objdump - adhuliya/ws-misc GitHub Wiki

Get the entry point of an elf.

See the Entry point address: which gives the virtual address of the entry instruction.

cmd> readelf -h <elf_file_name>
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:                              EXEC (Executable file)
  Machine:                           Advanced Micro Devices X86-64
  Version:                           0x1
  Entry point address:               0x800040
  Start of program headers:          2097152 (bytes into file)
  Start of section headers:          4212736 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           56 (bytes)
  Number of program headers:         12
  Size of section headers:           64 (bytes)
  Number of section headers:         35
  Section header string table index: 33

Get entry point using gdb

gdb <elf_file>
(gdb) info files
...
Entry point: 0x401030

Use the snippet below to set a break point and view the back trace, and reset the break point towards the starting of the program.

>gdb  -q  main
Reading symbols from /home/main...done.
(gdb) set backtrace past-main on
(gdb) b main
Breakpoint 1 at 0x40058a: file main.cpp, line 25.
(gdb) r
Starting program: /home/main

Breakpoint 1, main () at main.cpp:25
25        a();
(gdb) bt
#0  main () at main.cpp:25
#1  0x0000003a1d81ed1d in __libc_start_main () from /lib64/libc.so.6
#2  0x0000000000400499 in _start ()
(gdb) b _start
Breakpoint 2 at 0x400470
(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /home/main

Breakpoint 2, 0x0000000000400470 in _start ()
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