arm64: Create a Linux view of the ID registers

When adding support for new hardware extensions we may not want to
enable support for the FreeBSD and Linux ABIs at the same time. To
support this split the Linux ID register and hwcaps so they can be
configured separately.

Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D42372

arm64: Use the Linux sigframe to restore registers

When returning from a Linux signal use the Linux sigframe to find the
register values to restore.

Remove the FreeBSD ucontext from the stack as it's now unneeded.

Reviewed by: dchagin, emaste
Sponsored by: Arm Ltd
Differential Revision: https://reviews.freebsd.org/D42360

linux(4): Drop the outdated comment, nosys is fine since 39024a89

MFC after: 1 week

syscalls: fix missing SIGSYS for several ENOSYS errors

In particular, when the syscall number is too large, or when syscall is
dynamic. For that, add nosys_sysent structure to pass fake sysent to
syscall top code.

Reviewed by: dchagin, markj
Discussed with: jhb
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D41976

linux(4): Cleanup includes under arm64

No functional changes.

MFC after: 1 week

linux(4): Validate exec_setregs on arm64

The lr register is cleared at the beginning of the _dl_start and _start,
so there is no need to initialize it.
Gnu libc _start takes an rtld_fini pointer in x0 which is set by ld.so
for __libc_start_main, the kernel does not register any atexit pointers.

While here fix whitespaces.

MFC after: 1 week

linux(4): Remove sys/cdefs.h inclusion where it's not needed due to 685dc743

sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

linux(4): Use pwd_altroot() to tell namei() about ABI root path

PR: 72920
Differential Revision: https://reviews.freebsd.org/D40090
MFC after: 2 month

linux(4): Rework signal trampoline on Aarch64

To avoid clobbering of any registers by the trampoline code use Linux
way to call signal handlers. I.e., we are out from the kernel right into
the signal handler, put return address from the signal handler into the
link register.
The mysterious NOP is required for some unwinders (e.g. libc++) that
unconditionally subtract one from the result of _Unwind_GetIP() in order
to identify the calling function.

MFC after: 1 week

linux(4): Get rid of linux_vdso_sigcode

MFC after: 1 week

linux(4): Fix stack unwinding on arm64 [2/2]

To allow unwinders to go througth a previous to sigreturn frame we should
properly emulate the trampoline frame record which should points to the
previous frame and set the trampoline frame pointer to the emulated frame
before calling signal handler.

MFC after: 1 week

linux(4): Fix stack unwinding on arm64 [1/2]

An Aarch64 sigreturn trampoline frame can't currently be described in
a DWARF .eh_frame section, because Aarch64 does not define a register
number for PC and provide no direct way to encode PC of the previous
frame. Instead, unwinders (libgcc, gdb, libunwind) detect the sigreturn
frame by looking for the sigreturn instruction. If a sigreturn frame is
detected, unwinders restores all the gprs, SP and PC by assuming that
sp points to an rt_sigframe Linux kernel struct
When entering the kernel, the link register (lr) contains the return
address of the previous frame, the exception link register (elr) contains
the address of the next instruction after the one which generated the
exception, i.e., PC.

MFC after: 1 week

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

linux(4): Deduplicate linux_copyout_auxargs()

Export default MINSIGSTKSZ value for the x86 until we do not preserve AVX
registers in the signal context.

Differential Revision: https://reviews.freebsd.org/D39644
MFC after: 1 month

linux(4): Cleanup includes under arm64/linux

Cleanup unneeded includes, sort the rest according to style(9).
No functional changes.

MFC after: 2 weeks

linux(4): Deduplicate linux_trans_osrel().

MFC after: 1 week

linux(4): Deduplicate linux_copyout_strings().

It is still present in the 32-bit Linuxulator on amd64.

MFC after: 1 week

linux(4): Microoptimize linux_elf.h for future use.

In order to reduce code duplication move coredump support definitions
into the appropriate header and hide private definitions.

