From af1ce4b2e637ceb418ea72d51c49a3eee276a938 Mon Sep 17 00:00:00 2001
From: stefan <stefan@s00.xyz>
Date: Sat, 15 Apr 2023 05:02:02 +0000
Subject: added multiprocessor support

---
 sys/kern/entry.S | 28 ++++++++++++++++++++++------
 1 file changed, 22 insertions(+), 6 deletions(-)

(limited to 'sys/kern/entry.S')

diff --git a/sys/kern/entry.S b/sys/kern/entry.S
index 03ff76c..9bf72ea 100644
--- a/sys/kern/entry.S
+++ b/sys/kern/entry.S
@@ -1,8 +1,14 @@
 .section ".text.init"
 
+// entrypoint for boot hart(s). a0: hartid, a1: *fdt
 .globl _start
-_start:
-        /* disable interrupts and poging */ 
+
+
+// entrypoint for other harts. a0: hartid, a1: unused for now
+.global _mpentry 
+
+_start: 
+        /* disable interrupts and paging */ 
         csrw       satp, zero
         csrw       sie, zero
         csrw       sip, zero
@@ -12,7 +18,9 @@ _start:
         la         gp, __global_pointer$
         .option pop
 
-        /* setup stack */
+        /* setup stack. 
+	 * stack grows toward lower address so sp will mark end of frame.
+	 */
         addi       t0, a0, 1
         li         t1, PAGE_SIZE 
         la         sp, __stack_start
@@ -22,11 +30,11 @@ _start:
         /* setup thread pointer */ 
         mv        tp, a0
 
-        /* the label _boot_hart is shared between threads. only one hart will branch before it is no longer 0 */ 
+        /* the label _boot_hart is shared between threads. after the first atomic swap, all other harts will branch to mpentry */ 
         li         a2, 1
         lla        a3, _boot_hart
         amoswap.w  a3, a2, (a3)
-        bnez       a3,   2f
+        bnez       a3, _mpentry
 
         /* clear the bss section */  
         la         a2, __bss_start
@@ -39,9 +47,16 @@ _start:
         call       init
         j          _spin
 
+_mpentry:
+	/* satp = 0, sstatus.sie = 0, a0 = hartid, a1 = opaque	*/
+
+	call	 mpinit
+	/* shouldn't reach this point */
+	j 	_spin
+
 _spin:
 	wfi
-	j _spin
+	j 	_spin
 
 .section ".data"
 _boot_hart: 
@@ -51,3 +66,4 @@ _boot_hart:
 /* linker imports */
 .globl HEAP_START
 HEAP_START: .dword __heap_start
+
-- 
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