x86-32: use brk segment for allocating initial kernel pagetable

Impact: use new interface instead of previous ad hoc implementation

Rather than having special purpose init_pg_table_start/end variables
to delimit the kernel pagetable built by head_32.S, just use the brk
mechanism to extend the bss for the new pagetable.

This patch removes init_pg_table_start/end and pg0, defines __brk_base
(which is page-aligned and immediately follows _end), initializes
the brk region to start there, and uses it for the 32-bit pagetable.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 7 insertions, 7 deletions

diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index c32ca19d591a..db6652710e98 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -167,7 +167,7 @@ num_subarch_entries = (. - subarch_entries) / 4
 /*
  * Initialize page tables.  This creates a PDE and a set of page
  * tables, which are located immediately beyond _end.  The variable
- * init_pg_tables_end is set up to point to the first "safe" location.
+ * _brk_end is set up to point to the first "safe" location.
  * Mappings are created both at virtual address 0 (identity mapping)
  * and PAGE_OFFSET for up to _end+sizeof(page tables)+INIT_MAP_BEYOND_END.
  *
@@ -190,8 +190,7 @@ default_entry:
 
         xorl %ebx,%ebx                          /* %ebx is kept at zero */
 
-        movl $pa(pg0), %edi
-        movl %edi, pa(init_pg_tables_start)
+        movl $pa(__brk_base), %edi
         movl $pa(swapper_pg_pmd), %edx
         movl $PTE_IDENT_ATTR, %eax
 10:
@@ -216,7 +215,8 @@ default_entry:
         cmpl %ebp,%eax
         jb 10b
 1:
-        movl %edi,pa(init_pg_tables_end)
+        addl $__PAGE_OFFSET, %edi
+        movl %edi, pa(_brk_end)
         shrl $12, %eax
         movl %eax, pa(max_pfn_mapped)
 
@@ -227,8 +227,7 @@ default_entry:
 
 page_pde_offset = (__PAGE_OFFSET >> 20);
 
-        movl $pa(pg0), %edi
-        movl %edi, pa(init_pg_tables_start)
+        movl $pa(__brk_base), %edi
         movl $pa(swapper_pg_dir), %edx
         movl $PTE_IDENT_ATTR, %eax
 10:
@@ -249,7 +248,8 @@ page_pde_offset = (__PAGE_OFFSET >> 20);
         leal (INIT_MAP_BEYOND_END+PTE_IDENT_ATTR)(%edi),%ebp
         cmpl %ebp,%eax
         jb 10b
-        movl %edi,pa(init_pg_tables_end)
+        addl $__PAGE_OFFSET, %edi
+        movl %edi, pa(_brk_end)
         shrl $12, %eax
         movl %eax, pa(max_pfn_mapped)