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Kernel: Keep kernel base load address 2 MiB aligned

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This requirement comes from the fact the Prekernel mapping logic only
uses 2 MiB pages.
This unfortunately reduces the bits of entropy in kernel addresses from
16 bits to 7, but it could be further improved in the future by making
the Prekernel mapping logic a bit more dynamic.
This commit is contained in:
Idan Horowitz 2022-03-22 13:34:40 +02:00 • committed by Andreas Kling
parent 025cfacd46
commit d850e483f7
1 changed files with 4 additions and 6 deletions
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10
Kernel/Prekernel/init.cpp
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@ -91,17 +91,15 @@ extern "C" [[noreturn]] void init()
FlatPtr kernel_physical_base = 0x200000;
#if ARCH(I386)
FlatPtr kernel_load_base = 0xc0200000;
FlatPtr default_kernel_load_base = 0xc0200000;
#else
FlatPtr kernel_load_base = 0x2000200000;
FlatPtr default_kernel_load_base = 0x2000200000;
#endif
#if ARCH(X86_64)
// KASLR
static constexpr auto maximum_offset = 256 * MiB;
kernel_load_base = kernel_load_base + (generate_secure_seed() % maximum_offset);
kernel_load_base = kernel_load_base & ~(PAGE_SIZE - 1);
#endif
FlatPtr kernel_load_base = default_kernel_load_base + (generate_secure_seed() % maximum_offset);
kernel_load_base &= ~(2 * MiB - 1);
FlatPtr kernel_load_end = 0;
for (size_t i = 0; i < kernel_elf_header.e_phnum; i++) {