thermosphere: start exception handling

thermosphere/linker.ld

@@ -135,9 +135,11 @@ SECTIONS
         __end__ = ABSOLUTE(.);
     } >main
 
+    . = ALIGN(0x1000);
     __end__ = ABSOLUTE(.) ;
 
-    __stacks_top__ = ABSOLUTE(. + 0x1000);
+    __stacks_top__       = ABSOLUTE(. + 0x2000);
+    __excep_stacks_top__ = ABSOLUTE(. + 0x4000); /* Note: potentially overwrites warmboot firmware. */
 
     . = ALIGN(8);
 

thermosphere/src/exception_vectors.s

@@ -51,7 +51,49 @@
 .endm
 
 .macro save_all_regs
-    sub     sp, sp, #0x110
+    stp     x30, xzr, [sp, #-0x130]
+    bl      _save_all_regs
+.endm
+
+.macro pivot_stack_for_crash
+    // Ditch sp_el0 & elr_el1
+    // We don't use E2H so that's fine.
+    msr     elr_el1, x0
+    mov     x0, sp
+    msr     sp_el0, x0      // save stack pointer for the crash
+    bic     x0, x0, #0xFF
+    bic     x0, x0, #0x700
+    add     x0, x0, #0x1000
+    add     x0, x0, #0x800
+    mov     sp, x0
+    mrs     x0, elr_el1
+.endm
+
+/* Actual Vectors for Thermosphere. */
+.global thermosphere_vectors
+vector_base thermosphere_vectors
+
+/* Current EL, SP0 */
+/* Those are unused by us, except on same-EL double-faults. */
+.global unknown_exception
+unknown_exception:
+vector_entry synch_sp0
+    pivot_stack_for_crash
+    mov     x0, x30
+    adr     x1, thermosphere_vectors + 4
+    sub     x0, x0, x1
+    bl      handleUnknownException
+    b       .
+    check_vector_size synch_sp0
+
+vector_entry irq_sp0
+    bl      unknown_exception
+    .endfunc
+    .cfi_endproc
+    /* To save space, insert in an unused vector segment. */
+    _save_all_regs:
+
+    sub     sp, sp, #0x120
     stp     x0, x1, [sp, #0x00]
     stp     x2, x3, [sp, #0x10]
     stp     x4, x5, [sp, #0x20]
@@ -68,100 +110,35 @@
     stp     x26, x27, [sp, #0xD0]
     stp     x28, x29, [sp, #0xE0]
 
+    mov     x29, x30
+    ldp     x30, xzr, [sp, #-0x10] // See save_all_regs macro
+
     mrs     x20, sp_el1
-    mrs     x21, elr_el2
+    mrs     x21, sp_el0
-    mrs     x22, spsr_el2
+    mrs     x22, elr_el2
+    mrs     x23, spsr_el2
 
     stp     x30, x20, [sp, #0xF0]
     stp     x21, x22, [sp, #0x100]
-.endm
+    stp     x23, xzr, [sp, #0x110]
 
-/* Actual Vectors for Exosphere. */
+    mov     x30, x29
-.global exosphere_vectors
+    ret
-vector_base exosphere_vectors
-
-/* Current EL, SP0 */
-.global unknown_exception
-unknown_exception:
-vector_entry synch_sp0
-    b .
-    check_vector_size synch_sp0
-
-vector_entry irq_sp0
-    b unknown_exception
-    check_vector_size irq_sp0
 
 vector_entry fiq_sp0
-    b unknown_exception
+    bl      unknown_exception
-    check_vector_size fiq_sp0
-
-vector_entry serror_sp0
-    b unknown_exception
-    check_vector_size serror_sp0
-
-/* Current EL, SPx */
-vector_entry synch_spx
-    b unknown_exception
-    check_vector_size synch_spx
-
-vector_entry irq_spx
-    b unknown_exception
-    check_vector_size irq_spx
-
-vector_entry fiq_spx
-    b unknown_exception
-    check_vector_size fiq_spx
-
-vector_entry serror_spx
-    b unknown_exception
-    check_vector_size serror_spx
-    
-/* Lower EL, A64 */
-vector_entry synch_a64
-    save_all_regs
-
-    mov     x0, sp
-    mrs     x1, esr_el2
-
-    bl      . // FIXME!
-
-    b       _restore_all_regs
-    check_vector_size synch_a64
-
-vector_entry irq_a64
-    b unknown_exception
-    check_vector_size irq_a64
-
-vector_entry fiq_a64
-    b unknown_exception
-    check_vector_size fiq_a64
-
-vector_entry serror_a64
-    b unknown_exception
-    check_vector_size serror_a64
-
-
-/* Lower EL, A32 */
-vector_entry synch_a32
-    b unknown_exception
-    check_vector_size synch_a32
-
-vector_entry irq_a32
-    b unknown_exception
-    check_vector_size irq_a32
-
-vector_entry fiq_a32
-    b fiq_a64
     .endfunc
     .cfi_endproc
     /* To save space, insert in an unused vector segment. */
     _restore_all_regs:
     ldp     x30, x20, [sp, #0xF0]
     ldp     x21, x22, [sp, #0x100]
+    ldp     x23, xzr, [sp, #0x110]
 
     msr     sp_el1, x20
-    msr     elr_el2, x21
+    msr     sp_el0, x21
-    msr     spsr_el2, x22
+    msr     elr_el2, x22
+    msr     spsr_el2, x23
 
     ldp     x0, x1, [sp, #0x00]
     ldp     x2, x3, [sp, #0x10]
@@ -179,9 +156,77 @@ _restore_all_regs:
     ldp     x26, x27, [sp, #0xD0]
     ldp     x28, x29, [sp, #0xE0]
 
