597781f3e5
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>
122 lines
3.1 KiB
C
122 lines
3.1 KiB
C
/*
|
|
* highmem.c: virtual kernel memory mappings for high memory
|
|
*
|
|
* Provides kernel-static versions of atomic kmap functions originally
|
|
* found as inlines in include/asm-sparc/highmem.h. These became
|
|
* needed as kmap_atomic() and kunmap_atomic() started getting
|
|
* called from within modules.
|
|
* -- Tomas Szepe <szepe@pinerecords.com>, September 2002
|
|
*
|
|
* But kmap_atomic() and kunmap_atomic() cannot be inlined in
|
|
* modules because they are loaded with btfixup-ped functions.
|
|
*/
|
|
|
|
/*
|
|
* The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
|
|
* gives a more generic (and caching) interface. But kmap_atomic can
|
|
* be used in IRQ contexts, so in some (very limited) cases we need it.
|
|
*
|
|
* XXX This is an old text. Actually, it's good to use atomic kmaps,
|
|
* provided you remember that they are atomic and not try to sleep
|
|
* with a kmap taken, much like a spinlock. Non-atomic kmaps are
|
|
* shared by CPUs, and so precious, and establishing them requires IPI.
|
|
* Atomic kmaps are lightweight and we may have NCPUS more of them.
|
|
*/
|
|
#include <linux/mm.h>
|
|
#include <linux/highmem.h>
|
|
#include <asm/pgalloc.h>
|
|
#include <asm/cacheflush.h>
|
|
#include <asm/tlbflush.h>
|
|
#include <asm/fixmap.h>
|
|
|
|
void *kmap_atomic(struct page *page, enum km_type type)
|
|
{
|
|
unsigned long idx;
|
|
unsigned long vaddr;
|
|
|
|
/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
|
|
pagefault_disable();
|
|
if (!PageHighMem(page))
|
|
return page_address(page);
|
|
|
|
debug_kmap_atomic(type);
|
|
idx = type + KM_TYPE_NR*smp_processor_id();
|
|
vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
|
|
|
|
/* XXX Fix - Anton */
|
|
#if 0
|
|
__flush_cache_one(vaddr);
|
|
#else
|
|
flush_cache_all();
|
|
#endif
|
|
|
|
#ifdef CONFIG_DEBUG_HIGHMEM
|
|
BUG_ON(!pte_none(*(kmap_pte-idx)));
|
|
#endif
|
|
set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
|
|
/* XXX Fix - Anton */
|
|
#if 0
|
|
__flush_tlb_one(vaddr);
|
|
#else
|
|
flush_tlb_all();
|
|
#endif
|
|
|
|
return (void*) vaddr;
|
|
}
|
|
EXPORT_SYMBOL(kmap_atomic);
|
|
|
|
void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type)
|
|
{
|
|
#ifdef CONFIG_DEBUG_HIGHMEM
|
|
unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
|
|
unsigned long idx = type + KM_TYPE_NR*smp_processor_id();
|
|
|
|
if (vaddr < FIXADDR_START) { // FIXME
|
|
pagefault_enable();
|
|
return;
|
|
}
|
|
|
|
BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx));
|
|
|
|
/* XXX Fix - Anton */
|
|
#if 0
|
|
__flush_cache_one(vaddr);
|
|
#else
|
|
flush_cache_all();
|
|
#endif
|
|
|
|
/*
|
|
* force other mappings to Oops if they'll try to access
|
|
* this pte without first remap it
|
|
*/
|
|
pte_clear(&init_mm, vaddr, kmap_pte-idx);
|
|
/* XXX Fix - Anton */
|
|
#if 0
|
|
__flush_tlb_one(vaddr);
|
|
#else
|
|
flush_tlb_all();
|
|
#endif
|
|
#endif
|
|
|
|
pagefault_enable();
|
|
}
|
|
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)
|
|
{
|
|
unsigned long idx, vaddr = (unsigned long)ptr;
|
|
pte_t *pte;
|
|
|
|
if (vaddr < SRMMU_NOCACHE_VADDR)
|
|
return virt_to_page(ptr);
|
|
if (vaddr < PKMAP_BASE)
|
|
return pfn_to_page(__nocache_pa(vaddr) >> PAGE_SHIFT);
|
|
BUG_ON(vaddr < FIXADDR_START);
|
|
BUG_ON(vaddr > FIXADDR_TOP);
|
|
|
|
idx = virt_to_fix(vaddr);
|
|
pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
|
|
return pte_page(*pte);
|
|
}
|