kernel/aarch64: Add exception code + frame fixups

- Add handle_exception() as higher level logic to handle the exceptions
- Simplify frame.h
- Call C handler in vector.S
- Clean up stack after creating frame
- Add register dump on exception

Signed-off-by: Ian Moffett <ian@osmora.org>

5 files changed, 249 insertions, 85 deletions

diff --git a/sys/arch/aarch64/aarch64/exception.c b/sys/arch/aarch64/aarch64/exception.c
new file mode 100644
index 0000000..d6f1f97
--- /dev/null
+++ b/sys/arch/aarch64/aarch64/exception.c
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2023-2025 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <sys/syslog.h>
+#include <sys/param.h>
+#include <sys/cdefs.h>
+#include <machine/cdefs.h>
+#include <machine/exception.h>
+
+#define pr_trace(fmt, ...) kprintf("exception: " fmt, ##__VA_ARGS__)
+#define pr_error(...) pr_trace(__VA_ARGS__)
+
+static inline void
+log_esr_class(uint8_t class)
+{
+    switch (class) {
+    case EC_WF:
+        pr_error("trapped WF\n");
+        break;
+    case EC_MCRMRC:
+        pr_error("trapped MCR/MRC\n");
+        break;
+    case EC_MCRRC:
+        pr_trace("trapped MCRR/MRRC\n");
+        break;
+    case EC_LDCSTC:
+        pr_error("trapped LDC/STC\n");
+        break;
+    case EC_SVE:
+        pr_trace("trapped SVE/SIMD/FP operation\n");
+        break;
+    case EC_BRE:
+        pr_error("ibt: bad branch target\n");
+        break;
+    case EC_ILLX:
+        pr_error("illegal execution state\n");
+        break;
+    case EC_SVC64:
+        /* TODO */
+        pr_error("supervisor call (TODO)!!\n");
+        break;
+    case EC_PCALIGN:
+        pr_error("PC alignment fault\n");
+        break;
+    case EC_DABORT:
+    case EC_EDABORT:
+        pr_error("data abort\n");
+        break;
+    case EC_SPALIGN:
+        pr_error("SP alignment fault\n");
+        break;
+    case EC_SERR:
+        pr_error("system error\n");
+        break;
+    default:
+        pr_error("unknown exception\n");
+    }
+}
+
+static void
+regdump(struct trapframe *tf, uint64_t elr)
+{
+    kprintf(OMIT_TIMESTAMP
+        "X0=%p X1=%p X2=%p\n"
+        "X3=%p X4=%p X5=%p\n"
+        "X6=%p X7=%p X8=%p\n"
+        "X9=%p X10=%p X11=%p\n"
+        "X12=%p X13=%p X14=%p\n"
+        "X15=%p X16=%p X17=%p\n"
+        "X18=%p X19=%p X20=%p\n"
+        "X21=%p X22=%p X23=%p\n"
+        "X24=%p X25=%p X26=%p\n"
+        "X27=%p X28=%p X29=%p\n"
+        "X30=%p\n"
+        "ELR=%p\n",
+        tf->x0, tf->x1, tf->x2, tf->x3,
+        tf->x4, tf->x5, tf->x6, tf->x7,
+        tf->x8, tf->x9, tf->x10, tf->x11,
+        tf->x12, tf->x13, tf->x14, tf->x15,
+        tf->x16, tf->x17, tf->x18, tf->x19,
+        tf->x20, tf->x21, tf->x22, tf->x23,
+        tf->x24, tf->x25, tf->x26, tf->x27,
+        tf->x28, tf->x29, tf->x30, elr);
+}
+
+/*
+ * Handle an exception
+ *
+ * @esr: Copy of the Exception Syndrome Register
+ */
+void
+handle_exception(struct trapframe *tf)
+{
+    uint8_t class;
+
+    class = (tf->esr >> 26) & 0x3F;
+    log_esr_class(class);
+    regdump(tf, tf->elr);
+    for (;;) {
+        md_hlt();
+    }
+}
diff --git a/sys/arch/aarch64/aarch64/vector.S b/sys/arch/aarch64/aarch64/vector.S
index f38f24e..c8f77ca 100644
--- a/sys/arch/aarch64/aarch64/vector.S
+++ b/sys/arch/aarch64/aarch64/vector.S
@@ -36,54 +36,37 @@
     b \label
 .endm
 
