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elfutils.c
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/* SPDX-License-Identifier: Apache-2.0 */
/*
* Copyright (C) Semihalf, 2022
* Author: Marek Maślanka <[email protected]>
*/
#include <errno.h>
#include <error.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <getopt.h>
#include <gelf.h>
#ifdef SUPPORT_DISASS
#define PACKAGE 1 //requred by libbfd
#include <dis-asm.h>
#define MAX_DISASS_LINE_LEN 256
#endif
#define ERROR_UNSUPPORTED_READ_MOSTLY 30
static bool ShowDebugLog = 0;
#define LOG_ERR(fmt, ...) \
do \
{ \
fprintf(stderr, "ERROR (%s:%d): " fmt "\n", __FILE__, __LINE__, \
##__VA_ARGS__); \
exit(1); \
} while (0)
#define LOG_INFO(fmt, ...) \
do \
{ \
printf(fmt "\n", ##__VA_ARGS__); \
} while (0)
#define LOG_DEBUG(fmt, ...) \
do \
{ \
if (ShowDebugLog) \
printf(fmt "\n", ##__VA_ARGS__); \
} while (0)
#define CHECK_ALLOC(m) \
if (m == NULL) \
LOG_ERR("Failed to alloc memory in %s (%s:%d)", __func__, __FILE__, __LINE__)
#define invalidSym(sym) (sym.st_name == 0 && sym.st_info == 0 && sym.st_shndx == 0)
typedef struct
{
uint8_t *data;
size_t size;
} SymbolData;
typedef struct
{
char *name;
size_t index;
size_t secIndex;
bool isFun;
bool isVar;
size_t linkedSymbol;
size_t copiedIndex;
size_t st_size;
size_t st_value;
unsigned char st_info;
size_t *callees;
} Symbol;
static Symbol **Symbols = NULL;
static Elf_Scn **CopiedScnMap = NULL;
static size_t SectionsCount = 0;
static size_t SymbolsCount = 0;
typedef struct
{
Elf *elf;
GElf_Sym sym;
GElf_Shdr shdr;
SymbolData *symData;
} DisasmData;
static uint32_t crc32(uint8_t *data, uint32_t len)
{
uint32_t byte, crc, mask;
crc = 0xFFFFFFFF;
for (uint32_t i = 0; i < len; i++)
{
byte = data[i];
crc = crc ^ byte;
for (int j = 7; j >= 0; j--)
{
mask = -(crc & 1);
crc = (crc >> 1) ^ (0xEDB88320 & mask);
}
i = i + 1;
}
return ~crc;
}
static size_t appendString(GElf_Shdr *shdr, Elf_Data *data, const char *text)
{
size_t oldSize = data->d_size;
size_t newSize = data->d_size + strlen(text) + 1;
char *buf = (char *)calloc(1, newSize);
CHECK_ALLOC(buf);
memcpy(buf, data->d_buf, data->d_size);
strcpy(&buf[data->d_size], text);
data->d_buf = buf;
data->d_size = newSize;
shdr->sh_size = newSize;
return oldSize;
}
static GElf_Shdr getSectionHeader(Elf *elf, Elf64_Section index)
{
GElf_Shdr shdr = {0};
size_t shstrndx;
elf_getshdrstrndx(elf, &shstrndx);
Elf_Scn *scn = elf_getscn(elf, index);
if (scn)
gelf_getshdr(scn, &shdr);
return shdr;
}
static Elf_Scn *getSectionByName(Elf *elf, const char *secName)
{
Elf_Scn *scn = NULL;
GElf_Shdr shdr;
size_t shstrndx;
elf_getshdrstrndx(elf, &shstrndx);
while ((scn = elf_nextscn(elf, scn)) != NULL)
{
gelf_getshdr(scn, &shdr);
char *name = elf_strptr(elf, shstrndx, shdr.sh_name);
if (name != NULL && strcmp(name, secName) == 0)
return scn;
}
return NULL;
}
static Elf_Scn *getRelForSectionIndex(Elf *elf, Elf64_Section index)
{
Elf_Scn *scn = NULL;
GElf_Shdr shdr;
while ((scn = elf_nextscn(elf, scn)) != NULL)
{
gelf_getshdr(scn, &shdr);
if (shdr.sh_type == SHT_RELA && shdr.sh_info == index)
return scn;
}
return NULL;
}
static char *getSectionName(Elf *elf, Elf64_Section index)
{
size_t shstrndx;
elf_getshdrstrndx(elf, &shstrndx);
GElf_Shdr shdr = getSectionHeader(elf, index);
return elf_strptr(elf, shstrndx, shdr.sh_name);
}
