x86: fix early_ioremap()/btmap

fix a long-standing weakness of the early-ioremap allocator: it
uses a single pgd entry for the boot mappings, and was not properly
protecting itself against crossing a 2MB (4MB) boundary.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/include/asm-x86/fixmap_32.h b/include/asm-x86/fixmap_32.h
index 46bedb7..fde140f 100644 (file)
--- a/include/asm-x86/fixmap_32.h
+++ b/include/asm-x86/fixmap_32.h
@@ -90,10 +90,18 @@ enum fixed_addresses {
        FIX_PARAVIRT_BOOTMAP,
 #endif
        __end_of_permanent_fixed_addresses,
-       /* temporary boot-time mappings, used before ioremap() is functional */
+       /*
+        * 256 temporary boot-time mappings, used by early_ioremap(),
+        * before ioremap() is functional.
+        *
+        * We round it up to the next 512 pages boundary so that we
+        * can have a single pgd entry and a single pte table:
+        */
 #define NR_FIX_BTMAPS          64
 #define FIX_BTMAPS_NESTING     4
-       FIX_BTMAP_END = __end_of_permanent_fixed_addresses,
+       FIX_BTMAP_END =
+               __end_of_permanent_fixed_addresses + 512 -
+                       (__end_of_permanent_fixed_addresses & 511),
        FIX_BTMAP_BEGIN = FIX_BTMAP_END + NR_FIX_BTMAPS*FIX_BTMAPS_NESTING - 1,
        FIX_WP_TEST,
        __end_of_fixed_addresses