libpayload: Rework exception hook interface

This patch makes some slight changes to the exception hook interface.
The old code provides a different handler hook for every exception
type... however, in practice all those hook functions often need to look
very similar, so this creates more boilerplate than it removes. The new
interface just allows for a single hook with the exception type passed
as an argument, and the consumer can signal whether the exception was
handled through the return value. (Right now this still only supports
one consumer, but it could easily be extended to walk through a list of
hooks if the need arises.)

Also move the excepton state from an argument to a global. This avoids a
lot of boilerplate since some consumers need to change the state from
many places, so they would have to pass the same pointer around many
times. It also removes the false suggestion that the exception state was
not global and you could have multiple copies of it (which the exception
core doesn't support for any architecture).

On the ARM side, the exception state is separated from the exception
stack for easier access. (This requires some assembly changes, and I
threw in a few comments and corrected the immediate sigils from '$' to
the official '#' while I'm there.) Since the exception state is now both
stored and loaded through an indirection pointer, this allows for some
very limited reentrance (you could point it to a different struct while
handling an exception, and while you still won't be able to return to
the outer-level exception from there, you could at least swap out the
pointer and return back to System Mode in one go).

BUG=chrome-os-partner:18390
TEST=Made sure normal exceptions still get dumped correctly on both
archs.

Original-Change-Id: I5d9a934fab7c14ccb2c9d7ee4b3465c825521fa2
Original-Signed-off-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/202562
Original-Reviewed-by: Stefan Reinauer <reinauer@chromium.org>
(cherry picked from commit 97542110f0b385b9b8d89675866e65db8ca32aeb)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

*** Squashed to prevent build failures. ***

libpayload: align arm64 with new exception handling model

The exception handling was previously updated, however the
arm64 changes raced with hat one. Make the arm64 align with
the new model. Without these changes compilation will fail.

BUG=None
BRANCH=None
TEST=Can build libpayload for rush.

Original-Change-Id: I320b39a57b985d1f87446ea7757955664f8dba8f
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/204402
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Original-Commit-Queue: Furquan Shaikh <furquan@chromium.org>
(cherry picked from commit 0080df41b311ef20f9214b386fa4e38ee54aa1a1)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: I9a0bb3848cf5286f9f4bb08172a9f4a15278348e
Reviewed-on: http://review.coreboot.org/8117
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

2 files changed, 77 insertions, 94 deletions

diff --git a/payloads/libpayload/arch/x86/exception.c b/payloads/libpayload/arch/x86/exception.c
index e1ff3a54c6..f6bb8c9ccf 100644
--- a/payloads/libpayload/arch/x86/exception.c
+++ b/payloads/libpayload/arch/x86/exception.c
@@ -32,22 +32,29 @@
 #include <libpayload.h>
 #include <stdint.h>
 
-uint8_t exception_stack[0x1000] __attribute__((aligned(8)));
-extern void *exception_stack_end;
-extern struct exception_handler_state *exception_handler_state_handoff;
-
-struct exception_handler_state
-{
-	struct exception_state regs;
-	u32 error_code;
-	u32 vector;
-} __attribute__((packed));
-
-struct exception_handler_info
-{
-	const char *name;
-	void (*error_code_printer)(u32 code);
-	exception_hook hook;
+u32 exception_stack[0x400] __attribute__((aligned(8)));
+
+static exception_hook hook;
+static const char *names[EXC_COUNT] = {
+	[EXC_DE]  = "Divide by Zero",
+	[EXC_DB]  = "Debug",
+	[EXC_NMI] = "Non-Maskable-Interrupt",
+	[EXC_BP]  = "Breakpoint",
+	[EXC_OF]  = "Overflow",
+	[EXC_BR]  = "Bound Range",
+	[EXC_UD]  = "Invalid Opcode",
+	[EXC_NM]  = "Device Not Available",
+	[EXC_DF]  = "Double Fault",
+	[EXC_TS]  = "Invalid TSS",
+	[EXC_NP]  = "Segment Not Present",
+	[EXC_SS]  = "Stack Fault",
+	[EXC_GP]  = "General Protection Fault",
+	[EXC_PF]  = "Page Fault",
+	[EXC_MF]  = "x87 Floating Point",
+	[EXC_AC]  = "Alignment Check",
+	[EXC_MC]  = "Machine Check",
+	[EXC_XF]  = "SIMD Floating Point",
+	[EXC_SX]  = "Security",
 };
 
 static void print_segment_error_code(u32 code)
@@ -93,36 +100,6 @@ static void print_raw_error_code(u32 code)
 	printf("%#x", code);
 }
 