static Symbol **readSymbols(Elf *elf)
{
Symbol **syms;
Elf_Scn *scn = getSectionByName(elf, ".symtab");
if (scn == NULL)
LOG_ERR("Failed to find .symtab section");
GElf_Shdr shdr;
GElf_Sym sym;
Elf_Data *data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
syms = (Symbol **)calloc(cnt + 1, sizeof(Symbol *));
CHECK_ALLOC(syms);
for (size_t i = 0; i < cnt; i++)
{
gelf_getsym(data, i, &sym);
syms[i] = calloc(1, sizeof(Symbol));
CHECK_ALLOC(syms[i]);
// name
syms[i]->name = elf_strptr(elf, shdr.sh_link, sym.st_name);
// section index
syms[i]->secIndex = sym.st_shndx;
// is function
if ((sym.st_info == ELF64_ST_INFO(STB_GLOBAL, STT_FUNC) ||
(sym.st_info == ELF64_ST_INFO(STB_LOCAL, STT_FUNC))) &&
strlen(syms[i]->name) > 0)
{
syms[i]->isFun = true;
}
// is variable
if (sym.st_info == ELF64_ST_INFO(STB_GLOBAL, STT_OBJECT) ||
(sym.st_info == ELF64_ST_INFO(STB_LOCAL, STT_OBJECT)))
{
const char *scnName = getSectionName(elf, sym.st_shndx);
if (strstr(scnName, ".data.") == scnName ||
strstr(scnName, ".bss.") == scnName)
syms[i]->isVar = true;
if (strstr(scnName, ".rodata.") == scnName ||
strstr(scnName, ".rodata.str") != scnName)
syms[i]->isVar = true;
}
syms[i]->st_info = sym.st_info;
syms[i]->st_size = sym.st_size;
syms[i]->st_value = sym.st_value;
syms[i]->index = SymbolsCount++;
}
return syms;
}
static GElf_Sym getSymbolByName(Elf *elf, char *name, size_t *symIndex)
{
Elf_Scn *scn = getSectionByName(elf, ".symtab");
GElf_Shdr shdr;
GElf_Sym sym = {0};
Elf_Data *data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
*symIndex = 0;
for (size_t i = 0; i < cnt; i++)
{
gelf_getsym(data, i, &sym);
if (strcmp(elf_strptr(elf, shdr.sh_link, sym.st_name), name) == 0)
return sym;
(*symIndex)++;
}
memset(&sym, 0, sizeof(sym));
*symIndex = 0;
return sym;
}
static bool getSymbolByNameAndType(Elf *elf, const char *symName, const int type, GElf_Sym *sym)
{
Elf_Scn *scn = getSectionByName(elf, ".symtab");
if (scn == NULL)
LOG_ERR("Failed to find .symtab section");
GElf_Shdr shdr;
Elf_Data *data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
for (size_t i = 0; i < cnt; i++)
{
gelf_getsym(data, i, sym);
if ((sym->st_info == ELF64_ST_INFO(STB_LOCAL, type) ||
sym->st_info == ELF64_ST_INFO(STB_GLOBAL, type)) &&
strcmp(elf_strptr(elf, shdr.sh_link, sym->st_name), symName) == 0)
return true;
}
return false;
}
static GElf_Sym getSymbolByIndex(Elf *elf, size_t index)
{
Elf_Scn *scn = getSectionByName(elf, ".symtab");
GElf_Shdr shdr;
GElf_Sym sym = {0};
Elf_Data *data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
if (index < cnt)
gelf_getsym(data, index, &sym);
return sym;
}
static uint16_t getSymbolIndexByName(Elf *elf, const char *symName)
{
Elf_Scn *scn = getSectionByName(elf, ".symtab");
if (scn == NULL)
LOG_ERR("Failed to find .symtab section");
GElf_Sym sym;
GElf_Shdr shdr;
Elf_Data *data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
for (size_t i = 0; i < cnt; i++)
{
gelf_getsym(data, i, &sym);
if (strcmp(elf_strptr(elf, shdr.sh_link, sym.st_name), symName) == 0)
return i;
}
return 0;
}
static Symbol *getSymbolForRelocation(const GElf_Rela rela)
{
size_t symIndex = ELF64_R_SYM(rela.r_info);
if (Symbols[symIndex]->secIndex == 0)
return Symbols[symIndex];
if (Symbols[symIndex]->st_size > 0)
return Symbols[symIndex];
if (ELF64_ST_TYPE(Symbols[symIndex]->st_info) == STT_FUNC ||