MFC after: 1 week

Move kstack_contains() and GET_STACK_USAGE() to MD machine/stack.h

Reviewed by: jhb
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D38320

linux: populate sv_syscallnames in each sysentvec

This allows the syscallname() function to give a usable result for Linux
ABIs.

Reported by: jrtc27
Reviewed by: jrtc27, markj, jhb
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D37199

Rework how shared page related data is stored

Store the shared page address in struct vmspace.
Also instead of storing absolute addresses of various shared page
segments save their offsets with respect to the shared page address.
This will be more useful when the shared page address is randomized.

Approved by: mw(mentor)
Sponsored by: Stormshield
Obtained from: Semihalf
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D35393

linux(4): Properly build argument list for the signal handler

Provide arguments 2 and 3 if signal handler installed with SA_SIGINFO.

MFC after: 2 weeks

Retire sv_transtrap

Call translate_traps directly from sendsig().

MFC after: 2 weeks

linux(4): Retire unneeded translate_traps from arm64

MFC after: 2 weeks

linux(4): Add AT_MINSIGSTKSZ to arm64 port

MFC after: 2 weeks

linux(4): Implement signal trampoline for arm64 in a FreeBSD-way

The implemenation differs from others Linuxulators.
For unwinders Linux ucontext_t is stored, however native machine context
is used to store/restore process state to avoid code duplication.

As DWARF Aarch64 does not define a register number for PC and provides no
direct way to encode the PC of the previous frame, CFI cannot describe a
signal trampoline frame. So, modified the vdso linker script to discard
unused sections.

Extensions are not implemented.

MFC after: 2 weeks

linux(4): Move sigframe definitions to separate headers

The signal trampoine-related definitions are used only in the MD part
of code, wherefore moved from everywhere used linux.h to separate MD
headers.

MFC after: 2 weeks

exec: Introduce the PROC_PS_STRINGS() macro

Rather than fetching the ps_strings address directly from a process'
sysentvec, use this macro. With stack address randomization the
ps_strings address is no longer fixed.

Reviewed by: kib
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D33704

sysent: Add a sv_psstringssz field to struct sysentvec

The size of the ps_strings structure varies between ABIs, so this is
useful for computing the address of the ps_strings structure relative to
the top of the stack when stack address randomization is enabled.

Reviewed by: kib
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D33704

exec: Simplify sv_copyout_strings implementations a bit

Simplify control flow around handling of the execpath length and signal
trampoline. Cache the sysentvec pointer in a local variable.

No functional change intended.

Reviewed by: kib
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D33703

linux(4): Remove unused arm64 SDT declarations

Those tracepoints have been removed somewhere in the past.

Sponsored By: EPSRC

syscall_args: remove MAXARGS define

Use nitems instead and just use a magic `8` for the size of the args
array. MAXARGS was rarely used (only in arm64 code) and is an overly
generic name to polute the namespace with.

Requested by: kib in D33308

linux(4): Fix "set but not used" warnings

No functional changes.

Sponsored By: EPSRC

linux(4): Add struct clone_args for future clone3 system call.

In preparation for clone3 system call add struct clone_args and use it in
clone implementation.
Move all of clone related bits to the newly created linux_fork.h header.

Differential revision: https://reviews.freebsd.org/D31474
MFC after: 2 weeks

linux: implement signal delivery on arm64

Note that this still uses FreeBSD-style sigframe;
this will be addressed later.

Reviewed By: dchagin
Sponsored By: EPSRC
Differential Revision: https://reviews.freebsd.org/D31258

linux(4): Add arch name to the some printfs.

Reviewed by: emaste
Differential revision: https://reviews.freebsd.org/D30904
MFC after: 2 weeks

linux(4): Fixup the vDSO initialization order.

The vDSO initialisation order should be as follows:
- native abi init via exec_sysvec_init();
- vDSO symbols queued to the linux_vdso_syms list;
- linux_vdso_install();
- linux_exec_sysvec_init();

As the exec_sysvec_init() called with SI_ORDER_ANY (last) at SI_SUB_EXEC
order, move linux_vdso_install() and linux_exec_sysvec_init() to the
SI_SUB_EXEC+1 order.

