3 files changed, 47 insertions, 0 deletions
diff --git a/sys/rt/amd64/crt1.s b/sys/rt/amd64/crt1.s
new file mode 100644
index 0000000..aaad0ba
--- /dev/null
+++ b/sys/rt/amd64/crt1.s
@@ -0,0 +1,21 @@
+global  _start
+
+; NOTE: assumes program loader has put argc, argv, envc, envp on stack
+section .text
+_start:
+    xor rbp,rbp    ; base pointer undefined: set to 0
+    mov r9,rdx     ; 6th arg: function to register with atexit()
+    pop rsi        ; 2nd arg: argc
+    mov rdx,rsp    ; 3rd arg: argv
+    and rsp,$-16   ; align stack pointer to 16 bytes
+    mov $_fini,r8  ; 5th arg: fini
+    mov $_init,rcx ; 4th arg: init
+    mov $main,rdi  ; 1st arg: main
+
+    call rt·boot   ; int boot(
+                   ;       int(*main)(int,char*[],char*[]),
+                   ;       int argc,
+                   ;       char *argv[],
+                   ;       init, fini, atexit);
+
+.loop: jmp .loop  ; should never reach...
diff --git a/sys/rt/amd64/crti.s b/sys/rt/amd64/crti.s
new file mode 100644
index 0000000..eeba8b1
--- /dev/null
+++ b/sys/rt/amd64/crti.s
@@ -0,0 +1,17 @@
+global _init
+global _fini
+
+section .init
+_init:
+    ; call pushes an 8 byte return address on the stack
+    ; 64 bit ABI requires stack to be aligned to 16 bytes
+    ; we realign with another 8 byte address
+    push rbp
+    mov  rbp, rsp
+    ;; compiler inserts the rest here
+
+section .fini
+_fini:
+    push rbp ; see above
+    mov  rbp, rsp
+    ;; compiler inserts the rest here
diff --git a/sys/rt/amd64/crtn.s b/sys/rt/amd64/crtn.s
new file mode 100644
index 0000000..45d1a29
--- /dev/null
+++ b/sys/rt/amd64/crtn.s
@@ -0,0 +1,9 @@
+section .init
+    ;; compiler inserts here
+    pop rbp ;; undo our push
+    ret
+
+section .fini
+    ;; compiler inserts here
+    pop rbp ;; undo our push
+    ret