kmap_atomic: make kunmap_atomic() harder to misuse
kunmap_atomic() is currently at level -4 on Rusty's "Hard To Misuse"
list[1] ("Follow common convention and you'll get it wrong"), except in
some architectures when CONFIG_DEBUG_HIGHMEM is set[2][3].
kunmap() takes a pointer to a struct page; kunmap_atomic(), however, takes
takes a pointer to within the page itself. This seems to once in a while
trip people up (the convention they are following is the one from
kunmap()).
Make it much harder to misuse, by moving it to level 9 on Rusty's list[4]
("The compiler/linker won't let you get it wrong"). This is done by
refusing to build if the type of its first argument is a pointer to a
struct page.
The real kunmap_atomic() is renamed to kunmap_atomic_notypecheck()
(which is what you would call in case for some strange reason calling it
with a pointer to a struct page is not incorrect in your code).
The previous version of this patch was compile tested on x86-64.
[1] http://ozlabs.org/~rusty/index.cgi/tech/2008-04-01.html
[2] In these cases, it is at level 5, "Do it right or it will always
break at runtime."
[3] At least mips and powerpc look very similar, and sparc also seems to
share a common ancestor with both; there seems to be quite some
degree of copy-and-paste coding here. The include/asm/highmem.h file
for these three archs mention x86 CPUs at its top.
[4] http://ozlabs.org/~rusty/index.cgi/tech/2008-03-30.html
[5] As an aside, could someone tell me why mn10300 uses unsigned long as
the first parameter of kunmap_atomic() instead of void *?
Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
Cc: Russell King <linux@arm.linux.org.uk> (arch/arm)
Cc: Ralf Baechle <ralf@linux-mips.org> (arch/mips)
Cc: David Howells <dhowells@redhat.com> (arch/frv, arch/mn10300)
Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com> (arch/mn10300)
Cc: Kyle McMartin <kyle@mcmartin.ca> (arch/parisc)
Cc: Helge Deller <deller@gmx.de> (arch/parisc)
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org> (arch/parisc)
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> (arch/powerpc)
Cc: Paul Mackerras <paulus@samba.org> (arch/powerpc)
Cc: "David S. Miller" <davem@davemloft.net> (arch/sparc)
Cc: Thomas Gleixner <tglx@linutronix.de> (arch/x86)
Cc: Ingo Molnar <mingo@redhat.com> (arch/x86)
Cc: "H. Peter Anvin" <hpa@zytor.com> (arch/x86)
Cc: Arnd Bergmann <arnd@arndb.de> (include/asm-generic)
Cc: Rusty Russell <rusty@rustcorp.com.au> ("Hard To Misuse" list)
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/arm/include/asm/highmem.h b/arch/arm/include/asm/highmem.h
index feb988a..5aff581 100644
--- a/arch/arm/include/asm/highmem.h
+++ b/arch/arm/include/asm/highmem.h
@@ -36,7 +36,7 @@
extern void *kmap(struct page *page);
extern void kunmap(struct page *page);
extern void *kmap_atomic(struct page *page, enum km_type type);
-extern void kunmap_atomic(void *kvaddr, enum km_type type);
+extern void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type);
extern void *kmap_atomic_pfn(unsigned long pfn, enum km_type type);
extern struct page *kmap_atomic_to_page(const void *ptr);
#endif
diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
index 6ab2440..1fbdb55 100644
--- a/arch/arm/mm/highmem.c
+++ b/arch/arm/mm/highmem.c
@@ -82,7 +82,7 @@
}
EXPORT_SYMBOL(kmap_atomic);
-void kunmap_atomic(void *kvaddr, enum km_type type)
+void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type)
{
unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
unsigned int idx = type + KM_TYPE_NR * smp_processor_id();
@@ -103,7 +103,7 @@
}
pagefault_enable();
}
-EXPORT_SYMBOL(kunmap_atomic);
+EXPORT_SYMBOL(kunmap_atomic_notypecheck);
void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
{
