[PATCH ARM v6 14/14] mini-os: arm: show registers, stack and exception vector on fault

[Thomas Leonard <talex5@gmail.com>]

Signed-off-by: Thomas Leonard <talex5@gmail.com>

---

Exit with SHUTDOWN_crash on BUG or fault (suggested by Ian Campbell).
---
 extras/mini-os/ARM-TODO.txt     |  1 -
 extras/mini-os/arch/arm/arm32.S | 75 ++++++++++++++++++++++++++++---
 extras/mini-os/arch/arm/panic.c | 98 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 166 insertions(+), 8 deletions(-)
 create mode 100644 extras/mini-os/arch/arm/panic.c

diff --git a/extras/mini-os/ARM-TODO.txt b/extras/mini-os/ARM-TODO.txt
index c85ee5b..27507cd 100644
--- a/extras/mini-os/ARM-TODO.txt
+++ b/extras/mini-os/ARM-TODO.txt
@@ -1,4 +1,3 @@
-* support abort exception handling ( and others )
 * gic request_irq implementation, currently all IRQs all hardcoded in gic irq handler.
 * bind_*
 * add multiple cpu support (?)
diff --git a/extras/mini-os/arch/arm/arm32.S b/extras/mini-os/arch/arm/arm32.S
index 56429b1..fab9f9f 100644
--- a/extras/mini-os/arch/arm/arm32.S
+++ b/extras/mini-os/arch/arm/arm32.S
@@ -166,8 +166,69 @@ irqstack:
 	.fill (1024), 4, 0x0
 irqstack_end:
 
+fault_dump:
+	.fill 18, 4, 0x0		@ On fault, we save the registers + CPSR + handler address
+
 .popsection
 
+fault:
+	cpsid	aif			@ Disable interrupts
+
+	ldr	r13, =fault_dump
+	stmia	r13, {r0-r12}		@ Dump the non-banked registers directly (well, unless from FIQ mode)
+	str	r14, [r13, #15 << 2]	@ Our r14 is the faulting r15
+	mov	r0, r13
+
+	@ Save the caller's CPSR (our SPSR) too.
+	mrs	r1, SPSR
+	str	r1, [r13, #16 << 2]
+
+	@ Switch to the mode we came from to get r13 and r14.
+	@ If coming from user mode, use System mode instead so we're still
+	@ privileged.
+	and	r1, r1, #0x1f		@ r1 = SPSR mode
+	cmp	r1, #0x10		@ If from User mode
+	moveq	r1, #0x1f		@ Then use System mode instead
+
+	mrs	r3, CPSR		@ r3 = our CPSR
+	bic	r2, r3, #0x1f
+	orr	r2, r2, r1
+	msr	CPSR, r2		@ Change to mode r1
+
+	@ Save old mode's r13, r14
+	str	r13, [r0, #13 << 2]
+	str	r14, [r0, #14 << 2]
+
+	msr	CPSR, r3		@ Back to fault mode
+
+	ldr	r1, [r0, #17 << 2]
+	sub	r1, r1, #12		@ Fix to point at start of handler
+	str	r1, [r0, #17 << 2]
+
+	@ Call C code to format the register dump.
+	@ Clobbers the stack, but we're not going to return anyway.
+	ldr	sp, =_boot_stack_end
+	bl	dump_registers
+	b	do_exit
+
+@ We want to store a unique value to identify this handler, without corrupting
+@ any of the registers. So, we store r15 (which will point just after the branch).
+@ Later, we subtract 12 so the user gets pointed at the start of the exception
+@ handler.
+#define FAULT(name)			\
+.globl fault_##name;			\
+fault_##name:				\
+	ldr	r13, =fault_dump;	\
+	str	r15, [r13, #17 << 2];	\
+	b	fault
+
+FAULT(reset)
+FAULT(undefined_instruction)
+FAULT(svc)
+FAULT(prefetch_call)
+FAULT(prefetch_abort)
+FAULT(data_abort)
+
 @ exception base address
 .align 5
 .globl exception_vector_table
@@ -177,13 +238,13 @@ irqstack_end:
 @  instruction to clear an existing tag is required on context switches."
 @ -- ARM Cortex-A Series Programmer’s Guide (Version: 4.0)
 exception_vector_table:
-	b	. @ reset
-	b	. @ undefined instruction
-	b	. @ supervisor call
-	b	. @ prefetch call
-	b	. @ prefetch abort
-	b	. @ data abort
-	b	irq_handler @ irq
+	b	fault_reset
+	b	fault_undefined_instruction
+	b	fault_svc
+	b	fault_prefetch_call
+	b	fault_prefetch_abort
+	b	fault_data_abort
+	b	irq_handler @ IRQ
 	.word 0xe7f000f0    @ abort on FIQ
 
 irq_handler:
diff --git a/extras/mini-os/arch/arm/panic.c b/extras/mini-os/arch/arm/panic.c
new file mode 100644
index 0000000..d0547b0
--- /dev/null
+++ b/extras/mini-os/arch/arm/panic.c
@@ -0,0 +1,98 @@
+/******************************************************************************
+ * panic.c
+ *
+ * Displays a register dump and stack trace for debugging.
+ *
+ * Copyright (c) 2014, Thomas Leonard
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#include <mini-os/os.h>
+#include <mini-os/console.h>
+#include <arch_mm.h>
+
+extern int irqstack[];
+extern int irqstack_end[];
+
+typedef void handler(void);
+
+extern handler fault_reset;
+extern handler fault_undefined_instruction;
+extern handler fault_svc;
+extern handler fault_prefetch_call;
+extern handler fault_prefetch_abort;
+extern handler fault_data_abort;
+
+void dump_registers(int *saved_registers) {
+    static int in_dump = 0;
+    int *sp, *stack_top, *x;
+    char *fault_name;
+    void *fault_handler;
+    int i;
+
+    if (in_dump)
+    {
+        printk("Crash while in dump_registers! Not generating a second report.\n");
+        return;
+    }
+
+    in_dump = 1;
+
+    fault_handler = (handler *) saved_registers[17];
+    if (fault_handler == fault_reset)
+        fault_name = "reset";
+    else if (fault_handler == fault_undefined_instruction)
+        fault_name = "undefined_instruction";
+    else if (fault_handler == fault_svc)
+        fault_name = "svc";
+    else if (fault_handler == fault_prefetch_call)
+        fault_name = "prefetch_call";
+    else if (fault_handler == fault_prefetch_abort)
+        fault_name = "prefetch_abort";
+    else if (fault_handler == fault_data_abort)
+        fault_name = "data_abort";
+    else
+        fault_name = "unknown fault type!";
+
+    printk("Fault handler at %x called (%s)\n", fault_handler, fault_name);
+
+    for (i = 0; i < 16; i++) {
+        printk("r%d = %x\n", i, saved_registers[i]);
+    }
+    printk("CPSR = %x\n", saved_registers[16]);
+
+    printk("Stack dump (innermost last)\n");
+    sp = (int *) saved_registers[13];
+
+    if (sp >= _boot_stack && sp <= _boot_stack_end)
+        stack_top = _boot_stack_end;                    /* The boot stack */
+    else if (sp >= irqstack && sp <= irqstack_end)
+        stack_top = irqstack_end;                       /* The IRQ stack */
+    else
+        stack_top = (int *) ((((unsigned long) sp) | (__STACK_SIZE-1)) + 1);        /* A normal thread stack */
+
+    for (x = stack_top - 1; x >= sp; x--)
+    {
+        printk("  [%8p] %8x\n", x, *x);
+    }
+    printk("End of stack\n");
+
+    in_dump = 0;
+}
-- 
2.0.1


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