[PATCH v3 0/7] arm64: relax Image placement rules

[Ard Biesheuvel]

This series updates the mapping of the kernel Image and the linear mapping of
system memory to allow more freedom in the choice of Image placement without
affecting the accessibility of system RAM below the kernel Image, and the
mapping efficiency (i.e., memory can always be mapped in 512 MB or 1 GB blocks).

An added benefit of having the freedom to put the Image anywhere in physical
memory is that it decomplicates the logic that needs to be applied when using
kexec to boot another kernel. Furthermore, moving the kernel out of the linear
mapping is a preparatory step towards implementing kASLR. This will be addressed
in a followup series.

Changes since v2 (http://marc.info/?l=linux-arm-kernel&m=144309211310754):
- rebased onto v4.4-rc1, which adds support for 16k pages, resulting in minor
  changes requried to various parts of the code
- fix behavior under CONFIG_DEBUG_RODATA

Changes since v1:
- dropped somewhat unrelated patch #1 and patches #2 and #3 that have been
  merged separately
- rebased onto v4.2-rc3
- tweak the generic early_init_dt_add_memory_arch for our purposes rather than
  clone the implementation completely

Known issues:
- the mem= command line parameter works correctly now, but removes memory from
  the bottom first before clipping from the top, which may be undesirable since
  it may discard precious memory below the 4 GB boundary.

Patch #1 refactors the generic early_init_dt_add_memory_arch implementation to
allow to minimum memblock address to be overridden by the architecture.

Patch #2 changes the memblock_reserve logic so that unused page table
reservations are left unreserved in memblock.

Patch #3 refactors early_fixmap_init() so that we can reuse its core for
bootstrapping other memory mappings.

Patch #4 bootstraps the linear mapping explicitly. Up until now, this was done
implicitly due to the fact that the linear mapping starts at the base of the
kernel Image.

Patch #5 moves the mapping of the kernel Image outside of the linear mapping.

Patch #6 changes the attributes of the linear mapping to non-executable since
we don't execute code from it anymore.

Patch #7 allows the kernel to be loaded at any 2 MB aligned offset in physical
memory, by assigning PHYS_OFFSET based on the available memory and not based on
the physical address of the base of the kernel Image.

Ard Biesheuvel (7):
  of/fdt: make memblock minimum physical address arch configurable
  arm64: use more granular reservations for static page table
    allocations
  arm64: split off early mapping code from early_fixmap_init()
  arm64: mm: explicitly bootstrap the linear mapping
  arm64: move kernel mapping out of linear region
  arm64: map linear region as non-executable
  arm64: allow kernel Image to be loaded anywhere in physical memory

 Documentation/arm64/booting.txt         |  12 +-
 arch/arm64/include/asm/boot.h           |   7 +
 arch/arm64/include/asm/compiler.h       |   2 +
 arch/arm64/include/asm/kernel-pgtable.h |   5 +-
 arch/arm64/include/asm/memory.h         |  27 ++-
 arch/arm64/kernel/head.S                |  18 +-
 arch/arm64/kernel/vmlinux.lds.S         |  39 +++-
 arch/arm64/mm/dump.c                    |   3 +-
 arch/arm64/mm/init.c                    |  54 ++++-
 arch/arm64/mm/mmu.c                     | 224 +++++++++++++-------
 drivers/of/fdt.c                        |   5 +-
 11 files changed, 284 insertions(+), 112 deletions(-)

-- 
1.9.1