Spotted these while cleaning up <sys/cdefs.h> --- if we remove __USE_XOPEN2K8,
libchrome decides you "must" have futimes. Adding the missing functions (all
just alternative interfaces to utimensat(2) system call) lets us clean up
without breaking anything.
Change-Id: If44fab08ee3de0e31066d650d128a3c96323529b
There's no change to the generated stubs, because the script only cares
that this is a pointer type, not what it's a pointer to.
Change-Id: I766720965f0f3d201fc90677a076b26870485377
Move everything to where it should be.
Along the way, we lose <net/ethertypes.h>. glibc only has a handful of these
types, and they're all in <net/ethernet.h>, not <net/ethertypes.h>. I've taken
the liberty of not including the AppleTalk ones, since it is 2016.
Also, <net/if_ether.h> should be <netinet/if_ether.h> (though with different
contents).
Bug: http://b/28519060
Change-Id: Ia41c3fc136fd3e6b008c8d08018e0629134ea6fc
* Allow clone where both the child function and stack are null. It's
obviously wrong to ask to call a function without a stack, but it's not
necessarily wrong to supply no stack if you're also not supplying a
function.
* Reimplement fork in terms of the clone function, rather than using the
clone system call directly.
This is intended as a step towards enabling use of pid namespaces.
Change-Id: I03c89bd1dc540d8b4ed1c8fdf6644290744b9e91
http://clang.llvm.org/docs/AttributeReference.html#nonnull
_Nonnull is similar to the nonnull attribute in that it will instruct
compilers to warn the user if it can prove that a null argument is
being passed. Unlike the nonnull attribute, this annotation indicated
that a value *should not* be null, not that it *cannot* be null, or
even that the behavior is undefined. The important distinction is that
the optimizer will perform surprising optimizations like the
following:
void foo(void*) __attribute__(nonnull, 1);
int bar(int* p) {
foo(p);
// The following null check will be elided because nonnull
// attribute means that, since we call foo with p, p can be
// assumed to not be null. Thus this will crash if we are called
// with a null pointer.
if (src != NULL) {
return *p;
}
return 0;
}
int main() {
return bar(NULL);
}
Note that by doing this we are no longer attaching any sort of
attribute for GCC (GCC doesn't support attaching nonnull directly to a
parameter, only to the function and naming the arguments
positionally). This means we won't be getting a warning for this case
from GCC any more. People that listen to warnings tend to use clang
anyway, and we're quickly moving toward that as the default, so this
seems to be an acceptable tradeoff.
Change-Id: Ie05fe7cec2f19a082c1defb303f82bcf9241b88d
* Fix the return type of towlower_l/towupper_l.
* Implement wctrans/wctrans_l/towctrans/towctrans_l.
* Move declarations that POSIX says are available from both <wchar.h> and
<wctype.h> to <bits/wctype.h> and include from both POSIX headers.
* Write the missing tests.
Change-Id: I3221da5f3d7e8a2fb0a7619dc724de45f7b55398
Not efficient to iterate through given the large number of Android
ids (AID). Compile warning will result if you use these functions,
telling you as much. Not for general consumption, however for
example, some filesystem tests would like to see these to perform
all corners.
About 1/4 second for getpwent, and 1/8 second for getgrent to iterate
through all reserved Android aids.
Bug: 27999086
Change-Id: I7784273b7875c38e4954ae21d314f35e4bf8c2fc
* changes:
Move <sys/sysconf.h> to <bits/sysconf.h>.
Remove mbstowcs from <wchar.h>.
Extract getopt and friends to <bits/getopt.h>
Remove declaration of unlinkat from <fcntl.h>.
Extract ioctl to <bits/ioctl.h>.
Extract fcntl to <bits/fcntl.h>.
Extract strcasecmp and friends to <bits/strcasecmp.h>.
Make <bits/lockf.h> compile standalone.
Make <android/dlext.h> compile standalone.
Make the network headers compile standalone.
Remove duplicate declaration of mlock, munlock.
The XXXX now lines up to the underlying uid and has no offset.
Work with AID_OEM_RESERVED uids.
Test uses hard coded values to catch changes in the API expectations
that may occur in private/android_filesystem_config.h.
SideEffects: names change, some product dependencies.
Bug: 27999086
Change-Id: Ic2b4c36de74ae009a44e14711c75834293828207
- added grp_pwd.cpp containing POSIX passwd and group functions,
colocated because they share with the Android ID (AID) roots.
