GNU gdb (Debian 7.7.1+dfsg-5) 7.7.1 says foo not in executable format: File format not recognized

blastwave · 09-27-2017, 01:58 PM

I am baffled here.

The debugger won't. Here is what I did :

Code:

deb8_ppc64$ cat hello.c

#include <stdio.h>
#include <stdlib.h>
int main( int argc, char *argv[])
{
    fprintf ( stdout, "hello world.\n" );
    return (  EXIT_SUCCESS );
}

Compile it, run it and look at it :

Code:

deb8_ppc64$ gcc -m64 -g -o hello hello.c
deb8_ppc64$ ./hello
hello world.
deb8_ppc64$ 
deb8_ppc64$ file hello
hello: ELF 64-bit MSB executable, 64-bit PowerPC or cisco 7500, version 1 (SYSV), dynamically linked, interpreter /lib64/ld64.so.1, for GNU/Linux 2.6.32, BuildID[sha1]=c79bcf90665edeb4b1d9a5972c4f7ddf8ec9877d, not stripped
deb8_ppc64$

However debugger gdb says "no" :

Code:

deb8_ppc64$ which gdb
/usr/bin/gdb
deb8_ppc64$ ls -lap /usr/bin/gdb
-rwxr-xr-x 1 root root 6301688 Nov  9  2014 /usr/bin/gdb
deb8_ppc64$ /usr/bin/gdb hello
GNU gdb (Debian 7.7.1+dfsg-5) 7.7.1
Copyright (C) 2014 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "powerpc-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
"/usr/local/src/test/hello/hello": not in executable format: File format not recognized
(gdb) quit
deb8_ppc64$

What is going on here?

NevemTeve · 09-27-2017, 02:20 PM

Now try this with gcc option '-m32'

blastwave · 09-27-2017, 02:48 PM

Did that first. Works. However I need to debug a 64-bit piece of software. Clearly not "hello world".

The correct action to take here is to simply install gdb 8.0.1 and then give it a whirl.

blastwave · 09-27-2017, 06:41 PM

Problem solved .. I simply built a new gdb :

Code:

deb8_ppc64$ /usr/local/bin/gdb pi_ld 
GNU gdb (GDB) 8.0.1
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "powerpc64-unknown-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from pi_ld...done.
(gdb) break 57
Breakpoint 1 at 0x10000670: file pi_ld.c, line 57.
(gdb) run
Starting program: /usr/local/src/test/pi_ld 

NOTE : sizeof(long double) = 16


Breakpoint 1, main (argc=1, argv=0x3ffffffff8a8) at pi_ld.c:57
57          for ( j=0; j<sizeof(long double); j++ ) {
(gdb) print pi
$1 = 3.1415926535897932384626433832794812
(gdb) print &pi
$2 = (long double *) 0x3ffffffff440
(gdb) x/16xb 0x3ffffffff440
0x3ffffffff440: 0x40    0x09    0x21    0xfb    0x54    0x44    0x2d    0x18
0x3ffffffff448: 0x3c    0xa1    0xa6    0x26    0x33    0x14    0x5c    0x06
(gdb) cont
Continuing.
hex at memory addess &pi [ 0x3ffffffff440 ] ==  40 09 21 fb 54 44 2d 18 3c a1 a6 26 33 14 5c 06
[Inferior 1 (process 8222) exited normally]
(gdb) quit
deb8_ppc64$

Looks good to me.