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.
- Advertise the word size for CloudABI ABIs via the SV_LP64 flag. All of
the other ABIs include either SV_ILP32 or SV_LP64.
- Fix kdump to not assume a 32-bit ABI if the ABI flags field is non-zero
but SV_LP64 isn't set. Instead, only assume a 32-bit ABI if SV_ILP32 is
set and fallback to the unknown value of "00" if neither SV_LP64 nor
SV_ILP32 is set.
Reviewed by: kib, ed
Differential Revision: https://reviews.freebsd.org/D5560
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
Certain system calls have quirks applied to make them work as if called
on an older version of FreeBSD. As CloudABI executables don't have the
FreeBSD OS release number in the ELF header, this value is set to zero,
making the system calls fall back to typically historic, non-standard
behaviour.
Reviewed by: kib
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
Just like FreeBSD+Capsicum, CloudABI uses process descriptors. Return
the file descriptor number to the parent process.
To the child process we both return a special value for the file
descriptor number (CLOUDABI_PROCESS_CHILD). We also return the thread ID
of the new thread in the copied process, so the threading library can
reinitialize itself.
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
