MFC r341253, r341328, r342619, r342626, r342707, r342785, r342865

r341253:
The libstand's panic() appends its own '\n' to the message, so that users of the API
don't need to supply one.

r341328:
loader: create separate lists for fd, cd and hd, merge bioscd with biosdisk

Create unified block IO implementation in BIOS version, like it is done in UEFI
side. Implement fd, disk and cd device lists, this will split floppy devices
from disks and will allow us to have consistent, predictable device naming
(modulo BIOS issues).

r342619:
loader: create bio_alloc and bio_free for bios bounce buffer

We do have 16KB buffer space defined in pxe.c, move it to bio.c and implement
bio_alloc()/bio_free() interface to make it possible to use this space for
other BIOS calls (notably, from biosdisk.c).

r342626:
Add Copyright.

r342707:
i386_parsedev() needs to support fd devices

r342785:
With buggy int13 ah=15, we can mis-identify the floppy devices.

We have no option than trust INT13 ah=08 return code during the init phase.

r342865:
biospci_write_config args were backwards

biospci_write_config args swapped length and value to write. Some
hardware coped just fine, while other hardware had issues.

PR: 155441, 234460

MFC i386 stand cleanup: r337353-r337354, r337356, r337872, r337878, r337881,
r337890-r337891, r338188

r337353:
loader: cstyle cleanup for biosdisk.c

Also switch u_int to uint32_t. Also replace "write" by "dowrite".
No functional changes intended.

r337354:
loader: 337353 did miss to rename 2 write instances

2 write instances got somehow missed.

r337356:
loader: bd_open() should cleanup from disk_open() error

Since bd_open() does early increment for reference counter and bcache
allocation, it also should undo those in case of the error.

Also remove unused variables rdev, g_err.

r337872:
libi386: remove BD_SUPPORT_FRAGS

BD_SUPPORT_FRAGS is preprocessor knob to allow partial reads in bioscd/biosdisk
level. However, we already have support for partial reads in bcache, and there
is no need to have duplication via preprocessor controls.

Note that bioscd/biosdisk interface is assumed to perform IO in 512B blocks,
so the only translation we have to do is 512 <-> native block size.

r337878:
libi386: remove bd_read() and bd_write() wrappers

Those wroappers are nice, but do not really add much value.

r337881:
libi386: use BD_RD and BR_WR constants

Use BD_RD and BD_WR instead of 0 and 1.

r337890:
libi386: small style updates in biosdisk

Use break instead of return in for loop, as done earlier. Insert and remove
some blank lines. No functional changes intended.

r337891:
libi386: bd_io_workaround() is to be called for reads only

bd_io() can perform either reads or writes, we only need bd_io_workaround()
for reads.

r338188:
loader: bios loader should allow to chain load a file

The current chain command does accept only device, allow also a file to be used,
such as /boot/pmbr or /boot/mbr (or stored third party MBR/VBR block).

Also fix file descriptor leak.

MFC r330806-r330815, r330837, r330864, r330883

pc98 changes associated with the named commits are also included in this
commit, despite not having been made with the original commits due to its
removal in head.

r330806:
Minor cosmetic changes.

Make sure { on the same line as struct for all struct *devdesc. Move
some type definitions to next to the dv_type define, since that's what
sets the d_type.

r330807:
We can't use d_opendata for blkio storage.

open_disk uses d_opendata for it's own purpse. We can't store blkio
there. Fortunately, blkio is stored elsewhere and we never actually
retrieve blkio from d_opendata. Eliminate it as a source of confusion.
Eliminate all stores of d_opendata in efi since this layer doesn't own
that field.

r330808:
Make struct libi386_devdesc match the struct devdesc better

Move data to top and call it d_opendata.

r330809:
Use the actual struct devdesc at the start of all *_devdesc structs

The current system is fragile and requires very careful layout of all
*_devdesc structures. It also makes it hard to change the base
devdesc. Take a page from CAM and put the 'header' in all the derived
classes and adjust the code to match.

For OFW, move the iHandle h_handle out of a slot conflicting with
d_opendata. Due to quirks in the alignment rules, this worked.
However changing the code to use d_opendata storage now that it's a
pointer is hard, so just have a separate field for it.

All other cleanups were to make the *_devdesc structures match where
they'd taken some liberties that were none-the-less compatible enough
to work.

r330810:
Remove d_type from devdesc. It's not needed as we can fetch it from
d_dev->dv_type when we need it.

r330811:
GC unused routines.

Sponsored by: Netflix

r330812:
Use the one-line-per-file pattern here, and sort the file names.

Sponsored by: Netflix

r330813:
Move the env convenience routines out of boot1.c.

These routines are more generally useful. Even though boot1 is on its
way out, it's better to make these common during the transition than
copy them.

r330814:
Star BootCurrent entry when booting.

