[PATCH v4 3/5] build: Alloc space for sched list in the link file

[Jonathan Creekmore <jonathan.creekmore@gmail.com>]

Creates a section to contain scheduler entry pointers that are gathered
together into an array. This will allow, in a follow-on patch, scheduler
entries to be automatically gathered together into the array for
automatic parsing.

CC: Ian Campbell <ian.campbell@citrix.com>
CC: Stefano Stabellini <stefano.stabellini@citrix.com>
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <jbeulich@suse.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jonathan Creekmore <jonathan.creekmore@gmail.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>

---
Changed since v3:
  * Add defensive check for schedulers in the linker

Changed since v1:
  * rename the __start and __end symbols to better match
    the rest of the file
---
 xen/arch/arm/xen.lds.S | 5 +++++
 xen/arch/x86/xen.lds.S | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/xen/arch/arm/xen.lds.S b/xen/arch/arm/xen.lds.S
index 0488f37..2492def 100644
--- a/xen/arch/arm/xen.lds.S
+++ b/xen/arch/arm/xen.lds.S
@@ -57,6 +57,10 @@ SECTIONS
        . = ALIGN(PAGE_SIZE);
        *(.data.page_aligned)
        *(.data)
+       . = ALIGN(8);
+       __start_schedulers_array = .;
+       *(.data.schedulers)
+       __end_schedulers_array = .;
        *(.data.rel)
        *(.data.rel.*)
        CONSTRUCTORS
@@ -193,3 +197,4 @@ SECTIONS
  * code running on the boot time identity map cannot cross a section boundary.
  */
 ASSERT( _end_boot - start <= PAGE_SIZE, "Boot code is larger than 4K")
+ASSERT((__end_schedulers_array - __start_schedulers_array) > 0, "no schedulers compiled in")
diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index e18e08f..63f89af 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -80,6 +80,10 @@ SECTIONS
        __stop___pre_ex_table = .;
 
        *(.data.read_mostly)
+       . = ALIGN(8);
+       __start_schedulers_array = .;
+       *(.data.schedulers)
+       __end_schedulers_array = .;
        *(.data.rel.ro)
        *(.data.rel.ro.*)
   } :text
@@ -226,3 +230,4 @@ ASSERT(kexec_reloc_size - kexec_reloc <= PAGE_SIZE, "kexec_reloc is too large")
 #endif
 
 ASSERT((cpu0_stack & (STACK_SIZE - 1)) == 0, "cpu0_stack misaligned")
+ASSERT((__end_schedulers_array - __start_schedulers_array) > 0, "no schedulers compiled in")
-- 
2.6.4