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Ignore R_AARCH64_ABS32 relocations, instead of panicking, when emitting
the relocation table of the hypervisor. The toolchain might produce them
when generating function calls with kCFI to represent the 32-bit type ID
which can then be resolved across compilation units at link time. These
are NOT actual 32-bit addresses and are therefore not needed in the
final (runtime) relocation table (which is unlikely to use 32-bit
absolute addresses for arm64 anyway).
Signed-off-by: Pierre-Clément Tosi <ptosi@google.com>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20240610063244.2828978-5-ptosi@google.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
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gen-hyprel tool parses object files of the EL2 portion of KVM
and generates runtime relocation data. While only filtering for
R_AARCH64_ABS64 relocations in the input object files, it has an
allow-list of relocation types that are used for relative
addressing. Other, unexpected, relocation types are rejected and
cause the build to fail.
This allow-list did not include the position-relative relocation
types R_AARCH64_PREL64/32/16 and the recently introduced _PLT32.
While not seen used by toolchains in the wild, add them to the
allow-list for completeness.
Fixes: 8c49b5d43d4c ("KVM: arm64: Generate hyp relocation data")
Cc: <stable@vger.kernel.org>
Reported-by: Will Deacon <will@kernel.org>
Signed-off-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210331133048.63311-1-dbrazdil@google.com
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gen-hyprel is, for better or worse, a native-endian program:
it assumes that the ELF data structures are in the host's
endianness, and even assumes that the compiled kernel is
little-endian in one particular case.
None of these assumptions hold true though: people actually build
(use?) BE arm64 kernels, and seem to avoid doing so on BE hosts.
Madness!
In order to solve this, wrap each access to the ELF data structures
with the required byte-swapping magic. This requires to obtain
the kernel data structure, and provide per-endianess wrappers.
This result in a kernel that links and even boots in a model.
Fixes: 8c49b5d43d4c ("KVM: arm64: Generate hyp relocation data")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
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Add a post-processing step to compilation of KVM nVHE hyp code which
calls a custom host tool (gen-hyprel) on the partially linked object
file (hyp sections' names prefixed).
The tool lists all R_AARCH64_ABS64 data relocations targeting hyp
sections and generates an assembly file that will form a new section
.hyp.reloc in the kernel binary. The new section contains an array of
32-bit offsets to the positions targeted by these relocations.
Since these addresses of those positions will not be determined until
linking of `vmlinux`, each 32-bit entry carries a R_AARCH64_PREL32
relocation with addend <section_base_sym> + <r_offset>. The linker of
`vmlinux` will therefore fill the slot accordingly.
This relocation data will be used at runtime to convert the kernel VAs
at those positions to hyp VAs.
Signed-off-by: David Brazdil <dbrazdil@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210105180541.65031-5-dbrazdil@google.com
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