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Changed the set_segment_descriptor()'s usage of the limit/granularity

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flag. Now, it will choose how to set the granularity by evaluating the
limit.
This call was actually already used this way in the kernel, so that
the TLS and TSS segments were much too large (harmless but incorrect).


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@12231 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Axel Dörfler 2005-04-04 14:34:18 +00:00
parent 9d06770cdc
commit e5b0e0b5e3
2 changed files with 16 additions and 7 deletions
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15
headers/private/kernel/arch/x86/descriptors.h
View File

@ -86,15 +86,24 @@ set_segment_descriptor(struct segment_descriptor *desc, addr_t base, uint32 limi
{
set_segment_descriptor_base(desc, base);
desc->limit_00_15 = (addr_t)limit & 0x0ffff; // limit is 20 bits long
desc->limit_19_16 = ((addr_t)limit >> 16) & 0xf;
// limit is 20 bits long
if (limit & 0xfff00000) {
desc->limit_00_15 = ((addr_t)limit >> 12) & 0x0ffff;
desc->limit_19_16 = ((addr_t)limit >> 28) & 0xf;
desc->granularity = 1; // 4 KB granularity
} else {
desc->limit_00_15 = (addr_t)limit & 0x0ffff;
desc->limit_19_16 = ((addr_t)limit >> 16) & 0xf;
desc->granularity = 0; // 1 byte granularity
}
limit >>= 12;
desc->type = type;
desc->desc_type = DT_CODE_DATA_SEGMENT;
desc->privilege_level = privilegeLevel;
desc->present = 1;
desc->granularity = 1; // 4 GB size (in page size steps)
desc->available = 0; // system available bit is currently not used
desc->d_b = 1; // 32-bit code

8
src/kernel/boot/platform/bios_ia32/mmu.cpp
View File

@ -379,14 +379,14 @@ mmu_init_for_kernel(void)
// put standard segment descriptors in it
clear_segment_descriptor(&gdt[0]);
set_segment_descriptor(&gdt[1], 0, 0xfffff, DT_CODE_READABLE, DPL_KERNEL);
set_segment_descriptor(&gdt[1], 0, 0xffffffff, DT_CODE_READABLE, DPL_KERNEL);
// seg 0x08 - kernel 4GB code
set_segment_descriptor(&gdt[2], 0, 0xfffff, DT_DATA_WRITEABLE, DPL_KERNEL);
set_segment_descriptor(&gdt[2], 0, 0xffffffff, DT_DATA_WRITEABLE, DPL_KERNEL);
// seg 0x10 - kernel 4GB data
set_segment_descriptor(&gdt[3], 0, 0xfffff, DT_CODE_READABLE, DPL_USER);
set_segment_descriptor(&gdt[3], 0, 0xffffffff, DT_CODE_READABLE, DPL_USER);
// seg 0x1b - ring 3 user 4GB code
set_segment_descriptor(&gdt[4], 0, 0xfffff, DT_DATA_WRITEABLE, DPL_USER);
set_segment_descriptor(&gdt[4], 0, 0xffffffff, DT_DATA_WRITEABLE, DPL_USER);
// seg 0x23 - ring 3 user 4GB data
// gdt[5] and above will be filled later by the kernel