Reviewed by: trasz
Differential Revision: https://reviews.freebsd.org/D30902
MFC after 2 weeks

linux(4); Almost complete the vDSO.

The vDSO (virtual dynamic shared object) is a small shared library that the
kernel maps R/O into the address space of all Linux processes on image
activation. The vDSO is a fully formed ELF image, shared by all processes
with the same ABI, has no process private data.

The primary purpose of the vDSO:
- non-executable stack, signal trampolines not copied to the stack;
- signal trampolines unwind, mandatory for the NPTL;
- to avoid contex-switch overhead frequently used system calls can be
implemented in the vDSO: for now gettimeofday, clock_gettime.

The first two have been implemented, so add the implementation of system
calls.

System calls implemenation based on a native timekeeping code with some
limitations:
- ifunc can't be used, as vDSO r/o mapped to the process VA and rtld
can't relocate symbols;
- reading HPET memory is not implemented for now (TODO).

In case on any error vDSO system calls fallback to the kernel system
calls. For unimplemented vDSO system calls added prototypes which call
corresponding kernel system call.

Tested by: trasz (arm64)
Differential revision: https://reviews.freebsd.org/D30900
MFC after: 2 weeks

linux(4): Modify sv_onexec hook to return an error.

Temporary add stubs to the Linux emulation layer which calls the existing hook.

Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D30911
MFC after: 2 weeks

Pass the syscall number to capsicum permission-denied signals

The syscall number is stored in the same register as the syscall return
on amd64 (and possibly other architectures) and so it is impossible to
recover in the signal handler after the call has returned. This small
tweak delivers it in the `si_value` field of the signal, which is
sufficient to catch capability violations and emulate them with a call
to a more-privileged process in the signal handler.

This reapplies 3a522ba1bc852c3d4660a4fa32e4a94999d09a47 with a fix for
the static assertion failure on i386.

Approved by: markj (mentor)

Reviewed by: kib, bcr (manpages)

Differential Revision: https://reviews.freebsd.org/D29185

linux(4): remove unfinished vsyscall bits on arm64

The vsyscall mechanism is obsolete.

Reviewed By: dchagin, emaste
Sponsored By: EPSRC
Differential Revision: https://reviews.freebsd.org/D31091

Revert "Pass the syscall number to capsicum permission-denied signals"

This broke the i386 build.

This reverts commit 3a522ba1bc852c3d4660a4fa32e4a94999d09a47.

Pass the syscall number to capsicum permission-denied signals

The syscall number is stored in the same register as the syscall return
on amd64 (and possibly other architectures) and so it is impossible to
recover in the signal handler after the call has returned. This small
tweak delivers it in the `si_value` field of the signal, which is
sufficient to catch capability violations and emulate them with a call
to a more-privileged process in the signal handler.

Approved by: markj (mentor)

Reviewed by: kib, bcr (manpages)

Differential Revision: https://reviews.freebsd.org/D29185

linux(4): implement coredumps on arm64

Previously they only worked on amd64.

Sponsored By: EPSRC
Differential Revision: https://reviews.freebsd.org/D30975

linux(4): revert arm64 part of 447636e43c0

The arm64 part of the patch was incomplete and prevented
linux64.ko from loading due to missing symbol.

Sponsored By: EPSRC

linux(4): implement coredump support

Implement dumping core for Linux binaries on amd64, for both
32- and 64-bit executables. Some bits are still missing.

This is based on a prototype by chuck@.

Reviewed By: kib
Sponsored By: EPSRC
Differential Revision: https://reviews.freebsd.org/D30019

Add infrastructure required for Linux coredump support

This adds `sv_elf_core_osabi`, `sv_elf_core_abi_vendor`,
and `sv_elf_core_prepare_notes` fields to `struct sysentvec`,
and modifies imgact_elf.c to make use of them instead
of hardcoding FreeBSD-specific values. It also updates all
of the ABI definitions to preserve current behaviour.

