x86-64: finish cleanup_highmaps()'s job wrt. _brk_end

With the introduction of the .brk section, special care must be taken
that no unused page table entries remain if _brk_end and _end are
separated by a 2M page boundary. cleanup_highmap() runs very early and
hence cannot take care of that, hence potential entries needing to be
removed past _brk_end must be cleared once the brk allocator has done
its job.

[ Impact: avoids undesirable TLB aliases ]

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 17 insertions, 1 deletions

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index fd3da1dda1c9..ae4f7b5d7104 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -7,6 +7,7 @@
 #include <asm/page.h>
 #include <asm/page_types.h>
 #include <asm/sections.h>
+#include <asm/setup.h>
 #include <asm/system.h>
 #include <asm/tlbflush.h>
 
@@ -304,8 +305,23 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
 #endif
 
 #ifdef CONFIG_X86_64
-        if (!after_bootmem)
+        if (!after_bootmem && !start) {
+                pud_t *pud;
+                pmd_t *pmd;
+
                 mmu_cr4_features = read_cr4();
+
+                /*
+                 * _brk_end cannot change anymore, but it and _end may be
+                 * located on different 2M pages. cleanup_highmap(), however,
+                 * can only consider _end when it runs, so destroy any
+                 * mappings beyond _brk_end here.
+                 */
+                pud = pud_offset(pgd_offset_k(_brk_end), _brk_end);
+                pmd = pmd_offset(pud, _brk_end - 1);
+                while (++pmd <= pmd_offset(pud, (unsigned long)_end - 1))
+                        pmd_clear(pmd);
+        }
 #endif
         __flush_tlb_all();