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feat: revamp libraries to use ELF shared objects

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This commit is contained in:
Daniel Hammer
2026-04-08 18:35:32 +02:00
parent 28d0614511
commit 8a2a86696a
11 changed files with 638 additions and 233 deletions
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kernel/src/Api/LibSyscall.hpp
+19 -15
View File
@@ -23,11 +23,15 @@ namespace Montauk {
// Library entry tracking
struct LibEntry {
char path[128];
uint64_t baseAddr;
uint64_t loadBias;
uint32_t refcount;
bool inUse;
};
static uint64_t GetLibSlotBase(int libSlot) {
return Sched::LIB_BASE + (uint64_t(libSlot) * Sched::LIB_MAX_SIZE);
}
// Per-process library table
static LibEntry g_libTable[MaxProcesses][MaxLibsPerProcess];
@@ -37,7 +41,7 @@ namespace Montauk {
for (int i = 0; i < MaxLibsPerProcess; i++) {
g_libTable[slot][i].inUse = false;
g_libTable[slot][i].refcount = 0;
g_libTable[slot][i].baseAddr = 0;
g_libTable[slot][i].loadBias = 0;
g_libTable[slot][i].path[0] = '\0';
}
}
@@ -77,8 +81,8 @@ namespace Montauk {
}
// Load the library into the process's address space
uint64_t libBase = Sched::ElfLoadLib(path, proc->pml4Phys, libSlot);
if (libBase == 0) {
uint64_t loadBias = Sched::ElfLoadLib(path, proc->pml4Phys, libSlot);
if (loadBias == 0) {
Kt::KernelLogStream(Kt::ERROR, "Lib") << "Failed to load library: " << path;
return 0;
}
@@ -86,10 +90,10 @@ namespace Montauk {
// Store library info
g_libTable[slot][libSlot].inUse = true;
g_libTable[slot][libSlot].refcount = 1;
g_libTable[slot][libSlot].baseAddr = libBase;
g_libTable[slot][libSlot].loadBias = loadBias;
Lib::strncpy(g_libTable[slot][libSlot].path, path, sizeof(LibEntry::path));
Kt::KernelLogStream(Kt::OK, "Lib") << "Loaded library: " << path << " at base " << kcp::hex << libBase << kcp::dec;
Kt::KernelLogStream(Kt::OK, "Lib") << "Loaded library: " << path << " with load bias " << kcp::hex << loadBias << kcp::dec;
return (uint64_t)(libSlot + 1); // Handle = slot + 1 (0 = invalid)
}
@@ -108,7 +112,7 @@ namespace Montauk {
g_libTable[slot][libSlot].refcount--;
if (g_libTable[slot][libSlot].refcount == 0) {
// Actually unload - free the pages
uint64_t libBase = g_libTable[slot][libSlot].baseAddr;
uint64_t libBase = GetLibSlotBase(libSlot);
uint64_t libEnd = libBase + Sched::LIB_MAX_SIZE;
auto* proc = Sched::GetCurrentProcessPtr();
@@ -124,7 +128,7 @@ namespace Montauk {
}
g_libTable[slot][libSlot].inUse = false;
g_libTable[slot][libSlot].baseAddr = 0;
g_libTable[slot][libSlot].loadBias = 0;
g_libTable[slot][libSlot].path[0] = '\0';
}
@@ -133,7 +137,7 @@ namespace Montauk {
// Resolve a symbol in a loaded library.
// handle = library handle from LoadLib
// symbolOffset = offset of the symbol from the library's base address
// symbolOffset = ELF symbol value from the library's symbol table
// Returns the virtual address of the symbol, or 0 if not found.
