ref: 7856c56148a004d82cd49a8da232ee88ce5377c1
dir: /rt/start-freebsd.s/
.data
/* std._environment : byte[:][:] */
.globl sys$__environment
sys$__environment:
.envbase:
.quad 0 /* env size */
.envlen:
.quad 0 /* env ptr */
.globl sys$__cenvp
sys$__cenvp:
.quad 0
.text
/*
* The entry point for the whole program.
* This is called by the OS. In order, it:
* - Sets up all argc entries as slices
* - Sets up all envp entries as slices
* - Converts argc/argv to a slice
* - Stashes envp in std._environment
* - Stashes a raw envp copy in __cenvp (for syscalls to use)
* - Calls main()
*/
.globl _start
_start:
/* stack allocate sizeof(byte[:])*(argc + len(envp)) */
movq (%rdi),%rax
leaq 16(%rdi,%rax,8), %rbx /* argp = argv + 8*argc + 8 */
call count
addq %r9,%rax
imulq $16,%rax
subq %rax,%rsp
movq %rsp, %rdx /* saved args[:] */
/* convert envp to byte[:][:] for std._environment */
movq (%rdi),%rax
leaq 16(%rdi,%rax,8), %rbx /* envp = argv + 8*argc + 8 */
/* store envp for some syscalls to use without spurious conversion. */
movq %rbx,sys$__cenvp(%rip)
movq %r9,%rax
movq %rsp, %rcx
movq %r9,.envlen
movq %rdx,.envbase
call cvt
movq %rcx,%rdx
/* convert argc, argv to byte[:][:] for args. */
movq (%rdi), %rax /* argc */
leaq 8(%rdi), %rbx /* argv */
movq (%rdi), %rsi /* saved argc */
call cvt
pushq %rsi
pushq %rdx
/* call pre-main initializers */
call __init__
/* enter the main program */
call main
/* exit(0) */
xorq %rdi,%rdi
movq $1,%rax
syscall