- stubs.cpp contains all the truly empty functions (network and
protocol accessors)
Bug: 27999086
Change-Id: I036f9e2dd246f48302cb7c97d23176fa24d19c33
Implement the legacy SysV signal handling functions sighold(),
sigignore(), sigpause(), sigrelse(), and sigset() in terms of the newer
POSIX signal APIs. As of POSIX 2013 the SysV signal APIs are deprecated
but still required.
Change-Id: I4ca40e3d706605a7d1a30dc76c78b2b24586387d
Signed-off-by: Greg Hackmann <ghackmann@google.com>
The code to calculate thread stack and signal stack looks weird:
the thread stack size and signal stack size are related with
each other on 32-bit mode, but not on 64-bit mode. So change the
code to make the logic more resonable. This doesn't change anything
as we have defined SIGSTKSZ to 16K on arm64.
Bug: 28005110
Change-Id: I04d2488cfb96ee7e2d894d062c66cef950fec418
This function only exists for backwards compatibility, so leave it as it was.
Bug: http://b/26944282
Change-Id: I31973d1402660933103ee2d815649ab9569e4dfc
Although there is a test pthread.pthread_mutex_owner_tid_limit
to check pid_max, but bionic-unit-tests hangs before reaching
that test. So abort at libc initialization if not able to reach
the test when running bionic-unit-tests32. It is more friendly
for debugging.
Bug: 24016357
Change-Id: Ia70c2e36fd8a3a040d41ea5722c7b48a6134e102
POSIX makes "the CPU-time clock of the calling thread" (i.e.,
CLOCK_THREAD_CPUTIME_ID) a special case which returns EINVAL instead of
ENOTSUP.
However, the clock_nanosleep syscall treats this clock just like any
other, and returns -EOPNOTSUPP to indicate an unimplemented nanosleep
handler. So we need to handle this ourselves in userspace.
This change fixes the LTP clock_nanosleep01 testcase.
Change-Id: If3bed940d276834bcd114d8c17f96197e9384711
Signed-off-by: Greg Hackmann <ghackmann@google.com>
bionic has the Linux-specific mntent.h but is missing hasmntopt().
Change-Id: I0ab7b83626c969704add4e64b37a6fc715d4a723
Signed-off-by: Greg Hackmann <ghackmann@google.com>
{get,set}domainname aren't in POSIX but are widely-implemented
extensions.
The Linux kernel provides a setdomainname syscall but not a symmetric
getdomainname syscall, since it expects userspace to get the domain name
from uname(2).
Change-Id: I96726c242f4bb646c130b361688328b0b97269a0
Signed-off-by: Greg Hackmann <ghackmann@google.com>
This patch uses __kernel_vsyscall instead of "int 0x80"
as the syscall entry point. AT_SYSINFO points to
an adapter to mask the arch specific difference and gives a
performance boost on i386 architecture.
Change-ID: Ib340c604d02c6c25714a95793737e3cfdc3fc5d7
Signed-off-by: Mingwei Shi <mingwei.shi@intel.com>
Even though the size parameter to epoll_create(2) is (otherwise) unused,
passing in size <= 0 is explicitly documented as an error.
This change fixes the LTP epoll01 testcase.
Change-Id: I044a38be823c2fa956b57e77cc66571dfae8a4bb
Signed-off-by: Greg Hackmann <ghackmann@google.com>
The clone syscall accepts NULL child stacks, interpreting this to mean
the child gets a copy of the parent's stack with copy-on-write
semantics. However clone(2) is explicitly documented to treat this an
an error.
"Fortunately" every architecture's __bionic_clone implementation pushes
something onto the child stack before making the clone syscall. So we
know fixing this won't break legacy apps, because any app that tried
using a NULL child stack would have died with SIGSEGV.
This change fixes the LTP clone04 testcase.
Change-Id: I663b34f34bc8dad2aa405c46e4eed4418cccca0d
Signed-off-by: Greg Hackmann <ghackmann@google.com>
Also guard both these GNU extensions with _GNU_SOURCE.
Also improve the tests to test each case on both the current thread and
another thread, since the code paths are totally different.
Bug: http://b/27810459
Change-Id: I72b05bca5c5b6ca8ba4585b8edfb716a1c252f92
We don't have a compile-time limit on the number of threads,
and we don't have a definite run-time limit either.