static uint64_t Sys_DLSym(uint64_t handle, uint64_t symbolOffset) {
int slot = GetCurrentSlot();
@@ -144,11 +148,11 @@ namespace Montauk {
if (!g_libTable[slot][libSlot].inUse) return 0;
uint64_t libBase = g_libTable[slot][libSlot].baseAddr;
return libBase + symbolOffset;
uint64_t loadBias = g_libTable[slot][libSlot].loadBias;
return loadBias + symbolOffset;
}
// Get library base address (for userspace symbol resolution)
// Get library relocation base / load bias (for userspace symbol resolution)
static uint64_t Sys_GetLibBase(uint64_t handle) {
int slot = GetCurrentSlot();
if (slot < 0) return 0;
@@ -158,7 +162,7 @@ namespace Montauk {
if (!g_libTable[slot][libSlot].inUse) return 0;
return g_libTable[slot][libSlot].baseAddr;
return g_libTable[slot][libSlot].loadBias;
}
// Cleanup library table for a process slot
@@ -171,7 +175,7 @@ namespace Montauk {
// Unmap all libraries for this process
for (int i = 0; i < MaxLibsPerProcess; i++) {
if (g_libTable[slot][i].inUse) {
uint64_t libBase = g_libTable[slot][i].baseAddr;
uint64_t libBase = GetLibSlotBase(i);
uint64_t libEnd = libBase + Sched::LIB_MAX_SIZE;
for (uint64_t va = libBase; va < libEnd; va += 0x1000) {
@@ -184,7 +188,7 @@ namespace Montauk {
g_libTable[slot][i].inUse = false;
g_libTable[slot][i].refcount = 0;
g_libTable[slot][i].baseAddr = 0;
g_libTable[slot][i].loadBias = 0;
}
}
}
kernel/src/Sched/ElfLoader.cpp
+400 -31
View File
@@ -16,6 +16,368 @@
namespace Sched {
struct Elf64Dynamic {
int64_t d_tag;
union {
uint64_t d_val;
uint64_t d_ptr;
};
};
struct Elf64Rela {
uint64_t r_offset;
uint64_t r_info;
int64_t r_addend;
};
struct Elf64Sym {
uint32_t st_name;
uint8_t st_info;
uint8_t st_other;
uint16_t st_shndx;
uint64_t st_value;
uint64_t st_size;
};
struct DynamicInfo {
uint64_t hashVaddr = 0;
uint64_t symtabVaddr = 0;
uint64_t strtabVaddr = 0;
uint64_t strtabSize = 0;
uint64_t relaVaddr = 0;
uint64_t relaSize = 0;
uint64_t relaEnt = sizeof(Elf64Rela);
uint64_t jmprelVaddr = 0;
uint64_t pltrelSize = 0;
uint64_t pltRelType = 0;
uint64_t symEnt = sizeof(Elf64Sym);
};
static constexpr uint64_t DT_NULL = 0;
static constexpr uint64_t DT_PLTRELSZ = 2;
static constexpr uint64_t DT_HASH = 4;
static constexpr uint64_t DT_STRTAB = 5;
static constexpr uint64_t DT_SYMTAB = 6;
static constexpr uint64_t DT_RELA = 7;
static constexpr uint64_t DT_RELASZ = 8;
static constexpr uint64_t DT_RELAENT = 9;
static constexpr uint64_t DT_STRSZ = 10;
static constexpr uint64_t DT_SYMENT = 11;
static constexpr uint64_t DT_PLTREL = 20;
static constexpr uint64_t DT_JMPREL = 23;
static constexpr uint32_t R_X86_64_64 = 1;
static constexpr uint32_t R_X86_64_GLOB_DAT = 6;
static constexpr uint32_t R_X86_64_JUMP_SLOT = 7;
static constexpr uint32_t R_X86_64_RELATIVE = 8;
static constexpr uint16_t SHN_UNDEF = 0;
static constexpr uint8_t STB_WEAK = 2;
static constexpr uint32_t Elf64RelocType(uint64_t info) {
return static_cast<uint32_t>(info);
}
static constexpr uint32_t Elf64RelocSym(uint64_t info) {
return static_cast<uint32_t>(info >> 32);
}
static uint64_t AddSigned(uint64_t base, int64_t addend) {
if (addend >= 0) {
return base + static_cast<uint64_t>(addend);
}
return base - static_cast<uint64_t>(-addend);
}
static bool ValidateProgramHeaderTable(const Elf64Header* hdr, uint64_t fileSize) {
if (hdr->e_phentsize != sizeof(Elf64ProgramHeader)) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Unexpected program header size";
return false;
}
if (hdr->e_phoff > fileSize ||
hdr->e_phoff + uint64_t(hdr->e_phnum) * hdr->e_phentsize > fileSize) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Program headers outside file";
return false;
}
return true;
}
static bool ValidateLoadSegment(const Elf64ProgramHeader* phdr, uint64_t fileSize) {
if (phdr->p_filesz > phdr->p_memsz) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Segment file size exceeds memory size";
