[U-Boot] u-boot 2018.07/2018.09 'data abort' kernel start failure with GCC 8.2.0 on sun8i (H3)

[Auston Stewart]

Greetings,

  As others have reported (
https://lists.denx.de/pipermail/u-boot/2018-July/334126.html), a 'data
abort' occurs when attempting to load the kernel with recent u-boot
compiled with recent GCC on Allwinner (Sunxi) H3 boards. I ran into this
issue when performing a bootstrap of Shedbuilt GNU/Linux with upstream GCC
8.20, glibc 2.28 and binutils 2.31.1 on a Nano Pi Neo 512M board.
  I brought up this issue in IRC and did some debugging with xypron, who
asked that I message the list.

Configurations I've personally tested:
u-boot 2018.07 nanopi_neo_defconfig / GCC 8.2.0 + Kernel 4.17.14 / GCC
8.2.0 = broken
u-boot 2018.09-rc2 nanopi_neo_defconfig / GCC 8.2.0 + Kernel 4.17.14 / GCC
8.2.0 = broken
u-boot 2018.05 nanopi_neo_defconfig / GCC 7.3.0 + Kernel 4.17.14 / GCC
8.2.0 = works
u-boot 2018.03 nanopi_neo_defconfig / GCC 7.2.0 + Kernel 4.17.14 / GCC
8.2.0 = works
u-boot 2018.09-rc2 ARMv7 unaligned access patch (
https://lists.denx.de/pipermail/u-boot/2018-March/324202.html) /
nanopi_neo_defconfig / GCC 8.2.0 + Kernel 4.17.14 / GCC 8.2.0 = broken

Error (captured on Nano Pi Neo 512M with 2018.09-rc2):
(for complete log, see
https://gist.github.com/austons/222c6f1fd304d0832bec9964a4f569f0)
Starting kernel ...

data abort
pc : [<5ff9f16c>]          lr : [<5ff76ed7>]
reloc pc : [<4a02916c>]    lr : [<4a000ed7>]
sp : 5bf50588  ip : 5bf568da     fp : 40008000
r10: 5bf50698  r9 : 5bf55ee0     r8 : 00000400
r7 : 00000000  r6 : 40008000     r5 : 49ff8000  r4 : 00000000
r3 : 49ff8000  r2 : 49ff8000     r1 : 00000000  r0 : 00000000
Flags: nZCv  IRQs off  FIQs off  Mode UK6_32
Code: e12fff1e e52de008 fa000001 e3a00000 (e49df008)
Resetting CPU ...

  I have access to a number of H3/sun8i test devices to assist in
diagnosis. There is some speculation in the earlier thread that USB changes
post-2018.07rc1 could be a cause, but the only confirmed workaround is
reverting to earlier GCC.
  Thank you for your time. Please let me know if there are other details I
can provide.

Auston Stewart
Shedbuilt GNU/Linux
http://shedbuilt.net