Bug: http://b/27617302
Change-Id: I6a6fe083e7b655d24eb9e7ef7f3e0280d483080b
Do not initialize all of the global function pointers associated with
debug malloc until the initialization has completed correctly.
Bug: 27600760
Change-Id: I0621b54bc2d9fab63805d7992d384e550d6fed2a
Don't ask the kernel to copy data to userspace if we don't need it.
(Noticed while cleaning up sysconf to not call clock_getres.)
Change-Id: Icc0f7559775b8a2dcefe638ce831d06b75d67122
There are a hundred other reasons why we can't run on kernels old enough
to not have all the clocks covered by sysconf.
This was causing trouble for jemalloc 4.1.0 in a seccomp-constrained process
because jemalloc 4.1.0 introduced a call to sysconf that caused us to make
clock_getres syscalls for the first time, leading to SIGSYS.
Bug: http://b/27408522
Change-Id: I2eb6986d871bc03cbef278e5617734409c39e057
glibc, FreeBSD, OpenBSD, and Darwin all just leave the fd unchanged and
possibly uninitialized. Setting it to -1 seems friendlier, though.
Bug: http://b/27506278
Change-Id: I7acdc8eecbea4404d5fb4ba0b4d572245a323886
Make it easier to diagnose applications mucking with the contents of
jmp_buf by checksumming its contents.
Bug: http://b/27417786
Change-Id: I9989e2ea3979a36ae0bc4c9e1bacafddbacc731b
This involves actually implementing assembler __memset_chk for arm64,
but that's easily done.
Obviously I'd like this for all architectures (and all the string functions),
but this is low-hanging fruit...
Change-Id: I70ec48c91aafd1f0feb974a2555c51611de9ef82
Also remove an if that implied that IFA_BROADCAST is a possibility for
AF_INET6.
The existing tests fail if you have a point-to-point interface configured,
so no new test necessary.
Bug: http://b/27442503
Change-Id: I4c5823b32204ae6c15527853414c2a0cef320b53
Our FORTIFY _chk functions' implementations were very repetitive and verbose
but not very helpful. We'd also screwed up and put the SSIZE_MAX checks where
they would never fire unless you actually had a buffer as large as half your
address space, which probably doesn't happen very often.
Factor out the duplication and take the opportunity to actually show details
like how big the overrun buffer was, or by how much it was overrun.
Also remove the obsolete FORTIFY event logging.
Also remove the unused __libc_fatal_no_abort.
This change doesn't improve the diagnostics from the optimized assembler
implementations.
Change-Id: I176a90701395404d50975b547a00bd2c654e1252
...so memset it is, then.
I'll be glad when GCC is dead and we can use "= {}" like it's the 21st century.
Change-Id: I28d820d3926ac9bf44bf7c1e89e184726c840391
The purpose of this change is to silence Valgrind's warning about a
syscall parameter pointing to uninitialised bytes.
Change-Id: I2737235f9ac288dbc8ec4be0c6f1cef181c9b7d7
Add backtrace_string to convert a malloc_debug backtrace to a string.
Also move the backtrace functions to libc_malloc_debug_backtrace so that
libmemunreachable can reuse them.
Change-Id: I5ad67001c0b4d184903c762863a8588181d4873b
Since we set both fields to NULL all the time, we can alias the two
fields together on LP32 to provide build-time compatibility.
BUG=24918750
TEST=python now builds for Brillo boards
Change-Id: I3394aea80c9a5288669389f71d0e4132f2157e3c
Check if thread_id is in fact pthread_self before
locking on g_thread_list_lock in __pthread_internal_find.
The main reason for doing this is not performance but to allow
the linker use raise() which was not working because pthread_kill()
couldn't find pthread_self() thread because the global thread
list is initialized in libc.so and the linker's version of this
list is empty.
Bug: http://b/25867917
Change-Id: I18fe620e8cd465b30f0e1ff45fff32958f3c5c00
Our fopen/freopen/tmpfile are already always O_LARGEFILE, but let's add
the aliases for _LARGEFILE_SOURCE compatibility.
Bug: http://b/24807045
Change-Id: I5d99b3ef3c9f27ce70f13313f6a92e96c7f21f80
This file should have been deleted with the malloc debug rewrite, but
popped back into existence due to a merge conflict.
