From 4d89b8656ae7c0815b09699e4a6feaa9f209410e Mon Sep 17 00:00:00 2001
From: julianb0 <spectral@os-k.eu>
Date: Tue, 9 Jul 2019 20:02:36 +0200
Subject: [PATCH] it's a trap!

---
 ka/sys/intr/common.k | 22 +++++++++-------------
 vm/dv/CPUDEV         | 10 +++++-----
 2 files changed, 14 insertions(+), 18 deletions(-)

diff --git a/ka/sys/intr/common.k b/ka/sys/intr/common.k
index b0d059f..1c46a4c 100644
--- a/ka/sys/intr/common.k
+++ b/ka/sys/intr/common.k
@@ -2,23 +2,19 @@
 ; See the LICENSE file in the project root for more information.
 
 TrapHandlers.prolog:
-    sub rsp, rbp, 56
-    mov q[rbp-8], r10
-    mov q[rbp-16], r11
-    mov q[rbp-24], r12
-    mov q[rbp-32], r13
-    mov q[rbp-40], r14
-    mov q[rbp-48], r15
+    sub rsp, rbp, 32
+    mov q[rbp-8], r11
+    mov q[rbp-16], r12
+    mov q[rbp-24], r13
+    cmp q[rsp], r13
+    crash.z
 
     jmp rax ; go back
 
 TrapHandlers.epilog:
-    mov r10, q[rbp-8]
-    mov r11, q[rbp-16]
-    mov r12, q[rbp-24]
-    mov r13, q[rbp-32]
-    mov r14, q[rbp-40]
-    mov r15, q[rbp-48]
+    mov r11, q[rbp-8]
+    mov r12, q[rbp-16]
+    mov r13, q[rbp-24]
 
     mov ax0, r11
     call IDT.DoneHandling
diff --git a/vm/dv/CPUDEV b/vm/dv/CPUDEV
index 616ae8e..b312e4d 100644
--- a/vm/dv/CPUDEV
+++ b/vm/dv/CPUDEV
@@ -61,12 +61,12 @@ When called, a handler will receive the number of the E/I it is handling in R10,
 and its own RFRAME ID in R11. (in particular, if exception #25 happens and there are no
 handler for it, the handler #0 that will be called will receive '25' in R10, and '0' in R11).
 R11 is the value that must be passed to the 'initdone' iocall.
-The handler will also receive the previous RFRAME ID in R12, the previous RIP in R15 and the
-previous RPC in R14. R13's content is meaningful only to the processor.
+The handler will also receive the previous RFRAME ID in R12.
+R13 is also modified but its value is meaningful only to the processor.
 
-To return from an E/I, *after* having called 'idtdone', the handler must simply restore
-R10-R15's values to what they were when the handler started executing, and then use
-the 'IRET' instruction.
+To return from an E/I, *after* having called 'idtdone' (using the value originally in R11),
+the handler must simply restore R12's and R13's values to what they were when the handler
+started executing, and then use the 'IRET' instruction.
 
 Clearing the interrupt flag prevents (and queues) maskable hardware interrupts