ELF64_ST_TYPE(Symbols[symIndex]->st_info) == STT_OBJECT)
return Symbols[symIndex];
size_t secIndex = Symbols[symIndex]->secIndex;
Elf64_Sxword addend = rela.r_addend;
switch (ELF64_R_TYPE(rela.r_info))
{
case R_386_PC32:
case R_X86_64_PLT32:
addend += 4;
break;
}
for (Symbol **s = Symbols; *s != NULL; s++)
{
if (s[0]->index != symIndex && s[0]->secIndex == secIndex &&
(size_t)addend >= s[0]->st_value &&
(size_t)addend < s[0]->st_value + s[0]->st_size)
return s[0];
}
// example: referer to symbol (st_value == st_size == 0) that points to .rodata.str1.1
return Symbols[symIndex];
}
static GElf_Sym getLinkedSym(Elf *elf, GElf_Sym *sym)
{
Elf_Scn *scn = getSectionByName(elf, ".symtab");
GElf_Shdr shdr;
GElf_Sym tsym = {0};
Elf_Data *data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
for (size_t i = 0; i < cnt; i++)
{
gelf_getsym(data, i, &tsym);
if (memcmp(&tsym, sym, sizeof(*sym)) != 0 && tsym.st_name != 0 &&
tsym.st_shndx == sym->st_shndx)
return tsym;
}
memset(&tsym, 0, sizeof(tsym));
return tsym;
}
static SymbolData getSymbolData(Elf *elf, const char *name, char type, bool modReloc)
{
SymbolData result;
Elf_Scn *scn = getSectionByName(elf, ".symtab");
if (scn == NULL)
LOG_ERR("Failed to find .symtab section");
GElf_Shdr shdr;
GElf_Sym sym;
size_t secCount;
elf_getshdrnum(elf, &secCount);
Elf_Data *data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
for (size_t i = 0; i < cnt; i++)
{
gelf_getsym(data, i, &sym);
if (strcmp(elf_strptr(elf, shdr.sh_link, sym.st_name), name) == 0)
{
if (ELF64_ST_TYPE(sym.st_info) == type &&
sym.st_size > 0 && sym.st_shndx < secCount)
{
Elf_Scn *scn = elf_getscn(elf, sym.st_shndx);
Elf_Data *data = elf_getdata(scn, NULL);
result.data = &((uint8_t *)data->d_buf)[sym.st_value];
result.size = sym.st_size;
if (modReloc)
{
GElf_Rela rela;
GElf_Shdr shdr;
Elf_Scn *scn = getRelForSectionIndex(elf, sym.st_shndx);
if (scn == NULL)
continue;
Elf_Data *rdata = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
for (size_t i = 0; i < cnt; i++)
{
gelf_getrela(rdata, i, &rela);
if (rela.r_offset >= sym.st_value && rela.r_offset < sym.st_value + sym.st_size)
{
void *addr = &((uint8_t *)data->d_buf)[rela.r_offset];
if (ELF64_R_TYPE(rela.r_info) == R_X86_64_PC32)
*(uint32_t *)addr += -4;
else
*(uint32_t *)addr += rela.r_addend;
}
}
}
break;
}
}
}
return result;
}
#ifdef SUPPORT_DISASSEMBLE
static GElf_Sym getSymbolForReloc(Elf *elf, Elf64_Section sec, size_t offset)
{
GElf_Rela rela;
GElf_Shdr shdr;
GElf_Sym invalidSym = {};
Elf_Scn *scn = getRelForSectionIndex(elf, sec);
if(scn == NULL)
return invalidSym;
Elf_Data *data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
for (size_t i = 0; i < cnt; i++)
{
gelf_getrela(data, i, &rela);
if (rela.r_offset == offset)
return getSymbolByIndex(elf, ELF64_R_SYM(rela.r_info));
}
return invalidSym;
}
static GElf_Sym getSymbolByOffset(Elf *elf, Elf64_Section shndx, size_t offset)
{
Elf_Scn *scn = getSectionByName(elf, ".symtab");
GElf_Shdr shdr;
GElf_Sym sym = {};
Elf_Data *data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
for (size_t i = 0; i < cnt; i++)
{
gelf_getsym(data, i, &sym);
if (sym.st_name != 0 && sym.st_shndx == shndx && sym.st_value == offset)
return sym;
}
memset(&sym, 0, sizeof(sym));
return sym;
}
static int disasmPrintf(void *buf, const char *format, ...)
