ptos/amd64+ke: Add bugcheck support

Signed-off-by: Chloe M <chloe@mensia.org>

service/ptos/arch/amd64/ke/bugcheck.S

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: AMD64 bugcheck wrapper
+ * Author:      Chloe M.
+ */
+
+    .text
+    .globl KeBugCheck
+KeBugCheck:
+    cli                 /* Disable interrupts */
+    cld                 /* Just in case */
+    mov $1, %rax        /* Prep the lock */
+    xchg %rax, MpLock   /* Acquire the lock */
+    or %rax, %rax       /* Are we another core? */
+    jnz .LockOut        /* Yes, lock out */
+
+    /*
+     * During most cases in which an interrupt occurs, the processor
+     * is to automatically switch to its own interrupt stack and during
+     * such cases it is guaranteed that the stack is safe. However, we still
+     * cannot trust the stack as we do not know if we are coming from an interrupt
+     * or not and thus need to update it to avoid dodgy states from worsening our
+     * problem... Whatever it is...
+     */
+    lea StackTop(%rip), %rsp
+
+    /* From here we can call the actual bugcheck handler */
+    call KiBugCheck
+.LockOut:
+    hlt
+    jmp .LockOut
+
+    .section .data
+MpLock: .quad 0
+
+/* Our bugcheck stack */
+Stack:  .fill 4096, 1, 0
+StackTop:

service/ptos/head/ke/bugcheck.h

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Bugcheck interface
+ * Author:      Chloe M.
+ */
+
+#ifndef _KE_BUGCHECK_H_
+#define _KE_BUGCHECK_H_ 1
+
+#include <ptdef.h>
+
+/*
+ * A list of reasons to why a bug check can happen
+ *
+ * @BUGCHECK_MISC:          Misc reason
+ * @BUGCHECK_OOM:           Out of memory during critical operation
+ * @BUGCHECK_IO_ERROR:      Fatal I/O error
+ * @BUGCHECK_UNBOUND_RESRC: Fatal unbound resource
+ * @BUGCHECK_EXCEPTION:     Fatal exception
+ */
+typedef enum {
+    BUGCHECK_MISC,
+    BUGCHECK_OOM,
+    BUGCHECK_IO_ERROR,
+    BUGCHECK_UNBOUND_RESRC,
+    BUGCHECK_EXCEPTION
+} BUGCHECK_REASON;
+
+/*
+ * Signal to the user that something has gone terribly wrong
+ * during system operation and that the machine needs to come to
+ * a screetching halt.
+ *
+ * @Reason: Broad reason of bugcheck
+ * @Fmt:    Format specifier
+ * @<...>:  Variadic arguments
+ */
+NO_RETURN VOID KeBugCheck(BUGCHECK_REASON Reason, const CHAR *Fmt, ...);
+
+#endif  /* !_KE_BUGCHECK_H_ */

service/ptos/ke/bugcheck.c

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: Bugcheck handler
+ * Author:      Chloe M.
+ */
+
+#include <ex/trace.h>
+#include <ke/bugcheck.h>
+#include <drivers/bootvid/fbio.h>
+#include <ptdef.h>
+
+/* Used to safely obtain bugcheck reason */
+#define BUGCHECK_REASON(REASON)         \
+    ((REASON) >= NELEM(ReasonTable))    \
+        ? "bad"                         \
+        : ReasonTable[(REASON)]
+
+/* Prints the bugcheck banner */
+#define BUGCHECK_BANNER()                                                    \
+    TRACE(                                                                   \
+        "\033[31;40m! ***** \033[37;40mBUGCHECK \033[31;40m***** !\033[0m\n" \
+    );
+
+/* Globals to reduce stack usage */
+static va_list Ap;
+static CHAR BugCheckBuf[256];
+static CHAR BugCheckMsg[] =
+    "Something went wrong during system operation and the machine has\n"
+    "been halted to prevent data loss.\n\n";
+
+/* Table of reason strings */
+static CHAR *ReasonTable[] = {
+    [BUGCHECK_MISC] = "misc reason",
+    [BUGCHECK_OOM]  = "out of memory",
+    [BUGCHECK_IO_ERROR] = "i/o error",
+    [BUGCHECK_UNBOUND_RESRC] = "unbounded resource",
+    [BUGCHECK_EXCEPTION] = "fatal exception"
+};
+
+VOID
+KiBugCheck(BUGCHECK_REASON Reason, const CHAR *Fmt, ...)
+{
+    /* Enable the console if we don't have one */
+    if (!BootVidConsEn()) {
+        BootVidInitCons(NULL);
+    }
+
+    va_start(Ap, Fmt);
+    VFmtPrintf(BugCheckBuf, sizeof(BugCheckBuf), Fmt, Ap);
+
+    BUGCHECK_BANNER();
+    TRACE("\033[37;40m");
+    TRACE(BugCheckMsg);
+    TRACE("\033[31;40mbugcheck: \033[37;40m%s", BugCheckBuf);
+    TRACE("\033[31;40mreason: \033[37;40m%s\n", BUGCHECK_REASON(Reason));
+    TRACE("\033[37;40m");
+}