-    .section .data
-error:
-    .ascii "got exception, halting\n\0"
-
     .text
 x_sync_elx:
-    PUSH_XFRAME(TRAPNO_XSYNC)
-    ldr x0, =error
-    bl kprintf
-    POP_XFRAME()
-1:
-    hlt #0
+    PUSH_XFRAME(TRAPNO_XSYNC)   // Synchronous: sp+top @ X0
+    bl handle_exception         // Handle the exception
+    POP_XFRAME()                // Pop the trapframe
+1:  hlt #0                      // TODO
     b 1b
 
 x_irq_elx:
-    PUSH_XFRAME(TRAPNO_XSYNC)
-    ldr x0, =error
-    bl kprintf
-    POP_XFRAME()
-1:
-    hlt #0
+    PUSH_XFRAME(TRAPNO_XIRQ)    // IRQ: sp+top @ X0
+    bl handle_exception         // Handle the exception
+    POP_XFRAME()                // Pop the trapframe
+1:  hlt #0                      // TODO
     b 1b
 
 x_fiq_elx:
-    PUSH_XFRAME(TRAPNO_XSYNC)
-    ldr x0, =error
-    bl kprintf
-    POP_XFRAME()
-1:
-    hlt #0
+    PUSH_XFRAME(TRAPNO_XFIQ)    // FIQ: sp+top @ X0
+    bl handle_exception         // Handle the exception
+    POP_XFRAME()                // Pop the trapframe
+1:  hlt #0
     b 1b
 
 x_serr_elx:
-    PUSH_XFRAME(TRAPNO_XSYNC)
-    ldr x0, =error
-    bl kprintf
-    POP_XFRAME()
-1:
-    hlt #0
+    PUSH_XFRAME(TRAPNO_XSERR)   // SERR: sp+top @ X0
+    bl handle_exception         // Handle the exception
+    POP_XFRAME()                // Pop the trapframe
+1:  hlt #0                      // TODO
     b 1b
 
 x_unimpl:
-    PUSH_XFRAME(TRAPNO_XSYNC)
-    ldr x0, =error
-    bl kprintf
-    POP_XFRAME()
-1:
-    hlt #0
+1:  hlt #0
     b 1b
 
     .align 11         // Table aligned @ 2 KiB
diff --git a/sys/include/arch/aarch64/exception.h b/sys/include/arch/aarch64/exception.h
new file mode 100644
index 0000000..9e89c81
--- /dev/null
+++ b/sys/include/arch/aarch64/exception.h
@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2023-2025 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _MACHINE_EXCEPTION_H_
+#define _MACHINE_EXCEPTION_H_
+
+#include <sys/types.h>
+#include <machine/frame.h>
+
+/* Exception class */
+#define EC_UNKNOWN  0x00    /* Unknown type */
+#define EC_WF       0x01    /* Trapped WF instruction */
+#define EC_MCRMRC   0x03    /* Trapped MCR/MRC */
+#define EC_MCRRC    0x04    /* Trapped MCRR/MRRC */
+#define EC_LDCSTC   0x06    /* Trapped LDC/STC */
+#define EC_SVE      0x07    /* Trapped SVE/SIMD/FP op */
+#define EC_BRE      0x0D    /* Branch target exception */
+#define EC_ILLX     0x0E    /* Illegal execution state */
+#define EC_SVC64    0x15    /* AARCH64 SVC */
+#define EC_PCALIGN  0x22    /* PC alignment fault */
+#define EC_DABORT   0x24    /* Data abort (w/o ELx change) */
+#define EC_EDABORT  0x25    /* Data abort (w/ ELx change) */
+#define EC_SPALIGN  0x26    /* SP alignment fault */
+#define EC_SERR     0x2F    /* System error (what the fuck!) */
+
+void handle_exception(struct trapframe *tf);
+
+#endif  /* !_MACHINE_EXCEPTION_H_ */
diff --git a/sys/include/arch/aarch64/frame.h b/sys/include/arch/aarch64/frame.h
index f14fa01..143f4d0 100644
--- a/sys/include/arch/aarch64/frame.h
+++ b/sys/include/arch/aarch64/frame.h
@@ -31,46 +31,11 @@
 #define _MACHINE_FRAME_H_
 
 #include <sys/types.h>
+#include <sys/cdefs.h>
 
 typedef uint64_t lreg_t;
 typedef uint64_t frament_t;
 