{
char localBuf[MAX_DISASS_LINE_LEN];
va_list args;
va_start (args, format);
int len = vsnprintf(localBuf, sizeof(localBuf), format, args);
va_end (args);
char **buffer = (char **)buf;
buffer[0] = realloc(buffer[0], strlen(buffer[0]) + len + 1);
strcat(buffer[0], localBuf);
return len;
}
static void printFunAtAddr(bfd_vma vma, struct disassemble_info *inf)
{
DisasmData *data = (DisasmData *)inf->application_data;
int32_t x = *(uint32_t *)(data->symData->data + vma);
vma += data->sym.st_value;
GElf_Sym sym = getSymbolByOffset(data->elf, data->sym.st_shndx, vma);
if(invalidSym(sym))
sym = getSymbolForReloc(data->elf, data->sym.st_shndx, vma);
if(invalidSym(sym))
{
sym = getSymbolForReloc(data->elf, data->sym.st_shndx, vma);
const char *name = elf_strptr(data->elf, data->shdr.sh_link, data->sym.st_name);
(*inf->fprintf_func)(inf->stream, "<%s+0x%lX>", name, vma - data->sym.st_value);
}
else
{
const char *name = elf_strptr(data->elf, data->shdr.sh_link, sym.st_name);
(*inf->fprintf_func)(inf->stream, "%s", name);
}
}
char *disassembleBytes(uint8_t *inputBuf, size_t inputBufSize, DisasmData *data)
{
char *buf[] = { calloc(0, 1) };
disassemble_info disasmInfo = {};
init_disassemble_info(&disasmInfo, buf, disasmPrintf);
disasmInfo.arch = bfd_arch_i386;
disasmInfo.mach = bfd_mach_x86_64;
disasmInfo.read_memory_func = buffer_read_memory;
disasmInfo.buffer = inputBuf;
disasmInfo.buffer_vma = 0;
disasmInfo.buffer_length = inputBufSize;
disasmInfo.application_data = (void *)data;
disassemble_init_for_target(&disasmInfo);
disasmInfo.print_address_func = printFunAtAddr;
disassembler_ftype disasm = disassembler(bfd_arch_i386, false, bfd_mach_x86_64, NULL);
size_t pc = 0;
while (pc < inputBufSize)
{
pc += disasm(pc, &disasmInfo);
disasmInfo.fprintf_func(disasmInfo.stream, "\n");
}
return buf[0];
}
#endif
static uint32_t calcSymHash(Elf *elf, const GElf_Sym *sym)
{
Elf_Scn *scn = elf_getscn(elf, sym->st_shndx);
Elf_Data *data = elf_rawdata(scn, NULL);
uint32_t crc = crc32((uint8_t *)data->d_buf + sym->st_value, sym->st_size);
GElf_Rela rela;
GElf_Shdr shdr;
scn = getRelForSectionIndex(elf, sym->st_shndx);
if (scn == NULL)
return crc;
Elf_Data *rdata = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
scn = getSectionByName(elf, ".symtab");
gelf_getshdr(scn, &shdr);
Elf64_Word symtabLink = shdr.sh_link;
for (size_t i = 0; i < cnt; i++)
{
gelf_getrela(rdata, i, &rela);
if (rela.r_offset >= sym->st_value && rela.r_offset < sym->st_value + sym->st_size)
{
GElf_Sym rsym = getSymbolByIndex(elf, ELF64_R_SYM(rela.r_info));
if(invalidSym(rsym))
LOG_ERR("Can't find symbol at index: %ld", ELF64_R_SYM(rela.r_info));
int secIndex = rsym.st_shndx;
const char *name = NULL;
if(rsym.st_name == 0)
{
if (rsym.st_info == STT_SECTION)
{
name = getSectionName(elf, secIndex);
}
else
{
rsym = getLinkedSym(elf, &rsym);
if(invalidSym(rsym))
LOG_ERR("Can't find symbol at index: %ld", ELF64_R_SYM(rela.r_info));
name = elf_strptr(elf, symtabLink, rsym.st_name);
}
}
else
{
name = elf_strptr(elf, symtabLink, rsym.st_name);
}
if (name)
{
if (strstr(name, ".str.") || strstr(name, ".str1.") || strstr(name, ".rodata.str") == name)
{
Elf_Scn *scn = elf_getscn(elf, secIndex);
