John
3f7e02533f
[MBR} Successfully set VGA video mode 3 [Host/KernelCopy] Fix MBR_PACKET definition and buffer address [RawIMG] Fix linux iamge generation script [Host/GDTCreator] Fix low limit values
51 lines
No EOL
1.5 KiB
C++
51 lines
No EOL
1.5 KiB
C++
//
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// Created by John Stefanelli on 13/01/23.
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//
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#include <iostream>
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uint64_t makeEntry(uint32_t base, uint32_t limit, bool present, unsigned char dpl, bool executable, bool exec_write) {
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uint64_t value = 0x0;
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//auto* target = (uint8_t*) &value;
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uint8_t access_byte = (present ? 0x80 : 0x00) + ((dpl & 0x3) << 5) + 16 + (executable ? 8 : 0) + (exec_write ? 2 : 0);
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uint8_t flags = 0xC;
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value |= limit & 0xFFFF; //Low 16 bits of limit
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value |= (base & 0xFFFFFF) << 16; //Low 24 bits of base
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value |= ((uint64_t) access_byte) << 40;
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value |= ((uint64_t) limit & 0xF0000) << 32;
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value |= ((uint64_t) flags) << 52;
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value |= ((uint64_t) base & 0xFF000000) << 32;
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/*
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// Encode the limit
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target[0] = limit & 0xFF;
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target[1] = (limit >> 8) & 0xFF;
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target[6] = (limit >> 16) & 0x0F;
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// Encode the base
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target[2] = base & 0xFF;
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target[3] = (base >> 8) & 0xFF;
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target[4] = (base >> 16) & 0xFF;
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target[7] = (base >> 24) & 0xFF;
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// Encode the access byte
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target[5] = access_byte;
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// Encode the flags
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target[6] |= (flags << 4);
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*/
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return value;
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}
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int main(int argc, char** argv) {
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std::cout << std::hex << "Code: " << makeEntry(0, 0xFFFFF, true, 0x0, true, true) << std::endl;
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std::cout << std::hex << "Data: " << makeEntry(0, 0xFFFFF, true, 0x0, false, true) << std::endl;
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std::cout << std::hex << "User Code: " << makeEntry(0, 0xFFFFF, true, 0x3, true, true) << std::endl;
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std::cout << std::hex << "User Data: " << makeEntry(0, 0xFFFFF, true, 0x3, false, true) << std::endl;
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return 0;
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} |