-static struct exception_handler_info exceptions[EXC_COUNT] = {
-	[EXC_DE] =  { .name = "divide by zero" },
-	[EXC_DB] =  { .name = "debug" },
-	[EXC_NMI] =  { .name = "non-maskable-interrupt" },
-	[EXC_BP] =  { .name = "breakpoint" },
-	[EXC_OF] =  { .name = "overflow" },
-	[EXC_BR] =  { .name = "bound range" },
-	[EXC_UD] =  { .name = "invalid opcode" },
-	[EXC_NM] =  { .name = "device not available" },
-	[EXC_DF] =  { .name = "double fault",
-		      .error_code_printer = &print_raw_error_code },
-	[EXC_TS] = { .name = "invalid tss",
-		     .error_code_printer = &print_segment_error_code },
-	[EXC_NP] = { .name = "segment not present",
-		     .error_code_printer = &print_segment_error_code },
-	[EXC_SS] = { .name = "stack",
-		     .error_code_printer = &print_segment_error_code },
-	[EXC_GP] = { .name = "general protection",
-		     .error_code_printer = &print_segment_error_code },
-	[EXC_PF] = { .name = "page fault",
-		     .error_code_printer = &print_page_fault_error_code },
-	[EXC_MF] = { .name = "x87 floating point" },
-	[EXC_AC] = { .name = "alignment check",
-		     .error_code_printer = &print_raw_error_code },
-	[EXC_MC] = { .name = "machine check" },
-	[EXC_XF] = { .name = "SIMD floating point" },
-	[EXC_SX] = { .name = "security",
-		     .error_code_printer = &print_raw_error_code },
-};
-
 static void dump_stack(uintptr_t addr, size_t bytes)
 {
 	int i, j;
@@ -138,64 +115,70 @@ static void dump_stack(uintptr_t addr, size_t bytes)
 	}
 }
 
-static void dump_exception_state(struct exception_handler_state *state,
-				 struct exception_handler_info *info)
+static void dump_exception_state(void)
 {
-	if (info) {
-		printf("Exception %d (%s)\n", state->vector, info->name);
-
-		if (info->error_code_printer) {
-			printf("Error code: ");
-			info->error_code_printer(state->error_code);
-			printf("\n");
-		}
-	} else {
-		printf("Unrecognized exception %d\n", state->vector);
+	printf("%s Exception\n", names[exception_state->vector]);
+
+	printf("Error code: ");
+	switch (exception_state->vector) {
+	case EXC_PF:
+		print_page_fault_error_code(exception_state->error_code);
+		break;
+	case EXC_TS:
+	case EXC_NP:
+	case EXC_SS:
+	case EXC_GP:
+		print_segment_error_code(exception_state->error_code);
+		break;
+	case EXC_DF:
+	case EXC_AC:
+	case EXC_SX:
+		print_raw_error_code(exception_state->error_code);
+		break;
+	default:
+		printf("n/a");
+		break;
 	}
-	printf("EIP:    0x%08x\n", state->regs.eip);
-	printf("CS:     0x%04x\n", state->regs.cs);
-	printf("EFLAGS: 0x%08x\n", state->regs.eflags);
-	printf("EAX:    0x%08x\n", state->regs.eax);
-	printf("ECX:    0x%08x\n", state->regs.ecx);
-	printf("EDX:    0x%08x\n", state->regs.edx);
-	printf("EBX:    0x%08x\n", state->regs.ebx);
-	printf("ESP:    0x%08x\n", state->regs.esp);
-	printf("EBP:    0x%08x\n", state->regs.ebp);
-	printf("ESI:    0x%08x\n", state->regs.esi);
-	printf("EDI:    0x%08x\n", state->regs.edi);
-	printf("DS:     0x%04x\n", state->regs.ds);
-	printf("ES:     0x%04x\n", state->regs.es);
-	printf("SS:     0x%04x\n", state->regs.ss);
-	printf("FS:     0x%04x\n", state->regs.fs);
-	printf("GS:     0x%04x\n", state->regs.gs);
+	printf("\n");
+	printf("EIP:    0x%08x\n", exception_state->regs.eip);
+	printf("CS:     0x%04x\n", exception_state->regs.cs);
+	printf("EFLAGS: 0x%08x\n", exception_state->regs.eflags);
+	printf("EAX:    0x%08x\n", exception_state->regs.eax);
+	printf("ECX:    0x%08x\n", exception_state->regs.ecx);
+	printf("EDX:    0x%08x\n", exception_state->regs.edx);
+	printf("EBX:    0x%08x\n", exception_state->regs.ebx);
+	printf("ESP:    0x%08x\n", exception_state->regs.esp);
+	printf("EBP:    0x%08x\n", exception_state->regs.ebp);
+	printf("ESI:    0x%08x\n", exception_state->regs.esi);
+	printf("EDI:    0x%08x\n", exception_state->regs.edi);
+	printf("DS:     0x%04x\n", exception_state->regs.ds);
+	printf("ES:     0x%04x\n", exception_state->regs.es);
+	printf("SS:     0x%04x\n", exception_state->regs.ss);
+	printf("FS:     0x%04x\n", exception_state->regs.fs);
+	printf("GS:     0x%04x\n", exception_state->regs.gs);
 }
 
