7 files changed, 111 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
diff --git a/sys/rt/boot.c b/sys/rt/boot.c
new file mode 100644
index 0000000..197e861
--- /dev/null
+++ b/sys/rt/boot.c
@@ -0,0 +1,34 @@
+#include <rt.h>
+
+int
+rt·boot(
+    int  (*main)(int,char **,char **), int argc, char **argv,
+    int  (*init)(int, char **, char **), void (*fini)(void),
+    void (*exit)(void)
+)
+{
+    char **envp = argv+argc+1;
+    rt·environ = envp;
+
+    if(exit)
+        rt·context.exit = exit;
+
+    if(fini)
+        rt·context.fini = fini;
+
+    if(init){
+        rt·context.init = init;
+        init(argc, argv, envp);
+    }
+
+    /* XXX:
+     * we could call __libc_start_main of musl here:
+     * this would give us the normal C runtime along with ours
+     * which would allow seamless linking to other libraries
+     * or we can implement a compatibility layer
+     */
+    rt·exit(main(argc, argv, envp));
+
+    /* should never get here */
+    return 0;
+}
diff --git a/sys/rt/env.c b/sys/rt/env.c
new file mode 100644
index 0000000..ddd559d
--- /dev/null
+++ b/sys/rt/env.c
@@ -0,0 +1,3 @@
+#include <rt.h>
+
+char *rt·environ = 0;
diff --git a/sys/rt/exit.c b/sys/rt/exit.c
new file mode 100644
index 0000000..55a684a
--- /dev/null
+++ b/sys/rt/exit.c
@@ -0,0 +1,15 @@
+#include <rt.h>
+#include <sys.h>
+
+void
+rt·exit(int code)
+{
+    if(rt·context.fini)
+        rt·context.fini();
+    if(rt·context.exit)
+        rt·context.exit();
+
+    /* call exit syscalls here */
+
+    for(;;);
+}
diff --git a/sys/rt/include/rt.h b/sys/rt/include/rt.h
new file mode 100644
index 0000000..dd1598b
--- /dev/null
+++ b/sys/rt/include/rt.h
@@ -0,0 +1,12 @@
+#pragma once
+
+extern struct rt·context
+{
+    void (*init)(void);
+    void (*fini)(void);
+    void (*exit)(void);
+} rt·context;
+
+extern char **rt·environ;
+
+void rt·exit(int code);