[PATCH] x86: make __FIXADDR_TOP variable to allow it to make space for a hypervisor

Make __FIXADDR_TOP a variable, so that it can be set to not get in the way of
address space a hypervisor may want to reserve.

Original patch by Gerd Hoffmann <kraxel@suse.de>

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: Gerd Hoffmann <kraxel@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 68 insertions, 0 deletions

diff --git a/arch/i386/mm/init.c b/arch/i386/mm/init.c
index 353453d550a4..efd0bcdac65d 100644
--- a/arch/i386/mm/init.c
+++ b/arch/i386/mm/init.c
@@ -629,6 +629,48 @@ void __init mem_init(void)
                 (unsigned long) (totalhigh_pages << (PAGE_SHIFT-10))
                );
 
+#if 1 /* double-sanity-check paranoia */
+        printk("virtual kernel memory layout:\n"
+               "    fixmap  : 0x%08lx - 0x%08lx   (%4ld kB)\n"
+#ifdef CONFIG_HIGHMEM
+               "    pkmap   : 0x%08lx - 0x%08lx   (%4ld kB)\n"
+#endif
+               "    vmalloc : 0x%08lx - 0x%08lx   (%4ld MB)\n"
+               "    lowmem  : 0x%08lx - 0x%08lx   (%4ld MB)\n"
+               "      .init : 0x%08lx - 0x%08lx   (%4ld kB)\n"
+               "      .data : 0x%08lx - 0x%08lx   (%4ld kB)\n"
+               "      .text : 0x%08lx - 0x%08lx   (%4ld kB)\n",
+               FIXADDR_START, FIXADDR_TOP,
+               (FIXADDR_TOP - FIXADDR_START) >> 10,
+
+#ifdef CONFIG_HIGHMEM
+               PKMAP_BASE, PKMAP_BASE+LAST_PKMAP*PAGE_SIZE,
+               (LAST_PKMAP*PAGE_SIZE) >> 10,
+#endif
+
+               VMALLOC_START, VMALLOC_END,
+               (VMALLOC_END - VMALLOC_START) >> 20,
+
+               (unsigned long)__va(0), (unsigned long)high_memory,
+               ((unsigned long)high_memory - (unsigned long)__va(0)) >> 20,
+
+               (unsigned long)&__init_begin, (unsigned long)&__init_end,
+               ((unsigned long)&__init_end - (unsigned long)&__init_begin) >> 10,
+
+               (unsigned long)&_etext, (unsigned long)&_edata,
+               ((unsigned long)&_edata - (unsigned long)&_etext) >> 10,
+
+               (unsigned long)&_text, (unsigned long)&_etext,
+               ((unsigned long)&_etext - (unsigned long)&_text) >> 10);
+
+#ifdef CONFIG_HIGHMEM
+        BUG_ON(PKMAP_BASE+LAST_PKMAP*PAGE_SIZE > FIXADDR_START);
+        BUG_ON(VMALLOC_END                     > PKMAP_BASE);
+#endif
+        BUG_ON(VMALLOC_START                   > VMALLOC_END);
+        BUG_ON((unsigned long)high_memory      > VMALLOC_START);
+#endif /* double-sanity-check paranoia */
+
 #ifdef CONFIG_X86_PAE
         if (!cpu_has_pae)
                 panic("cannot execute a PAE-enabled kernel on a PAE-less CPU!");
diff --git a/arch/i386/mm/pgtable.c b/arch/i386/mm/pgtable.c
index a9f4910a22f8..10126e3f8174 100644
--- a/arch/i386/mm/pgtable.c
+++ b/arch/i386/mm/pgtable.c
@@ -12,6 +12,7 @@
 #include <linux/slab.h>
 #include <linux/pagemap.h>
 #include <linux/spinlock.h>
+#include <linux/module.h>
 
 #include <asm/system.h>
 #include <asm/pgtable.h>
@@ -139,6 +140,12 @@ void set_pmd_pfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags)
         __flush_tlb_one(vaddr);
 }
 
+static int fixmaps;
+#ifndef CONFIG_COMPAT_VDSO
+unsigned long __FIXADDR_TOP = 0xfffff000;
+EXPORT_SYMBOL(__FIXADDR_TOP);
+#endif
+
 void __set_fixmap (enum fixed_addresses idx, unsigned long phys, pgprot_t flags)
 {
         unsigned long address = __fix_to_virt(idx);
@@ -148,6 +155,25 @@ void __set_fixmap (enum fixed_addresses idx, unsigned long phys, pgprot_t flags)
                 return;
         }
         set_pte_pfn(address, phys >> PAGE_SHIFT, flags);
+        fixmaps++;
+}
+
+/**
+ * reserve_top_address - reserves a hole in the top of kernel address space
+ * @reserve - size of hole to reserve
+ *
+ * Can be used to relocate the fixmap area and poke a hole in the top
+ * of kernel address space to make room for a hypervisor.
+ */
+void reserve_top_address(unsigned long reserve)
+{
+        BUG_ON(fixmaps > 0);
+#ifdef CONFIG_COMPAT_VDSO
+        BUG_ON(reserve != 0);
+#else
+        __FIXADDR_TOP = -reserve - PAGE_SIZE;
+        __VMALLOC_RESERVE += reserve;
+#endif
 }
 
 pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)