CloudABI executables already provide support for passing in vDSOs. This
functionality is used by the emulator for OS X to inject system call
handlers. On FreeBSD, we could use it to optimize calls to
gettimeofday(), etc.
Though I don't have any plans to optimize any system calls right now,
let's go ahead and already pass in a vDSO. This will allow us to
simplify the executables, as the traditional "syscall" shims can be
removed entirely. It also means that we gain more flexibility with
regards to adding and removing system calls.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D7438
Some time ago I made a change to merge together the memory scope
definitions used by mmap (MAP_{PRIVATE,SHARED}) and lock objects
(PTHREAD_PROCESS_{PRIVATE,SHARED}). Though that sounded pretty smart
back then, it's backfiring. In the case of mmap it's used with other
flags in a bitmask, but for locking it's an enumeration. As our plan is
to automatically generate bindings for other languages, that looks a bit
sloppy.
Change all of the locking functions to use separate flags instead.
Obtained from: https://github.com/NuxiNL/cloudabi
The type definitions and constants that were used by COMPAT_CLOUDABI64
are a literal copy of some headers stored inside of CloudABI's C
library, cloudlibc. What is annoying is that we can't make use of
cloudlibc's system call list, as the format is completely different and
doesn't provide enough information. It had to be synced in manually.
We recently decided to solve this (and some other problems) by moving
the ABI definitions into a separate file:
https://github.com/NuxiNL/cloudabi/blob/master/cloudabi.txt
This file is processed by a pile of Python scripts to generate the
header files like before, documentation (markdown), but in our case more
importantly: a FreeBSD system call table.
This change discards the old files in sys/contrib/cloudabi and replaces
them by the latest copies, which requires some minor changes here and
there. Because cloudabi.txt also enforces consistent names of the system
call arguments, we have to patch up a small number of system call
implementations to use the new argument names.
The new header files can also be included directly in FreeBSD kernel
space without needing any includes/defines, so we can now remove
cloudabi_syscalldefs.h and cloudabi64_syscalldefs.h. Patch up the
sources to include the definitions directly from sys/contrib/cloudabi
instead.
CloudABI purely operates on file descriptor rights (CAP_*). File
descriptor access modes (O_ACCMODE) are emulated on top of rights.
Instead of accepting the traditional flags argument, file_open() copies
in an fdstat_t object that contains the initial rights the descriptor
should have, but also file descriptor flags that should persist after
opening (APPEND, NONBLOCK, *SYNC). Only flags that don't persist (EXCL,
TRUNC, CREAT, DIRECTORY) are passed in as an argument.
file_open() first converts the rights, the persistent flags and the
non-persistent flags to fflags. It then calls into vn_open(). If
successful, it installs the file descriptor with the requested
rights, trimming off rights that don't apply to the type of
the file that has been opened.
Unlike kern_openat(), this function does not support /dev/fd/*. I can't
think of a reason why we need to support this for CloudABI.
Obtained from: https://github.com/NuxiNL/freebsd
Differential Revision: https://reviews.freebsd.org/D3235
CloudABI uses a structure called cloudabi_sockstat_t. Think of it as
'struct stat' for sockets. It is used by functions such as
getsockname(), getpeername(), some of the getsockopt() values, etc.
This change implements the sock_stat_get() system call that returns a
copy of this structure. The accept() system call should also return a
full copy of this structure eventually, but for now we're only
interested in the peer address. Add a TODO() to make sure this is
patched up later on.
Differential Revision: https://reviews.freebsd.org/D3218
Summary:
CloudABI provides access to two different stat structures:
- fdstat, containing file descriptor level status: oflags, file
descriptor type and Capsicum rights, used by cap_rights_get(),
fcntl(F_GETFL), getsockopt(SO_TYPE).
- filestat, containing your regular file status: timestamps, inode
number, used by fstat().
Unlike FreeBSD's stat::st_mode, CloudABI file descriptor types don't
have overloaded meanings (e.g., returning S_ISCHR() for kqueues). Add a
utility function to extract the type of a file descriptor accurately.
CloudABI does not work with O_ACCMODEs. File descriptors have two sets
of Capsicum-style rights: rights that apply to the file descriptor
itself ('base') and rights that apply to any new file descriptors
yielded through openat() ('inheriting'). Though not perfect, we can
pretty safely decompose Capsicum rights to such a pair. This is done in
convert_capabilities().
Test Plan: Tests for these system calls are fairly extensive in cloudlibc.
Reviewers: jonathan, mjg, #manpages
Reviewed By: mjg
Subscribers: imp
Differential Revision: https://reviews.freebsd.org/D3171
Summary:
CloudABI provides two different types of futex objects: read-write locks
and condition variables. There is no need to provide separate support
for once objects and thread joining, as these are efficiently simulated
by blocking on a read-write lock. Mutexes simply use read-write locks.
Condition variables always have a lock object associated to them. They
always know to which lock a thread needs to be migrated if woken up.
This allows us to implement requeueing. A broadcast on a condition
variable will never cause multiple threads to be woken up at once. They
will be woken up iteratively.
This implementation still has lots of room for improvement. Locking is
coarse and right now we use linked lists to store all of the locks and
condition variables, instead of using a hash table. The primary goal of
this implementation was to behave correctly. Performance will be
improved as we go.
Test Plan:
This futex implementation has been in use for the last couple of months
and seems to work pretty well. All of the cloudlibc and libc++ unit
tests seem to pass.
Reviewers: dchagin, kib, vangyzen
Subscribers: imp
Differential Revision: https://reviews.freebsd.org/D3148
Though the standard C library uses a 'struct timespec' using a 64-bit
'time_t', there is no need to use such a type at the system call level.
CloudABI uses a simple 64-bit unsigned timestamp in nanoseconds. This is
sufficient to express any time value from 1970 to 2554.
The CloudABI low-level interface also supports fetching timestamp values
with a lower precision. Instead of overloading the clock ID argument for
this purpose, the system call provides a precision argument that may be
used to specify the maximum slack. The current system call
implementation does not use this information, but it's good to already
have this available.
Expose cloudabi_convert_timespec(), as we're going to need this for
fstat() as well.
Obtained from: https://github.com/NuxiNL/freebsd
Summary:
For CloudABI we need to put two things on the stack of new processes:
the argument data (a binary blob; not strings) and a startup data
structure. The startup data structure contains interesting things such
as a pointer to the ELF program header, the thread ID of the initial
thread, a stack smashing protection canary, and a pointer to the
argument data.
Fetching system call arguments and setting the return value is similar
to FreeBSD. The only differences are that system call 0 does not exist
and that we call into cloudabi_convert_errno() to convert the error
code. We also need this function in a couple of other places, so we'd
better reuse it here.
Reviewers: dchagin, kib
Reviewed By: kib
Subscribers: imp
Differential Revision: https://reviews.freebsd.org/D3098
