We're currently seeing how hard it would be to run CloudABI binaries on
operating systems cannot be modified easily (Windows, Mac OS X). The
idea is that we want to just run them without any sandboxing. Now
that CloudABI executables are PIE, this is already a bit easier, but TLS
is still problematic:
- CloudABI executables want to write to the %fs, which typically
requires extra system calls by the emulator every time it needs to
switch between CloudABI's and its own TLS.
- If CloudABI executables overwrite the %fs base unconditionally, it
also becomes harder for the emulator to store a backup of the old
value of %fs. To solve this, let's no longer overwrite %fs, but just
%fs:0.
As CloudABI's C library does not use a TCB, this space can now be used
by an emulator to keep track of its internal state. The executable can
now safely overwrite %fs:0, as long as it makes sure that the TCB is
copied over to the new TLS area.
Ensure that there is an initial TLS area set up when the process starts,
only containing a bogus TCB. We don't really care about its contents on
FreeBSD.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D5836
- Set BI_CAN_EXEC_DYN, so we can execute ET_DYN ELF files in addition to
regular ET_EXECs.
- Provide an AT_BASE entry in the auxiliary vector, so the executable
knows at which address it got loaded and can apply relocations.
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.
In order to make it easier to support CloudABI on ARM64, move out all of
the bits from the AMD64 cloudabi_sysvec.c into a new file
cloudabi_module.c that would otherwise remain identical. This reduces
the AMD64 specific code to just ~160 lines.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D3974
There is still one TODO item for these calls: add file descriptor
passing. The data structures are already prepared for this. It's just
the translation that's missing.
Obtained from: http://github.com/NuxiNL/freebsd
Blocking on locks and condition variables can be accomplished by polling
and using the special filters CONDVAR, LOCK_RDLOCK and LOCK_WRLOCK.
For now it wouldn't make sense to implement this functionality into
kqueue() itself, for the reason that they are CloudABI specific and
would require us to resize 'struct kevent' to hold all of the parameters
of interest.
Add a bandaid to the CloudABI poll system call to call into the futex
code directly if it detects specific combinations of events that are
used by the C library.
Obtained from: https://github.com/NuxiNL/freebsd
This change implements two functions, cloudabi64_kevent_copyin() and
cloudabi64_kevent_copyout(), that convert CloudABI structures to
FreeBSD's struct kevent. CloudABI uses two structures: subscription_t
and event_t. The former is used for input, whereas the latter is used
for output. Unlike struct kevent, fields aren't overloaded for multiple
purposes or for separate event types.
For poll() we call into the newly introduced kern_kevent_anonymous()
function that allows us to poll without a file descriptor. This function
is not only used by poll(), but also by functions such as
sleep() and clock_nanosleep().
Reviewed by: jmg
Obtained from: https://github.com/NuxiNL/freebsd
Differential Revision: https://reviews.freebsd.org/D3308
Futex object scopes have been renamed from using their own constants to
simply reusing the existing CLOUDABI_MAP_{PRIVATE,SHARED} flags, as they
are more accurate in this context.
Summary:
Remove the stub system call that was put in place during the system call
import and replace it by a target-dependent version stored in sys/amd64.
Initialize the thread in a way similar to cpu_set_upcall_kse(). We
provide the entry point with two arguments: the thread ID and the
argument pointer.
Test Plan:
Thread creation still seems to work, both for FreeBSD and CloudABI
binaries.
Reviewers: dchagin, mjg, kib
Reviewed By: kib
Subscribers: imp
Differential Revision: https://reviews.freebsd.org/D3110
The first system call is used to set the user TLS address. Right now
this system call is invoked by the C library for both the initial thread
and additional threads unconditionally, but in the future we'll only
call this if the architecture does not support this. On recent x86-64
CPUs we could use the WRFSBASE instruction.
This system call was erroneously placed in sys/compat/cloudabi64, even
though it does not depend on any pointer size dependent datastructure.
Move it to the right place.
Obtained from: https://github.com/NuxiNL/freebsd
Add a routine similar to copyinuio() and freebsd32_copyinuio() that
copies in CloudABI's struct iovecs. These are then translated into
FreeBSD format and placed in a 'struct uio', so we can call into the
kern_*() functions.
Obtained from: https://github.com/NuxiNL/freebsd
CloudABI is a pure capability-based runtime environment for UNIX. It
works similar to Capsicum, except that processes already run in
capabilities mode on startup. All functionality that conflicts with this
model has been omitted, making it a compact binary interface that can be
supported by other operating systems without too much effort.
CloudABI is 'secure by default'; the idea is that it should be safe to
run arbitrary third-party binaries without requiring any explicit
hardware virtualization (Bhyve) or namespace virtualization (Jails). The
rights of an application are purely determined by the set of file
descriptors that you grant it on startup.
The datatypes and constants used by CloudABI's C library (cloudlibc) are
defined in separate files called syscalldefs_mi.h (pointer size
independent) and syscalldefs_md.h (pointer size dependent). We import
these files in sys/contrib/cloudabi and wrap around them in
cloudabi*_syscalldefs.h.
We then add stubs for all of the system calls in sys/compat/cloudabi or
sys/compat/cloudabi64, depending on whether the system call depends on
the pointer size. We only have nine system calls that depend on the
pointer size. If we ever want to support 32-bit binaries, we can simply
add sys/compat/cloudabi32 and implement these nine system calls again.
The next step is to send in code reviews for the individual system call
implementations, but also add a sysentvec, to allow CloudABI executabled
to be started through execve().
More information about CloudABI:
- GitHub: https://github.com/NuxiNL/cloudlibc
- Talk at BSDCan: https://www.youtube.com/watch?v=SVdF84x1EdA
Differential Revision: https://reviews.freebsd.org/D2848
Reviewed by: emaste, brooks
Obtained from: https://github.com/NuxiNL/freebsd
