Linux sandbox: start adding syscall wrappers

Linux sandbox: start adding syscall wrappers

Add some syscall wrappers instead of calling syscall() inline.
This adds some type safety and will make it easier to switch the
underlying syscall implementation.

This fixes a few issues with SYS_CLONE being called with the wrong number of
parameters.

BUG=435194
Committed: https://crrev.com/610a4a61dd805269d0cbe4b3435a7082f51e02cb
Cr-Commit-Position: refs/heads/master@{#305051}

[jln (very slow on Chromium), 2014-11-11 08:02:39]

jln@chromium.org changed reviewers:
+ mdempsky@chromium.org

[jln (very slow on Chromium), 2014-11-11 08:02:53]

Matthew: could you please take a look at this small cleanup CL?

[mdempsky, 2014-11-20 00:31:43]

lgtm

https://codereview.chromium.org/684993005/diff/40001/sandbox/linux/services/s...
File sandbox/linux/services/syscall_wrappers.h (right):

https://codereview.chromium.org/684993005/diff/40001/sandbox/linux/services/s...
sandbox/linux/services/syscall_wrappers.h:23: SANDBOX_EXPORT long
sys_clone(unsigned long flags,
Most of the calls seem to be for sys_clone(flags, 0, 0, 0, 0).  I wonder if it
makes sense to provide an overload for

    sys_clone(unsigned long flags);

that can pass the zero arguments and also sanity check that
CLONE_CHILD_CLEARTID, CLONE_CHILD_SETTID, CLONE_PARENT_SETTID, and CLONE_VM are
all cleared?

Even if not, I think the style guide wants the call sites to use nullptr instead
of 0?

[jln (very slow on Chromium), 2014-11-20 18:04:50]

https://codereview.chromium.org/684993005/diff/40001/sandbox/linux/services/s...
File sandbox/linux/services/syscall_wrappers.h (right):

https://codereview.chromium.org/684993005/diff/40001/sandbox/linux/services/s...
sandbox/linux/services/syscall_wrappers.h:23: SANDBOX_EXPORT long
sys_clone(unsigned long flags,
On 2014/11/20 00:31:43, mdempsky wrote:
> Most of the calls seem to be for sys_clone(flags, 0, 0, 0, 0).  I wonder if it
> makes sense to provide an overload for
> 
>     sys_clone(unsigned long flags);
> 
> that can pass the zero arguments and also sanity check that
> CLONE_CHILD_CLEARTID, CLONE_CHILD_SETTID, CLONE_PARENT_SETTID, and CLONE_VM
are
> all cleared?
> 
> Even if not, I think the style guide wants the call sites to use nullptr
instead
> of 0?

Yeah, you're right, this needs to be cleaned-up. I started doing that, but I
fear to go down that rabit hole: a bunch of call to sys_clone need to actually
be rewritten properly.

I'll do that in a follow-up CL.

[jln (very slow on Chromium), 2014-11-20 18:05:29]

The CQ bit was checked by jln@chromium.org

[commit-bot: I haz the power, 2014-11-20 18:06:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/684993005/40001

[commit-bot: I haz the power, 2014-11-20 18:58:34]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2014-11-20 18:59:17]

Patchset 3 (id:??) landed as
https://crrev.com/610a4a61dd805269d0cbe4b3435a7082f51e02cb
Cr-Commit-Position: refs/heads/master@{#305051}