linux-stable.git/arch/um, branch linux-3.4.y

vm: add VM_FAULT_SIGSEGV handling support

2015-04-14T09:33:57+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
Signed-off-by: Linus Torvalds 
[bwh: Backported to 3.2:
 - Adjust filenames, context
 - Drop arc, metag, nios2 and lustre changes
 - For sh, patch both 32-bit and 64-bit implementations to use goto bad_area
 - For s390, pass int_code and trans_exc_code as arguments to do_no_context()
   and do_sigsegv()]
Signed-off-by: Ben Hutchings 
[lizf: Backported to 3.4:
 - adjust context in arch/power/mm/fault.c
 - apply the original change in upstream commit for s390]
Signed-off-by: Zefan Li

um: add missing declaration of 'getrlimit()' and friends

2013-12-12T06:34:11+00:00

commit fdfa4c952844fce881df8c76de9c7180cbe913ab upstream.

arch/um/os-Linux/start_up.c: In function 'check_coredump_limit':
arch/um/os-Linux/start_up.c:338:16: error: storage size of 'lim' isn't known
arch/um/os-Linux/start_up.c:339:2: error: implicit declaration of function 'getrlimit' [-Werror=implicit-function-declaration]

Signed-off-by: Sergei Trofimovich 
CC: Jeff Dike 
CC: Richard Weinberger 
CC: Al Viro 
CC: user-mode-linux-devel@lists.sourceforge.net
CC: user-mode-linux-user@lists.sourceforge.net
CC: linux-kernel@vger.kernel.org
Signed-off-by: Richard Weinberger 
Signed-off-by: Greg Kroah-Hartman

uml: check length in exitcode_proc_write()

2013-11-13T03:01:49+00:00

commit 201f99f170df14ba52ea4c52847779042b7a623b upstream.

We don't cap the size of buffer from the user so we could write past the
end of the array here.  Only root can write to this file.

Reported-by: Nico Golde 
Reported-by: Fabian Yamaguchi 
Signed-off-by: Dan Carpenter 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

um: Implement a custom pte_same() function

2012-06-01T07:18:18+00:00

commit f15b9000eb1d09bbaa4b0a6b2089d7e1f64e84b3 upstream.

UML uses the _PAGE_NEWPAGE flag to mark pages which are not jet
installed on the host side using mmap().
pte_same() has to ignore this flag, otherwise unuse_pte_range()
is unable to unuse the page because two identical
page tables entries with different _PAGE_NEWPAGE flags would not
match and swapoff() would never return.

Analyzed-by: Hugh Dickins 
Signed-off-by: Richard Weinberger 
Signed-off-by: Greg Kroah-Hartman

um: Fix __swp_type()

2012-06-01T07:18:18+00:00

commit 2b76ebaa728f8a3967c52aa189261c72fe56a6f1 upstream.

The current __swp_type() function uses a too small bitshift.
Using more than one swap files causes bad pages because
the type bits clash with other page flags.

Analyzed-by: Hugh Dickins 
Signed-off-by: Richard Weinberger 
Signed-off-by: Greg Kroah-Hartman

um: uml_setup_stubs': warning: unused variable 'pages'

2012-04-09T22:13:45+00:00

Fix the following gcc complain
arch/um/kernel/skas/mmu.c: In function 'uml_setup_stubs':
arch/um/kernel/skas/mmu.c:106:16: warning: unused variable 'pages' [-Wunused-variable]

Signed-Signed-off-by: Boaz Harrosh 
Signed-off-by: Richard Weinberger

um: Use asm-generic/switch_to.h

2012-04-09T22:13:45+00:00

Signed-off-by: Richard Weinberger

um: Disintegrate asm/system.h

2012-04-09T22:13:45+00:00

Signed-off-by: Richard Weinberger 
Reported-by: Toralf Förster 
CC: dhowells@redhat.com

um: switch cow_user.h to htobe{32,64}/betoh{32,64}

2012-04-09T22:13:45+00:00

... rather than open-coding the 64bit versions.  endian.h has those guys.

Signed-off-by: Al Viro 
Signed-off-by: Richard Weinberger

um: fix linker script generation

2012-04-09T17:59:00+00:00

while we can't just use -U$(SUBARCH), we still need to kill idiotic define
(implicit -Di386=1), both for SUBARCH=i386 and SUBARCH=x86/CONFIG_64BIT=n
builds.

Signed-off-by: Al Viro