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Kernel: Use the whole kernel PD range when randomizing the KASLR offset

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Now that we reclaim the memory range that is created by KASLR before
the start of the kernel image, there's no need to be conservative with
the KASLR offset.
This commit is contained in:
Idan Horowitz 2022-03-22 19:10:17 +02:00 • committed by Idan Horowitz
parent e0c7727934
commit f0166efe8c
6 changed files with 5 additions and 8 deletions
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2
Kernel/Prekernel/Prekernel.h
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@ -13,6 +13,7 @@
#endif
#define MAX_KERNEL_SIZE 0x4000000
#define KERNEL_PD_SIZE 0x31000000
#ifdef __cplusplus
namespace Kernel {
@ -22,7 +23,6 @@ struct [[gnu::packed]] BootInfo {
u32 end_of_prekernel_image;
u64 physical_to_virtual_offset;
u64 kernel_mapping_base;
u64 default_kernel_load_base;
u64 kernel_load_base;
# if ARCH(X86_64)
u32 gdt64ptr;

3
Kernel/Prekernel/init.cpp
View file

@ -97,7 +97,7 @@ extern "C" [[noreturn]] void init()
#endif
// KASLR
static constexpr auto maximum_offset = 256 * MiB;
FlatPtr maximum_offset = (FlatPtr)KERNEL_PD_SIZE - MAX_KERNEL_SIZE - 2 * MiB; // The first 2 MiB are used for mapping the pre-kernel
FlatPtr kernel_load_base = default_kernel_load_base + (generate_secure_seed() % maximum_offset);
kernel_load_base &= ~(2 * MiB - 1);
@ -184,7 +184,6 @@ extern "C" [[noreturn]] void init()
info.end_of_prekernel_image = (PhysicalPtr)end_of_prekernel_image;
info.physical_to_virtual_offset = kernel_load_base - kernel_physical_base;
info.kernel_mapping_base = kernel_mapping_base;
info.default_kernel_load_base = default_kernel_load_base;
info.kernel_load_base = kernel_load_base;
#if ARCH(X86_64)
info.gdt64ptr = (PhysicalPtr)gdt64ptr;