diff --git a/arch/frv/include/asm/highmem.h b/arch/frv/include/asm/highmem.h
index 68e4677..cb4c317 100644
--- a/arch/frv/include/asm/highmem.h
+++ b/arch/frv/include/asm/highmem.h
@@ -152,7 +152,7 @@
asm volatile("tlbpr %0,gr0,#4,#1" : : "r"(vaddr) : "memory"); \
} while(0)
-static inline void kunmap_atomic(void *kvaddr, enum km_type type)
+static inline void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type)
{
switch (type) {
case 0: __kunmap_atomic_primary(0, 2); break;
diff --git a/arch/mips/include/asm/highmem.h b/arch/mips/include/asm/highmem.h
index 25adfb0..75753ca 100644
--- a/arch/mips/include/asm/highmem.h
+++ b/arch/mips/include/asm/highmem.h
@@ -48,14 +48,14 @@
extern void *__kmap(struct page *page);
extern void __kunmap(struct page *page);
extern void *__kmap_atomic(struct page *page, enum km_type type);
-extern void __kunmap_atomic(void *kvaddr, enum km_type type);
+extern void __kunmap_atomic_notypecheck(void *kvaddr, enum km_type type);
extern void *kmap_atomic_pfn(unsigned long pfn, enum km_type type);
extern struct page *__kmap_atomic_to_page(void *ptr);
#define kmap __kmap
#define kunmap __kunmap
#define kmap_atomic __kmap_atomic
-#define kunmap_atomic __kunmap_atomic
+#define kunmap_atomic_notypecheck __kunmap_atomic_notypecheck
#define kmap_atomic_to_page __kmap_atomic_to_page
#define flush_cache_kmaps() flush_cache_all()
diff --git a/arch/mips/mm/highmem.c b/arch/mips/mm/highmem.c
index 127d732..6a2b1bf 100644
--- a/arch/mips/mm/highmem.c
+++ b/arch/mips/mm/highmem.c
@@ -64,7 +64,7 @@
}
EXPORT_SYMBOL(__kmap_atomic);
-void __kunmap_atomic(void *kvaddr, enum km_type type)
+void __kunmap_atomic_notypecheck(void *kvaddr, enum km_type type)
{
#ifdef CONFIG_DEBUG_HIGHMEM
unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
@@ -87,7 +87,7 @@
pagefault_enable();
}
-EXPORT_SYMBOL(__kunmap_atomic);
+EXPORT_SYMBOL(__kunmap_atomic_notypecheck);
/*
* This is the same as kmap_atomic() but can map memory that doesn't
diff --git a/arch/mn10300/include/asm/highmem.h b/arch/mn10300/include/asm/highmem.h
index 90f2abb..b0b187a 100644
--- a/arch/mn10300/include/asm/highmem.h
+++ b/arch/mn10300/include/asm/highmem.h
@@ -91,7 +91,7 @@
return vaddr;
}
-static inline void kunmap_atomic(unsigned long vaddr, enum km_type type)
+static inline void kunmap_atomic_notypecheck(unsigned long vaddr, enum km_type type)
{
#if HIGHMEM_DEBUG
enum fixed_addresses idx = type + KM_TYPE_NR * smp_processor_id();
diff --git a/arch/parisc/include/asm/cacheflush.h b/arch/parisc/include/asm/cacheflush.h
index 4556d82..dba11ae 100644
--- a/arch/parisc/include/asm/cacheflush.h
+++ b/arch/parisc/include/asm/cacheflush.h
@@ -132,7 +132,7 @@
return page_address(page);
}
-static inline void kunmap_atomic(void *addr, enum km_type idx)
+static inline void kunmap_atomic_notypecheck(void *addr, enum km_type idx)
{
kunmap_parisc(addr);
pagefault_enable();
diff --git a/arch/powerpc/include/asm/highmem.h b/arch/powerpc/include/asm/highmem.h
index a74c4ee..d10d64a 100644
--- a/arch/powerpc/include/asm/highmem.h
+++ b/arch/powerpc/include/asm/highmem.h
@@ -62,7 +62,7 @@
extern void kunmap_high(struct page *page);
extern void *kmap_atomic_prot(struct page *page, enum km_type type,
pgprot_t prot);
-extern void kunmap_atomic(void *kvaddr, enum km_type type);
+extern void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type);
static inline void *kmap(struct page *page)
{
diff --git a/arch/powerpc/mm/highmem.c b/arch/powerpc/mm/highmem.c
index c2186c7..857d417 100644
--- a/arch/powerpc/mm/highmem.c
+++ b/arch/powerpc/mm/highmem.c
@@ -52,7 +52,7 @@
}
EXPORT_SYMBOL(kmap_atomic_prot);
-void kunmap_atomic(void *kvaddr, enum km_type type)
+void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type)
{
#ifdef CONFIG_DEBUG_HIGHMEM
unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
@@ -74,4 +74,4 @@
#endif
pagefault_enable();
}
-EXPORT_SYMBOL(kunmap_atomic);
+EXPORT_SYMBOL(kunmap_atomic_notypecheck);
diff --git a/arch/sparc/include/asm/highmem.h b/arch/sparc/include/asm/highmem.h
index 3de42e7..ec23b0a 100644
--- a/arch/sparc/include/asm/highmem.h
+++ b/arch/sparc/include/asm/highmem.h
@@ -71,7 +71,7 @@
}
extern void *kmap_atomic(struct page *page, enum km_type type);
-extern void kunmap_atomic(void *kvaddr, enum km_type type);
+extern void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type);
extern struct page *kmap_atomic_to_page(void *vaddr);
#define flush_cache_kmaps() flush_cache_all()
diff --git a/arch/sparc/mm/highmem.c b/arch/sparc/mm/highmem.c
index 7916feb..e139e9c 100644
--- a/arch/sparc/mm/highmem.c
+++ b/arch/sparc/mm/highmem.c
@@ -65,7 +65,7 @@
}
EXPORT_SYMBOL(kmap_atomic);
-void kunmap_atomic(void *kvaddr, enum km_type type)
+void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type)
{
#ifdef CONFIG_DEBUG_HIGHMEM
unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
@@ -100,7 +100,7 @@
pagefault_enable();
}
-EXPORT_SYMBOL(kunmap_atomic);
+EXPORT_SYMBOL(kunmap_atomic_notypecheck);
/* We may be fed a pagetable here by ptep_to_xxx and others. */
struct page *kmap_atomic_to_page(void *ptr)
diff --git a/arch/x86/include/asm/highmem.h b/arch/x86/include/asm/highmem.h
index a726650..8caac76 100644
--- a/arch/x86/include/asm/highmem.h
+++ b/arch/x86/include/asm/highmem.h
@@ -61,7 +61,7 @@
void kunmap(struct page *page);
void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot);
void *kmap_atomic(struct page *page, enum km_type type);
-void kunmap_atomic(void *kvaddr, enum km_type type);
+void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type);
void *kmap_atomic_pfn(unsigned long pfn, enum km_type type);
void *kmap_atomic_prot_pfn(unsigned long pfn, enum km_type type, pgprot_t prot);
struct page *kmap_atomic_to_page(void *ptr);
diff --git a/arch/x86/mm/highmem_32.c b/arch/x86/mm/highmem_32.c
index 63a6ba6..5e8fa12 100644
--- a/arch/x86/mm/highmem_32.c
+++ b/arch/x86/mm/highmem_32.c
@@ -53,7 +53,7 @@
return kmap_atomic_prot(page, type, kmap_prot);
}
-void kunmap_atomic(void *kvaddr, enum km_type type)
+void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type)
{
unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
@@ -102,7 +102,7 @@
EXPORT_SYMBOL(kmap);
EXPORT_SYMBOL(kunmap);
EXPORT_SYMBOL(kmap_atomic);
-EXPORT_SYMBOL(kunmap_atomic);
+EXPORT_SYMBOL(kunmap_atomic_notypecheck);
EXPORT_SYMBOL(kmap_atomic_prot);
EXPORT_SYMBOL(kmap_atomic_to_page);
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index caafd05..67460f0 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -2,6 +2,7 @@
#define _LINUX_HIGHMEM_H
#include <linux/fs.h>
+#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/uaccess.h>
@@ -72,7 +73,7 @@
}
#define kmap_atomic_prot(page, idx, prot) kmap_atomic(page, idx)
-#define kunmap_atomic(addr, idx) do { pagefault_enable(); } while (0)
+#define kunmap_atomic_notypecheck(addr, idx) do { pagefault_enable(); } while (0)
#define kmap_atomic_pfn(pfn, idx) kmap_atomic(pfn_to_page(pfn), (idx))
#define kmap_atomic_to_page(ptr) virt_to_page(ptr)
@@ -81,6 +82,13 @@
#endif /* CONFIG_HIGHMEM */
+/* Prevent people trying to call kunmap_atomic() as if it were kunmap() */
+/* kunmap_atomic() should get the return value of kmap_atomic, not the page. */
+#define kunmap_atomic(addr, idx) do { \
+ BUILD_BUG_ON(__same_type((addr), struct page *)); \
+ kunmap_atomic_notypecheck((addr), (idx)); \
+ } while (0)
+
/* when CONFIG_HIGHMEM is not set these will be plain clear/copy_page */
#ifndef clear_user_highpage
static inline void clear_user_highpage(struct page *page, unsigned long vaddr)
