My program operates like this:
exe -p param1 -i param2 -o param3
It crashed and generated a core dump file, core.pid.
I want to analyze the core dump file by
gdb ./exe -p param1 -i param2 -o param3 core.pid
But GDB recognizes the parameters of the EXE file as GDB's input.
How do I analyze a core dump file in this situation?
You can use the core with gdb in many ways, but passing parameters which is to be passed to executable to gdb is not the way to use core file. This could also be the reason you got that error. You can use the core file in following ways:gdb <executable> <core-file> or gdb <executable> -c <core-file> or
gdb <executable>
...
(gdb) core <core-file>
When using core file you don't have to pass arguments. The crash scenario is shown in gdb (checked with gdb Version 7.1 on Ubuntu) . For example:
$ ./crash -p param1 -o param2
Segmentation fault (core dumped)
$ gdb ./crash core
GNU gdb (GDB) 7.1-ubuntu
...
Core was generated by `./crash -p param1 -o param2'. <<<<< See this line shows crash scenario
Program terminated with signal 11, Segmentation fault.
#0 __strlen_ia32 () at ../sysdeps/i386/i686/multiarch/../../i586/strlen.S:99
99 ../sysdeps/i386/i686/multiarch/../../i586/strlen.S: No such file or directory.
in ../sysdeps/i386/i686/multiarch/../../i586/strlen.S
(gdb)
If you want to pass parameters to the executable to be debugged in gdb use --args.
For example:
$ gdb --args ./crash -p param1 -o param2
GNU gdb (GDB) 7.1-ubuntu
...
(gdb) r
Starting program: /home/@@@@/crash -p param1 -o param2
Program received signal SIGSEGV, Segmentation fault.
__strlen_ia32 () at ../sysdeps/i386/i686/multiarch/../../i586/strlen.S:99
99 ../sysdeps/i386/i686/multiarch/../../i586/strlen.S: No such file or directory.
in ../sysdeps/i386/i686/multiarch/../../i586/strlen.S
(gdb)
Man pages will be helpful to see other gdb options.
Simple usage of GDB, to debug coredump files:
gdb <executable_path> <coredump_file_path>
Coredump file for a "process" gets created, as "core.pid" file. After you get inside the gdb-prompt, (on execution of the above command), type;
...
(gdb) where
This will get you with the information, of the stack, where you can analayze the cause of crash/fault. Other command, for same purposes is;
...
(gdb) bt full
This is same as above. By convention, it lists the whole stack info (which ultimately leads to the crash location).
Just skip the params, gdb doesn't need them:
gdb ./exe core.pid
From RMS's gdb Debugger Tutorial:
prompt > myprogram
Segmentation fault (core dumped)
prompt > gdb myprogram
...
(gdb) core core.pid
...
Make sure your file really is a core image -- check it using file.
A slightly different approach will allow you to skip GDB entirely. If all you want is a backtrace, the linux-specific utility 'catchsegv' will catch SIGSEGV and display a backtrace.
objdump + gdb minimal runnable example
TL;DR:
objdump -s coreto dump memoryGDB to find failing line, previously mentioned at: How do I analyze a program's core dump file with GDB when it has command-line parameters?
Now for the full educational test setup:
main.c
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int myfunc(int i) {
*(int*)(NULL) = i; /* line 7 */
return i - 1;
}
int main(int argc, char **argv) {
/* Setup some memory. */
char data_ptr[] = "string in data segment";
char *mmap_ptr;
char *text_ptr = "string in text segment";
(void)argv;
mmap_ptr = (char *)malloc(sizeof(data_ptr) + 1);
strcpy(mmap_ptr, data_ptr);
mmap_ptr[10] = 'm';
mmap_ptr[11] = 'm';
mmap_ptr[12] = 'a';
mmap_ptr[13] = 'p';
printf("text addr: %p\n", text_ptr);
printf("data addr: %p\n", data_ptr);
printf("mmap addr: %p\n", mmap_ptr);
/* Call a function to prepare a stack trace. */
return myfunc(argc);
}
Compile, and run to generate core:
gcc -ggdb3 -std=c99 -Wall -Wextra -pedantic -o main.out main.c
ulimit -c unlimited
rm -f core
./main.out
Output:
text addr: 0x4007d4
data addr: 0x7ffec6739220
mmap addr: 0x1612010
Segmentation fault (core dumped)
GDB points us to the exact line where the segfault happened, which is what most users want while debugging:
gdb -q -nh main.out core
then:
Reading symbols from main.out...done.
[New LWP 27479]
Core was generated by `./main.out'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x0000000000400635 in myfunc (i=1) at main.c:7
7 *(int*)(NULL) = i;
(gdb) bt
#0 0x0000000000400635 in myfunc (i=1) at main.c:7
#1 0x000000000040072b in main (argc=1, argv=0x7ffec6739328) at main.c:28
which points us directly to the buggy line 7.
Binutils analysis
First:
file core
tells us that the core file is actually an ELF file:
core: ELF 64-bit LSB core file x86-64, version 1 (SYSV), SVR4-style, from './main.out'
which is why we are able to inspect it more directly with usual binutils tools.
