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RELR as a relocation packing format for relative relocations for
reducing the size of relative relocation records. In a position
independent executable there are often many relative relocation
records, and our vmlinux is a PIE.
The LLD linker (since 17.0.0) and the BFD linker (since 2.43) supports
packing the relocations in the RELR format for LoongArch, with the flag
-z pack-relative-relocs.
Commits 5cf896fb6be3eff ("arm64: Add support for relocating the kernel
with RELR relocations") and ccb2d173b983984bfa ("Makefile: use -z
pack-relative-relocs") have already added the framework to use RELR.
We just need to wire it up and process the RELR relocation records in
relocate_relative() in addition to the RELA relocation records.
A ".p2align 3" directive is added to la_abs macro or the BFD linker
cannot pack the relocation records against the .la_abs section (the
". = ALIGN(8);" directive in vmlinux.lds.S is too late in the linking
process).
With defconfig and CONFIG_RELR vmlinux.efi is 2.1 MiB (6%) smaller, and
vmlinuz.efi (using gzip compression) is 384 KiB (2.8%) smaller.
Link: https://groups.google.com/d/topic/generic-abi/bX460iggiKg
Link: https://reviews.llvm.org/D138135#4531389
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d89ecf33ab6d
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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To clarify, the previous version functioned flawlessly. However, it's
worth noting that the LLVM's LoongArch backend currently lacks support
for cross-section label calculations. With this patch, we enable the use
of clang to compile relocatable kernels.
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: WANG Rui <wangrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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Modified relocate_kernel() doesn't return new kernel's entry point but
the random_offset. In this way we share the start_kernel() processing
with the normal kernel, which avoids calling 'jr a0' directly and allows
some other operations (e.g, kasan_early_init) before start_kernel() when
KASLR (CONFIG_RANDOMIZE_BASE) is turned on.
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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Provide kaslr_offset() to get the kernel offset when KASLR is enabled.
Signed-off-by: Feiyang Chen <chenfeiyang@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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This patch adds support for relocating the kernel to a random address.
Entropy is derived from the banner, which will change every build and
random_get_entropy() which should provide additional runtime entropy.
The kernel is relocated by up to RANDOMIZE_BASE_MAX_OFFSET bytes from
its link address. Because relocation happens so early during the kernel
booting, the amount of physical memory has not yet been determined. This
means the only way to limit relocation within the available memory is
via Kconfig. So we limit the maximum value of RANDOMIZE_BASE_MAX_OFFSET
to 256M (0x10000000) because our memory layout has many holes.
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Xi Ruoyao <xry111@xry111.site> # Fix compiler warnings
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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This config allows to compile kernel as PIE and to relocate it at any
virtual address at runtime: this paves the way to KASLR.
Runtime relocation is possible since relocation metadata are embedded
into the kernel.
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Xi Ruoyao <xry111@xry111.site> # Use arch_initcall
Signed-off-by: Jinyang He <hejinyang@loongson.cn> # Provide la_abs relocation code
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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Since commit 40cd01a9c324("efi/loongarch: libstub: remove dependency on
flattened DT"), we can parse the FDT from efi system table.
And now, LoongArch is coming to support booting with FDT, so we add the
relevant booting support as well as parameter parsing.
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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Current cache probe and flush methods have some drawbacks:
1, Assume there are 3 cache levels and only 3 levels;
2, Assume L1 = I + D, L2 = V, L3 = S, V is exclusive, S is inclusive.
However, the fact is I + D, I + D + V, I + D + S and I + D + V + S are
all valid. So, refactor the cache probe and flush methods to adapt more
types of cache hierarchy.
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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Add basic boot, setup and reset routines for LoongArch. Now, LoongArch
machines use UEFI-based firmware. The firmware passes configuration
information to the kernel via ACPI and DMI/SMBIOS.
Currently an existing interface between the kernel and the bootloader
is implemented. Kernel gets 2 values from the bootloader, passed in
registers a0 and a1; a0 is an "EFI boot flag" distinguishing UEFI and
non-UEFI firmware, while a1 is a pointer to an FDT with systable,
memmap, cmdline and initrd information.
The standard UEFI boot protocol (EFISTUB) will be added later.
Cc: linux-efi@vger.kernel.org
Cc: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: WANG Xuerui <git@xen0n.name>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Co-developed-by: Yun Liu <liuyun@loongson.cn>
Signed-off-by: Yun Liu <liuyun@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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