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arm64: Work around convergence issue with LLD linker

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LLD will occasionally error out with a '__init_end does not converge'
error if INIT_IDMAP_DIR_SIZE is defined in terms of _end, as this
results in a circular dependency.

Counter this by dimensioning the initial IDMAP page tables based on a
new boundary marker 'kimage_limit', and define it such that its value
should not change as a result of the initdata segment being pushed over
a 64k segment boundary due to changes in INIT_IDMAP_DIR_SIZE, provided
that its value doesn't change by more than 2M between linker passes.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20250531123005.3866382-2-ardb+git@google.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Ard Biesheuvel 2025-05-31 14:30:05 +02:00 • committed by Will Deacon
parent e21560b7d3
commit dc0a083948
2 changed files with 12 additions and 1 deletions
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2
arch/arm64/include/asm/kernel-pgtable.h
View file

@ -58,7 +58,7 @@
#define INIT_DIR_SIZE (PAGE_SIZE * (EARLY_PAGES(SWAPPER_PGTABLE_LEVELS, KIMAGE_VADDR, _end, EXTRA_PAGE) \
+ EARLY_SEGMENT_EXTRA_PAGES))
#define INIT_IDMAP_DIR_PAGES (EARLY_PAGES(INIT_IDMAP_PGTABLE_LEVELS, KIMAGE_VADDR, _end, 1))
#define INIT_IDMAP_DIR_PAGES (EARLY_PAGES(INIT_IDMAP_PGTABLE_LEVELS, KIMAGE_VADDR, kimage_limit, 1))
#define INIT_IDMAP_DIR_SIZE ((INIT_IDMAP_DIR_PAGES + EARLY_IDMAP_EXTRA_PAGES) * PAGE_SIZE)
#define INIT_IDMAP_FDT_PAGES (EARLY_PAGES(INIT_IDMAP_PGTABLE_LEVELS, 0UL, UL(MAX_FDT_SIZE), 1) - 1)

11
arch/arm64/kernel/image-vars.h
View file

@ -146,6 +146,17 @@ KVM_NVHE_ALIAS(kvm_protected_mode_initialized);
_kernel_codesize = ABSOLUTE(__inittext_end - _text);
#endif
/*
* LLD will occasionally error out with a '__init_end does not converge' error
* if INIT_IDMAP_DIR_SIZE is defined in terms of _end, as this results in a
* circular dependency. Counter this by dimensioning the initial IDMAP page
* tables based on kimage_limit, which is defined such that its value should
* not change as a result of the initdata segment being pushed over a 64k
* segment boundary due to changes in INIT_IDMAP_DIR_SIZE, provided that its
* value doesn't change by more than 2M between linker passes.
*/
kimage_limit = ALIGN(ABSOLUTE(_end + SZ_64K), SZ_2M);
#undef ASSERT
#endif /* __ARM64_KERNEL_IMAGE_VARS_H */