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Clean up the GDT class

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This commit is contained in:
Eryn Wells 2016-03-02 02:02:34 -05:00
parent 00e961435e
commit fcae11348d
2 changed files with 19 additions and 21 deletions
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37
src/Descriptors.cc
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@ -41,14 +41,6 @@ GDT::systemGDT()
* Public
*/
GDT::DescriptorSpec
GDT::DescriptorSpec::null()
{
// Specify ring 0 and RO data segment here because their values are 0.
return {0, 0, 0, 0, 0, 0, 0, DPL::Ring0, 0, Type::DataRO};
}
GDT::DescriptorSpec
GDT::DescriptorSpec::kernelSegment(uint32_t base,
uint32_t limit,
@ -58,20 +50,20 @@ GDT::DescriptorSpec::kernelSegment(uint32_t base,
}
GDT::Descriptor
Descriptor
GDT::DescriptorSpec::descriptor()
const
{
Descriptor descriptor = 0;
uint8_t g = static_cast<uint8_t>(hasCoarseGranularity);
uint8_t db = static_cast<uint8_t>(has32BitOperations);
uint8_t l = static_cast<uint8_t>(hasNative64BitCode);
uint8_t avl = static_cast<uint8_t>(hasNative64BitCode);
uint8_t p = static_cast<uint8_t>(isPresent);
uint8_t dpl = static_cast<uint8_t>(privilegeLevel);
uint8_t s = static_cast<uint8_t>(isCodeDataSegment);
uint8_t typ = static_cast<uint8_t>(type);
const auto g = uint8_t(hasCoarseGranularity);
const auto db = uint8_t(has32BitOperations);
const auto l = uint8_t(hasNative64BitCode);
const auto avl = uint8_t(hasNative64BitCode);
const auto p = uint8_t(isPresent);
const auto dpl = uint8_t(privilegeLevel);
const auto s = uint8_t(isCodeDataSegment);
const auto typ = uint8_t(type);
descriptor = base & 0xFF000000; // Bits 31:24 of the base address.
descriptor |= (g << 23); // Granularity field
@ -80,9 +72,9 @@ GDT::DescriptorSpec::descriptor()
descriptor |= (avl << 20); // AVL field
descriptor |= limit & 0x000F0000; // Bits 19:16 of the segment limit.
descriptor |= (p << 15); // P field
descriptor |= (dpl << 13) & 0x00006000; // DPL field
descriptor |= (dpl << 13); // DPL field
descriptor |= (s << 12); // S field
descriptor |= (typ << 8) & 0x00000F00; // Type field: see Type
descriptor |= (typ << 8); // Type field: see Type
descriptor |= (base >> 16) & 0x000000FF; // Bits 23:16 of the base address.
// Shift everything up by 32 to make room for the lower 4 bytes
@ -104,6 +96,9 @@ void
GDT::setDescriptor(size_t index,
const GDT::DescriptorSpec& spec)
{
if (index >= GDT::Size) {
return;
}
table[index] = spec.descriptor();
}
@ -111,12 +106,16 @@ GDT::setDescriptor(size_t index,
void
GDT::setNullDescriptor(size_t index)
{
if (index >= GDT::Size) {
return;
}
table[index] = 0;
}
void
GDT::load()
const
{
PseudoDescriptor gdt {Size * sizeof(Descriptor) - 1, uint32_t(&table)};

3
src/Descriptors.hh
View file

@ -67,7 +67,6 @@ struct GDT
bool isCodeDataSegment; // S field
Type type; // Type field
static DescriptorSpec null();
static DescriptorSpec kernelSegment(uint32_t base, uint32_t limit, Type type);
Descriptor descriptor() const;
@ -84,7 +83,7 @@ struct GDT
void setNullDescriptor(size_t index);
/** Load this GDT into the CPU and flush the registers. */
void load();
void load() const;
private:
// TODO: Maybe eventually I can make this variable? Maybe use templates?