Change-Id: I74e53daaf3febf650b20e3da5329558ac84c5bcd
If snprintf() is called from the linker, it may erroneously return a
null string. The libc internal __libc_format_buffer() does not have
this problem, so it is now used instead.
Bug: 26756577
Change-Id: I37a97e27f59b3c0a087f54a6603cc3aff7f07522
This has been requested a few times over the years. This is basically
a very late rebase of https://android-review.googlesource.com/45470
which was abandoned years ago. One addition is that this version has
_FILE_OFFSET_BITS=64 support.
POSIX puts this in <unistd.h>. glibc also has it in <fcntl.h>.
Bug: http://b/13077650
Change-Id: I5862b1dc326e326c01ad92438ecc1578d19ba739
Broke the build. There's no such file as bionic_sdk_version.h anywhere in the tree.
This reverts commit 892b61d340.
Change-Id: Iec3f4588edfb1d1524bb5f16451fd05dc6ebe44a
Posix standards says sem_wait is interruptible by the delivery
of a signal. To keep compatiblity with old apps, only fix that
in newer sdk versions.
Bug: 26743454
Change-Id: I924cbb436658e3e0f397c922d866ece99b8241a3
The major components of the rewrite:
- Completely remove the qemu shared library code. Nobody was using it
and it appears to have broken at some point.
- Adds the ability to enable/disable different options independently.
- Adds a new option that can enable the backtrace on alloc/free when
a process gets a specific signal.
- Adds a new way to enable malloc debug. If a special property is
set, and the process has an environment variable set, then debug
malloc will be enabled. This allows something that might be
a derivative of app_process to be started with an environment variable
being enabled.
- get_malloc_leak_info() used to return one element for each pointer that
had the exact same backtrace. The new version returns information for
every one of the pointers with same backtrace. It turns out ddms already
automatically coalesces these, so the old method simply hid the fact
that there where multiple pointers with the same amount of backtrace.
- Moved all of the malloc debug specific code into the library.
Nothing related to the malloc debug data structures remains in libc.
- Removed the calls to the debug malloc cleanup routine. Instead, I
added an atexit call with the debug malloc cleanup routine. This gets
around most problems related to the timing of doing the cleanup.
The new properties and environment variables:
libc.debug.malloc.options
Set by option name (such as "backtrace"). Setting this to a bad value
will cause a usage statement to be printed to the log.
libc.debug.malloc.program
Same as before. If this is set, then only the program named will
be launched with malloc debug enabled. This is not a complete match,
but if any part of the property is in the program name, malloc debug is
enabled.
libc.debug.malloc.env_enabled
If set, then malloc debug is only enabled if the running process has the
environment variable LIBC_DEBUG_MALLOC_ENABLE set.
Bug: 19145921
Change-Id: I7b0e58cc85cc6d4118173fe1f8627a391b64c0d7
This is just a subset of the recently-implemented getifaddrs(3), though if
we want to handle interfaces (such as "rmnet_*") that don't have an address,
we need to either expose ifaddrs_storage and keep track of which interfaces
we've already seen (which is pretty messy), or refactor the netlink code so
we can reuse it and just extract the information we need for if_nameindex(3).
This patch goes the latter route.
Also clean up if_nametoindex(3) and if_indextoname(3).
Change-Id: I5ffc5df0bab62286cdda2e7af06f032c767119a8
Also fix a bug where we were mutating the address/broadcast address
of an existing entry rather than the new entry, and use 'const' to
ensure we don't make that mistake again.
Change-Id: I31c127a5d21879b52c85cd0f7ed2e66554a21e39
Exactly which functions get a stack protector is up to the compiler, so
let's separate the code that sets up the environment stack protection
requires and explicitly build it with -fno-stack-protector.
Bug: http://b/26276517
Change-Id: I8719e23ead1f1e81715c32c1335da868f68369b5
Currently, reads of ro.* properties are treated differently than
writes of ro.* properties. When writing an ro.* property, we ignore
the "ro." portion of the property, and base the security decision
on the label of the remaining portion.
