libc: Implement stubbed clock()

Nadav says:
The clock() function is stubbed. We can easily implement it by calling
clock_gettime(CLOCK_PROCESS_CPUTIME_ID).

Closes #275.

Reviewed-by: Glauber Costa <glommer@cloudius-systems.com>
Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
runtime: stub initgroups

empty implementation will suit us.

Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
runtime: basic prctl functionality

First of all, we need the symbol. But so far it is fine returning EINVAL to
everybody except for PR_SET_DUMPABLE. There are situations (see man prctl) in
which this flag is automatically cleared. Some programs (nginx here) will then
proceed to set it to make sure it is on. The flag itself is meanginless to us,
since we are not producing per-thread coredumps, and when we do dump, we will
dump regardless of this. But we need the call to suceed.

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
af_local: allow ioctl on unix sockets

The current code does not allow ioctls on unix sockets, but real world
applications - nginx in my example will issue them. I am starting by
implementing FIONBIO to set blocking/nonblocking mode.

I notice here that we already have a flag in the read and write functions, and
they seem to handle that flag: the internal pipe_buffer implementation does
check and act on it.

So let's just flip it.

Reviewed-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
mmu: export function to measure the amount of mmaped area

It will be used for procfs compatibility. Applications may want to know how much
memory is potentially available through mmap mappings (not necessarily allocated).

Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
sched: export total sys and user time statistics

This is one of the statistics that shows up in /proc/self/stat under Linux, but
this is generally interesting for applications. Since we don't have kernel mode
and userspace mode, it is very hard to differentiate between "time spent in
userspace" and "kernel time spent on behalf of the process". Therefore, we will
present system time as always 0. If we wanted, we could at least differentiate
clearly osv-specific threads as system time, but there is no need to go through
the trouble now.

Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
linux: provide a /proc/$$/stat compatibility file

MongoDB wants it. In general, I am providing the information that is easy
to get, and ignoring the ones which are not - with the exception of process
count, that seemed easy enough to implement.

This is the kind of thing Mongo does with it:

2014-04-15T09:54:12.322+0000 [clientcursormon] mem (MB) res:670160 virt:25212
2014-04-15T09:54:12.323+0000 [clientcursormon]  mapped (incl journal view):160
2014-04-15T09:54:12.324+0000 [clientcursormon]  connections:0

Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
mmu: implement madvise for MADV_DONTNEED

The jemalloc memory allocator will make intense use of MADV_DONTNEED to flush
pages it is no longer using. Respect that advice.

Let's keep returning -1 for the remaining cases so we don't fool anybody

Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
vfs: simple flock implementation

This patch implements a version of flock that only performs error checking.
It assumes any valid operation succeeds, since we are using a single-process
model.

Signed-off-by: Glauber Costa <glommer@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
vmxnet3: fix avail count on txq_gc

txq_encap decrements txq.avail for each mbuf, so we need to increment same number here.

Reviewed-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
Signed-off-by: Takuya ASADA <syuu@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
zfs: fix read() of directory to return EISDIR

Posix allows read() on directories in some filesystems. However, Linux
always returns EISDIR in this case, so because we're emulating Linux,
so should we, for every filesystem. All our filesystems except ZFS
(e.g., ramfs) already return EISDIR when reading a directory, but ZFS
doesn't, so this patch adds the missing check in ZFS.

This patch is related to issue #94: the first step to fixing #94 is to
return the right error when reading a directory.

This patch also adds a test case, which can be compiled both on OSv and
Linux, to verify they both have the same behavior. Before the patch, the
test succeeded on Linux but failed on OSv when the directory is on ZFS.

Instead of fixing zfs_read like I do in this patch, I could have also fixed
sys_read() in vfs_syscalls.cc which is the top layer of all read()
operations, and I could have done there
   (fp->f_dentry && fp->f_dentry->d_vnode->v_type == VDIR) {
      return EISDIR;
   }
to cover all the filesystems. I decided not to do that, because all
filesystems except ZFS already have this check, and because the lower
layers like zfs_read() already have more natural access to d_vnode.

Reviewed-by: Glauber Costa <glommer@cloudius-systems.com>
Signed-off-by: Nadav Har'El <nyh@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
mmu: map page as dirty on write fault

Mapping page as dirty saves CPU from doing additional memory access to
write out dirty bit when access will succeed.

Signed-off-by: Gleb Natapov <gleb@cloudius-systems.com>
mmu: mark COW ptes to skip them during protection changes

Write permission should not be granted to ptes that has no write
permission because they are COW, but currently there is no way to
distinguish between write protection due to vma permission and write
protection due to COW. Use bit reserved for software use in pte as a
marker for COW ptes and check it during permission changes.

Signed-off-by: Gleb Natapov <gleb@cloudius-systems.com>
pagecache: use boost::variant to store rmap of a cached page

rmap will usually contain only one element so using unordered_set for it
is a little bit heavy. boost::variant allow us to use direct pointer in
common case and fall back to unordered_set only when more than one
elements are added.

Signed-off-by: Gleb Natapov <gleb@cloudius-systems.com>
pagecache: assert if sys_read() fails

sys_read() error should be propagated to an application, but for now
assert here instead of silent memory corruption.

Signed-off-by: Gleb Natapov <gleb@cloudius-systems.com>
mmu: propagate IO errors during msync() to an application

Signed-off-by: Gleb Natapov <gleb@cloudius-systems.com>
pagecache: add traces to pagecache function

Useful for debugging cache related problems.

Signed-off-by: Gleb Natapov <gleb@cloudius-systems.com>
mmu: separate page unmapping and freeing.

Unmap page as soon as possible instead of waiting for max_pages to
accumulate. Will allow to free pages outside of vma_list_mutex in the
feature.

Signed-off-by: Gleb Natapov <gleb@cloudius-systems.com>
pagecache: move cache management code into pagecache.cc

Signed-off-by: Gleb Natapov <gleb@cloudius-systems.com>
pagecache: remove redundant locking

All pagecache functions run under vma_list_lock, so no additional
locking is needed.

Signed-off-by: Gleb Natapov <gleb@cloudius-systems.com>