linux-toradex.git/arch/parisc/mm, branch v3.14.53

vm: add VM_FAULT_SIGSEGV handling support

2015-04-29T08:31:55+00:00

commit 33692f27597fcab536d7cbbcc8f52905133e4aa7 upstream.

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 
[shengyong: Backport to 3.14
 - adjust context
 - ignore modification for arch nios2, because 3.14 does not support it
 - add SIGSEGV handling to powerpc/cell spu_fault.c, because 3.14 does not
   separate it to copro_fault.c
 - add SIGSEGV handling to mm/memory.c, because 3.14 does not separate it
   to gup.c
]
Signed-off-by: Sheng Yong 
Signed-off-by: Greg Kroah-Hartman

parisc: ratelimit userspace segfault printing

2014-06-07T17:28:23+00:00

commit fef47e2a2e1e75fe50a10f634a80f16808348cc6 upstream.

Ratelimit printing of userspace segfaults and make it runtime
configurable via the /proc/sys/debug/exception-trace variable. This
should resolve syslog from growing way too fast and thus prevents
possible system service attacks.

Signed-off-by: Helge Deller 
Signed-off-by: Greg Kroah-Hartman

mm, show_mem: remove SHOW_MEM_FILTER_PAGE_COUNT

2014-01-22T00:19:44+00:00

Commit 4b59e6c47309 ("mm, show_mem: suppress page counts in
non-blockable contexts") introduced SHOW_MEM_FILTER_PAGE_COUNT to
suppress PFN walks on large memory machines.  Commit c78e93630d15 ("mm:
do not walk all of system memory during show_mem") avoided a PFN walk in
the generic show_mem helper which removes the requirement for
SHOW_MEM_FILTER_PAGE_COUNT in that case.

This patch removes PFN walkers from the arch-specific implementations
that report on a per-node or per-zone granularity.  ARM and unicore32
still do a PFN walk as they report memory usage on each bank which is a
much finer granularity where the debugging information may still be of
use.  As the remaining arches doing PFN walks have relatively small
amounts of memory, this patch simply removes SHOW_MEM_FILTER_PAGE_COUNT.

[akpm@linux-foundation.org: fix parisc]
Signed-off-by: Mel Gorman 
Acked-by: David Rientjes 
Cc: Tony Luck 
Cc: Russell King 
Cc: James Bottomley 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

parisc: fix kernel memory layout in vmlinux.ld.S

2013-11-30T21:09:21+00:00

When building a 64bit kernel sometimes functions in the .init section were not
able to reach the standard kernel function. Main reason for this problem is,
that the linkage tables (.plt, .opd, .dlt) tend to become pretty huge and thus
the distance gets too big for short calls.

One option to avoid this is to use the -mlong-calls compiler option, but this
increases the binary size and introduces a performance penalty.

Instead, with this patch we just lay out the binary differently.  Init code is
stored first, followed by text, R/O and finally R/W data. This means, that init
and text code is now much closer to each other, which is sufficient to reach
each other by short calls.

Signed-off-by: Helge Deller

parisc: improve SIGBUS/SIGSEGV error reporting

2013-11-19T22:36:18+00:00

This patch fixes most of the Linux Test Project testcases, e.g. fstat05.

Signed-off-by: Helge Deller

parisc: signal fixup - SIGBUS vs. SIGSEGV

2013-11-07T21:29:24+00:00

Clean up code to send correct signal on invalid memory accesses:
Send SIGBUS instead of SIGSEGV for memory accesses outside of mmap'ed
areas

This fixes the mmap13 testcase from the Linux Test Project.

Signed-off-by: Helge Deller

parisc: provide macro to create exception table entries

2013-11-07T21:25:33+00:00

Provide a macro ASM_EXCEPTIONTABLE_ENTRY() to create exception table
entries and convert all open-coded places to use that macro.

This patch is a first step toward creating a exception table which only
holds 32bit pointers even on a 64bit kernel. That way in my own kernel
I was able to reduce the in-kernel exception table from 44kB to 22kB.

Signed-off-by: Helge Deller

parisc: optimize variable initialization in do_page_fault

2013-10-13T15:45:40+00:00

The attached change defers the initialization of the variables tsk, mm
and flags until they are needed. As a result, the code won't crash if a
kernel probe is done with a corrupt context and the code will be better
optimized.

Signed-off-by: John David Anglin  
Signed-off-by: Helge Deller

arch/parisc/mm/fault.c: fix uninitialized variable usage

2013-09-30T21:31:02+00:00

The FAULT_FLAG_WRITE flag has been set based on uninitialized variable.

Fixes a regression added by commit 759496ba6407 ("arch: mm: pass
userspace fault flag to generic fault handler")

Signed-off-by: Felipe Pena 
Cc: Johannes Weiner 
Cc: Michal Hocko 
Cc: "James E.J. Bottomley" 
Cc: Helge Deller 
Signed-off-by: Andrew Morton 
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