See e7a9e52740/init/property_service.cpp
line 120-126
For example, for writing, the label associated with
"ro.build.fingerprint" comes from the /property_contexts file
entry:
# ro.build.fingerprint is either set in /system/build.prop, or is
# set at runtime by system_server.
build.fingerprint u:object_r:fingerprint_prop:s0
However, we fail to follow this same special case when sorting
properties into files. Instead, ro.build.fingerprint is assigned
u:object_r:default_prop:s0 instead of u:object_r:fingerprint_prop:s0
Ignore the "ro." portion when sorting properties into files.
This will make reads and writes of properties use the same label.
Bug: 21852512
Change-Id: Ie88ffc6b78b31fc8ddf370ae27c218546fb25a83
This reverts commit 76814a8250.
This differs from the original in fixing the GCC -Werror build:
bionic/libc/bionic/ifaddrs.cpp: In function 'void __handle_netlink_response(ifaddrs**, nlmsghdr*)':
bionic/libc/bionic/ifaddrs.cpp:113:62: error: use of old-style cast [-Werror=old-style-cast]
ifinfomsg* ifi = reinterpret_cast<ifinfomsg*>(NLMSG_DATA(hdr));
This appears to be a GCC bug; the GCC command-line correctly uses -isystem,
and manually adding #pragma GCC system_header doesn't help. So just turn the
warning off for GCC for now. We won't need to worry about building with GCC
soon anyway.
Bug: http://b/26238832
Change-Id: I01615bd335edf11baf487b1c83a9157cd780f4a1
Time to dust off the old libcore implementation from gingerbread and add it
to bionic. Unlike the original, this actually looks at both RTM_NEWLINK and
RTM_NEWADDR.
Bug: http://b/26238832
Change-Id: I7bb4b432deb766065b66b9c9ff36ed68249aba82
It actually means "crash immediately". Well, it's an error. And callers are
much more likely to realize their mistake if we crash immediately rather
than return EINVAL. Historically, glibc has crashed and bionic -- before
the recent changes -- returned EINVAL, so this is a behavior change.
Change-Id: I0c2373a6703b20b8a97aacc1e66368a5885e8c51
This change removes endpwent, dlmalloc_inspect_all, dlmalloc_trim
from lp64 libc.so. It also removed necessety of having brillo
version scripts for lp64 platforms.
Bug: http://b/26164862
Change-Id: I4e9b38907bb1dc410f0eb6d2f5d5944fe713da51
Treat subsequent calls to __system_properties_init() as a
reinitialization of system properties and revoke access to prop files
that have been previously mapped but that the process's current context
does not have access to. Additionally reset the no_access_ flag in
case permissions have loosened and previously unaccessible files can now
be accessed.
This is meant to work around an issue that setcon() does not revoke
mmap() mappings, so we must manually revoke them after a successful
setcon() call.
Bug 26114086
Change-Id: I4d690abb6817283ca64ac26ea4c1dad398a98fbc
Currently, if the debug.atrace.tags.enableflags property is not found,
it is set to a safe value such that a pointer to this property can be
stored for later access. This may result in selinux denials because not
all processes write permissions for this property or permission to
connect to the property write socket at all.
Change I6d953c0c281fd72ad3eba8a479fd258023579b5b writes this property to
a safe value upon boot, which greatly decreases the cases in which this
property will not be accessible and removes the need to write it here.
This commit removes this write.
Bug 26115803
Change-Id: Ief72c5f731d3a1231b5080eb531fa0a491a8b1d1
We need to ensure %gs:20 is set up early enough for -fstack-protector-strong
on x86, and that __set_tls doesn't get stack protector checks because it's a
prerequisite for them. x86 devices/emulators won't boot without this.
Bug: http://b/26073874
Change-Id: Icf0d34294648cc0c8cb406a3617befe0d45c525a
POSIX defined bcopy to handle overlapping memory akin to memmove and
bionic appears to have always done so.
Change-Id: I2599113411e3532913270ba1c1b49e35cbc5f106
This reverts commit c8bae05f3f.
We were breaking init (ueventd) because we initialize system properties
before we initialize stdio. The new system property implementation uses
stdio to read from /property_contexts, so we end up touching stdio data
structures before they've been initialized.
This second attempt takes things further by removing the stdio initialization
function altogether. The data structures for stdin/stdout/stderr can be
statically initialized as data, and -- since we already had to give the
atexit implementation a backdoor for stdio -- we can just admit that we
need to clean up stdio, and that we always do so last.
This patch also removes the 17 statically pre-allocated file structures,
so the first fopen will now allocate a block of 10 (the usual overflow
behavior). I did this just to make my life simpler, but it's not actually
necessary to remove it if we want it back.
