ref: b0b7605bb866cccae5ea15cb9b8b18524ecc84d6
dir: /lib/sys/syscall+linux-x64.s/
.globl sys$syscall
sys$syscall:
/*
hack: We load 6 args regardless of
how many we actually have. This may
load junk values, but if the syscall
doesn't use them, it's going to be
harmless.
*/
movq %rdi,%rax
/* 8(%rsp): hidden type arg */
movq 16(%rsp),%rdi
movq 24(%rsp),%rsi
movq 32(%rsp),%rdx
movq 40(%rsp),%r10
movq 48(%rsp),%r8
movq 56(%rsp),%r9
syscall
ret
/* clone(flags, stack, ptid, tls, ctid, regs) */
.globl sys$fnclone
sys$fnclone:
pushq %r15
/* %rsp is modified by clone(), so it's saved here */
movq 16(%rsp),%r15
/*
%rdi: flags, %rsi: stack, %rdx: ptid,
%rcx: tls, %r8: ctid, %r9: regs
*/
movq $56,%rax /* syscall num */
movq %rcx,%r10 /* tls */
syscall
cmpq $0,%rax
jb .doneparent
/* fn() */
testl %eax,%eax
jnz .doneparent
call *%r15
/* exit(0) */
movq $60, %rax /* exit */
movq $0, %rdi /* arg: 0 */
syscall
.doneparent:
popq %r15
ret