libpayload: Make it possible to install callbacks for particular exceptions.

To support a GDB stub, it will be necessary to trap various exceptions which
will be used to implement breakpoints, single stepping, etc.

BUG=None
TEST=Built and booted on Link with hooks installed and saw that they
triggered when exceptions occurred. Built and booted on nyan.
BRANCH=None

Original-Change-Id: Iab659365864a3055159a50b8f6e5c44290d3ba2b
Original-Signed-off-by: Gabe Black <gabeblack@google.com>
Original-Reviewed-on: https://chromium-review.googlesource.com/179602
Original-Reviewed-by: Gabe Black <gabeblack@chromium.org>
Original-Tested-by: Gabe Black <gabeblack@chromium.org>
Original-Commit-Queue: Gabe Black <gabeblack@chromium.org>
(cherry picked from commit 8db0897b1ddad600e247cb4df147c757a8187626)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I5e7f724b99988cd259909dd3bd01166fa52317ec
Reviewed-on: http://review.coreboot.org/7656
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

3 files changed, 53 insertions, 81 deletions

diff --git a/payloads/libpayload/arch/arm/exception.c b/payloads/libpayload/arch/arm/exception.c
index 099d2a46fa..f0ce0ea8c3 100644
--- a/payloads/libpayload/arch/arm/exception.c
+++ b/payloads/libpayload/arch/arm/exception.c
@@ -29,19 +29,27 @@
 
 #include <arch/cache.h>
 #include <arch/exception.h>
+#include <exception.h>
 #include <libpayload.h>
 #include <stdint.h>
 
-uint8_t exception_stack[0x100] __attribute__((aligned(8)));
+uint8_t exception_stack[0x1000] __attribute__((aligned(8)));
 extern void *exception_stack_end;
 
-void exception_undefined_instruction(uint32_t *);
-void exception_software_interrupt(uint32_t *);
-void exception_prefetch_abort(uint32_t *);
-void exception_data_abort(uint32_t *);
-void exception_not_used(uint32_t *);
-void exception_irq(uint32_t *);
-void exception_fiq(uint32_t *);
+struct exception_handler_info
+{
+	const char *name;
+	exception_hook hook;
+};
+
+static struct exception_handler_info exceptions[EXC_COUNT] = {
+	[EXC_UNDEF]  = { "_undefined_instruction" },
+	[EXC_SWI]    = { "_software_interrupt" },
+	[EXC_PABORT] = { "_prefetch_abort" },
+	[EXC_DABORT] = { "_data_abort" },
+	[EXC_IRQ]    = { "_irq" },
+	[EXC_FIQ]    = { "_fiq" },
+};
 
 static void dump_stack(uintptr_t addr, size_t bytes)
 {
@@ -77,59 +85,25 @@ static void print_regs(uint32_t *regs)
 	}
 }
 
-void exception_undefined_instruction(uint32_t *regs)
-{
-	printf("exception _undefined_instruction\n");
-	print_regs(regs);
-	dump_stack(regs[13], 512);
-	halt();
-}
-
-void exception_software_interrupt(uint32_t *regs)
-{
-	printf("exception _software_interrupt\n");
-	print_regs(regs);
-	dump_stack(regs[13], 512);
-	halt();
-}
-
-void exception_prefetch_abort(uint32_t *regs)
-{
-	printf("exception _prefetch_abort\n");
-	print_regs(regs);
-	dump_stack(regs[13], 512);
-	halt();
-}
-
-void exception_data_abort(uint32_t *regs)
-{
-	printf("exception _data_abort\n");
-	print_regs(regs);
-	dump_stack(regs[13], 512);
-	halt();
-}
-
-void exception_not_used(uint32_t *regs)
-{
-	printf("exception _not_used\n");
-	print_regs(regs);
-	dump_stack(regs[13], 512);
-	halt();
-}
-
-void exception_irq(uint32_t *regs)
+void exception_dispatch(struct exception_state *state, int idx);
+void exception_dispatch(struct exception_state *state, int idx)
 {
-	printf("exception _irq\n");
-	print_regs(regs);
-	dump_stack(regs[13], 512);
-	halt();
-}
-
-void exception_fiq(uint32_t *regs)
-{
-	printf("exception _fiq\n");
-	print_regs(regs);
-	dump_stack(regs[13], 512);
+	if (idx >= EXC_COUNT) {
+		printf("Bad exception index %d.\n", idx);
+	} else {
+		struct exception_handler_info *info = &exceptions[idx];
+		if (info->hook) {
+			info->hook(idx, state);
+			return;
+		}
+
+		if (info->name)
+			printf("exception %s\n", info->name);
+		else
+			printf("exception _not_used.\n");
+	}
+	print_regs(state->regs);
+	dump_stack(state->regs[13], 512);
 	halt();
 }
 
