kernel.git/arch/mips/mm/highmem.c, branch linux-3.2.y

mm: fix race in kunmap_atomic()

2010-10-28T01:03:05Z

Christoph reported a nice splat which illustrated a race in the new stack based kmap_atomic implementation. The problem is that we pop our stack slot before we're completely done resetting its state -- in particular clearing the PTE (sometimes that's CONFIG_DEBUG_HIGHMEM). If an interrupt happens before we actually clear the PTE used for the last slot, that interrupt can reuse the slot in a dirty state, which triggers a BUG in kmap_atomic(). Fix this by introducing kmap_atomic_idx() which reports the current slot index without actually releasing it and use that to find the PTE and delay the _pop() until after we're completely done. Signed-off-by: Peter Zijlstra Reported-by: Christoph Hellwig Acked-by: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: stack based kmap_atomic()

2010-10-26T23:52:08Z

Keep the current interface but ignore the KM_type and use a stack based approach. The advantage is that we get rid of crappy code like: #define __KM_PTE \ (in_nmi() ? KM_NMI_PTE : \ in_irq() ? KM_IRQ_PTE : \ KM_PTE0) and in general can stop worrying about what context we're in and what kmap slots might be appropriate for that. The downside is that FRV kmap_atomic() gets more expensive. For now we use a CPP trick suggested by Andrew: #define kmap_atomic(page, args...) __kmap_atomic(page) to avoid having to touch all kmap_atomic() users in a single patch. [ not compiled on: - mn10300: the arch doesn't actually build with highmem to begin with ] [akpm@linux-foundation.org: coding-style fixes] [akpm@linux-foundation.org: fix up drivers/gpu/drm/i915/intel_overlay.c] Acked-by: Rik van Riel Signed-off-by: Peter Zijlstra Acked-by: Chris Metcalf Cc: David Howells Cc: Hugh Dickins Cc: Ingo Molnar Cc: Thomas Gleixner Cc: "H. Peter Anvin" Cc: Steven Rostedt Cc: Russell King Cc: Ralf Baechle Cc: David Miller Cc: Paul Mackerras Cc: Benjamin Herrenschmidt Cc: Dave Airlie Cc: Li Zefan Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

kmap_atomic: make kunmap_atomic() harder to misuse

2010-08-10T03:44:54Z

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 Cc: Russell King (arch/arm) Cc: Ralf Baechle (arch/mips) Cc: David Howells (arch/frv, arch/mn10300) Cc: Koichi Yasutake (arch/mn10300) Cc: Kyle McMartin (arch/parisc) Cc: Helge Deller (arch/parisc) Cc: "James E.J. Bottomley" (arch/parisc) Cc: Benjamin Herrenschmidt (arch/powerpc) Cc: Paul Mackerras (arch/powerpc) Cc: "David S. Miller" (arch/sparc) Cc: Thomas Gleixner (arch/x86) Cc: Ingo Molnar (arch/x86) Cc: "H. Peter Anvin" (arch/x86) Cc: Arnd Bergmann (include/asm-generic) Cc: Rusty Russell ("Hard To Misuse" list) Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

MIPS: Highmem: Fix build error

2010-02-22T20:42:11Z

arch/mips/mm/highmem.c: In function 'kmap_init': arch/mips/mm/highmem.c:130: error: 'init_mm' undeclared (first use in this function) arch/mips/mm/highmem.c:130: error: (Each undeclared identifier is reported only once arch/mips/mm/highmem.c:130: error: for each function it appears in.) Signed-off-by: Yoichi Yuasa Cc: linux-mips Patchwork: http://patchwork.linux-mips.org/patch/980/ Signed-off-by: Ralf Baechle

MIPS: Build fix - include into all smp_processor_id() users.

2009-06-24T17:34:39Z

Some of the were relying into smp.h being dragged in by another header which of course is fragile. uses smp_processor_id() only in macros and including smp.h there leads to an include loop, so don't change cpu-info.h. Signed-off-by: Ralf Baechle

MIPS: Fix highmem.

2009-05-14T12:50:29Z

Commit 351336929ccf222ae38ff0cb7a8dd5fd5c6236a0 (kernel.org) rsp. b3594a089f1c17ff919f8f78505c3f20e1f6f8ce (linux-mips.org): > From: Chris Dearman > Date: Wed, 19 Sep 2007 00:58:24 +0100 > Subject: [PATCH] [MIPS] Allow setting of the cache attribute at run time. > > Slightly tacky, but there is a precedent in the sparc archirecture code. introduces the variable _page_cachable_default, which defaults to zero and. is used to create the prototype PTE for __kmap_atomic in arch/mips/mm/init.c:kmap_init before initialization in arch/mips/mm/c-r4k.c:coherency_setup, so the default value of 0 will be used as the CCA of kmap atomic pages which on many processors is not a defined CCA value and may result in writes to kmap_atomic pages getting corrupted. Debugged by Jon Fraser (jfraser@broadcom.com). Signed-off-by: Ralf Baechle

mm: use debug_kmap_atomic

2009-04-01T15:59:14Z

Use debug_kmap_atomic in kmap_atomic, kmap_atomic_pfn, and iomap_atomic_prot_pfn. Signed-off-by: Akinobu Mita Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

MIPS: Use BUG_ON() where possible.

2009-03-30T12:49:44Z

Based on original patch by Stoyan Gaydarov which missed a few places. Signed-off-by: Ralf Baechle

[MIPS] unexport __kmap_atomic_to_page

2008-05-12T15:46:51Z

This patch removes the no longer used export of __kmap_atomic_to_page. Signed-off-by: Adrian Bunk Signed-off-by: Ralf Baechle

[MIPS] Remove LIMITED_DMA support

2007-05-11T13:28:31Z

This code was needed only by Jaguar ATX. Signed-off-by: Franck Bui-Huu Signed-off-by: Ralf Baechle