kernel/linux.git/arch/sh/mm/fault.c, branch linux-4.4.y

mm/fault, arch: Use pagefault_disable() to check for disabled pagefaults in the handler

2015-05-19T06:39:15+00:00

Introduce faulthandler_disabled() and use it to check for irq context and disabled pagefaults (via pagefault_disable()) in the pagefault handlers. Please note that we keep the in_atomic() checks in place - to detect whether in irq context (in which case preemption is always properly disabled). In contrast, preempt_disable() should never be used to disable pagefaults. With !CONFIG_PREEMPT_COUNT, preempt_disable() doesn't modify the preempt counter, and therefore the result of in_atomic() differs. We validate that condition by using might_fault() checks when calling might_sleep(). Therefore, add a comment to faulthandler_disabled(), describing why this is needed. faulthandler_disabled() and pagefault_disable() are defined in linux/uaccess.h, so let's properly add that include to all relevant files. This patch is based on a patch from Thomas Gleixner. Reviewed-and-tested-by: Thomas Gleixner Signed-off-by: David Hildenbrand Signed-off-by: Peter Zijlstra (Intel) Cc: David.Laight@ACULAB.COM Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: airlied@linux.ie Cc: akpm@linux-foundation.org Cc: benh@kernel.crashing.org Cc: bigeasy@linutronix.de Cc: borntraeger@de.ibm.com Cc: daniel.vetter@intel.com Cc: heiko.carstens@de.ibm.com Cc: herbert@gondor.apana.org.au Cc: hocko@suse.cz Cc: hughd@google.com Cc: mst@redhat.com Cc: paulus@samba.org Cc: ralf@linux-mips.org Cc: schwidefsky@de.ibm.com Cc: yang.shi@windriver.com Link: http://lkml.kernel.org/r/1431359540-32227-7-git-send-email-dahi@linux.vnet.ibm.com Signed-off-by: Ingo Molnar

vm: add VM_FAULT_SIGSEGV handling support

2015-01-29T18:51:32+00:00

The core VM already knows about VM_FAULT_SIGBUS, but cannot return a "you should SIGSEGV" error, because the SIGSEGV case was generally handled by the caller - usually the architecture fault handler. That results in lots of duplication - all the architecture fault handlers end up doing very similar "look up vma, check permissions, do retries etc" - but it generally works. However, there are cases where the VM actually wants to SIGSEGV, and applications _expect_ SIGSEGV. In particular, when accessing the stack guard page, libsigsegv expects a SIGSEGV. And it usually got one, because the stack growth is handled by that duplicated architecture fault handler. However, when the generic VM layer started propagating the error return from the stack expansion in commit fee7e49d4514 ("mm: propagate error from stack expansion even for guard page"), that now exposed the existing VM_FAULT_SIGBUS result to user space. And user space really expected SIGSEGV, not SIGBUS. To fix that case, we need to add a VM_FAULT_SIGSEGV, and teach all those duplicate architecture fault handlers about it. They all already have the code to handle SIGSEGV, so it's about just tying that new return value to the existing code, but it's all a bit annoying. This is the mindless minimal patch to do this. A more extensive patch would be to try to gather up the mostly shared fault handling logic into one generic helper routine, and long-term we really should do that cleanup. Just from this patch, you can generally see that most architectures just copied (directly or indirectly) the old x86 way of doing things, but in the meantime that original x86 model has been improved to hold the VM semaphore for shorter times etc and to handle VM_FAULT_RETRY and other "newer" things, so it would be a good idea to bring all those improvements to the generic case and teach other architectures about them too. Reported-and-tested-by: Takashi Iwai Tested-by: Jan Engelhardt Acked-by: Heiko Carstens # "s390 still compiles and boots" Cc: linux-arch@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds

arch: mm: pass userspace fault flag to generic fault handler

2013-09-12T22:38:01+00:00

Unlike global OOM handling, memory cgroup code will invoke the OOM killer in any OOM situation because it has no way of telling faults occuring in kernel context - which could be handled more gracefully - from user-triggered faults. Pass a flag that identifies faults originating in user space from the architecture-specific fault handlers to generic code so that memcg OOM handling can be improved. Signed-off-by: Johannes Weiner Reviewed-by: Michal Hocko Cc: David Rientjes Cc: KAMEZAWA Hiroyuki Cc: azurIt Cc: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm, oom: remove statically defined arch functions of same name

2012-12-13T01:38:34+00:00

out_of_memory() is a globally defined function to call the oom killer. x86, sh, and powerpc all use a function of the same name within file scope in their respective fault.c unnecessarily. Inline the functions into the pagefault handlers to clean the code up. Signed-off-by: David Rientjes Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Thomas Gleixner Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Paul Mundt Reviewed-by: Michal Hocko Reviewed-by: KAMEZAWA Hiroyuki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

readahead: fault retry breaks mmap file read random detection

2012-10-09T07:22:47+00:00

.fault now can retry. The retry can break state machine of .fault. In filemap_fault, if page is miss, ra->mmap_miss is increased. In the second try, since the page is in page cache now, ra->mmap_miss is decreased. And these are done in one fault, so we can't detect random mmap file access. Add a new flag to indicate .fault is tried once. In the second try, skip ra->mmap_miss decreasing. The filemap_fault state machine is ok with it. I only tested x86, didn't test other archs, but looks the change for other archs is obvious, but who knows :) Signed-off-by: Shaohua Li Cc: Rik van Riel Cc: Wu Fengguang Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

sh: Fix up recursive fault in oops with unset TTB.

2012-07-25T04:11:13+00:00

Presently the oops code looks for the pgd either from the mm context or the cached TTB value. There are presently cases where the TTB can be unset or otherwise cleared by hardware, which we weren't handling, resulting in recursive faults on the NULL pgd. In these cases we can simply reload from swapper_pg_dir and continue on as normal. Cc: stable@vger.kernel.org Signed-off-by: Paul Mundt

sh64: Fix up vmalloc fault range check.

2012-05-18T11:01:16+00:00

With the previous attempt reverted this switches to conditionalizing the end address. Nominally VMALLOC_END, but extended for P3_ADDR_MAX in the store queue case. Signed-off-by: Paul Mundt

Revert "sh: Ensure fixmap and store queue space can co-exist."

2012-05-18T10:30:05+00:00

This reverts commit 20e7c297efeca0861adcca073a0d283da659834b. With store queues enabled the area above P4SEG has special properties from the MMU's point of view, which was causing fixmap failure. We'll have to do something else to satisfy the vmalloc range check. Signed-off-by: Paul Mundt

sh: Enable shared page fault handler for _32/_64.

2012-05-14T06:33:28+00:00

This moves the now generic _32 page fault handling code to a shared place and adapts the _64 implementation to make use of it. Signed-off-by: Paul Mundt

sh: Move in the SH-5 TLB miss.

2008-01-28T04:18:50+00:00

Signed-off-by: Paul Mundt