[tip:x86/vdso] x86, mm: Ensure correct alignment of the fixmap

tip-bot for Andy Lutomirski
2014-05-05T22:24:55Z

Commit-ID: 73159fdcdb9be3eda61b846864352c29371baeb6
Gitweb: http://git.kernel.org/tip/73159fdcdb9be3eda61b846864352c29371baeb6
Author: Andy Lutomirski <luto@amacapital.net>
AuthorDate: Mon, 5 May 2014 12:19:31 -0700
Committer: H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Mon, 5 May 2014 13:18:25 -0700

x86, mm: Ensure correct alignment of the fixmap

The early_ioremap code requires that its buffers not span a PMD
boundary. The logic for ensuring that only works if the fixmap is
aligned, so assert that it's aligned correctly.

To make this work reliably, reserve_top_address needs to be
adjusted.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Link: http://lkml.kernel.org/r/e59a5f4362661f75dd4841fa74e1f2448045e245.1399317206.git.luto@amacapital.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
arch/x86/mm/ioremap.c | 6 ++++++
arch/x86/mm/pgtable.c | 6 +++---
2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 597ac15..6ef98c5 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -355,6 +355,12 @@ void __init early_ioremap_init(void)
{
pmd_t *pmd;

+#ifdef CONFIG_X86_64
+ BUILD_BUG_ON((fix_to_virt(0) + PAGE_SIZE) & ((1 << PMD_SHIFT) - 1));
+#else
+ WARN_ON((fix_to_virt(0) + PAGE_SIZE) & ((1 << PMD_SHIFT) - 1));
+#endif
+
early_ioremap_setup();

pmd = early_ioremap_pmd(fix_to_virt(FIX_BTMAP_BEGIN));
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index c96314a..5f8bdda 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -449,9 +449,9 @@ void __init reserve_top_address(unsigned long reserve)
{
#ifdef CONFIG_X86_32
BUG_ON(fixmaps_set > 0);
- printk(KERN_INFO "Reserving virtual address space above 0x%08x\n",
- (int)-reserve);
- __FIXADDR_TOP = -reserve - PAGE_SIZE;
+ __FIXADDR_TOP = round_down(-reserve, 1 << PMD_SHIFT) - PAGE_SIZE;
+ printk(KERN_INFO "Reserving virtual address space above 0x%08lx (rounded to 0x%08lx)\n",
+ -reserve, __FIXADDR_TOP + PAGE_SIZE);
#endif
}