ELF Einstiegspunkt ist nicht gültig

Question

ich einen Haltepunkt an der Eintrittsstelle in einer abgespeckten ELF zu setzen versuchen. Die ELF wurde auf Virtual Box Linux-Maschine kompiliert und gestrippt.

root@xxxx:~# readelf -e yyyy_not_patched 
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:        DYN (Shared object file) 
    Machine:       Advanced Micro Devices X86-64 
    Version:       0x1 
    Entry point address:    0x650 
    Start of program headers:   64 (bytes into file) 
    Start of section headers:   6792 (bytes into file) 
    Flags:        0x0 
    Size of this header:    64 (bytes) 
    Size of program headers:   56 (bytes) 
    Number of program headers:   9 
    Size of section headers:   64 (bytes) 
    Number of section headers:   31 
    Section header string table index: 30 

Programm Header verweisen auf:

Program Headers: 

    Type   Offset    VirtAddr   PhysAddr 
       FileSiz   MemSiz    Flags Align 

PHDR   0x0000000000000040 0x0000000000000040 0x0000000000000040 
       0x00000000000001f8 0x00000000000001f8 R E 0x8 
INTERP   0x0000000000000238 0x0000000000000238 0x0000000000000238 
       0x000000000000001c 0x000000000000001c R  0x1 
     [Requesting program interpreter: /lib64/ld-linux-x86-64.so.2] 
LOAD   0x0000000000000000 0x0000000000000000 0x0000000000000000 
       0x00000000000009ec 0x00000000000009ec R E 0x200000 
LOAD   0x0000000000000dd8 0x0000000000200dd8 0x0000000000200dd8 
       0x0000000000000268 0x0000000000000278 RW  0x200000 
DYNAMIC  0x0000000000000df0 0x0000000000200df0 0x0000000000200df0 
       0x00000000000001e0 0x00000000000001e0 RW  0x8 
NOTE   0x0000000000000254 0x0000000000000254 0x0000000000000254 
       0x0000000000000044 0x0000000000000044 R  0x4 
GNU_EH_FRAME 0x00000000000008a0 0x00000000000008a0 0x00000000000008a0 
       0x000000000000003c 0x000000000000003c R  0x4 
GNU_STACK  0x0000000000000000 0x0000000000000000 0x0000000000000000 
       0x0000000000000000 0x0000000000000000 RW  0x10 
GNU_RELRO  0x0000000000000dd8 0x0000000000200dd8 0x0000000000200dd8 
       0x0000000000000228 0x0000000000000228 R  0x1 
" 

Wenn Sie einen Haltepunkt in der GDB Einstellung I "Kein Zugriff auf Speicher an der Adresse 0x650"

root@xxxx:~# gdb yyyy_not_patched 

Reading symbols from login_not_patched...(no debugging symbols found)...done. 

(gdb) b *0x650 
Breakpoint 1 at 0x650 
(gdb) r 
Starting program: /root/yyyy_not_patched 
Warning: 
Cannot insert breakpoint 1. 
Cannot access memory at address 0x650 

Jede Idee bin bekommen, was das sein könnte Problem?

Answer 1

Jede Idee, was das Problem sein könnte?

Dieses:

Type:        DYN (Shared object file) 

bedeutet, dass Sie bei einer position-independent executable (eine spezielle Form einer Shared Library) suchen. Solche ausführbaren Dateien sind in eine zufällige Adresse verlegt, bevor sie anfangen zu laufen, so Unterbrechungs 0x650 funktionieren nicht auf unrelocated Adresse einstellen.

Was funktioniert:

(gdb) set stop-on-solib-events 1 
(gdb) run 
(gdb) info proc map 

# Figure out where the executable got loaded 

(gdb) b *($exe_load_address + 0x650) 

Beispiel:

$ readelf -h a.out | grep 'Entry point' 
Entry point address:    0x620 

$ gdb -q ./a.out 
(gdb) set stop-on-solib-events 1 
(gdb) run 
Starting program: /tmp/a.out 
Stopped due to shared library event (no libraries added or removed) 

(gdb) info proc map 
process 67394 
Mapped address spaces: 

     Start Addr   End Addr  Size  Offset objfile 
    0x555555554000  0x555555555000  0x1000  0x0 /tmp/a.out 
    0x555555754000  0x555555756000  0x2000  0x0 /tmp/a.out 
    0x7ffff7dda000  0x7ffff7dfd000 0x23000  0x0 /lib/x86_64-linux-gnu/ld-2.19.so 
    ... 

(gdb) b *(0x555555554000+0x620) 
Breakpoint 1 at 0x555555554620 
(gdb) c 
Continuing. 
Stopped due to shared library event: 
    Inferior loaded /lib/x86_64-linux-gnu/libc.so.6 
(gdb) c 
Continuing. 

Breakpoint 1, 0x0000555555554620 in _start() 
(gdb) bt 
#0 0x0000555555554620 in _start()