92 lines
4.0 KiB
C
92 lines
4.0 KiB
C
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#include <kernel/chroma.h>
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/************************
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*** Team Kitty, 2020 ***
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*** Chroma ***
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***********************/
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/*
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* This file provides utility functions for parsing ELF headers.
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* This exists so that the kernel can find itself for remapping,
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* but I may end up using ELF as the kernel's executable format.
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* Writing an ELF loader is on the to-do list, after all.
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! This needs to be cleaned up.
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! This creates a mess of numbers on the print
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! This is hacky and hardcoded as heck and needs to be fixed
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*/
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extern size_t KernelLocation;
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int ParseKernelHeader(size_t InitrdPtr) {
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int flag = 0;
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SerialPrintf("[ boot] Searching for kernel... Constants start at 0x%p / 0x%p\r\n", ((size_t) (&_kernel_text_start) - KernelAddr) + InitrdPtr, (size_t) (&_kernel_text_start));
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// We stop at the constants in the kernel, otherwise we'll read the constant ELF64MAGIC which is stored inside the kernel...
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size_t headerLoc = 0;
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for(size_t i = InitrdPtr; i < ((size_t) (&_kernel_text_start) - KernelAddr) + InitrdPtr; i++) {
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if(*((volatile uint32_t*)(i)) == ELF64MAGIC) {
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SerialPrintf("[ boot] Matched kernel header at 0x%p.\r\n", i);
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headerLoc = i;
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}
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if(FIXENDIAN32(*((volatile uint32_t*)(i))) == ELF64MAGIC) {
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SerialPrintf("[ boot] Matched little-endian kernel header at 0x%p.\r\n", i);
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headerLoc = i;
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}
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}
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if(headerLoc) {
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/* For whatever reason, reading a size_t here fails. The max that seems to work is uint16_t, so we read in the
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* 64 bit address by constructing it from 4 individual reads.
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* Note that these 4 reads are little endian, so we need to flip them around individually
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*/
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uint16_t EntryPoint0 = FIXENDIAN16(*((volatile uint16_t*)(headerLoc + ELFENTRY_OFF)));
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uint16_t EntryPoint1 = FIXENDIAN16(*((volatile uint16_t*)(headerLoc + ELFENTRY_OFF + 2)));
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uint16_t EntryPoint2 = FIXENDIAN16(*((volatile uint16_t*)(headerLoc + ELFENTRY_OFF + 4)));
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uint16_t EntryPoint3 = FIXENDIAN16(*((volatile uint16_t*)(headerLoc + ELFENTRY_OFF + 6)));
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size_t EntryPoint = ((size_t) EntryPoint0 << 48) | ((size_t) EntryPoint1 << 32) | ((size_t) EntryPoint2 << 16) | ((size_t) EntryPoint3);
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/* At this point, EntryPoint is a little-endian 64 bit integer. That means we have to fix its endianness in order to read it */
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SerialPrintf("[ boot] Fixing entry point from 0x%p to 0x%p\r\n", EntryPoint, FIXENDIAN64(EntryPoint));
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EntryPoint = FIXENDIAN64(EntryPoint);
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/* Now we can continue as normal */
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uint8_t HeaderClass = *((volatile uint8_t*)(headerLoc + ELF_IDENT_CLASS_OFF));
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uint16_t ExecutableType = (uint16_t) *((volatile uint8_t*)(headerLoc + ELFTYPE_OFF));
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uint16_t MachineType = (uint16_t) *((volatile uint8_t*)(headerLoc + ELFMACHINE_OFF));
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SerialPrintf(
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"[ boot] ELF header at 0x%p.\r\n\tConsidering ELF with:\r\n\tBitness %d: %d\r\n\tEntry point 0x%p\r\n\tFile type %s : 0x%x\r\n\tArchitecture %s : 0x%x\r\n",
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headerLoc,
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HeaderClass == 2 ? 64 : 32,
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HeaderClass,
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EntryPoint,
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ExecutableType == FIXENDIAN16(0x0200) ? "EXECUTABLE" : "OTHER",
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FIXENDIAN16(ExecutableType),
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MachineType == FIXENDIAN16(0x3E00) ? "AMD64" : "OTHER",
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FIXENDIAN16(MachineType));
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if(EntryPoint == (size_t) (&_kernel_text_start)) {
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SerialPrintf("[ boot] Header at 0x%p matches kernel header.\r\n", headerLoc);
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flag = 1;
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// At this point, we've found the right ELF64 executable!
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// Great, now we can map it into the proper place
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KernelLocation = headerLoc;
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}
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if(!flag) {
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for(char i = 0; i < 64; i++) {
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SerialPrintf("[ boot] Header dump part %x: 0x%x\r\n", i, *((volatile uint8_t*)(headerLoc + i)));
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}
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}
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}
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return flag;
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}
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