Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC rr225973:
Convert ARM to the syscallenter/syscallret system call sequence handlers.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Extend struct sysvec with new method sv_schedtail, which is used for an
explicit process at fork trampoline path instead of eventhadler(schedtail)
invocation for each child process.

Remove eventhandler(schedtail) code and change linux ABI to use newly added
sysvec method.

While here replace explicit comparing of module sysentvec structure with the
newly created process sysentvec to detect the linux ABI.

Discussed with: kib

MFC after: 2 Week

Fix the R_ARM_ABS32 relocation implementation. The memory address
contains the addend that we need to include.

Obtained from: Juniper Networks.
Fixed by: Santhanakrishnan Balraj <sbalraj@juniper.net>

Reorganize syscall entry and leave handling.

Extend struct sysvec with three new elements:
sv_fetch_syscall_args - the method to fetch syscall arguments from
usermode into struct syscall_args. The structure is machine-depended
(this might be reconsidered after all architectures are converted).
sv_set_syscall_retval - the method to set a return value for usermode
from the syscall. It is a generalization of
cpu_set_syscall_retval(9) to allow ABIs to override the way to set a
return value.
sv_syscallnames - the table of syscall names.

Use sv_set_syscall_retval in kern_sigsuspend() instead of hardcoding
the call to cpu_set_syscall_retval().

The new functions syscallenter(9) and syscallret(9) are provided that
use sv_*syscall* pointers and contain the common repeated code from
the syscall() implementations for the architecture-specific syscall
trap handlers.

Syscallenter() fetches arguments, calls syscall implementation from
ABI sysent table, and set up return frame. The end of syscall
bookkeeping is done by syscallret().

Take advantage of single place for MI syscall handling code and
implement ptrace_lwpinfo pl_flags PL_FLAG_SCE, PL_FLAG_SCX and
PL_FLAG_EXEC. The SCE and SCX flags notify the debugger that the
thread is stopped at syscall entry or return point respectively. The
EXEC flag augments SCX and notifies debugger that the process address
space was changed by one of exec(2)-family syscalls.

The i386, amd64, sparc64, sun4v, powerpc and ia64 syscall()s are
changed to use syscallenter()/syscallret(). MIPS and arm are not
converted and use the mostly unchanged syscall() implementation.

Reviewed by: jhb, marcel, marius, nwhitehorn, stas
Tested by: marcel (ia64), marius (sparc64), nwhitehorn (powerpc),
stas (mips)
MFC after: 1 month

Make sure that the primary native brandinfo always gets added
first and the native ia32 compat as middle (before other things).
o(ld)brandinfo as well as third party like linux, kfreebsd, etc.
stays on SI_ORDER_ANY coming last.

The reason for this is only to make sure that even in case we would
overflow the MAX_BRANDS sized array, the native FreeBSD brandinfo
would still be there and the system would be operational.

Reviewed by: kib
MFC after: 1 month

Implement a facility for dynamic per-cpu variables.
- Modules and kernel code alike may use DPCPU_DEFINE(),
DPCPU_GET(), DPCPU_SET(), etc. akin to the statically defined
PCPU_*. Requires only one extra instruction more than PCPU_* and is
virtually the same as __thread for builtin and much faster for shared
objects. DPCPU variables can be initialized when defined.
- Modules are supported by relocating the module's per-cpu linker set
over space reserved in the kernel. Modules may fail to load if there
is insufficient space available.
- Track space available for modules with a one-off extent allocator.
Free may block for memory to allocate space for an extent.

Reviewed by: jhb, rwatson, kan, sam, grehan, marius, marcel, stas

Fix KBI breakage by r190520 which affects older linux.ko binaries:

1) Move the new field (brand_note) to the end of the Brandinfo structure.
2) Add a new flag BI_BRAND_NOTE that indicates that the brand_note pointer
is valid.
3) Use the brand_note field if the flag BI_BRAND_NOTE is set and as old
modules won't have the flag set, so the new field brand_note would be
ignored.

Suggested by: jhb
Reviewed by: jhb
Approved by: kib (mentor)
MFC after: 6 days

Implement new way of branding ELF binaries by looking to a
".note.ABI-tag" section.

The search order of a brand is changed, now first of all the
".note.ABI-tag" is looked through.

Move code which fetch osreldate for ELF binary to check_note() handler.

PR: 118473
Approved by: kib (mentor)

Add sv_flags field to struct sysentvec with intention to provide description
of the ABI of the currently executing image. Change some places to test
the flags instead of explicit comparing with address of known sysentvec
structures to determine ABI features.

Discussed with: dchagin, imp, jhb, peter

Provide L2 cache synchronization (write back + invalidation) on ARM.

Note the cpu_l2cache_wbinv_* routines are no-ops on systems not populated with
L2 caches.

Obtained from: Marvell, Semihalf

Change the static struct sysentvec and struct Elf_Brandinfo initializers
to the C99 style. At least, it is easier to read sysent definitions
that way, and search for the actual instances of sigcode etc.

Explicitely initialize sysentvec.sv_maxssiz that was missed in most
sysvecs.

No objection from: jhb
MFC after: 1 month

Allow FreeBSD's native ELF image activators to execute shared libraries the
same way it was enabled for Linux binares in linuxulator.

This allows binaries built with -pie. Many ports auto-detect -fPIE support
in GCC 4.2 and build binaries FreeBSD was unable to run.

Remove kern.elf32.can_exec_dyn sysctl. Instead extend Brandinfo structure
with flags bitfield and set BI_CAN_EXEC_DYN flag for all brands that usually
allow executing elf dynamic binaries (aka shared libraries). When it is
requested to execute ET_DYN elf image check if this flag is on after we
know the elf brand allowing execution if so.

PR: kern/87615
Submitted by: Marcin Koziej <creep@desk.pl>

Get kernel modules to work.

Use sigcode.

Add __elfN(dump_thread). This function is called from __elfN(coredump)
to allow dumping per-thread machine specific notes. On ia64 we use this
function to flush the dirty registers onto the backingstore before we
write out the PRSTATUS notes.

Tested on: alpha, amd64, i386, ia64 & sparc64
Not tested on: arm, powerpc

Make a small revision to the api between the elf linker core and the
elf_reloc() backends for two reasons. First, to support the possibility
of there being two elf linkers in the kernel (eg: amd64), and second, to
pass the relocbase explicitly (for relocating .o format kld files).

Import FreeBSD/arm kernel bits.
It only supports sa1110 (on simics) right now, but xscale support should come
soon.
Some of the initial work has been provided by :
Stephane Potvin <sepotvin at videotron.ca>
Most of this comes from NetBSD.