[PATCH v2 0/4] arm64: simplify and optimize kernel mapping

[Ard Biesheuvel]

This series makes a couple of minor changes that should result in the
kernel being mapped in a more efficient manner.

First of all, it introduces 'segment' to describe the various chunks that
make up the kernel runtime mapping, and replaces some instances of chunk
with segment (#1)

Then, it merges the .head.text with the .text section (patch #3) after moving
everything except the kernel and EFI header into the __init section (patch #2)

Then, it standardizes the segment alignment to 64 KB for all page sizes.
(patch #4). In the example below (4 KB granule, with Jeremy's PTE_CONT
patch applied), we lose 80 KB in total to padding (some of which is covered
by .init), but the resulting mappings do look somewhat better.

Before:

0xffff000008082000-0xffff000008090000    56K  ro x  SHD AF         UXN MEM
0xffff000008090000-0xffff000008200000  1472K  ro x  SHD AF CON     UXN MEM
0xffff000008200000-0xffff000008600000     4M  ro x  SHD AF     BLK UXN MEM
0xffff000008600000-0xffff000008660000   384K  ro x  SHD AF CON     UXN MEM
0xffff000008660000-0xffff00000866c000    48K  ro x  SHD AF         UXN MEM
0xffff00000866c000-0xffff000008670000    16K  ro NX SHD AF         UXN MEM
0xffff000008670000-0xffff000008900000  2624K  ro NX SHD AF CON     UXN MEM
0xffff000008900000-0xffff000008909000    36K  ro NX SHD AF         UXN MEM
0xffff000008c39000-0xffff000008c40000    28K  RW NX SHD AF         UXN MEM
0xffff000008c40000-0xffff000008d50000  1088K  RW NX SHD AF CON     UXN MEM
0xffff000008d50000-0xffff000008d57000    28K  RW NX SHD AF         UXN MEM

After:

0xffff000008080000-0xffff000008200000  1536K  ro x  SHD AF CON     UXN MEM
0xffff000008200000-0xffff000008600000     4M  ro x  SHD AF     BLK UXN MEM
0xffff000008600000-0xffff000008670000   448K  ro x  SHD AF CON     UXN MEM
0xffff000008670000-0xffff000008910000  2688K  ro NX SHD AF CON     UXN MEM
0xffff000008c50000-0xffff000008d60000  1088K  RW NX SHD AF CON     UXN MEM
0xffff000008d60000-0xffff000008d6b000    44K  RW NX SHD AF         UXN MEM

Changes since v2:
- add patch #1 to introduce 'segment' to describe the parts of the static kernel
  Image that are mapped with different permissions and/or lifetimes
- drop dependency on 4 KB pages for CONFIG_DEBUG_ALIGN_RODATA (#4)

Ard Biesheuvel (4):
  arm64: use 'segment' rather than 'chunk' to describe mapped kernel
    regions
  arm64: move early boot code to the .init segment
  arm64: cover the .head.text section in the .text segment mapping
  arm64: simplify kernel segment mapping granularity

 arch/arm64/Kconfig.debug        |  2 +-
 arch/arm64/kernel/efi-entry.S   |  2 +-
 arch/arm64/kernel/head.S        | 32 +++++++++-----------
 arch/arm64/kernel/image.h       |  4 +++
 arch/arm64/kernel/vmlinux.lds.S | 26 +++++++++-------
 arch/arm64/mm/mmu.c             | 22 +++++++-------
 6 files changed, 47 insertions(+), 41 deletions(-)

-- 
2.5.0