Elf_Data *data = elf_getdata(scn, NULL);
GElf_Shdr shdr;
gelf_getshdr(scn, &shdr);
if ((Elf64_Sxword)shdr.sh_size > rela.r_addend)
name = (char *)data->d_buf + rela.r_addend;
}
if (strstr(name, ".text.unlikely.") == name)
name += strlen(".text.unlikely.");
else if (strstr(name, ".text.") == name)
name += strlen(".text.");
crc += crc32((uint8_t *)name, strlen(name));
}
}
}
return crc;
}
static bool equalFunctions(Elf *elf, Elf *secondElf, const char *funName)
{
SymbolData symData1 = getSymbolData(elf, funName, STT_FUNC, false);
SymbolData symData2 = getSymbolData(secondElf, funName, STT_FUNC, false);
if (symData1.size != symData2.size)
return false;
GElf_Sym sym1;
GElf_Sym sym2;
getSymbolByNameAndType(elf, funName, STT_FUNC, &sym1);
getSymbolByNameAndType(secondElf, funName, STT_FUNC, &sym2);
return calcSymHash(elf, &sym1) == calcSymHash(secondElf, &sym2);
}
static void findModifiedSymbols(Elf *elf, Elf *secondElf)
{
Elf_Scn *scn = getSectionByName(elf, ".symtab");
if (scn == NULL)
LOG_ERR("Failed to find .symtab section");
GElf_Shdr shdr;
GElf_Sym sym;
size_t secCount;
elf_getshdrnum(elf, &secCount);
Elf_Data *data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
for (size_t i = 0; i < cnt; i++)
{
gelf_getsym(data, i, &sym);
if (sym.st_size == 0 || sym.st_shndx == 0 || sym.st_shndx >= secCount || sym.st_name == 0)
continue;
const char *name = elf_strptr(elf, shdr.sh_link, sym.st_name);
if (ELF64_ST_TYPE(sym.st_info) == STT_FUNC)
{
GElf_Sym secondSym;
if (!getSymbolByNameAndType(secondElf, name, STT_FUNC, &secondSym))
{
printf("New function: %s\n", name);
}
else
{
if (!equalFunctions(elf, secondElf, name))
printf("Modified function: %s\n", name);
}
}
else if (ELF64_ST_TYPE(sym.st_info) == STT_OBJECT)
{
GElf_Sym secondSym;
if (!getSymbolByNameAndType(secondElf, name, STT_OBJECT, &secondSym))
{
char *bssName = malloc(strlen(name) + 6);
CHECK_ALLOC(bssName);
char *dataName = malloc(strlen(name) + 7);
CHECK_ALLOC(dataName);
char *rodataName = malloc(strlen(name) + 9);
CHECK_ALLOC(rodataName);
snprintf(bssName, strlen(name) + 6, ".bss.%s", name);
snprintf(dataName, strlen(name) + 7, ".data.%s", name);
snprintf(rodataName, strlen(name) + 9, ".rodata.%s", name);
const char *scnName = getSectionName(elf, sym.st_shndx);
if (strcmp(scnName, bssName) == 0 ||
strcmp(scnName, dataName) == 0 ||
strcmp(scnName, rodataName) == 0 ||
strcmp(scnName, ".bss") == 0 ||
strcmp(scnName, ".data") == 0 ||
strcmp(scnName, ".rodata") == 0)
printf("New variable: %s\n", name);
free(rodataName);
free(dataName);
free(bssName);
}
}
}
}
static Elf *createNewElf(const char *outFile)
{
int fd = open(outFile, O_RDWR|O_TRUNC|O_CREAT, 0666);
if (fd == -1)
LOG_ERR("Failed to create file: %s", outFile);
Elf *elf = elf_begin(fd, ELF_C_WRITE, 0);
Elf64_Ehdr *m_ehdr = elf64_newehdr(elf);
m_ehdr->e_ident[EI_MAG0] = ELFMAG0;
m_ehdr->e_ident[EI_MAG1] = ELFMAG1;
m_ehdr->e_ident[EI_MAG2] = ELFMAG2;
m_ehdr->e_ident[EI_MAG3] = ELFMAG3;
m_ehdr->e_ident[EI_CLASS] = ELFCLASS64;
m_ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
m_ehdr->e_ident[EI_VERSION] = EV_CURRENT;
m_ehdr->e_machine = EM_X86_64;
m_ehdr->e_type = ET_REL;
m_ehdr->e_version = EV_CURRENT;
