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

Commit

  0698fac4ac2a ("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

diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index cabdd8f4a2482e2b2362794b3071173c87431b3a..e8e1c866e413a287924656851a202f1c480613b7 100644 (file)
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -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