The main problem

When assembling your first programs with AS, and linking it to external libraries like this :

armv7a-hardfloat-linux-gnueabi-as -o test.o test.S

armv7a-hardfloat-linux-gnueabi-ld.gold --hash-style=sysv -o test test.o -lc

You might be confronted to this error when executing your program :

$ ./test

-bash: ./test: No such file or directory

Using strace to pinpoint the problem will result to something like this :

execve("./test", ["./test"], [/* 28 vars */]) = -1 ENOENT (No such file or directory)

write(2, "strace: exec: No such file or di"..., 40strace: exec: No such file or directory

) = 40

exit_group(1)                           = ?

+++ exited with 1 +++

Looking at execve manual page, ENOENT is described like this :

The executable is not a script. The file clearly exists. However, the ELF interpreter ?

When running readelf -l elf_executable you can see which interpreter the executable tries to use. In this case, the output is :

Elf file type is EXEC (Executable file)

Entry point 0x81b8

There are 5 program headers, starting at offset 52

Program Headers:

  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align

  PHDR           0x000034 0x00008034 0x00008034 0x000a0 0x000a0 R   0x4

  INTERP         0x0000d4 0x000080d4 0x000080d4 0x00013 0x00013 R   0x1

      [Requesting program interpreter: /usr/lib/libc.so.1]

  LOAD           0x000000 0x00008000 0x00008000 0x00208 0x00208 R E 0x1000

  LOAD           0x000208 0x00009208 0x00009208 0x000cc 0x000cc RW  0x1000

  DYNAMIC        0x000208 0x00009208 0x00009208 0x000a0 0x000a0 RW  0x4

Section to Segment mapping:

  Segment Sections...

   00    

   01     .interp

   02     .interp .dynsym .dynstr .hash .gnu.version .gnu.version_r .rel.plt .plt .text

   03     .dynamic .data .got

   04     .dynamic

The line Requesting program interpreter shows which ELF interpreter the system tries to use. On this system /usr/lib/libc.so.1 does not exist, which is why executing the program returns "File not found".

However, on a Linux system for example, the standard ELF interpreter is not libc but ld.

The solution

Define the system dynamic linker as the ELF interpreter using the --dynamic-linker directive when linking the program.

When linking programs for Linux ARM systems :

armv7a-hardfloat-linux-gnueabi-ld.gold --hash-style=sysv --dynamic-linker=/lib/ld-linux-armhf.so.3 -o test test.o -lc

When linking programs for Android ARM systems :

armv7a-hardfloat-linux-gnueabi-ld.gold --hash-style=sysv --dynamic-linker=/system/bin/linker -o test test.o -lc