From 8bfb0c8da5b224ebfd4118aad94a68a4c240e344 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Sun, 17 Dec 2023 20:24:15 -0500
Subject: kernel/amd64: trap: Fix stack issues

This fixes a bug relating to a lack of error code (pushed by hardware)
misaligning the stack.

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/arch/amd64/trap.S             | 18 +++++----------
 sys/include/arch/amd64/frameasm.h | 46 ++++++++++++++++++++++++++-------------
 2 files changed, 37 insertions(+), 27 deletions(-)

diff --git a/sys/arch/amd64/trap.S b/sys/arch/amd64/trap.S
index 46e36bb..9dc1f6a 100644
--- a/sys/arch/amd64/trap.S
+++ b/sys/arch/amd64/trap.S
@@ -37,8 +37,7 @@ __KERNEL_META "$Hyra$: trap.S, Ian Marco Moffett, \
 .text
 .globl breakpoint_handler
 breakpoint_handler:
-    push $0
-    push_trapframe $TRAP_BREAKPOINT
+    push_trapframe_ec $TRAP_BREAKPOINT
 
     handle_trap
 
@@ -48,8 +47,7 @@ breakpoint_handler:
 
 .globl arith_err
 arith_err:
-    push $0
-    push_trapframe $TRAP_ARITH_ERR
+    push_trapframe_ec $TRAP_ARITH_ERR
 
     handle_trap
 
@@ -59,8 +57,7 @@ arith_err:
 
 .globl overflow
 overflow:
-    push $0
-    push_trapframe $TRAP_OVERFLOW
+    push_trapframe_ec $TRAP_OVERFLOW
 
     handle_trap
 
@@ -70,8 +67,7 @@ overflow:
 
 .globl bound_range
 bound_range:
-    push $0
-    push_trapframe $TRAP_BOUND_RANGE
+    push_trapframe_ec $TRAP_BOUND_RANGE
 
     handle_trap
 
@@ -81,8 +77,7 @@ bound_range:
 
 .globl invl_op
 invl_op:
-    push $0
-    push_trapframe $TRAP_INVLOP
+    push_trapframe_ec $TRAP_INVLOP
 
     handle_trap
 
@@ -142,8 +137,7 @@ page_fault:
 
 .globl nmi
 nmi:
-    push $0
-    push_trapframe $TRAP_NMI
+    push_trapframe_ec $TRAP_NMI
 
     handle_trap
 
diff --git a/sys/include/arch/amd64/frameasm.h b/sys/include/arch/amd64/frameasm.h
index bf02d00..2d251e7 100644
--- a/sys/include/arch/amd64/frameasm.h
+++ b/sys/include/arch/amd64/frameasm.h
@@ -31,21 +31,13 @@
 #define _AMD64_FRAMEASM_H_
 
 /*
- * XXX: Before this macro is invoked,
- *      you should determine if an error
- *      code will be present already on the
- *      stack. If not, push a null qword as
- *      padding (e.g push $0).
- *
- *      There *must* be a value used
- *      as an error code whether that be
- *      a real error code or just padding.
- *
- *      Failing to do so will result in
- *      undefined behaviour.
+ * If the interrupt has an error code, this macro shall
+ * be used to create the trapframe.
  *
+ * XXX: A trapframe created with this must be popped with
+ *      pop_trapframe_ec
  */
-.macro push_trapframe trapno
+.macro push_trapframe_ec trapno
     push %r15
     push %r14
     push %r13
@@ -64,7 +56,11 @@
     push \trapno
 .endm
 
-.macro pop_trapframe
+/*
+ * If the interrupt has an error code, this macro shall
+ * be used to cleanup the trapframe.
+ */
+.macro pop_trapframe_ec
     add $8, %rsp        /* Trapno */
     pop %rax
     pop %rcx
@@ -80,7 +76,27 @@
     pop %r13
     pop %r14
     pop %r15
+.endm
+
+/*
+ * If the interrupt has no error code, this macro
+ * shall be used to create the trapframe.
+ *
+ * XXX: A trapframe created with this must be popped
+ *      with pop_trapframe
+ */
+.macro push_trapframe trapno
+    push $0
+    push_trapframe_ec \trapno
+.endm
+
+
+/*
+ * If the interrupt has no error code, this macro shall
+ * be used to cleanup the trapframe.
+ */
+.macro pop_trapframe
+    pop_trapframe_ec
     add $8, %rsp        /* Pop error code */
-    iretq
 .endm
 #endif  /* !_AMD64_FRAMEASM_H_ */
-- 
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