-    add     sp, sp, #0x110
+    add     sp, sp, #0x210
     eret
 
+vector_entry serror_sp0
+    bl      unknown_exception
+    check_vector_size serror_sp0
+
+/* Current EL, SPx */
+vector_entry synch_spx
+    /* Only crashes go through there! */
+    pivot_stack_for_crash
+
+    save_all_regs
+
+    mov     x0, sp
+    mrs     x1, esr_el2
+
+    bl      handleSameElSyncException
+    b       .
+    check_vector_size synch_spx
+
+vector_entry irq_spx
+    bl      unknown_exception
+    check_vector_size irq_spx
+
+vector_entry fiq_spx
+    bl      unknown_exception
+    check_vector_size fiq_spx
+
+vector_entry serror_spx
+    bl      unknown_exception
+    check_vector_size serror_spx
+
+/* Lower EL, A64 */
+vector_entry synch_a64
+    save_all_regs
+
+    mov     x0, sp
+    mrs     x1, esr_el2
+
+    bl      handleLowerElSyncException
+
+    b       _restore_all_regs
+    check_vector_size synch_a64
+
+vector_entry irq_a64
+    bl      unknown_exception
+    check_vector_size irq_a64
+
+vector_entry fiq_a64
+    bl      unknown_exception
+    check_vector_size fiq_a64
+
+vector_entry serror_a64
+    bl      unknown_exception
+    check_vector_size serror_a64
+
+
+/* Lower EL, A32 */
+vector_entry synch_a32
+    bl      unknown_exception
+    check_vector_size synch_a32
+
+vector_entry irq_a32
+    bl      unknown_exception
+    check_vector_size irq_a32
+
+vector_entry fiq_a32
+    b       fiq_a64
+    check_vector_size fiq_a32
+
 vector_entry serror_a32
-    b unknown_exception
+    bl      unknown_exception
     check_vector_size serror_a32

thermosphere/src/exceptions.c

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2019 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "exceptions.h"
+#include "log.h"
+
+static void dumpStackFrame(const ExceptionStackFrame *frame, bool sameEl)
+{
+#ifndef NDEBUG
+    for (u32 i = 0; i < 30; i += 2) {
+        serialLog("x%d\t\t%08lx\t\tx%d\t\t%08lx\r\n", i, frame->x[i], i + 1, frame->x[i + 1]);
+    }
+
+    serialLog("x30\t\t%08lx\r\n\r\n", frame->x[30]);
+    serialLog("elr_el2\t\t%08lx\r\n", frame->elr_el2);
+    serialLog("spsr_el2\t%08lx\r\n", frame->spsr_el2);
+    if (sameEl) {
+        serialLog("sp_el2\t\t%08lx\r\n", frame->sp_el2);
+    } else {
+        serialLog("sp_el0\t\t%08lx\r\n", frame->sp_el0);
+    }
+    serialLog("sp_el1\t\t%08lx\r\n", frame->sp_el1);
+#endif
+}
+
+void handleLowerElSyncException(ExceptionStackFrame *frame, u32 esr)
+{
+    serialLog("Lower EL sync exception, ESR = 0x%08lx\r\n", esr);
+    dumpStackFrame(frame, false);
+}
+
+void handleSameElSyncException(ExceptionStackFrame *frame, u32 esr)
+{
+    serialLog("Same EL sync exception, ESR = 0x%08lx\r\n", esr);
+    dumpStackFrame(frame, true);
+}
+
+void handleUnknownException(u32 offset)
+{
+    serialLog("Unknown exception! (offset 0x%03lx)\r\n", offset);
+}

thermosphere/src/exceptions.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2019 Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+#include "utils.h"
+
+typedef struct ExceptionStackFrame {
+    u64 x[31]; // x0 .. x30
+    u64 sp_el1;
+    union {
+        u64 sp_el2;
+        u64 sp_el0;
+    };
+    u64 elr_el2;
+    u64 spsr_el2;
+} ExceptionStackFrame;

thermosphere/src/main.c

@@ -8,5 +8,6 @@ int main(void)
 
     //uart_send(UART_C, "0123\n", 3);
     serialLog("Hello from Thermosphere!\r\n");
+    __builtin_trap();
     return 0;
 }

thermosphere/src/start.s

@@ -32,8 +32,9 @@ g_kernelEntrypoint:
     .quad   0
 
 start:
-    // Disable interrupts
+    // Disable interrupts, select sp_el2
     msr     daifset, 0b1111
+    msr     spsel, #1
 
     // Save arg, load entrypoint & spsr
     mov     x19, x0

thermosphere/tegra.mem

@@ -1,5 +1,5 @@
 MEMORY
 {
     NULL  : ORIGIN = 0,           LENGTH = 0x1000
-    main  : ORIGIN = 0x80000000,  LENGTH = 0xD000 - 0x1000 /* 0x1000 for stacks. */
+    main  : ORIGIN = 0x80000000,  LENGTH = 0xD000 - 0x2000 /* 0x2000 for stacks. */
 }