Linus Torvalds 33692f2759 vm: add VM_FAULT_SIGSEGV handling support ... 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 fee7e49d45 ("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 <tiwai@suse.de> Tested-by: Jan Engelhardt <jengelh@inai.de> Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> # "s390 still compiles and boots" Cc: linux-arch@vger.kernel.org Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2015-01-29 10:51:32 -08:00
..
cmm.c	s390: convert use of typedef ctl_table to struct ctl_table	2013-10-28 08:36:25 +01:00
dump_pagetables.c	s390/mm: remove change bit override support	2014-09-25 10:52:09 +02:00
extable.c	s390/exceptions: switch to relative exception table entries	2012-09-26 15:45:10 +02:00
extmem.c	s390/comments: unify copyright messages and remove file names	2012-07-20 11:15:04 +02:00
fault.c	vm: add VM_FAULT_SIGSEGV handling support	2015-01-29 10:51:32 -08:00
gup.c	s390/gup: handle zero nr_pages case correctly	2013-10-24 17:17:01 +02:00
hugetlbpage.c	s390/mm: remove change bit override support	2014-09-25 10:52:09 +02:00
init.c	mm: export symbol dependencies of is_zero_pfn()	2014-09-14 16:25:14 +02:00
maccess.c	/dev/mem: Use more consistent data types	2014-11-10 15:59:21 +01:00
Makefile	s390/mem_detect: move memory detection code to mm folder	2013-05-02 15:50:22 +02:00
mem_detect.c	s390/mm: Convert bootmem to memblock	2014-05-20 08:58:40 +02:00
mmap.c	s390/mmap: randomize mmap base for bottom up direction	2013-11-13 12:09:08 +09:00
page-states.c	s390/cmma: remove "cmma disable" code in case of dump again	2014-05-20 08:58:42 +02:00
pageattr.c	mm/debug-pagealloc: make debug-pagealloc boottime configurable	2014-12-13 12:42:48 -08:00
pgtable.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux	2015-01-15 10:50:29 +13:00
vmem.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux	2014-10-14 03:47:00 +02:00