 void exception_dispatch(void)
 {
-	struct exception_handler_state *state =
-		exception_handler_state_handoff;
+	u32 vec = exception_state->vector;
+	die_if(vec >= EXC_COUNT || !names[vec], "Bad exception vector %u", vec);
 
-	struct exception_handler_info *info = NULL;
-	if (state->vector < EXC_COUNT)
-		info = &exceptions[state->vector];
+	if (hook && hook(vec))
+		return;
 
-	if (info && info->hook) {
-		info->hook(state->vector, &state->regs);
-	} else {
-		dump_exception_state(state, info);
-		dump_stack(state->regs.esp, 512);
-		halt();
-	}
+	dump_exception_state();
+	dump_stack(exception_state->regs.esp, 512);
+	halt();
 }
 
 void exception_init(void)
 {
-	exception_stack_end = exception_stack + sizeof(exception_stack);
+	exception_stack_end = exception_stack + ARRAY_SIZE(exception_stack);
 	exception_init_asm();
 }
 
-void exception_install_hook(int type, exception_hook hook)
+void exception_install_hook(exception_hook h)
 {
-	die_if(type >= EXC_COUNT, "Out of bound exception type %d.\n", type);
-	exceptions[type].hook = hook;
+	die_if(hook, "Implement support for a list of hooks if you need it.");
+	hook = h;
 }
diff --git a/payloads/libpayload/arch/x86/exception_asm.S b/payloads/libpayload/arch/x86/exception_asm.S
index de612ba057..a8f9a1d254 100644
--- a/payloads/libpayload/arch/x86/exception_asm.S
+++ b/payloads/libpayload/arch/x86/exception_asm.S
@@ -31,8 +31,8 @@
 	.global exception_stack_end
 exception_stack_end:
 	.long 0
-	.global exception_handler_state_handoff
-exception_handler_state_handoff:
+	.global exception_state
+exception_state:
 	.long 0
 
 /* Some temporary variables which are used while saving exception state. */
@@ -138,11 +138,11 @@ exception_common:
 
 	/*
 	 * Call the C exception handler. It will find the exception state
-	 * using the exception_handler_state_handoff global pointer. Not
+	 * using the exception_state global pointer. Not
 	 * passing parameters means we don't have to worry about what ABI
 	 * is being used.
 	 */
-	mov	%esp, exception_handler_state_handoff
+	mov	%esp, exception_state
 	call	exception_dispatch
 
 	/*