return false;
}
if (phdr->p_offset > fileSize || phdr->p_offset + phdr->p_filesz > fileSize) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Segment outside file";
return false;
}
return true;
}
static bool ValidateLibElfHeader(const Elf64Header* hdr) {
if (hdr->e_ident[0] != 0x7f ||
hdr->e_ident[1] != 'E' ||
hdr->e_ident[2] != 'L' ||
hdr->e_ident[3] != 'F') {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Invalid ELF magic";
return false;
}
if (hdr->e_ident[4] != 2) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Not a 64-bit ELF";
return false;
}
if (hdr->e_ident[5] != 1) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Not little-endian";
return false;
}
if (hdr->e_type != ET_DYN) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Library is not ET_DYN (type=" << (uint64_t)hdr->e_type << ")";
return false;
}
if (hdr->e_machine != EM_X86_64) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Not x86_64 (machine=" << (uint64_t)hdr->e_machine << ")";
return false;
}
return true;
}
static bool VirtToFileOffset(const Elf64Header* hdr, uint64_t fileSize,
uint64_t virtualAddress, uint64_t size, uint64_t* outOffset) {
for (uint16_t i = 0; i < hdr->e_phnum; i++) {
auto* phdr = (const Elf64ProgramHeader*)((const uint8_t*)hdr + hdr->e_phoff + i * hdr->e_phentsize);
if (phdr->p_type != PT_LOAD || phdr->p_filesz == 0) {
continue;
}
if (!ValidateLoadSegment(phdr, fileSize)) {
return false;
}
if (virtualAddress < phdr->p_vaddr) {
continue;
}
if (virtualAddress + size > phdr->p_vaddr + phdr->p_filesz) {
continue;
}
*outOffset = phdr->p_offset + (virtualAddress - phdr->p_vaddr);
return true;
}
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Failed to translate virtual address " << kcp::hex
<< virtualAddress << kcp::dec << " to file offset";
return false;
}
static bool WriteUser64(uint64_t pml4Phys, uint64_t virtualAddress, uint64_t value) {
uint64_t physBase = Memory::VMM::Paging::GetPhysAddr(pml4Phys, virtualAddress);
if (physBase == 0) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Relocation target not mapped";
return false;
}
uint64_t physAddress = physBase + (virtualAddress & 0xFFFULL);
*(uint64_t*)Memory::HHDM(physAddress) = value;
return true;
}
static bool ApplyRelaBlock(uint64_t pml4Phys, uint64_t loadBias,
const Elf64Rela* relas, uint64_t relaCount,
const Elf64Sym* dynsym, uint64_t dynsymCount,
const char* dynstr, uint64_t dynstrSize) {
for (uint64_t i = 0; i < relaCount; i++) {
const Elf64Rela& rela = relas[i];
uint32_t type = Elf64RelocType(rela.r_info);
uint32_t symIndex = Elf64RelocSym(rela.r_info);
uint64_t targetVA = loadBias + rela.r_offset;
uint64_t value = 0;
switch (type) {
case 0:
continue;
case R_X86_64_RELATIVE:
value = AddSigned(loadBias, rela.r_addend);
break;
case R_X86_64_GLOB_DAT:
case R_X86_64_JUMP_SLOT:
case R_X86_64_64: {
if (symIndex >= dynsymCount) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Relocation symbol index out of range";
return false;
}
const Elf64Sym& sym = dynsym[symIndex];
if (sym.st_shndx == SHN_UNDEF) {
uint8_t bind = sym.st_info >> 4;
if (bind == STB_WEAK) {
value = 0;
break;
}
const char* name = "<unnamed>";
if (dynstr != nullptr && sym.st_name < dynstrSize) {
name = dynstr + sym.st_name;
}
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Unresolved dynamic symbol: " << name;
return false;
}
value = AddSigned(loadBias + sym.st_value, rela.r_addend);
break;
}
default:
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Unsupported relocation type=" << (uint64_t)type;
return false;
}
if (!WriteUser64(pml4Phys, targetVA, value)) {
return false;
}
}
return true;
}
static bool ApplyDynamicRelocations(const uint8_t* fileData, uint64_t fileSize,
const Elf64Header* hdr, uint64_t pml4Phys,
uint64_t loadBias) {
const Elf64ProgramHeader* dynamicPhdr = nullptr;
