[Xen-devel] [PATCH] xen/x86: Reorder .data and .init when linking

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

In preparation for using superpage mappings, .data and .bss will both want to
be mapped as read-write.  By making them adjacent, they can share the same
superpage and will not require superpage alignment between themselves.

While making this change, fix a latent alignment bug whereby the alignment for
.bss.stack_aligned was in .init.  __init_end only needs page alignment (due to
being reclaimed after boot), while .bss.stack_aligned really does needs
STACK_SIZE alignment.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>

v2:
 * New
v3:
 * Swap __bss_start and its alignment.
---
 xen/arch/x86/xen.lds.S | 63 +++++++++++++++++++++++++-------------------------
 1 file changed, 32 insertions(+), 31 deletions(-)

diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 8390ec2..f78309d 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -74,36 +74,6 @@ SECTIONS
 #endif
   } :text
 
-  . = ALIGN(SMP_CACHE_BYTES);
-  .data.read_mostly : {
-       /* Exception table */
-       __start___ex_table = .;
-       *(.ex_table)
-       __stop___ex_table = .;
-
-       /* Pre-exception table */
-       __start___pre_ex_table = .;
-       *(.ex_table.pre)
-       __stop___pre_ex_table = .;
-
-       *(.data.read_mostly)
-       . = ALIGN(8);
-       __start_schedulers_array = .;
-       *(.data.schedulers)
-       __end_schedulers_array = .;
-       *(.data.rel.ro)
-       *(.data.rel.ro.*)
-  } :text
-
-  .data : {                    /* Data */
-       . = ALIGN(PAGE_SIZE);
-       *(.data.page_aligned)
-       *(.data)
-       *(.data.rel)
-       *(.data.rel.*)
-       CONSTRUCTORS
-  } :text
-
   . = ALIGN(PAGE_SIZE);             /* Init code and data */
   __init_begin = .;
   .init.text : {
@@ -163,10 +133,41 @@ SECTIONS
        *(.xsm_initcall.init)
        __xsm_initcall_end = .;
   } :text
-  . = ALIGN(STACK_SIZE);
+  . = ALIGN(PAGE_SIZE);
   __init_end = .;
 
+  . = ALIGN(SMP_CACHE_BYTES);
+  .data.read_mostly : {
+       /* Exception table */
+       __start___ex_table = .;
+       *(.ex_table)
+       __stop___ex_table = .;
+
+       /* Pre-exception table */
+       __start___pre_ex_table = .;
+       *(.ex_table.pre)
+       __stop___pre_ex_table = .;
+
+       *(.data.read_mostly)
+       . = ALIGN(8);
+       __start_schedulers_array = .;
+       *(.data.schedulers)
+       __end_schedulers_array = .;
+       *(.data.rel.ro)
+       *(.data.rel.ro.*)
+  } :text
+
+  .data : {                    /* Data */
+       . = ALIGN(PAGE_SIZE);
+       *(.data.page_aligned)
+       *(.data)
+       *(.data.rel)
+       *(.data.rel.*)
+       CONSTRUCTORS
+  } :text
+
   .bss : {                     /* BSS */
+       . = ALIGN(STACK_SIZE);
        __bss_start = .;
        *(.bss.stack_aligned)
        . = ALIGN(PAGE_SIZE);
-- 
2.1.4


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