x86, mm: Ensure correct alignment of the fixmap

amluto · H. Peter Anvin · commit 73159fdcdb9b · 2014-05-05T13:18:25.000-07:00
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>
diff --git 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
@@ -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
 }
 

Original file line number	Diff line number	Diff line change
`@@ -449,9 +449,9 @@ void __init reserve_top_address(unsigned long reserve)`
`449`	`449`	`{`
`450`	`450`	`#ifdef CONFIG_X86_32`
`451`	`451`	`BUG_ON(fixmaps_set > 0);`
`452`		`- printk(KERN_INFO "Reserving virtual address space above 0x%08x\n",`
`453`		`- (int)-reserve);`
`454`		`- __FIXADDR_TOP = -reserve - PAGE_SIZE;`
	`452`	`+ __FIXADDR_TOP = round_down(-reserve, 1 << PMD_SHIFT) - PAGE_SIZE;`
	`453`	`+ printk(KERN_INFO "Reserving virtual address space above 0x%08lx (rounded to 0x%08lx)\n",`
	`454`	`+ -reserve, __FIXADDR_TOP + PAGE_SIZE);`
`455`	`455`	`#endif`
`456`	`456`	`}`
`457`	`457`