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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
..
cache-dbg-flush-by-reg.S MN10300: Fix one of the kernel debugger cacheflush variants 2011-06-07 19:03:52 -07:00
cache-dbg-flush-by-tag.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-dbg-inv-by-reg.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-dbg-inv-by-tag.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-dbg-inv.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-disabled.c MN10300: Handle missing sys_cacheflush() when caching disabled 2010-09-28 18:01:14 -07:00
cache-flush-by-reg.S MN10300: AM34: Add cacheflushing by using the AM34 purge registers 2010-10-27 17:28:45 +01:00
cache-flush-by-tag.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-flush-icache.c MN10300: Cache: Implement SMP global cache flushing 2010-10-27 17:28:47 +01:00
cache-inv-by-reg.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-inv-by-tag.S MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
cache-inv-icache.c MN10300: The SMP_ICACHE_INV_FLUSH_RANGE IPI command does not exist 2011-03-14 14:45:29 +00:00
cache-smp-flush.c MN10300: Cache: Implement SMP global cache flushing 2010-10-27 17:28:47 +01:00
cache-smp-inv.c MN10300: Cache: Implement SMP global cache flushing 2010-10-27 17:28:47 +01:00
cache-smp.c mn10300: convert old cpumask API into new one 2011-05-25 08:39:39 -07:00
cache-smp.h MN10300: Cache: Implement SMP global cache flushing 2010-10-27 17:28:47 +01:00
cache.c MN10300: Cache: Implement SMP global cache flushing 2010-10-27 17:28:47 +01:00
cache.inc MN10300: The icache invalidate functions should disable the icache first 2011-03-18 16:54:29 +00:00
dma-alloc.c mn10300: mm/dma-alloc.c needs <linux/export.h> 2012-07-11 16:04:42 -07:00
extable.c
fault.c vm: add VM_FAULT_SIGSEGV handling support 2015-01-29 10:51:32 -08:00
init.c mm/mn10300: prepare for removing num_physpages and simplify mem_init() 2013-07-03 16:07:37 -07:00
Kconfig.cache MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
Makefile MN10300: Create general kernel debugger cache flushing 2011-03-18 16:54:30 +00:00
misalignment.c Disintegrate asm/system.h for MN10300 2012-03-28 18:30:02 +01:00
mmu-context.c MN10300: Make the use of PIDR to mark TLB entries controllable 2010-10-27 17:28:49 +01:00
pgtable.c mn10300: add missing pgtable_page_ctor/dtor calls 2013-11-15 09:32:16 +09:00
tlb-mn10300.S MN10300: Use the [ID]PTEL2 registers rather than [ID]PTEL for TLB control 2010-10-27 17:28:50 +01:00
tlb-smp.c arch,mn10300: Convert smp_mb__*() 2014-04-18 14:20:39 +02:00