arm64: include stack storage within ramstage

Instead of defining the stacks by Kconfig options include
the stack sizes for all the CPUs including each of their
exception stacks. This allows for providing each CPU
on startup a stack to work with.

Note: this currently inherits CONFIG_STACK_SIZE from x86 because
of the Kconfig mess of options not being guarded.

BUG=chrome-os-partner:31545
BRANCH=None
TEST=Built and booted into the kernel on ryu.

Change-Id: Ie5fa1a8b78ed808a14efeb1717b98d6b0dd85eef
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 6524993f016aac2ac8cd9dba9fbdd9a59260a2b6
Original-Change-Id: Ica09dc256e6ce1dd032433d071894af5f445acdb
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/214669
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/9013
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/arch/arm64/include/armv8/arch/cpu.h

@@ -52,4 +52,10 @@ struct cpu_info *cpu_info(void);
  */
 unsigned int smp_processor_id(void);
 
+/* Return the top of the stack for the specified cpu. */
+void *cpu_get_stack(unsigned int cpu);
+
+/* Return the top of the exception stack for the specified cpu. */
+void *cpu_get_exception_stack(unsigned int cpu);
+
 #endif /* __ARCH_CPU_H__ */

src/arch/arm64/stage_entry.S

@@ -30,13 +30,58 @@
 #error Need to know what ELx processor starts up in.
 #endif
 
+#define STACK_SZ CONFIG_STACK_SIZE
+#define EXCEPTION_STACK_SZ CONFIG_STACK_SIZE
+
+/*
+ * The stacks for each of the armv8 cores grows down from _estack. It is sized
+ * according to MAX_CPUS. Additionally provide exception stacks for each CPU.
+ */
+.section .bss, "aw", @nobits
+.global _stack
+.global _estack
+.balign STACK_SZ
+_stack:
+.space CONFIG_MAX_CPUS*STACK_SZ
+_estack:
+
+.global _stack_exceptions
+.global _estack_exceptions
+.balign EXCEPTION_STACK_SZ
+_stack_exceptions:
+.space CONFIG_MAX_CPUS*EXCEPTION_STACK_SZ
+_estack_exceptions:
+
+ENTRY(cpu_get_stack)
+	mov	x1, #STACK_SZ
+	mul	x0, x0, x1
+	ldr	x1, 1f
+	sub	x0, x1, x0
+	ret
+.align 3
+1:
+	.quad	_estack
+ENDPROC(cpu_get_stack)
+
+ENTRY(cpu_get_exception_stack)
+	mov	x1, #EXCEPTION_STACK_SZ
+	mul	x0, x0, x1
+	ldr	x1, 1f
+	sub	x0, x1, x0
+	ret
+.align 3
+1:
+	.quad	_estack_exceptions
+ENDPROC(cpu_get_exception_stack)
+
+
 ENTRY(seed_stack)
 	/*
 	 * Initialize the stack to a known value. This is used to check for
 	 * stack overflow later in the boot process.
 	 */
 	ldr	x0, .stack_bottom
-	ldr	x1, .stack_top
+	mov	x1, sp
 	ldr	x2, =0xdeadbeefdeadbeef
 	ldr	x3, =0x8
 
@@ -59,36 +104,26 @@ ENDPROC(seed_stack)
  * stack while keeping SP_ELx reserved for exception entry.
  */
 ENTRY(arm64_c_environment)
-	ldr	x0, .exception_stack_top
+	bl	smp_processor_id	/* x0 = cpu */
-	cmp	x0, #0
+	mov	x24, x0
-	b.eq	2f
+
+
+	/* Set the exception stack for this cpu. */
+	bl	cpu_get_exception_stack
 	msr	SPSel, #1
 	isb
-
 	mov	sp, x0
 
-	2:
 	/* Have stack pointer use SP_EL0. */
 	msr	SPSel, #0
 	isb
 
-	/* Load up the stack if non-zero. */
+	/* Set stack for this cpu. */
-	ldr	x0, .stack_top
+	mov	x0, x24		/* x0 = cpu */
-	cmp	x0, #0
+	bl	cpu_get_stack
-	b.eq	1f
 	mov	sp, x0
-	1:
 
-	ldr	x1, .entry
+	b	seed_stack
-	br	x1
-
-	.align 4
-	.exception_stack_top:
-		.quad CONFIG_EXCEPTION_STACK_TOP
-	.stack_top:
-		.quad _estack
-	.entry:
-		.quad seed_stack
 ENDPROC(arm64_c_environment)
 
 CPU_RESET_ENTRY(arm64_cpu_startup)