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kernel/x86: Re-introduce the 1MB lower barrier.

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It was removed in 2008 to make VM86 work, which is now gone.

Fixes #14911.
This commit is contained in:
Augustin Cavalier
2019-02-20 15:37:06 -05:00
parent 10aa58d7c3
commit 01796e78f4
1 changed files with 7 additions and 10 deletions
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headers/private/kernel/arch/x86/arch_kernel.h
+7 -10
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@@ -45,9 +45,9 @@
// There is a 2MB hole just before the end of the bottom half of the address // There is a 2MB hole just before the end of the bottom half of the address
// space. This means that if userland passes in a buffer that crosses into the // space. This means that if userland passes in a buffer that crosses into the
// uncanonical address region, it will be caught through a page fault. // uncanonical address region, it will be caught through a page fault.
#define USER_BASE 0x0 #define USER_BASE 0x100000
#define USER_BASE_ANY 0x100000 #define USER_BASE_ANY USER_BASE
#define USER_SIZE (0x800000000000 - 0x200000) #define USER_SIZE (0x800000000000 - (0x200000 + 0x100000))
#define USER_TOP (USER_BASE + (USER_SIZE - 1)) #define USER_TOP (USER_BASE + (USER_SIZE - 1))
#define KERNEL_USER_DATA_BASE 0x7f0000000000 #define KERNEL_USER_DATA_BASE 0x7f0000000000
@@ -80,14 +80,11 @@
* kernel. There is a gap of 64kb between the user and kernel space. The 64kb * kernel. There is a gap of 64kb between the user and kernel space. The 64kb
* region assures a user space thread cannot pass a buffer into the kernel as * region assures a user space thread cannot pass a buffer into the kernel as
* part of a syscall that would cross into kernel space. * part of a syscall that would cross into kernel space.
* Furthermore no areas are placed in the lower 1Mb unless the application * Further, there is a 1MB hole starting at 0x0 to prevent NULL from being mapped.
* explicitly requests it to find null pointer references.
* TODO: introduce the 1Mb lower barrier again - it's only used for vm86 mode,
* and this should be moved into the kernel (and address space) completely.
*/ */
#define USER_BASE 0x0 #define USER_BASE 0x100000
#define USER_BASE_ANY 0x100000 #define USER_BASE_ANY USER_BASE
#define USER_SIZE (KERNEL_BASE - 0x10000) #define USER_SIZE (KERNEL_BASE - (0x10000 + 0x100000))
#define USER_TOP (USER_BASE + (USER_SIZE - 1)) #define USER_TOP (USER_BASE + (USER_SIZE - 1))
#define KERNEL_USER_DATA_BASE 0x60000000 #define KERNEL_USER_DATA_BASE 0x60000000