arm: Fix checkstack() to use correct stack size

checkstack() runs at the end of ramstage to warn about stack overflows,
and it assumes that CONFIG_STACK_SIZE is always the size of the stack to
check. This is only true for systems that bring up multiprocessing in
ramstage and assign a separate stack for each core, like x86 and ARM64.
Other architectures like ARM and MIPS (for now) don't touch secondary
CPUs at all and currently don't look like they'll ever need to, so they
generally stay on the same (SRAM-based) stack they have been on since
their bootblock.

This patch tries to model that difference by making these architectures
explicitly set CONFIG_STACK_SIZE to zero, and using that as a cue to
assume the whole (_estack - _stack) area in checkstack() instead. Also
adds a BUG() to the stack overflow check, since that is currently just
as non-fatal as the BIOS_ERR message (despite the incorrect "SYSTEM
HALTED" output) but a little more easy to spot. Such a serious failure
should not drown out in all the normal random pieces of lower case boot
spam (also, I was intending to eventually have a look at assert() and
BUG() to hopefully make them a little more useful/noticeable if I ever
find the time for it).

BRANCH=None
BUG=None
TEST=Booted Pinky, noticed it no longer complains about stack overflows.
Built Falco, Ryu and Urara.

Change-Id: I6826e0ec24201d4d83c5929b281828917bc9abf4
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 54229a725e8907b84a105c04ecea33b8f9b91dd4
Original-Change-Id: I49f70bb7ad192bd1c48e077802085dc5ecbfd58b
Original-Signed-off-by: Julius Werner <jwerner@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/235894
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/9610
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/arch/arm/Kconfig

@@ -31,3 +31,8 @@ config ARM_BOOTBLOCK_CUSTOM
 config ARM_LPAE
 	bool
 	default n
+
+# Mark SMP stack size as 0 since we keep using SRAM stack throughout ramstage.
+config STACK_SIZE
+	hex
+	default 0x0

src/arch/mips/Kconfig

@@ -39,3 +39,8 @@ config ARCH_ROMSTAGE_MIPS
 config ARCH_RAMSTAGE_MIPS
 	bool
 	default n
+
+# Mark SMP stack size as 0 since we keep using SRAM stack throughout ramstage.
+config STACK_SIZE
+	hex
+	default 0x0

src/lib/stack.c

@@ -20,31 +20,35 @@ it with the version available from LANL.
  * rminnich@lanl.gov
  */
 
+#include <assert.h>
 #include <lib.h>
 #include <console/console.h>
+#include <symbols.h>
 
 int checkstack(void *top_of_stack, int core)
 {
+	/* Not all archs use CONFIG_STACK_SIZE, those who don't set it to 0. */
+	size_t stack_size = CONFIG_STACK_SIZE ? CONFIG_STACK_SIZE : _stack_size;
 	int i;
-	u32 *stack = (u32 *) (top_of_stack - CONFIG_STACK_SIZE);
+	u32 *stack = (u32 *) (top_of_stack - stack_size);
 
 	if (stack[0] != 0xDEADBEEF){
 		printk(BIOS_ERR, "Stack overrun on CPU%d. "
-			"Increase stack from current %d bytes\n",
-			core, CONFIG_STACK_SIZE);
+			"Increase stack from current %zu bytes\n",
+			core, stack_size);
+		BUG();
 		return -1;
 	}
 
-	for(i = 1; i < CONFIG_STACK_SIZE/sizeof(stack[0]); i++){
+	for(i = 1; i < stack_size/sizeof(stack[0]); i++){
 		if (stack[i] == 0xDEADBEEF)
 			continue;
 		printk(BIOS_SPEW, "CPU%d: stack: %p - %p, ",
-			core, stack,
-			&stack[CONFIG_STACK_SIZE/sizeof(stack[0])]);
+			core, stack, &stack[stack_size/sizeof(stack[0])]);
 		printk(BIOS_SPEW, "lowest used address %p, ", &stack[i]);
 		printk(BIOS_SPEW, "stack used: %ld bytes\n",
-			(unsigned long)&stack[CONFIG_STACK_SIZE /
-			sizeof(stack[0])] - (unsigned long)&stack[i]);
+			(unsigned long)&stack[stack_size / sizeof(stack[0])]
+			- (unsigned long)&stack[i]);
 		return 0;
 	}