for (uint16_t i = 0; i < hdr->e_phnum; i++) {
auto* phdr = (const Elf64ProgramHeader*)(fileData + hdr->e_phoff + i * hdr->e_phentsize);
if (phdr->p_type == PT_DYNAMIC) {
dynamicPhdr = phdr;
break;
}
}
if (dynamicPhdr == nullptr) {
return true;
}
if (dynamicPhdr->p_offset > fileSize || dynamicPhdr->p_offset + dynamicPhdr->p_filesz > fileSize) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Dynamic section outside file";
return false;
}
DynamicInfo info;
uint64_t dynCount = dynamicPhdr->p_filesz / sizeof(Elf64Dynamic);
auto* dyn = (const Elf64Dynamic*)(fileData + dynamicPhdr->p_offset);
for (uint64_t i = 0; i < dynCount; i++) {
if (dyn[i].d_tag == DT_NULL) {
break;
}
switch (dyn[i].d_tag) {
case DT_HASH: info.hashVaddr = dyn[i].d_ptr; break;
case DT_SYMTAB: info.symtabVaddr = dyn[i].d_ptr; break;
case DT_STRTAB: info.strtabVaddr = dyn[i].d_ptr; break;
case DT_STRSZ: info.strtabSize = dyn[i].d_val; break;
case DT_RELA: info.relaVaddr = dyn[i].d_ptr; break;
case DT_RELASZ: info.relaSize = dyn[i].d_val; break;
case DT_RELAENT: info.relaEnt = dyn[i].d_val; break;
case DT_JMPREL: info.jmprelVaddr = dyn[i].d_ptr; break;
case DT_PLTRELSZ: info.pltrelSize = dyn[i].d_val; break;
case DT_PLTREL: info.pltRelType = dyn[i].d_val; break;
case DT_SYMENT: info.symEnt = dyn[i].d_val; break;
default:
break;
}
}
if (info.relaSize == 0 && info.pltrelSize == 0) {
return true;
}
if (info.symEnt != sizeof(Elf64Sym)) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Unexpected dynamic symbol size";
return false;
}
if (info.relaEnt != sizeof(Elf64Rela)) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Unexpected RELA entry size";
return false;
}
if (info.symtabVaddr == 0 || info.hashVaddr == 0) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Missing dynamic symbol metadata";
return false;
}
uint64_t hashOffset = 0;
if (!VirtToFileOffset(hdr, fileSize, info.hashVaddr, sizeof(uint32_t) * 2, &hashOffset)) {
return false;
}
auto* hashWords = (const uint32_t*)(fileData + hashOffset);
uint64_t dynsymCount = hashWords[1];
uint64_t dynsymOffset = 0;
if (!VirtToFileOffset(hdr, fileSize, info.symtabVaddr,
dynsymCount * sizeof(Elf64Sym), &dynsymOffset)) {
return false;
}
auto* dynsym = (const Elf64Sym*)(fileData + dynsymOffset);
const char* dynstr = nullptr;
if (info.strtabVaddr != 0 && info.strtabSize != 0) {
uint64_t dynstrOffset = 0;
if (!VirtToFileOffset(hdr, fileSize, info.strtabVaddr, info.strtabSize, &dynstrOffset)) {
return false;
}
dynstr = (const char*)(fileData + dynstrOffset);
}
if (info.relaSize != 0) {
uint64_t relaOffset = 0;
if (!VirtToFileOffset(hdr, fileSize, info.relaVaddr, info.relaSize, &relaOffset)) {
return false;
}
auto* relas = (const Elf64Rela*)(fileData + relaOffset);
if (!ApplyRelaBlock(pml4Phys, loadBias, relas, info.relaSize / sizeof(Elf64Rela),
dynsym, dynsymCount, dynstr, info.strtabSize)) {
return false;
}
}
if (info.pltrelSize != 0) {
if (info.pltRelType != DT_RELA) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Unsupported PLT relocation format";
return false;
}
uint64_t jmprelOffset = 0;
if (!VirtToFileOffset(hdr, fileSize, info.jmprelVaddr, info.pltrelSize, &jmprelOffset)) {
return false;
}
auto* pltRelas = (const Elf64Rela*)(fileData + jmprelOffset);
if (!ApplyRelaBlock(pml4Phys, loadBias, pltRelas, info.pltrelSize / sizeof(Elf64Rela),
dynsym, dynsymCount, dynstr, info.strtabSize)) {
return false;
}
}
return true;
}
static bool ValidateElfHeader(const Elf64Header* hdr) {
// Check ELF magic: 0x7f 'E' 'L' 'F'
if (hdr->e_ident[0] != 0x7f ||
@@ -177,43 +539,48 @@ namespace Sched {
Elf64Header* hdr = (Elf64Header*)fileData;
// Validate ELF header
if (hdr->e_ident[0] != 0x7f ||
hdr->e_ident[1] != 'E' ||
hdr->e_ident[2] != 'L' ||
hdr->e_ident[3] != 'F') {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Invalid ELF magic";