m_ehdr->e_shstrndx = 1;
GElf_Shdr shdr;
Elf_Scn *strtabScn = elf_newscn(elf);
Elf_Data *newData = elf_newdata(strtabScn);
gelf_getshdr(strtabScn, &shdr);
static uint8_t blank[1] = {'\0'};
newData->d_buf = blank;
newData->d_size = 1;
Elf64_Word shname = appendString(&shdr, newData, ".strtab");
Elf64_Word symtabname = appendString(&shdr, newData, ".symtab");
shdr.sh_type = SHT_STRTAB;
shdr.sh_name = appendString(&shdr, newData, ".shstrtab");
gelf_update_shdr(strtabScn, &shdr);
Elf_Scn *shstrtabScn = elf_newscn(elf);
newData = elf_newdata(shstrtabScn);
newData->d_buf = blank;
newData->d_size = 1;
gelf_getshdr(shstrtabScn, &shdr);
shdr.sh_size = 1;
shdr.sh_type = SHT_STRTAB;
shdr.sh_name = shname;
gelf_update_shdr(shstrtabScn, &shdr);
Elf_Scn *symtabScn = elf_newscn(elf);
newData = elf_newdata(symtabScn);
gelf_getshdr(symtabScn, &shdr);
GElf_Sym emptySym = {0};
newData->d_type = ELF_T_SYM;
newData->d_buf = malloc(sizeof(GElf_Sym));
CHECK_ALLOC(newData->d_buf);
memcpy(newData->d_buf, &emptySym, sizeof(GElf_Sym));
newData->d_size = sizeof(GElf_Sym);
shdr.sh_size = sizeof(GElf_Sym);
shdr.sh_link = elf_ndxscn(getSectionByName(elf, ".strtab"));
shdr.sh_type = SHT_SYMTAB;
shdr.sh_name = symtabname;
shdr.sh_entsize = sizeof(GElf_Sym);
gelf_update_shdr(symtabScn, &shdr);
return elf;
}
void checkStaticKeys(Elf *elf, bool *symToCopy)
{
Elf_Scn *scn = getSectionByName(elf, "__jump_table");
if (scn == NULL)
return;
Elf_Scn *relScn = getRelForSectionIndex(elf, elf_ndxscn(scn));
if (relScn == NULL)
LOG_ERR("Can't find relocation section for __jump_table");
GElf_Rela rela;
GElf_Shdr shdr;
Elf_Data *data = elf_getdata(relScn, NULL);
gelf_getshdr(relScn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
for (size_t i = 0; i < cnt; i+=3)
{
gelf_getrela(data, i, &rela);
Symbol *symbol = getSymbolForRelocation(rela);
if (symToCopy[symbol->index])
{
gelf_getrela(data, i + 2, &rela);
const char *keyName = Symbols[ELF64_R_SYM(rela.r_info)]->name;
LOG_INFO("The '%s' function uses static key `%s` that is not yet "
"supported by DEKU.", symbol->name, keyName);
}
}
}
static Elf_Scn *copySection(Elf *elf, Elf *outElf, Elf64_Section index, bool copyData)
{
if (CopiedScnMap[index] != NULL)
return CopiedScnMap[index];
if (index >= SectionsCount)
LOG_ERR("Try to copy section that is out range (%d/%ld)", index, SectionsCount);
size_t shstrndx;
GElf_Shdr newShdr;
GElf_Shdr oldShdr;
GElf_Shdr strshdr;
elf_getshdrstrndx(elf, &shstrndx);
Elf_Scn *strtabScn = getSectionByName(outElf, ".shstrtab");
Elf_Data *strData = elf_getdata(strtabScn, NULL);
gelf_getshdr(strtabScn, &strshdr);
Elf_Scn *oldScn = elf_getscn(elf, index);
Elf_Data *oldData = elf_getdata(oldScn, NULL);
Elf_Scn *newScn = elf_newscn(outElf);
Elf_Data *newData = elf_newdata(newScn);
gelf_getshdr(oldScn, &oldShdr);
gelf_getshdr(newScn, &newShdr);
newShdr.sh_type = oldShdr.sh_type;
newShdr.sh_flags = oldShdr.sh_flags;
newShdr.sh_entsize = oldShdr.sh_entsize;
newShdr.sh_name = appendString(&strshdr, strData, elf_strptr(elf, shstrndx, oldShdr.sh_name));
newData->d_type = oldData->d_type;
if (copyData)
{
newShdr.sh_size = oldShdr.sh_size;
newData->d_buf = calloc(1, oldData->d_size);
