 22:34 core_pattern
-rw-r--r--. 1 root root 0 Oct 20 00:24 core_pipe_limit
-rw-r--r--. 1 root root 0 Oct 20 00:24 core_uses_pid
[root@localhost kernel]# cat core_pattern
|/usr/lib/systemd/systemd-coredump %P %u %g %s %t %c %h %e
[root@localhost kernel]# echo "/corefile/core-%e-%p-%t" > core_pattern
[root@localhost kernel]# cat core_pattern
/corefile/core-%e-%p-%t
生菜core的代码
#include <unistd.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <stdio.h>
#define CORE_SIZE 1024 * 1024 * 500
int main()
{
struct rlimit rlmt;
if (getrlimit(RLIMIT_CORE, &rlmt) == -1) {
return -1;
}
printf("Before set rlimit CORE dump current is:%d, max is:%d\n", (int)rlmt.rlim_cur, (int)rlmt.rlim_max);
rlmt.rlim_cur = (rlim_t)CORE_SIZE;
rlmt.rlim_max = (rlim_t)CORE_SIZE;
if (setrlimit(RLIMIT_CORE, &rlmt) == -1) {
return -1;
}
if (getrlimit(RLIMIT_CORE, &rlmt) == -1) {
return -1;
}
printf("After set rlimit CORE dump current is:%d, max is:%d\n", (int)rlmt.rlim_cur, (int)rlmt.rlim_max);
/*测试非法内存，产生core文件*/
int *ptr = NULL;
*ptr = 10;
return 0;
}
执行后得到
[root@localhost test_Core]# ls
a.out main.cpp test.cpp
[root@localhost test_Core]# ./a.out
Before set rlimit CORE dump current is:4194304, max is:4194304
After set rlimit CORE dump current is:524288000, max is:524288000
Segmentation fault (core dumped)
[root@localhost test_Core]# ls
a.out main.cpp test.cpp
[root@localhost test_Core]# cd /corefile/
[root@localhost corefile]# ls
core-a.out-4191-1603124814
查看core文件
[root@localhost test_Core]# readelf -h core-a.out-4191-1603124814
ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: CORE (Core file)
Machine: Advanced Micro Devices X86-64
Version: 0x1
Entry point address: 0x0
Start of program headers: 64 (bytes into file)
Start of section headers: 0 (bytes into file)
Flags: 0x0
Size of this header: 64 (bytes)
Size of program headers: 56 (bytes)
Number of program headers: 19
Size of section headers: 0 (bytes)
Number of section headers: 0
Section header string table index: 0
[root@localhost test_Core]# file core-a.out-4191-1603124814
core-a.out-4191-1603124814: ELF 64-bit LSB core file x86-64, version 1 (SYSV), SVR4-style, from './a.out', real uid: 0, effective uid: 0, real gid: 0, effective gid: 0, execfn: './a.out', platform: 'x86_64'
GDB调试core文件
[root@localhost test_Core]# mv /corefile/core-a.out-4191-1603124814 core-a.out-4191-1603124814
[root@localhost test_Core]# ls
a.out core-a.out-4191-1603124814 main.cpp test.cpp
[root@localhost test_Core]# gdb ./a.out core-a.out-4191-1603124814
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Reading symbols from ./a.out...done.
[New LWP 4191]
Core was generated by `./a.out'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x00000000004006e9 in main () at main.cpp:28
28 *ptr = 10;
Missing separate debuginfos, use: yum debuginfo-install glibc-2.28-72.el8_1.1.x86_64
(gdb) bt
#0 0x00000000004006e9 in main () at main.cpp:28
(gdb)
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