A quick look at the ELF standard shows that there is actually an ELF type dedicated to it:
Elf32_Ehd.e_type == ET_CORE
Further format information can be found at:
man 5 core
Then:
readelf -Wa core
gives some hints about the file structure. Memory appears to be contained in regular program headers:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
NOTE 0x000468 0x0000000000000000 0x0000000000000000 0x000b9c 0x000000 0
LOAD 0x002000 0x0000000000400000 0x0000000000000000 0x001000 0x001000 R E 0x1000
LOAD 0x003000 0x0000000000600000 0x0000000000000000 0x001000 0x001000 R 0x1000
LOAD 0x004000 0x0000000000601000 0x0000000000000000 0x001000 0x001000 RW 0x1000
and there is some more metadata present in a notes area. Notably, I guess the PC must be there (TODO confirm):
Displaying notes found at file offset 0x00000468 with length 0x00000b9c:
Owner Data size Description
CORE 0x00000150 NT_PRSTATUS (prstatus structure)
CORE 0x00000088 NT_PRPSINFO (prpsinfo structure)
CORE 0x00000080 NT_SIGINFO (siginfo_t data)
CORE 0x00000130 NT_AUXV (auxiliary vector)
CORE 0x00000246 NT_FILE (mapped files)
Page size: 4096
Start End Page Offset
0x0000000000400000 0x0000000000401000 0x0000000000000000
/home/ciro/test/main.out
0x0000000000600000 0x0000000000601000 0x0000000000000000
/home/ciro/test/main.out
0x0000000000601000 0x0000000000602000 0x0000000000000001
/home/ciro/test/main.out
0x00007f8d939ee000 0x00007f8d93bae000 0x0000000000000000
/lib/x86_64-linux-gnu/libc-2.23.so
0x00007f8d93bae000 0x00007f8d93dae000 0x00000000000001c0
/lib/x86_64-linux-gnu/libc-2.23.so
0x00007f8d93dae000 0x00007f8d93db2000 0x00000000000001c0
/lib/x86_64-linux-gnu/libc-2.23.so
0x00007f8d93db2000 0x00007f8d93db4000 0x00000000000001c4
/lib/x86_64-linux-gnu/libc-2.23.so
0x00007f8d93db8000 0x00007f8d93dde000 0x0000000000000000
/lib/x86_64-linux-gnu/ld-2.23.so
0x00007f8d93fdd000 0x00007f8d93fde000 0x0000000000000025
/lib/x86_64-linux-gnu/ld-2.23.so
0x00007f8d93fde000 0x00007f8d93fdf000 0x0000000000000026
/lib/x86_64-linux-gnu/ld-2.23.so
CORE 0x00000200 NT_FPREGSET (floating point registers)
LINUX 0x00000340 NT_X86_XSTATE (x86 XSAVE extended state)
objdump can easily dump all memory with:
objdump -s core
which contains:
Contents of section load1:
4007d0 01000200 73747269 6e672069 6e207465 ....string in te
4007e0 78742073 65676d65 6e740074 65787420 xt segment.text
Contents of section load15:
7ffec6739220 73747269 6e672069 6e206461 74612073 string in data s
7ffec6739230 65676d65 6e740000 00a8677b 9c6778cd egment....g{.gx.
Contents of section load4:
1612010 73747269 6e672069 6e206d6d 61702073 string in mmap s
1612020 65676d65 6e740000 11040000 00000000 egment..........
which matches exactly with the stdout value in our run.
Tested in Ubuntu 16.04 amd64, GCC 6.4.0, binutils 2.26.1.
It doesn't matter executable have arguments or not, To run GDB on any binary with a generated core file Syntax is below.
Syntax:
gdb <binary name> <generated core file>
Eg:
gdb l3_entity 6290-corefile
let me take the below example for more understanding.
bash-4.1$**gdb l3_entity 6290-corefile**
**Core was generated** by `/dir1/dir2/dir3/l3_entity **Program terminated with signal SIGABRT, Aborted.**
#0
#1
#2
#3
#4
#5
#6
#7
#8
#9
#10
(gdb)
From the above output, you can guess something about core whether it is a NULL access or SIGABORT etc..
These numbers #0 to #10 are the stack frames of GDB. These stack frames are not of your binary. in the above 0 - 10 frames if you suspect anything wrong select that frame
(gdb) frame 8
Now to see more details about it:
(gdb) list +
To investigate issue further you can print the suspected variable values here at this point of time.
(gdb) print thread_name
You can analyze the core dump file using "gdb" command.
gdb - The GNU Debugger
syntax:
# gdb executable-file core-file
ex: # gdb out.txt core.xxx
Thanks.
Simply type command
$ gdb <Binary> <codeDump>
or
$ gdb <binary>
$ gdb) core <coreDump>
No need to provide any command line arguement. The code dump generated due to earlier exercise.
来源：https://stackoverflow.com/questions/8305866/how-do-i-analyze-a-programs-core-dump-file-with-gdb-when-it-has-command-line-pa