@@ -146,3 +120,9 @@ void exception_init(void)
 	set_vbar((uintptr_t)exception_table);
 	exception_stack_end = exception_stack + sizeof(exception_stack);
 }
+
+void exception_install_hook(int type, exception_hook hook)
+{
+	die_if(type >= EXC_COUNT, "Out of bounds exception index %d.\n", type);
+	exceptions[type].hook = hook;
+}
diff --git a/payloads/libpayload/arch/arm/exception_asm.S b/payloads/libpayload/arch/arm/exception_asm.S
index 1f369bcc05..6a28c5cdef 100644
--- a/payloads/libpayload/arch/arm/exception_asm.S
+++ b/payloads/libpayload/arch/arm/exception_asm.S
@@ -43,59 +43,51 @@ exception_table:
 	b	8f
 
 1:
-	ldr	sp, _not_used
+	mov	sp, $0
 	b	exception_common
 2:
-	ldr	sp, _undefined_instruction
+	mov	sp, $1
 	b	exception_common
 3:
-	ldr	sp, _software_interrupt
+	mov	sp, $2
 	b	exception_common
 4:
-	ldr	sp, _prefetch_abort
+	mov	sp, $3
 	b	exception_common
 5:
-	ldr	sp, _data_abort
+	mov	sp, $4
 	b	exception_common
 6:
-	ldr	sp, _not_used
+	mov	sp, $5
 	b	exception_common
 7:
-	ldr	sp, _irq
+	mov	sp, $6
 	b	exception_common
 8:
-	ldr	sp, _fiq
+	mov	sp, $7
 	b	exception_common
 
 exception_common:
-	str	sp, exception_handler
+	str	sp, exception_idx
 	ldr	sp, exception_stack_end
 	push	{ lr }
 	stmfd	sp, { sp, lr }^
 	sub	sp, sp, $8
 	push	{ r0 - r12 }
 	mov	r0, sp
-	mov	lr, pc
-	ldr	pc, exception_handler
+	ldr	r1, exception_idx
+	blx	exception_dispatch
 	pop	{ r0 - r12 }
 	add	sp, sp, $8
 	ldmfd	sp!, { pc }^
 
 
 	.align 2
-_undefined_instruction:	.word exception_undefined_instruction
-_software_interrupt:	.word exception_software_interrupt
-_prefetch_abort:	.word exception_prefetch_abort
-_data_abort:		.word exception_data_abort
-_not_used:		.word exception_not_used
-_irq:			.word exception_irq
-_fiq:			.word exception_fiq
-
 	.global exception_stack_end
 exception_stack_end:
 	.word 0
 
-exception_handler:
+exception_idx:
 	.word 0
 
 	.thumb
diff --git a/payloads/libpayload/arch/arm/main.c b/payloads/libpayload/arch/arm/main.c
index 4e7c05dfe1..cff992fce6 100644
--- a/payloads/libpayload/arch/arm/main.c
+++ b/payloads/libpayload/arch/arm/main.c
@@ -27,7 +27,7 @@
  * SUCH DAMAGE.
  */
 
-#include <arch/exception.h>
+#include <exception.h>
 #include <libpayload.h>
 
 unsigned int main_argc;    /**< The argc value to pass to main() */