-/* General purpose registers */
-struct gpregs {
-    frament_t trapno;
-    lreg_t x0;
-    lreg_t x1;
-    lreg_t x2;
-    lreg_t x3;
-    lreg_t x4;
-    lreg_t x5;
-    lreg_t x6;
-    lreg_t x7;
-    lreg_t x8;
-    lreg_t x9;
-    lreg_t x10;
-    lreg_t x11;
-    lreg_t x12;
-    lreg_t x13;
-    lreg_t x14;
-    lreg_t x15;
-    lreg_t x16;
-    lreg_t x17;
-    lreg_t x18;
-    lreg_t x19;
-    lreg_t x20;
-    lreg_t x21;
-    lreg_t x22;
-    lreg_t x23;
-    lreg_t x24;
-    lreg_t x25;
-    lreg_t x26;
-    lreg_t x27;
-    lreg_t x28;
-    lreg_t x29;
-    lreg_t x30;
-};
-
 /* Stack regs */
 struct sregs {
     lreg_t sp_el0;
@@ -85,14 +50,41 @@ struct pstat {
     lreg_t spsr_el3;
 };
 
-struct trapframe {
-    struct gpregs gp;
-    struct sregs stack;
-    struct pstat status;
-    lreg_t elr_el1;
-    lreg_t elr_el2;
-    lreg_t elr_el3;
-    lreg_t pc;
+struct __aligned(16) trapframe {
+    lreg_t x30;
+    lreg_t x29;
+    lreg_t x28;
+    lreg_t x27;
+    lreg_t x26;
+    lreg_t x25;
+    lreg_t x24;
+    lreg_t x23;
+    lreg_t x22;
+    lreg_t x21;
+    lreg_t x20;
+    lreg_t x19;
+    lreg_t x18;
+    lreg_t x17;
+    lreg_t x16;
+    lreg_t x15;
+    lreg_t x14;
+    lreg_t x13;
+    lreg_t x12;
+    lreg_t x11;
+    lreg_t x10;
+    lreg_t x9;
+    lreg_t x8;
+    lreg_t x7;
+    lreg_t x6;
+    lreg_t x5;
+    lreg_t x4;
+    lreg_t x3;
+    lreg_t x2;
+    lreg_t x1;
+    lreg_t x0;
+    lreg_t elr;
+    lreg_t esr;
+    frament_t trapno;
 };
 
 #define TF_IP(TFP) ((TFP)->pc)
diff --git a/sys/include/arch/aarch64/frameasm.h b/sys/include/arch/aarch64/frameasm.h
index 5664ff5..ca7f81a 100644
--- a/sys/include/arch/aarch64/frameasm.h
+++ b/sys/include/arch/aarch64/frameasm.h
@@ -31,13 +31,14 @@
 #define _MACHINE_FRAMEASM_H_
 
 /* XXX: Must be 16-byte aligned!!! */
-#define XFRAME_STACK_SIZE (34 * 8)
+#define XFRAME_STACK_SIZE (38 * 8)
 
 /* Trap numbers */
-#define TRAPNO_XSYNC  #0     /* Synchronous */
-#define TRAPNO_XIRQ   #1     /* IRQ */
-#define TRAPNO_XFIQ   #2     /* FIQ */
-#define TRAPNO_XSERR  #3     /* System error */
+#define TRAPNO_UNKNOWN #0
+#define TRAPNO_XSYNC   #1     /* Synchronous */
+#define TRAPNO_XIRQ    #2     /* IRQ */
+#define TRAPNO_XFIQ    #3     /* FIQ */
+#define TRAPNO_XSERR   #4     /* System error */
 
 #define PUSH_XFRAME(TRAPNO)          \
     sub sp, sp, #XFRAME_STACK_SIZE ; \
@@ -57,11 +58,16 @@
     stp x4, x3, [sp, #(26 * 8)]    ; \
     stp x2, x1, [sp, #(28 * 8)]    ; \
     str x0, [sp, #(30 * 8)]        ; \
+                                   ; \
+    mrs x0, elr_el1                ; \
+    str x0, [sp, #(31 * 8)]        ; \
+    mrs x0, esr_el1                ; \
+    str x0, [sp, #(32 * 8)]        ; \
     mov x0, TRAPNO                 ; \
-    str x0, [sp, #(31 * 8)]
+    str x0, [sp, #(33 * 8)]        ; \
+    mov x0, sp
 
 #define POP_XFRAME()                  \
-    add sp, sp, #8                  ; \
     ldr x0, [sp, #(30 * 8)]         ; \
     ldp x2, x1, [sp, #(28 * 8)]     ; \
     ldp x4, x3, [sp, #(26 * 8)]     ; \
@@ -78,5 +84,6 @@
     ldp x26, x25, [sp, #(4 * 8)]    ; \
     ldp x28, x27, [sp, #(2 * 8)]    ; \
     ldp x30, x29, [sp, #(0 * 8)]    ; \
+    add sp, sp, #XFRAME_STACK_SIZE
 
 #endif  /* !_MACHINE_FRAMEASM_H_ */