This makes it possible to implement non-native ELF coredump
support without unnecessary code duplication. It will be used
for Linux coredumps.

Reviewed By: kib
Sponsored By: EPSRC
Differential Revision: https://reviews.freebsd.org/D30921

linux(4): Retire linux_kplatform.

Assuming we can't run on i486, i586 class cpu, retire linux_kplatform var
and use hardcoded 'machine' value in linux_newuname().

I have added linux_kplatform for consistency with linux_platform which is
placed in to vdso to avoid excess copyout it on stack for AT_PLATFORM at
exec time.

This is the first stage of Linuxulator's vdso revision.

Reviewed by: trasz, imp
Differential Revision: https://reviews.freebsd.org/D30774
MFC after: 2 weeks

Add quirks for Linux ABI signals handling

Require queueing of the signals with default action, and disable
dequeueing SIGCHLD on wait for live process.

Reported and tested by: dchagin
Reviewed by: dchagin, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D30675

linuxolator: Add compat.linux.setid_allowed knob

PR: 21463
Reported by: kris
Reviewed by: dchagin
Tested by: trasz
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D28154

linux: export AT_HWCAP and AT_HWCAP2 on aarch64

The flag values seem to be the same between Linux and FreeBSD.
Comparing to a Linux VM on the same hardware, we're missing
HWCAP_EVTSTRM, HWCAP_CPUID, HWCAP_DCPOP, HWCAP_USCAT, HWCAP_PACA,
and HWCAP_PACG.

Reviewed By: mhorne, emaste
Sponsored By: EPSRC
Differential Revision: https://reviews.freebsd.org/D30540

linux: fix architecture returned for uname on aarch64

Previously it would return "arm64", which was breaking build
for Linux kernel. While here, reshuffle entries in the auxv
vector to match real Linux.

Reviewed By: emaste
Sponsored By: EPSRC
Differential Revision: https://reviews.freebsd.org/D30500

arm64: clear debug registers after execve(2)

This is both intuitive and required, as any previous breakpoint settings
may not be applicable to the new process.

Reported by: arichardson
Reviewed by: kib
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D29672

aarch64: Clear TLS registers during exec().

These are not stored in the trapframe so must be cleared explicitly.

This is similar to one of the MIPS changes in 822d2d6ac94f.

Reviewed by: andrew
Obtained from: CheriBSD
MFC after: 1 week
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D28711

Arch64: Clear VFP state on execve()

I noticed that many of the math-related tests were failing on AArch64.
After a lot of debugging, I noticed that the floating point exception flags
were not being reset when starting a new process. This change resets the
VFP inside exec_setregs() to ensure no VFP register state is leaked from
parent processes to children.

This commit also moves the clearing of fpcr that was added in 65618fdda0f27
from fork() to execve() since that makes more sense: fork() can retain
current register values, but execve() should result in a well-defined
clean state.

Reviewed By: andrew
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D29060

linux: Unmap the VDSO page when unloading

linux_shared_page_init() creates an object and grabs and maps a single
page to back the VDSO. When destroying the VDSO object, we failed to
destroy the mapping and free KVA. Fix this.

Reviewed by: kib
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D28696

Linuxolator: Replace use of eventhandlers by sysent hooks.

Reviewed by: markj
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D27309

Fix misnomer - linux_to_bsd_errno() does the exact opposite.

Reported by: arichardson
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D26965

Get rid of sa->narg. It serves no purpose; use sa->callp->sy_narg instead.

Reviewed by: kib
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D26458

Get rid of sv_errtbl and SV_ABI_ERRNO().

Reviewed by: kib
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D26388

Move SV_ABI_ERRNO translation into linux-specific code, to simplify
the syscall path and declutter it a bit. No functional changes intended.

Reviewed by: kib (earlier version)
MFC after: 2 weeks
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D26378

Convert canary, execpathp, and pagesizes to pointers.

Use AUXARGS_ENTRY_PTR to export these pointers. This is a followup to
r359987 and r359988.