Sponsored by: Netflix

r330815:
Print the load and device path as well as BootCurrent and BootOrder

Sponsored by: Netflix

r330837:
biosdisk.c should not set d_opendata.

Same as 330807, d_opendata is owned by open_disk and we should not
set it.

M stand/i386/libi386/biosdisk.c

r330864:
Prefer uintXX_t to u_intXX_t

A foolish consistency is the hobgoblin of little minds, adored by
little statesmen and philosophers and divines. With consistency a
great soul has simply nothing to do. -- Ralph Waldo Emerson

r330883:
Fix typo that misteriously passes compilation.

MFC r325834,r325997,326502: Move sys/boot to stand/

This is effectively a direct commit to stable/11, due to differences between
stable/11 and head. Changes to DTS in sys/boot/fdt/dts were often
accompanied by kernel changes. Many of these were also risc-v updates that
likely had many more dependencies to MFC.

Because of this, sys/boot/fdt/dts remains as-is while everything else in
sys/boot relocates to stand/.

r325834: Move sys/boot to stand. Fix all references to new location

r325997: Remove empty directories.

r326502: Document the sys/boot -> stand move in hier.7 and the top-level README.

MFC Loader Fixes 2017q2: r316437,r316577,r316578,r316585,r316590,r316612,
r316625,r316628,r316654,r316682,r316704,r316771,r317092,r317097,r317099,
r317652,r317785,r317886,r317887,r318142,r318320,r318356,r318678,r318754,
r318982,r318986,r318987,r318988,r318989,r318990,r318991,r318992,r318993,
r318994,r318999,r319083,r319084,r319085,r320011,r320234,r320288,r320304,
r320467,r320482

r316437: Small cleanup to make i386/loader match efi/loader boot environment
code

r316577: loader: part.c cstyle cleanup

r316578: loader: want mechanism to avoid RA with bcache

r316585: loader: zfs reader should check all labels

r316590: libstand/dosfs: cache FAT32 in 128 Kb blocks to save loader memory

r316612: In r298230 the value of HEAP_MIN was changed from 3MB to 64MB.
Correct a comment.

r316625: Do not use -msoft-float with intention of disabling FP on aarch64

r316628: Silence GCC warning by initializing the local variable.

r316654: loader: r316585 did miss userboot update

r316682: loader: r316585 did miss sparc/ofw

r316704: loader.efi: only fetch zfs pool guid for the actual boot device

r316771: loader: Avoid possible overflow via environment variable

r317092: loader: zfs reader vdev_probe should check for minimum device size

r317097: loader: F_READ/F_WRITE should be checked against masked flag

r317099: loader: uboot disk ioctl should call disk_ioctl

r317652: loader.efi: ResetSystem does not use data with EFI_SUCCESS

r317785: zfsboot: drvsize() may be unusable on some systems

r317886: distinguish NFS versus TFTP boot by rootpath

r317887: loader: network read rework

r318142: libstand: NULL pointer dereference in rarp

r318320: loader: add ip layer code into libstand

r318356: libstand: increase nfs max read size to 16k

r318678: Replacing iterating over rootpath by strsep(3).

r318754: Pass -N directly to ld via -Wl rather than passing it to the
compiler driver.

r318982: Pass a "FREEBSD" user-class in PXE dhcp request

r318986: add a comment on vendor index 19 and 20 to avoid confusion

r318987: Support URI scheme for root-path in netbooting

r318988: Always build tftpfs support along with nfs for pxeboot

r318989: Always issue the pxe request

r318990: Partially revert r314948

r318991: Document recent changes on pxeboot

r318992: Capitalize DHCP

r318993: Use the usual FreeBSD spelling for the DHCP user class

r318994: Catch with the change in the user class

r318999: Update the comments concerning net_parse_rootpath to reflect what
it is now

r319083: Followup on the user-class changes

r319084: Small cleanup in dev_net.c

r319085: use the same option list for dhcp discovery and request

r320011: Add chain loader support for loader

r320234: Make structure padding explicit in EFI_MEMORY_DESCRIPTOR

r320288: Allow Clang's integrated assembler to assemble boot0

r320304: loader.efi: Disable smbios for arm

r320467: loader: chain load relocate data declaration is bad

r320482: As with arm64 mark the EFI PE header as allocated on arm.

PR: 218473

Add chain loader support for loader

Implement simple chain loader in loader; this update does add chain command,
taking device or file as argument to load and start new boot loader.

In case of BIOS, the chain will read the boot block to address 0000:7c00 and
jumps on it. In case of UEFI, the chain command is to be used with efi
application, typically stored in EFI System Partition.

The update also does add simple menu entry, if the variable chain_disk is set.
The value of the variable chain_disk is used as argument for chain loading.

Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D5992