if (!ValidateLibElfHeader(hdr) || !ValidateProgramHeaderTable(hdr, fileSize)) {
Memory::g_heap->Free(fileData);
return 0;
}
if (hdr->e_ident[4] != 2) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Not a 64-bit ELF";
uint64_t slotBase = LIB_BASE + (uint64_t(slot) * LIB_MAX_SIZE);
uint64_t minLoadStart = ~0ULL;
uint64_t maxLoadEnd = 0;
bool hasLoadSegment = false;
for (uint16_t i = 0; i < hdr->e_phnum; i++) {
auto* phdr = (Elf64ProgramHeader*)(fileData + hdr->e_phoff + i * hdr->e_phentsize);
if (phdr->p_type != PT_LOAD || phdr->p_memsz == 0) {
continue;
}
if (!ValidateLoadSegment(phdr, fileSize)) {
Memory::g_heap->Free(fileData);
return 0;
}
uint64_t segStart = phdr->p_vaddr & ~0xFFFULL;
uint64_t segEnd = (phdr->p_vaddr + phdr->p_memsz + 0xFFFULL) & ~0xFFFULL;
if (segStart < minLoadStart) minLoadStart = segStart;
if (segEnd > maxLoadEnd) maxLoadEnd = segEnd;
hasLoadSegment = true;
}
if (!hasLoadSegment) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Library has no loadable segments";
Memory::g_heap->Free(fileData);
return 0;
}
if (hdr->e_ident[5] != 1) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Not little-endian";
if (maxLoadEnd - minLoadStart > LIB_MAX_SIZE) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Library image exceeds slot size";
Memory::g_heap->Free(fileData);
return 0;
}
// Libraries are built as ET_EXEC at a fixed base (0x60000000)
if (hdr->e_type != ET_EXEC) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Library not ET_EXEC (type=" << (uint64_t)hdr->e_type << ")";
Memory::g_heap->Free(fileData);
return 0;
}
if (hdr->e_machine != EM_X86_64) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Not x86_64 (machine=" << (uint64_t)hdr->e_machine << ")";
Memory::g_heap->Free(fileData);
return 0;
}
// Calculate library base for this slot (each slot gets LIB_MAX_SIZE region)
uint64_t libBase = LIB_BASE + (uint64_t(slot) * LIB_MAX_SIZE);
uint64_t loadBias = slotBase - minLoadStart;
// Process program headers
for (uint16_t i = 0; i < hdr->e_phnum; i++) {
@@ -227,9 +594,7 @@ namespace Sched {
continue;
}
// The library is linked at 0x400000. We need to relocate it to libBase.
// target_vaddr = libBase + (file_vaddr - 0x400000)
uint64_t targetSegStart = libBase + (phdr->p_vaddr - 0x400000ULL);
uint64_t targetSegStart = loadBias + phdr->p_vaddr;
uint64_t targetSegFileEnd = targetSegStart + phdr->p_filesz; // only file data
uint64_t targetSegMemEnd = targetSegStart + phdr->p_memsz; // includes bss
@@ -251,7 +616,7 @@ namespace Sched {
uint64_t pageEnd = pageStart + 0x1000;
// Check that we're within the library region
if (pageStart < libBase || pageEnd > libBase + LIB_MAX_SIZE) {
if (pageStart < slotBase || pageEnd > slotBase + LIB_MAX_SIZE) {
Kt::KernelLogStream(Kt::ERROR, "ELF") << "Segment outside library region";
Memory::g_heap->Free(fileData);
return 0;
@@ -282,10 +647,14 @@ namespace Sched {
}
}
if (!ApplyDynamicRelocations(fileData, fileSize, hdr, pml4Phys, loadBias)) {
Memory::g_heap->Free(fileData);
return 0;
}
Memory::g_heap->Free(fileData);
// Return the library base address for this slot
return libBase;
return loadBias;
}
}
kernel/src/Sched/ElfLoader.hpp
+3 -2
View File
@@ -38,7 +38,9 @@ namespace Sched {
};
static constexpr uint32_t PT_LOAD = 1;
static constexpr uint32_t PT_DYNAMIC = 2;
static constexpr uint16_t ET_EXEC = 2;
static constexpr uint16_t ET_DYN = 3;
static constexpr uint16_t EM_X86_64 = 62;
// Fixed base address for shared libraries.
@@ -51,8 +53,7 @@ namespace Sched {
uint64_t ElfLoad(const char* vfsPath, uint64_t pml4Phys);
// Load a shared library into a fixed address range.
// Loads at LIB_BASE for the given slot.
// Returns the library base virtual address on success, or 0 on failure.
// Returns the relocation base / load bias on success, or 0 on failure.
uint64_t ElfLoadLib(const char* vfsPath, uint64_t pml4Phys, int slot);
}