Subject: [PATCH v2 0/5] ARM: simplify handover from UEFI to decompressor

From: Ard Biesheuvel <[email-masked]>
Date: Mon, 13 Apr 2020 18:21:30 +0200

The EFI stub in the ARM kernel runs in the context of the firmware, which
means it runs with the caches and MMU on. Currently, we relocate the zImage
so it appears in the first 128 MiB, disable the MMU and caches and invoke
the decompressor via its ordinary entry point. However, since we can pass
the base of DRAM directly, there is no need to relocate the zImage, which
also means there is no need to disable and re-enable the caches and create
new page tables etc.

This simplification is implemented by patch #5. Patches #1 - #4 are
prerequisite changes to permit the decompressor to execute from the
offset chosen by the UEFI firmware.

Note that this applies onto v5.7-rc1 with Geert's patch 'ARM: boot: Obtain
start of physical memory from DTB' applied [0]

Changes since v1:
- tweak some asm sequences in #2 to fix the Thumb2 build
- switch immediately to the new stack in #5

Cc: Geert Uytterhoeven <[email-masked]>
Cc: Nicolas Pitre <[email-masked]>
Cc: Linus Walleij <[email-masked]>
Cc: Russell King <[email-masked]>

[0] https://lore.kernel.org/linux-arm-kernel/[email-masked]/

Ard Biesheuvel (5):
  ARM: decompressor: move headroom variable out of LC0
  ARM: decompressor: split off _edata and stack base into separate
    object
  ARM: decompressor: defer loading of the contents of the LC0 structure
  ARM: decompressor: move GOT into .data for EFI enabled builds
  ARM: decompressor: run decompressor in place if loaded via UEFI

 arch/arm/boot/compressed/head.S           | 89 ++++++++------------
 arch/arm/boot/compressed/vmlinux.lds.S    |  5 ++
 drivers/firmware/efi/libstub/arm32-stub.c | 45 ++--------
 3 files changed, 45 insertions(+), 94 deletions(-)

-- 
2.17.1

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