CHECK_ALLOC(newData->d_buf);
newData->d_size = oldData->d_size;
if (oldData->d_buf)
memcpy(newData->d_buf, oldData->d_buf, oldData->d_size);
}
gelf_update_shdr(newScn, &newShdr);
gelf_update_shdr(strtabScn, &strshdr);
CopiedScnMap[index] = newScn;
return newScn;
}
static Elf64_Word copyStrtabItem(Elf *elf, Elf *outElf, size_t offset)
{
GElf_Shdr strshdr;
Elf_Scn *strtabScn = getSectionByName(outElf, ".strtab");
Elf_Data *strData = elf_getdata(strtabScn, NULL);
gelf_getshdr(strtabScn, &strshdr);
size_t strtabIdx = elf_ndxscn(getSectionByName(elf, ".strtab"));
char *text = elf_strptr(elf, strtabIdx, offset);
Elf64_Word newStrOffset = appendString(&strshdr, strData, text);
gelf_update_shdr(strtabScn, &strshdr);
return newStrOffset;
}
static void swapSymbolIndex(Elf *elf, size_t left, size_t right)
{
Elf_Scn *scn = NULL;
GElf_Shdr shdr;
size_t shstrndx;
elf_getshdrstrndx(elf, &shstrndx);
while ((scn = elf_nextscn(elf, scn)) != NULL)
{
gelf_getshdr(scn, &shdr);
if (shdr.sh_type != SHT_RELA)
continue;
GElf_Rela rela;
Elf_Data *data = elf_getdata(scn, NULL);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
for (size_t i = 0; i < cnt; i++)
{
gelf_getrela(data, i, &rela);
if (ELF64_R_SYM(rela.r_info) == left)
{
rela.r_info = ELF64_R_INFO(right, ELF64_R_TYPE(rela.r_info));
gelf_update_rela(data, i, &rela);
}
else if (ELF64_R_SYM(rela.r_info) == right)
{
rela.r_info = ELF64_R_INFO(left, ELF64_R_TYPE(rela.r_info));
gelf_update_rela(data, i, &rela);
}
}
}
}
static void sortSymtab(Elf *elf)
{
Elf_Scn *scn = getSectionByName(elf, ".symtab");
if (scn == NULL)
LOG_ERR("Failed to find .symtab section");
GElf_Shdr shdr;
GElf_Sym sym;
Elf_Data *data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
int firstGlobalIndex = 0;
size_t cnt = shdr.sh_size / shdr.sh_entsize;
for (size_t i = 0; i < cnt; i++)
{
gelf_getsym(data, i, &sym);
if (firstGlobalIndex == 0 && ELF64_ST_BIND(sym.st_info) == STB_GLOBAL)
firstGlobalIndex = i;
if (firstGlobalIndex != 0 && ELF64_ST_BIND(sym.st_info) == STB_LOCAL)
{
GElf_Sym globalSym;
gelf_getsym(data, firstGlobalIndex, &globalSym);
gelf_update_sym(data, i, &globalSym);
gelf_update_sym(data, firstGlobalIndex, &sym);
swapSymbolIndex(elf, i, firstGlobalIndex);
firstGlobalIndex = 0;
i = 0;
}
}
// update section info
shdr.sh_info = firstGlobalIndex;
gelf_update_shdr(scn, &shdr);
}
static Elf64_Word appendStringToScn(Elf *elf, char *scnName, char *text)
{
GElf_Shdr shdr;
Elf_Scn *scn = getSectionByName(elf, scnName);
Elf_Data *data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
Elf64_Word result = appendString(&shdr, data, text);
gelf_update_shdr(scn, &shdr);
return result;
}
static size_t copySymbol(Elf *elf, Elf *outElf, size_t index, bool copySec)
{
GElf_Sym oldSym;
GElf_Shdr shdr;
Elf_Scn *scn;
Elf_Data *data;
GElf_Sym newSym;
if (Symbols[index]->copiedIndex)
return Symbols[index]->copiedIndex;
scn = getSectionByName(elf, ".symtab");
data = elf_getdata(scn, NULL);
gelf_getshdr(scn, &shdr);
gelf_getsym(data, index, &oldSym);
scn = getSectionByName(outElf, ".symtab");
gelf_getshdr(scn, &shdr);
size_t newIndex = shdr.sh_size/shdr.sh_entsize;
data = elf_getdata(scn, NULL);
