xen/ppc: Add .text.exceptions section for exception vectors

On Power, the exception vectors must lie at a fixed address, depending
on the state of the Alternate Interrupt Location (AIL) field of the
Logical Partition Control Register (LPCR). Create a .text.exceptions
section in the linker script at an address suitable for AIL=3 plus an
accompanying assertion to pave the way for implementing exception
support.

Signed-off-by: Shawn Anastasio <sanastasio@raptorengineering.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/ppc/include/asm/config.h

@@ -42,6 +42,9 @@
 
 #define XEN_VIRT_START _AC(0xc000000000000000, UL)
 
+/* Fixed address for start of the section containing exception vectors */
+#define EXCEPTION_VECTORS_START _AC(0xc000000000000100, UL)
+
 #define VMAP_VIRT_START (XEN_VIRT_START + GB(1))
 #define VMAP_VIRT_SIZE  GB(1)
 

xen/arch/ppc/xen.lds.S

@@ -24,6 +24,10 @@ SECTIONS
         _stext = .;            /* Text section */
         *(.text.header)
 
+        . = ALIGN(256);
+        HIDDEN(_stext_exceptions = .);
+        *(.text.exceptions)
+
         *(.text.cold)
         *(.text.unlikely .text.*_unlikely .text.unlikely.*)
 
@@ -184,3 +188,6 @@ ASSERT(IS_ALIGNED(__bss_end,        POINTER_ALIGN), "__bss_end is misaligned")
 
 ASSERT(!SIZEOF(.got),      ".got non-empty")
 ASSERT(!SIZEOF(.got.plt),  ".got.plt non-empty")
+
+ASSERT(_stext_exceptions == EXCEPTION_VECTORS_START,
+       ".text.exceptions not at expected location -- .text.header too big?");