PIE support for x86_64 (untested)

crt/x86_64/Scrt1.s

+/* Written 2011 Nicholas J. Kain, released as Public Domain */
+.weak _init
+.weak _fini
+.text
+.global _start
+_start:
+	xor %rbp,%rbp   /* rbp:undefined -> mark as zero 0 (ABI) */
+	mov %rdx,%r9    /* 6th arg: ptr to register with atexit() */
+	pop %rsi        /* 2nd arg: argc */
+	mov %rsp,%rdx   /* 3rd arg: argv */
+	andq $-16,%rsp  /* align stack pointer */
+	push %rax       /* 8th arg: glibc ABI compatible */
+	push %rsp       /* 7th arg: glibc ABI compatible */
+	lea _fini(%rip),%r8           /* 5th arg: fini/dtors function */
+	lea _init(%rip),%rcx          /* 4th arg: init/ctors function */
+	mov main@GOTPCREL(%rip),%rdi  /* 1st arg: application entry ip */
+	call __libc_start_main@PLT    /* musl init will run the program */
+1:	jmp 1b