Assembly

Common Functions and Code written in Assembly Language

• Intel(x86-32)
• ATT&T
• MIPS

Compiling x86 on Mac OSX and FreeBSD

Steps:

• nasm -o hello.tmp -f macho hello.s
• ld -arch i386 -macosx_version_min 10.6 -no_pie -e _main -o hello.o hello.tmp
• ./hello.o

One-Liner:

• nasm -o hello.tmp -f macho hello.s && ld -arch i386 -macosx_version_min 10.6 -no_pie -e _main -o hello.o hello.tmp && ./hello.o

Important:

Note: I use .tmp in order to go from (.s) - assembly -> (.tmp) - temporary -> (.o) - binary

Note: I also use "&&" in order to stop execution if anything goes wrong

For nasm:

• -o hello.tmp - outfile
• -f macho - specify format
  • Linux - elf or elf64
  • Mac OSX - macho

For ld:

• -arch i386 - specify architecture (32 bit assembly)
• -macosx_version_min 10.6 (Mac OSX - complains about default specification)
• -no_pie (Mac OSX - removes ld warning)
• -e main - specify main symbol name (Mac OSX - default is start)
• -o hello.o - outfile

For Shell:

• ./hello.o - execution

Compilation Issues:

Mac OSX

"ld: warning: PIE disabled. Absolute addressing (perhaps -mdynamic-no-pic) not allowed in code signed PIE, but used in _start from hello.o. To fix this warning, don't compile with -mdynamic-no-pic or link with -Wl,-no_pie"

• Add the "-no_pie" option to "ld" when linking

"ld: warning: -macosx_version_min not specified, assuming 10.6"

• Add the "-macosx_version_min 10.6" option to "ld" when linking

Other

"ld: warning: option -m is obsolete and being ignored"

• Older option

"ld: warning: option -s is obsolete and being ignored"

• Older option