Augustin Cavalier
8f149016fb
x86_64 already does this and it seems to work fine. Since stack areas grow downwards and should always have a guard page, overruns shouldn't be too much of a concern (for that matter, randomization still makes a difference here also, it seems.) This allows us to regain another ~256 MB or so of contiguous address space (areas smaller than that could still be inserted in the 0x6.. to 0x7.. block, but if you had 10MB of free address space below 0x6.., and 246MB above it, you couldn't allocate a 256MB block.) Part of #19592.
35 lines
1.2 KiB
C
35 lines
1.2 KiB
C
/*
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** Copyright 2001-2002, Travis Geiselbrecht. All rights reserved.
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** Distributed under the terms of the NewOS License.
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*/
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#ifndef _KERNEL_ARCH_ARM_KERNEL_H
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#define _KERNEL_ARCH_ARM_KERNEL_H
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#include <arch/cpu.h>
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// memory layout
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#define KERNEL_LOAD_BASE 0x80000000
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#define KERNEL_BASE 0x80000000
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#define KERNEL_SIZE 0x80000000
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#define KERNEL_TOP (KERNEL_BASE + (KERNEL_SIZE - 1))
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/*
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** User space layout is a little special:
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** The user space does not completely cover the space not covered by the kernel.
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** This is accomplished by starting user space at 1Mb and running to 64kb short of kernel space.
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** The lower 1Mb reserved spot makes it easy to find null pointer references and guarantees a
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** region wont be placed there. The 64kb region assures a user space thread cannot pass
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** a buffer into the kernel as part of a syscall that would cross into kernel space.
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*/
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#define USER_BASE 0x100000
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#define USER_BASE_ANY USER_BASE
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#define USER_SIZE (0x80000000 - (0x10000 + USER_BASE))
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#define USER_TOP (USER_BASE + (USER_SIZE - 1))
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#define KERNEL_USER_DATA_BASE 0x70000000
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#define USER_STACK_REGION 0x70000000
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#define USER_STACK_REGION_SIZE ((USER_TOP - USER_STACK_REGION) + 1)
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#endif /* _KERNEL_ARCH_ARM_KERNEL_H */
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