arm64: mm: check at build time that PAGE_OFFSET divides the VA space evenly
Commit 8439e62a1561 ("arm64: mm: use bit ops rather than arithmetic in pa/va translations") changed the boundary check against PAGE_OFFSET from an arithmetic comparison to a bit test. This means we now silently assume that PAGE_OFFSET is a power of 2 that divides the kernel virtual address space into two equal halves. So make that assumption explicit. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Catalin Marinas
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6d2aa549de
@ -170,6 +170,13 @@ void __init arm64_memblock_init(void)
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{
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const s64 linear_region_size = -(s64)PAGE_OFFSET;
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/*
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* Ensure that the linear region takes up exactly half of the kernel
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* virtual address space. This way, we can distinguish a linear address
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* from a kernel/module/vmalloc address by testing a single bit.
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*/
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BUILD_BUG_ON(linear_region_size != BIT(VA_BITS - 1));
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/*
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* Select a suitable value for the base of physical memory.
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*/
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