MFC r331374:
Fixes for ptrace(PT_GETXSTATE_INFO) related to the padding in struct
ptrace_xstate_info).

Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

MFC r322762, r322799, r322832, r322833:
Make WRFSBASE and WRGSBASE instructions functional.

Bump stable/11 __FreeBSD_version.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Disallow a debugger on 64bit system to set fs/gs bases of the 32bit
process beyond the end of the process address space. Such setting is
not dangerous to the kernel integrity, but it causes confusing
application misbehaviour.

Sponsored by: The FreeBSD Foundation
MFC after: 12 days

Add x86 PT_GETFSBASE, PT_GETGSBASE machine-depended ptrace requests to
obtain the thread %fs and %gs bases. Add x86 PT_SETFSBASE and
PT_SETGSBASE requests to set the bases from debuggers. The set
requests, similarly to the sysarch({I386,AMD64}_SET_FSBASE),
override the corresponding segment registers.

The main purpose of the operations is to retrieve and modify the tcb
address for debuggee.

Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks

Ensure that the supplied data length is large enough to hold the base
FPU state to avoid passing a negative length to fpusetregs() / npxsetregs().

Differential Revision: https://reviews.freebsd.org/D1861
Reviewed by: kib, emaste

Improve support for XSAVE with debuggers.
- Dump an NT_X86_XSTATE note if XSAVE is in use. This note is designed
to match what Linux does in that 1) it dumps the entire XSAVE area
including the fxsave state, and 2) it stashes a copy of the current
xsave mask in the unused padding between the fxsave state and the
xstate header at the same location used by Linux.
- Teach readelf() to recognize NT_X86_XSTATE notes.
- Change PT_GET/SETXSTATE to take the entire XSAVE state instead of
only the extra portion. This avoids having to always make two
ptrace() calls to get or set the full XSAVE state.
- Add a PT_GET_XSTATE_INFO which returns the length of the current
XSTATE save area (so the size of the buffer needed for PT_GETXSTATE)
and the current XSAVE mask (%xcr0).

Differential Revision: https://reviews.freebsd.org/D1193
Reviewed by: kib
MFC after: 2 weeks

The PT_I386_{GET,SET}XMMREGS and PT_{GET,SET}XSTATE operate on the
stopped threads. Implementation assumes that the thread's FPU context
is spilled into the PCB due to stop. This is mostly true, except when
FPU state for the thread is not initialized. Then the requests operate
on the garbage state which is currently left in the PCB, causing
confusion.

The situation is indeed observed after a signal delivery and before
#NM fault on execution of any FPU instruction in the signal handler,
since sendsig(9) drops FPU state for current thread, clearing
PCB_FPUINITDONE. When inspecting context state for the signal handler,
debugger sees the FPU state of the main program context instead of the
clear state supposed to be provided to handler.

Fix this by forcing clean FPU state in PCB user FPU save area by
performing getfpuregs(9) before accessing user FPU save area in
ptrace_machdep.c.

Note: this change will be merged to i386 kernel as well, where it is
much more important, since e.g. gdb on i386 uses PT_I386_GETXMMREGS to
inspect FPU context on CPUs that support SSE. Amd64 version of gdb
uses PT_GETFPREGS to inspect both 64 and 32 bit processes, which does
not exhibit the bug.

Reported by: bde
MFC after: 1 week

Copy amd64 ptrace.h to x86 and merge with i386 ptrace.h. Replace
amd64/i386/pc98 ptrace.h with stubs.

For amd64 PT_GETXSTATE and PT_SETXSTATE have been redefined to match the
i386 values. The old values are still supported but should no longer be
used.

Reviewed by: kib

Add support for the extended FPU states on amd64, both for native
64bit and 32bit ABIs. As a side-effect, it enables AVX on capable
CPUs.

In particular:

- Query the CPU support for XSAVE, list of the supported extensions
and the required size of FPU save area. The hw.use_xsave tunable is
provided for disabling XSAVE, and hw.xsave_mask may be used to
select the enabled extensions.

- Remove the FPU save area from PCB and dynamically allocate the
(run-time sized) user save area on the top of the kernel stack,
right above the PCB. Reorganize the thread0 PCB initialization to
postpone it after BSP is queried for save area size.

- The dumppcb, stoppcbs and susppcbs now do not carry the FPU state as
well. FPU state is only useful for suspend, where it is saved in
dynamically allocated suspfpusave area.

- Use XSAVE and XRSTOR to save/restore FPU state, if supported and
enabled.

- Define new mcontext_t flag _MC_HASFPXSTATE, indicating that
mcontext_t has a valid pointer to out-of-struct extended FPU
state. Signal handlers are supplied with stack-allocated fpu
state. The sigreturn(2) and setcontext(2) syscall honour the flag,
allowing the signal handlers to inspect and manipilate extended
state in the interrupted context.

- The getcontext(2) never returns extended state, since there is no
place in the fixed-sized mcontext_t to place variable-sized save
area. And, since mcontext_t is embedded into ucontext_t, makes it
impossible to fix in a reasonable way. Instead of extending
getcontext(2) syscall, provide a sysarch(2) facility to query
extended FPU state.

- Add ptrace(2) support for getting and setting extended state; while
there, implement missed PT_I386_{GET,SET}XMMREGS for 32bit binaries.

- Change fpu_kern KPI to not expose struct fpu_kern_ctx layout to
consumers, making it opaque. Internally, struct fpu_kern_ctx now
contains a space for the extended state. Convert in-kernel consumers
of fpu_kern KPI both on i386 and amd64.

First version of the support for AVX was submitted by Tim Bird
<tim.bird am sony com> on behalf of Sony. This version was written
from scratch.

Tested by: pho (previous version), Yamagi Burmeister <lists yamagi org>
MFC after: 1 month