Change-Id: I936b2eb5e88e4ebaf5516121872b71fc88e5609c
This reverts commit 4371961e00.
This broke booting; ueventd crashes with a null pointer dereference
somewhere in __sfp (but the kernel doesn't unwind, so I don't know
what was calling __sfp).
Change-Id: I65375fdfdf1d339a06558b4057b580cacd6324e2
Primarily a debug feature that can be switched at runtime to permit
developer to have the option of high-resolution Android logs with
either CLOCK_REALTIME (default) or CLOCK_MONOTONIC to correlate with
other system activities like kernel logs or systrace.
Bug: 23668800
Change-Id: Ib29024899540f51a72cad5dde25517a7134d68f7
If a __system_property* function is called before
__system_properties_init() then the app will will abort. This commit
returns either an error code or a safe return value instead.
Bug 26027140
Change-Id: I95ffd143e9563658ab67a397991e84fb4c46ab77
Several parts in pthread_internal_t should be initialized
to zero, like tls, key_data and thread_local_dtors. So
just clear the whole pthread_internal_t is more convenient.
Bug: 25990348
Change-Id: Ibb6d1200ea5e6e1afbc77971f179197e8239f6ea
The purpose of this change is to add read access control to the property
space.
In the current design, a process either has access to the single
/dev/__properties__ file and therefore all properties that it contains
or it has access to no properties. This change separates properties
into multiple property files based on their selabel, which allows
creation of sepolicies that allow read access of only specific sets of
properties to specific domains.
Bug 21852512
Change-Id: Ice265db79201ca811c6b6cf6d851703f53224f03
Previously we call __sinit() lazily. But it is likely to cause data
races like in https://android-review.googlesource.com/#/c/183237/. So
we prefer to call __sinit() explicitly at libc initialization.
Bug: 25392375
Change-Id: I181ea7a4b2e4c7350b45f2e6c86886ea023e80b8
Currently we use __thread variable to store thread_local_dtors,
which makes tsan test fork_atexit.cc hang. The problem is as below:
The main thread creates a worker thread, the worker thread calls
pthread_exit() -> __cxa_thread_finalize() -> __emutls_get_address()
-> pthread_once(emutls_init) -> emutls_init().
Then the main thread calls fork(), the child process cals
exit() -> __cxa_thread_finalize() -> __emutls_get_address()
-> pthread_once(emutls_init).
So the child process is waiting for pthread_once(emutls_init)
to finish which will never occur.
It might be the test's fault because POSIX standard says if a
multi-threaded process calls fork(), the new process may only
execute async-signal-safe operations until exec functions are
called. And exit() is not async-signal-safe. But we can make
bionic more reliable by not using __thread in
__cxa_thread_finalize().
Bug: 25392375
Change-Id: Ife403dd7379dad8ddf1859c348c1c0adea07afb3
It is reported by tsan that funlockfile() can unlock an unlocked mutex.
It happens when printf() is called before fopen() or other stdio stuff.
As FLOCKFILE(fp) is called before __sinit(), _stdio_handles_locking is false,
and _FLOCK(fp) will not be locked. But then cantwrite(fp) in __vfprintf()
calls__sinit(), which makes _stdio_handles_locking become true, and
FUNLOCKFILE(fp) unlocks _FLOCK(fp).
Change _stdio_handles_locking into _caller_handles_locking,
so __sinit() won't change its value. Add test due to my previous fault.
Bug: 25392375
Change-Id: I483e3c3cdb28da65e62f1fd9615bf58c5403b4dd
Currently is_private_anonymous is calculated as true if _either_
MAP_PRIVATE or MAP_ANONYMOUS is set, which is a mistake.
According to Documentation/vm/ksm.txt, "KSM only merges anonymous
(private) pages, never pagecache (file) pages". MAP_PRIVATE can
still be set on file cache pages so in order to not redundantly
set MADV_MERGEABLE on pages that are not fitted for it, both
MAP_PRIVATE and MAP_ANONYMOUS should be set.
Along with this fix, add an extra check that the mapped page is
not a stack page before setting MADV_MERGEABLE for it. Stack pages
change too quickly and always end up in KSM 'page_volatile' list.
Change-Id: If4954142852f17cc61f02985ea1cb625a7f3dec6
