From 991f1167df58616f4275c290fd0aa14baf7861f8 Mon Sep 17 00:00:00 2001
From: Ian Moffett <ian@osmora.org>
Date: Sun, 10 Mar 2024 19:55:30 -0400
Subject: kernel/amd64: trap: Add stack-segment fault ISR

Signed-off-by: Ian Moffett <ian@osmora.org>
---
 sys/arch/amd64/amd64/machdep.c |  1 +
 sys/arch/amd64/amd64/trap.S    | 10 ++++++++++
 sys/arch/amd64/amd64/trap.c    | 10 ++++++++--
 sys/include/arch/amd64/trap.h  |  2 ++
 4 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/sys/arch/amd64/amd64/machdep.c b/sys/arch/amd64/amd64/machdep.c
index 6342aab..e5fe83e 100644
--- a/sys/arch/amd64/amd64/machdep.c
+++ b/sys/arch/amd64/amd64/machdep.c
@@ -78,6 +78,7 @@ interrupts_init(void)
     idt_set_desc(0x8, IDT_TRAP_GATE_FLAGS, ISR(double_fault), 0);
     idt_set_desc(0xA, IDT_TRAP_GATE_FLAGS, ISR(invl_tss), 0);
     idt_set_desc(0xB, IDT_TRAP_GATE_FLAGS, ISR(segnp), 0);
+    idt_set_desc(0xC, IDT_TRAP_GATE_FLAGS, ISR(ss_fault), 0);
     idt_set_desc(0xD, IDT_TRAP_GATE_FLAGS, ISR(general_prot), 0);
     idt_set_desc(0xE, IDT_TRAP_GATE_FLAGS, ISR(page_fault), 0);
     idt_load();
diff --git a/sys/arch/amd64/amd64/trap.S b/sys/arch/amd64/amd64/trap.S
index 5a77955..66dd2a9 100644
--- a/sys/arch/amd64/amd64/trap.S
+++ b/sys/arch/amd64/amd64/trap.S
@@ -144,3 +144,13 @@ nmi:
     /* TODO */
     cli
     hlt
+
+.globl ss_fault
+ss_fault:
+    push_trapframe_ec $TRAP_SS
+
+    handle_trap
+
+    /* TODO */
+    cli
+    hlt
diff --git a/sys/arch/amd64/amd64/trap.c b/sys/arch/amd64/amd64/trap.c
index b73048d..c1cff56 100644
--- a/sys/arch/amd64/amd64/trap.c
+++ b/sys/arch/amd64/amd64/trap.c
@@ -44,7 +44,8 @@ static const char *trap_type[] = {
     [TRAP_SEGNP]        = "segment not present",
     [TRAP_PROTFLT]      = "general protection",
     [TRAP_PAGEFLT]      = "page fault",
-    [TRAP_NMI]          = "non-maskable interrupt"
+    [TRAP_NMI]          = "non-maskable interrupt",
+    [TRAP_SS]           = "stack-segment fault"
 };
 
 static const int TRAP_COUNT = __ARRAY_COUNT(trap_type);
@@ -54,12 +55,17 @@ dbg_errcode(struct trapframe *tf)
 {
     uint64_t ec = tf->error_code;
 
-    if (tf->trapno == TRAP_PAGEFLT) {
+    switch (tf->trapno) {
+    case TRAP_PAGEFLT:
         kprintf("bits (pwui): %c%c%c%c\n",
                 __TEST(ec, __BIT(0)) ? 'p' : '-',
                 __TEST(ec, __BIT(1)) ? 'w' : '-',
                 __TEST(ec, __BIT(2)) ? 'u' : '-',
                 __TEST(ec, __BIT(4)) ? 'i' : '-');
+        break;
+    case TRAP_SS:
+        kprintf("ss: 0x%x\n", ec);
+        break;
     }
 }
 
diff --git a/sys/include/arch/amd64/trap.h b/sys/include/arch/amd64/trap.h
index 1019999..c75fa28 100644
--- a/sys/include/arch/amd64/trap.h
+++ b/sys/include/arch/amd64/trap.h
@@ -47,6 +47,7 @@
 #define TRAP_PROTFLT        9       /* General protection */
 #define TRAP_PAGEFLT        10      /* Page fault */
 #define TRAP_NMI            11      /* Non-maskable interrupt */
+#define TRAP_SS             12      /* Stack-segment fault */
 
 /* Trap is coming from user mode */
 #define TRAP_USER           0x100
@@ -65,6 +66,7 @@ void segnp(void *sf);
 void general_prot(void *sf);
 void page_fault(void *sf);
 void nmi(void *sf);
+void ss_fault(void *sf);
 void trap_handler(struct trapframe *tf);
 #else
 .macro handle_trap
-- 
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