Clients of libsa are expected to implement exit(). The current exit just
loops forever. It is better to really exit: when running as init that
will reboot the system. When not running as init, other programs can
recover (not that we support running as init, but when we do in the
future, this is still the rigtht thing).
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Add support for aarch64. exec.c and ldscript are copied from the EFI
version with #ifdefs for the differences. Once complete, I'll refactor
them. host_syscall.S implements a generic system call. tramp.S is a
first attempt to create a tramoline that we can use to jump to the
aarch64 kernel. Add aarch64-specific startup and stat files as well.
exec.c tweaked slightly to avoid bringing in bi_load(), which will come
in later. Includes tweaks to stat due to name differences between names
on different Linux architectures.
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Linux 2.4 introduced getdents64. Switch to using it because aarch64
doesn't have getdents as that syscall was obsoleted before that port was
created.
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Create a wrapper for the mount system call. To ensure a sane early boot
environment and to gather data we need for kexec, we may need to mount
some special filesystems.
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Early in boot, we need to create the normal stdin/out/err env for the
boot loader to run in. To do that, we need to open the console and
duplicate the file descriptors which requires dup(2). Implement a
wrapper as host_dup.
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Linux's /dev/fd is implemented inside of /proc/self/fd, so we may need
to create a symlink to it early in boot. "/dev/fd" and "/dev/std*" might
not be strictly required for the boot loader, but should be present for
maximum flexibility.
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Add host_getpid() so we can know if we're running as init(8) or not. If
we are, we may chose to do early system setup / sanity operations.
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Implement stat(2) and fstat(2) in terms of newfstatat and newfstat
system calls respectively (assume we have a compat #define when
there's no newfstat and just a regular fstat and do so for ppc).
Snag struct kstat (the Linux kernel stat(2), et al interface) from musl
and attribute properly.
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Just have the MD code provide syscall and have generic code for the
rest.
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Differential Revision: https://reviews.freebsd.org/D33515
