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Clean up some redundant code in the KASLR placement handling logic. No
functional change intended.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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The EFI stub's kernel placement logic randomizes the physical placement
of the kernel by taking all available memory into account, and picking a
region at random, based on a random seed.
When KASLR is disabled, this seed is set to 0x0, and this results in the
lowest available region of memory to be selected for loading the kernel,
even if this is below LOAD_PHYSICAL_ADDR. Some of this memory is
typically reserved for the GFP_DMA region, to accommodate masters that
can only access the first 16 MiB of system memory.
Even if such devices are rare these days, we may still end up with a
warning in the kernel log, as reported by Tom:
swapper/0: page allocation failure: order:10, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0
Fix this by tweaking the random allocation logic to accept a low bound
on the placement, and set it to LOAD_PHYSICAL_ADDR.
Fixes: a1b87d54f4e4 ("x86/efistub: Avoid legacy decompressor when doing EFI boot")
Reported-by: Tom Englund <tomenglund26@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218404
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
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Alexandre Ghiti <alexghiti@rivosinc.com> says:
The following KASLR implementation allows to randomize the kernel mapping:
- virtually: we expect the bootloader to provide a seed in the device-tree
- physically: only implemented in the EFI stub, it relies on the firmware to
provide a seed using EFI_RNG_PROTOCOL. arm64 has a similar implementation
hence the patch 3 factorizes KASLR related functions for riscv to take
advantage.
The new virtual kernel location is limited by the early page table that only
has one PUD and with the PMD alignment constraint, the kernel can only take
< 512 positions.
* b4-shazam-merge:
riscv: libstub: Implement KASLR by using generic functions
libstub: Fix compilation warning for rv32
arm64: libstub: Move KASLR handling functions to kaslr.c
riscv: Dump out kernel offset information on panic
riscv: Introduce virtual kernel mapping KASLR
Link: https://lore.kernel.org/r/20230722123850.634544-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Fix the following warning which appears when compiled for rv32 by using
unsigned long type instead of u64.
../drivers/firmware/efi/libstub/efi-stub-helper.c: In function 'efi_kaslr_relocate_kernel':
../drivers/firmware/efi/libstub/efi-stub-helper.c:846:28: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
846 | (u64)_end < EFI_ALLOC_LIMIT) {
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Song Shuai <songshuaishuai@tinylab.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20230722123850.634544-5-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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This prepares for riscv to use the same functions to handle the pĥysical
kernel move when KASLR is enabled.
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Song Shuai <songshuaishuai@tinylab.org>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Sami Tolvanen <samitolvanen@google.com>
Link: https://lore.kernel.org/r/20230722123850.634544-4-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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