ARM: Add an empty secure stack section

Until now we've been using memory beyond psci_text_end as stack space
for the secure monitor or PSCI implementation, even if space was not
allocated for it.

This was partially fixed in ("ARM: allocate extra space for PSCI stack
in secure section during link phase"). However, calculating stack space
from psci_text_end in one place, while allocating the space in another
is error prone.

This patch adds a separate empty secure stack section, with space for
CONFIG_ARMV7_PSCI_NR_CPUS stacks, each 1 KB. There's also
__secure_stack_start and __secure_stack_end symbols. The linker script
handles calculating the correct VMAs for the stack section. For
platforms that relocate/copy the secure monitor before using it, the
space is not allocated in the executable, saving space.

For platforms that do not define CONFIG_ARMV7_PSCI_NR_CPUS, a whole page
of stack space for 4 CPUs is allocated, matching the previous behavior.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

arch/arm/cpu/u-boot.lds

@@ -8,6 +8,7 @@
  */
 
 #include <config.h>
+#include <asm/psci.h>
 
 OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
 OUTPUT_ARCH(arm)
@@ -68,18 +69,31 @@ SECTIONS
 		*(._secure.text)
 	}
 
-	. = LOADADDR(.__secure_start) +
-		SIZEOF(.__secure_start) +
-		SIZEOF(.secure_text);
-
+	.secure_stack ALIGN(ADDR(.secure_text) + SIZEOF(.secure_text),
+			    CONSTANT(COMMONPAGESIZE)) (NOLOAD) :
 #ifdef __ARMV7_PSCI_STACK_IN_RAM
-	/* Align to page boundary and skip 2 pages */
-	. = (. & ~ 0xfff) + 0x2000;
-#undef __ARMV7_PSCI_STACK_IN_RAM
+		AT(ADDR(.secure_stack))
+#else
+		AT(LOADADDR(.secure_text) + SIZEOF(.secure_text))
+#endif
+	{
+		KEEP(*(.__secure_stack_start))
+
+		/* Skip addreses for stack */
+		. = . + CONFIG_ARMV7_PSCI_NR_CPUS * ARM_PSCI_STACK_SIZE;
+
+		/* Align end of stack section to page boundary */
+		. = ALIGN(CONSTANT(COMMONPAGESIZE));
+
+		KEEP(*(.__secure_stack_end))
+	}
+
+#ifndef __ARMV7_PSCI_STACK_IN_RAM
+	/* Reset VMA but don't allocate space if we have secure SRAM */
+	. = LOADADDR(.secure_stack);
 #endif
 
-	__secure_end_lma = .;
-	.__secure_end : AT(__secure_end_lma) {
+	.__secure_end : AT(ADDR(.__secure_end)) {
 		*(.__secure_end)
 		LONG(0x1d1071c);	/* Must output something to reset LMA */
 	}

arch/arm/include/asm/armv7.h

@@ -126,6 +126,8 @@ void _smp_pen(void);
 
 extern char __secure_start[];
 extern char __secure_end[];
+extern char __secure_stack_start[];
+extern char __secure_stack_end[];
 
 #endif /* CONFIG_ARMV7_NONSEC */
 

arch/arm/include/asm/psci.h

@@ -47,6 +47,10 @@
 #define ARM_PSCI_0_2_FN_SYSTEM_OFF		ARM_PSCI_0_2_FN(8)
 #define ARM_PSCI_0_2_FN_SYSTEM_RESET		ARM_PSCI_0_2_FN(9)
 
+/* 1KB stack per core */
+#define ARM_PSCI_STACK_SHIFT	10
+#define ARM_PSCI_STACK_SIZE	(1 << ARM_PSCI_STACK_SHIFT)
+
 #ifndef __ASSEMBLY__
 #include <asm/types.h>
 

arch/arm/lib/sections.c

@@ -27,6 +27,8 @@ char __rel_dyn_start[0] __attribute__((section(".__rel_dyn_start")));
 char __rel_dyn_end[0] __attribute__((section(".__rel_dyn_end")));
 char __secure_start[0] __attribute__((section(".__secure_start")));
 char __secure_end[0] __attribute__((section(".__secure_end")));
+char __secure_stack_start[0] __attribute__((section(".__secure_stack_start")));
+char __secure_stack_end[0] __attribute__((section(".__secure_stack_end")));
 char __efi_runtime_start[0] __attribute__((section(".__efi_runtime_start")));
 char __efi_runtime_stop[0] __attribute__((section(".__efi_runtime_stop")));
 char __efi_runtime_rel_start[0] __attribute__((section(".__efi_runtime_rel_start")));