data->d_buf = realloc(data->d_buf, data->d_size + sizeof(GElf_Sym));
CHECK_ALLOC(data->d_buf);
newSym = oldSym;
char symType = ELF64_ST_TYPE(oldSym.st_info);
if (oldSym.st_shndx > 0 && oldSym.st_shndx < SectionsCount &&
copySec)
{
Elf_Scn *scn = copySection(elf, outElf, oldSym.st_shndx, true);
newSym.st_shndx = elf_ndxscn(scn);
if (oldSym.st_name != 0)
{
newSym.st_info = ELF64_ST_INFO(STB_GLOBAL, symType);
// TODO: Avoid modify symbol name for functions
if (symType == STT_FUNC)
{
char *symName = strdup(Symbols[index]->name);
CHECK_ALLOC(symName);
char *n;
while ((n = strchr(symName, '.')) != NULL)
*n = '_';
newSym.st_name = appendStringToScn(outElf, ".strtab", symName);
free(symName);
}
else
{
newSym.st_name = appendStringToScn(outElf, ".strtab", Symbols[index]->name);
}
}
}
else // mark symbol as "external"
{
if (symType == STT_OBJECT && oldSym.st_name != 0)
{
if (strstr(getSectionName(elf, oldSym.st_shndx), ".read_mostly"))
{
fprintf(stderr, "ERROR (%s:%d): Changes to the source code " \
"affects the %s variable marked with the " \
"__read_mostly macro. This is not yet supported by " \
"DEKU.\n", __FILE__, __LINE__, Symbols[index]->name);
exit(ERROR_UNSUPPORTED_READ_MOSTLY);
}
}
if (oldSym.st_shndx > 0 && oldSym.st_shndx < SectionsCount)
newSym.st_shndx = 0;
newSym.st_size = 0;
newSym.st_info = ELF64_ST_INFO(STB_GLOBAL, symType);
if (oldSym.st_name != 0)
newSym.st_name = copyStrtabItem(elf, outElf, oldSym.st_name);
}
memcpy((uint8_t *)data->d_buf + data->d_size, &newSym, sizeof(GElf_Sym));
data->d_size += sizeof(GElf_Sym);
shdr.sh_size = data->d_size;
gelf_update_shdr(scn, &shdr);
Symbols[index]->copiedIndex = newIndex;
return newIndex;
}
static void copyRelSection(Elf *elf, Elf *outElf, Elf64_Section index, size_t relTo, GElf_Sym *fromSym)
{
Elf_Scn *outScn = copySection(elf, outElf, index, false);
GElf_Shdr shdr;
gelf_getshdr(outScn, &shdr);
shdr.sh_link = elf_ndxscn(getSectionByName(outElf, ".symtab"));
shdr.sh_info = relTo;
gelf_update_shdr(outScn, &shdr);
GElf_Rela rela;
size_t j = shdr.sh_size / shdr.sh_entsize;
Elf_Scn *scn = elf_getscn(elf, index);
Elf_Data *data = elf_getdata(scn, NULL);
Elf_Data *outData = elf_getdata(outScn, NULL);
gelf_getshdr(scn, &shdr);
size_t cnt = shdr.sh_size / shdr.sh_entsize;
outData->d_size += shdr.sh_size;
outData->d_buf = realloc(outData->d_buf, outData->d_size);
CHECK_ALLOC(outData->d_buf);
for (size_t i = 0; i < cnt; i++)
{
gelf_getrela(data, i, &rela);
if (fromSym != NULL &&
(rela.r_offset < fromSym->st_value || rela.r_offset > fromSym->st_value + fromSym->st_size))
continue;
size_t newSymIndex;
size_t symIndex = ELF64_R_SYM(rela.r_info);
GElf_Shdr shdr = getSectionHeader(elf, Symbols[symIndex]->secIndex);
const char *secName = getSectionName(elf, Symbols[symIndex]->secIndex);
if (shdr.sh_flags & SHF_STRINGS ||
strstr(secName, ".rodata.__func__") == secName)
{
newSymIndex = copySymbol(elf, outElf, symIndex, true);
}
else
{
Symbol *sym = fromSym == NULL ? Symbols[symIndex] : getSymbolForRelocation(rela);
bool isFuncOrVar = Symbols[sym->index]->isFun || Symbols[sym->index]->isVar;
bool copySec = fromSym == NULL ? true : !isFuncOrVar;
newSymIndex = copySymbol(elf, outElf, sym->index, copySec);