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efi/arm: Deal with ADR going out of range in efi_enter_kernel()

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  0698fac4ac ("efi/arm: Clean EFI stub exit code from cache instead of avoiding it")

introduced a PC-relative reference to 'call_cache_fn' into
efi_enter_kernel(), which lives way at the end of head.S. In some cases,
the ARM version of the ADR instruction does not have sufficient range,
resulting in a build error:

  arch/arm/boot/compressed/head.S:1453: Error: invalid constant (fffffffffffffbe4) after fixup

ARM defines an alternative with a wider range, called ADRL, but this does
not exist for Thumb-2. At the same time, the ADR instruction in Thumb-2
has a wider range, and so it does not suffer from the same issue.

So let's switch to ADRL for ARM builds, and keep the ADR for Thumb-2 builds.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200409130434.6736-6-ardb@kernel.org
This commit is contained in:
Ard Biesheuvel 2020-04-09 15:04:30 +02:00 committed by Ingo Molnar
parent 21cb9b4143
commit a94691680b
1 changed files with 2 additions and 1 deletions
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3
arch/arm/boot/compressed/head.S
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@ -1450,7 +1450,8 @@ ENTRY(efi_enter_kernel)
@ running beyond the PoU, and so calling cache_off below from
@ inside the PE/COFF loader allocated region is unsafe unless
@ we explicitly clean it to the PoC.
adr r0, call_cache_fn @ region of code we will
ARM( adrl r0, call_cache_fn )
THUMB( adr r0, call_cache_fn ) @ region of code we will
adr r1, 0f @ run with MMU off
bl cache_clean_flush
bl cache_off