From 9695ea005d4af93dcd60f74f10fd3c54499a182f Mon Sep 17 00:00:00 2001
From: Nicholas Noll <nbnoll@eml.cc>
Date: Thu, 11 Nov 2021 16:31:58 -0800
Subject: chore: split up base library into individual files for smaller
 binaries

---
 sys/base/coro/unix_x64.s | 113 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)
 create mode 100644 sys/base/coro/unix_x64.s

(limited to 'sys/base/coro/unix_x64.s')

diff --git a/sys/base/coro/unix_x64.s b/sys/base/coro/unix_x64.s
new file mode 100644
index 0000000..d7de2a2
--- /dev/null
+++ b/sys/base/coro/unix_x64.s
@@ -0,0 +1,113 @@
+; Nicholas Noll 2019
+;
+; ===================================================================
+%use altreg
+
+    bits 64
+    default rel
+    global _newcoro
+    global _coroyield
+
+; ===================================================================
+    section .text
+; -------------------------------------------------------------------
+
+%assign L.coro  -8
+%assign L.func  -16
+
+coroinit:
+    mov     R7, [RBP + L.coro]
+    mov     R6, R0 
+    call    [RBP + L.func]
+
+rerun:
+    mov     R7, [RBP + L.coro]
+    mov     R6, R0
+    call    _coroyield
+    jmp     rerun
+
+; -------------------------------------------------------------------
+; # Register Mapping
+; 
+; R0   R1   R2   R3   R4   R5   R6   R7   R8  ...
+; RAX  RCX  RDX  RBX  RSP  RBP  RSI  RDI  R8  ...
+; 
+; # Sys V calling convention
+; func(R7, R6, R2, R1, R8, R9, Z0-7): R0
+;
+; # Stack layout of an in-flight coro
+; *coro
+; *func
+; *bp (base pointer of stack)
+; ....... STACK .........
+; Saved Clobbers
+;
+; ###
+; Stack layout of an init coro
+; Stores the func pointer to init 
+; Stores the clobber registers.
+;
+; L.coro        [8] 
+; L.func        [7]
+; coroinit      [6]
+; RBP           [5]
+; R3            [4]
+; R12           [3]
+; R13           [2]
+; R14           [1]
+; R15           [0]
+
+%define WORDSZ 8
+%define NSAVES 9 
+
+; coro *coro·new(co *coro, fn func, bp *stack)
+_newcoro:
+    lea     R0, [coroinit]              ; Store address of init function
+    lea     R1, [R2 - NSAVES*WORDSZ]    ; Store offset address of stack
+    
+    mov     [R1 + 8*WORDSZ], R7         ; Store context pointer
+    mov     [R1 + 7*WORDSZ], R6         ; Store function pointer
+    mov     [R1 + 6*WORDSZ], R0         ; Store initializer pointer
+    mov     [R1 + 5*WORDSZ], R2         ; Store stack base pointer
+
+    xor     R0, R0
+
+    ; Start of mutable stack
+    ; Blank out the clobbers
+    mov     [R1 + 4*WORDSZ], R0 ; R3
+    mov     [R1 + 3*WORDSZ], R0 ; R12
+    mov     [R1 + 2*WORDSZ], R0 ; R13
+    mov     [R1 + 1*WORDSZ], R0 ; R14
+    mov     [R1 + 0*WORDSZ], R0 ; R15
+
+    mov     [R7], R1
+    ret
+
+; Saves register state
+%macro pushclobs 0
+    push     RBP
+    push     R3
+    push     R12
+    push     R13
+    push     R14
+    push     R15
+%endmacro
+
+; Restores register state
+%macro popclobs 0
+    pop      R15
+    pop      R14
+    pop      R13
+    pop      R12
+    pop      R3
+    pop      RBP
+%endmacro
+
+; uintptr coro.yield(co *coro, data uintptr)
+_coroyield:
+    pushclobs
+    mov     R0, R6      ; Move return value into return register.
+    xchg    RSP, [R7]   ; Atomically swap the stack pointer with the yieldee. 
+    popclobs
+
+    ret
-- 
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