Reviewed by: jhb
Obtained from: CheriBSD
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D24446

Add compat.linux.emul_path, so it can be set to something other
than "/compat/linux". Useful when you have several compat directories
with different Linux versions and you don't want to clash with files
installed by linux-c7 packages.

Reviewed by: bcr (manpages)
MFC after: 2 weeks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D22574

Copy out aux args after the argument and environment vectors.

Partially revert r354741 and r354754 and go back to allocating a
fixed-size chunk of stack space for the auxiliary vector. Keep
sv_copyout_auxargs but change it to accept the address at the end of
the environment vector as an input stack address and no longer
allocate room on the stack. It is now called at the end of
copyout_strings after the argv and environment vectors have been
copied out.

This should fix a regression in r354754 that broke the stack alignment
for newer Linux amd64 binaries (and probably broke Linux arm64 as
well).

Reviewed by: kib
Tested on: amd64 (native, linux64 (only linux-base-c7), and i386)
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D22695

Fix arm64 build after r355373

Sponsored by: The FreeBSD Foundation

Use uintptr_t instead of register_t * for the stack base.

- Use ustringp for the location of the argv and environment strings
and allow destp to travel further down the stack for the stackgap
and auxv regions.
- Update the Linux copyout_strings variants to move destp down the
stack as was done for the native ABIs in r263349.
- Stop allocating a space for a stack gap in the Linux ABIs. This
used to hold translated system call arguments, but hasn't been used
since r159992.

Reviewed by: kib
Tested on: md64 (amd64, i386, linux64), i386 (i386, linux)
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D22501

Check for errors from copyout() and suword*() in sv_copyout_args/strings.

Reviewed by: brooks, kib
Tested on: amd64 (amd64, i386, linux64), i386 (i386, linux)
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D22401

Use a sv_copyout_auxargs hook in the Linux ELF ABIs.

Reviewed by: emaste
Tested on: amd64 (linux64 only), i386
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D22356

arm64 linuxulator: default to RW stack (no X)

This matches Linux's default arm64 data / stack permissions.

MFC after: 1 week
Sponsored by: The FreeBSD Foundation

linux: futex_mtx should follow futex_list

Move futex_mtx to linux_common.ko for amd64 and aarch64 along
with respective list/mutex init/destroy.

PR: 240989
Reported by: Alex S <iwtcex@gmail.com>

Linuxulator depends on a fundamental kernel settings such as SMP. Many
of them listed in opt_global.h which is not generated while building
modules outside of a kernel and such modules never match real cofigured
kernel.

So, we should prevent our users from building obviously defective modules.

Therefore, remove the root cause of the building of modules outside of a
kernel - the possibility of building modules with DEBUG or KTR flags.
And remove all of DEBUG printfs as it is incomplete and in threaded
programms not informative, also a half of system call does not have DEBUG
printf. For debuging Linux programms we have dtrace, ktr and ktrace ability.

PR: 222861
Reviewed by: trasz
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D20178

Remove sv_pagesize, originally introduced with r100384.

In all of the architectures we have today, we always use PAGE_SIZE.
While in theory one could define different things, none of the
current architectures do, even the ones that have transitioned from
32-bit to 64-bit like i386 and arm. Some ancient mips binaries on
other systems used 8k instead of 4k, but we don't support running
those and likely never will due to their age and obscurity.

Reviewed by: imp (who also contributed the commit message)
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D19280

Remove iBCS2, part2: general kernel

Reviewed by: kib (previous version)
Sponsored by: The FreeBSD Foundation

Make cpu_set_syscall_retval common between the existing FreeBSD ABI and
the Linuxulator. We need to translate error values onto Linux errno values
and return them to userspace when a syscall fails. We also need to preserve
x1 as all registers are preserved other than the return value.

Reviewed by: emaste
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D16008

Initial arm64 linuxulator linux_sysvec

This is sufficient to run Linux arm64 'hello world' and other simple
binaries.

Reviewed by: andrew
Sponsored by: Turing Robotic Industries
Differential Revision: https://reviews.freebsd.org/D15834