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arm64: head: Ignore bogus KASLR displacement on non-relocatable kernels 

Even non-KASLR kernels can be built as relocatable, to work around
broken bootloaders that violate the rules regarding physical placement
of the kernel image - in this case, the physical offset modulo 2 MiB is
used as the KASLR offset, and all absolute symbol references are fixed
up in the usual way. This workaround is enabled by default.

CONFIG_RELOCATABLE can also be disabled entirely, in which case the
relocation code and the code that captures the offset are omitted from
the build. However, since commit aacd149b62 ("arm64: head: avoid
relocating the kernel twice for KASLR"), this code got out of sync, and
we still add the offset to the kernel virtual address before populating
the page tables even though we never capture it. This means we add a
bogus value instead, breaking the boot entirely.

Fixes: aacd149b62 ("arm64: head: avoid relocating the kernel twice for KASLR")
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Mikulas Patocka <mpatocka@redhat.com>
Link: https://lore.kernel.org/r/20220827070904.2216989-1-ardb@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Ard Biesheuvel 2022-08-27 09:09:04 +02:00 committed by Will Deacon
parent 4831be702b
commit e62b9e6f25
1 changed files with 2 additions and 0 deletions
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arch/arm64/kernel/head.S
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@ -371,7 +371,9 @@ SYM_FUNC_END(create_idmap)
SYM_FUNC_START_LOCAL(create_kernel_mapping)
adrp x0, init_pg_dir
mov_q x5, KIMAGE_VADDR // compile time __va(_text)
#ifdef CONFIG_RELOCATABLE
add x5, x5, x23 // add KASLR displacement
#endif
adrp x6, _end // runtime __pa(_end)
adrp x3, _text // runtime __pa(_text)
sub x6, x6, x3 // _end - _text