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elf.c
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elf.c
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// SPDX-License-Identifier: GPL-2.0
/*
* Executable and linkable format (ELF)
*
* Copyright (C) 2019 Fredrik Noring
*/
#include <stdbool.h>
#include <stddef.h>
#include <string.h>
#include "iopmod/tool/elf.h"
bool elf_offset_in_section(Elf_Off offset, const Elf_Shdr *shdr)
{
return shdr->sh_offset <= offset &&
offset < shdr->sh_offset + shdr->sh_size;
}
bool elf_addr_in_section(Elf_Addr addr, const Elf_Shdr *shdr)
{
return shdr->sh_addr <= addr &&
addr < shdr->sh_addr + shdr->sh_size;
}
/**
* elf_ent_for_offset - pointer given an ELF offset
* @offset: ELF offset
* @ehdr: ELF header of module
*
* Return: pointer for a given ELF offset
*/
void *elf_ent_for_offset(Elf_Off offset, Elf_Ehdr *ehdr)
{
return &((u8 *)ehdr)[offset];
}
void *elf_ent_for_addr(Elf_Addr addr, Elf_Ehdr *ehdr)
{
Elf_Shdr *shdr;
elf_for_each_section (shdr, ehdr)
if (shdr->sh_type == SHT_PROGBITS &&
elf_addr_in_section(addr, shdr)) {
u8 *offset = elf_ent_for_offset(shdr->sh_offset, ehdr);
return &offset[addr - shdr->sh_addr];
}
return NULL;
}
Elf_Addr elf_addr_for_ent(void *ent, Elf_Ehdr *ehdr)
{
Elf_Off offset = (u8 *)ent - (u8 *)ehdr;
Elf_Shdr *shdr;
elf_for_each_section (shdr, ehdr)
if (elf_offset_in_section(offset, shdr))
return offset - shdr->sh_offset + shdr->sh_addr;
return -1;
}
/**
* elf_strings - base of ELF module string table
* @ehdr: ELF header of module
*
* Return: pointer to base of ELF module table
*/
char *elf_strings(Elf_Ehdr *ehdr)
{
if (ehdr->e_shstrndx == SHN_UNDEF)
return NULL;
Elf_Shdr *shdr = &elf_first_section(ehdr)[ehdr->e_shstrndx];
return elf_ent_for_offset(shdr->sh_offset, ehdr);
}
/**
* elf_section_name - name of section
* @shdr: header of section to provide name for
* @ehdr: ELF header of module for section
*
* Return: name of given section
*/
char *elf_section_name(Elf_Shdr *shdr, Elf_Ehdr *ehdr)
{
return &elf_strings(ehdr)[shdr->sh_name];
}
/**
* elf_first_section_with_name - first section with given name
* @name: name of section to search for
* @ehdr: ELF header of module to search
*
* Return: pointer to the first occurrence of the section, or %NULL if it does
* not exist
*/
Elf_Shdr *elf_first_section_with_name(const char *name, Elf_Ehdr *ehdr)
{
Elf_Shdr *shdr;
elf_for_each_section (shdr, ehdr)
if (strcmp(elf_section_name(shdr, ehdr), name) == 0)
return shdr;
return NULL;
}
/**
* elf_first_section - first ELF section
* @ehdr: ELF header of module
*
* Return: pointer to the first ELF section, or %NULL if it does not exist
*/
Elf_Shdr *elf_first_section(Elf_Ehdr *ehdr)
{
return ehdr->e_shnum ? elf_ent_for_offset(ehdr->e_shoff, ehdr) : NULL;
}
/**
* elf_next_section - next ELF section
* @shdr: header of current section
* @ehdr: ELF header of module
*
* Return: section following the current section, or %NULL
*/
Elf_Shdr *elf_next_section(Elf_Shdr *shdr, Elf_Ehdr *ehdr)
{
Elf_Shdr *next = &shdr[1];
Elf_Shdr *past = &elf_first_section(ehdr)[ehdr->e_shnum];
return next == past ? NULL: next;
}
void *elf_first_ent(Elf_Shdr *shdr, Elf_Ehdr *ehdr)
{
return shdr->sh_size >= shdr->sh_entsize ?
elf_ent_for_offset(shdr->sh_offset, ehdr) : NULL;
}
void *elf_next_ent(void *ent, Elf_Shdr *shdr, Elf_Ehdr *ehdr)
{
u8 *this = ent;
u8 *next = &this[shdr->sh_entsize];
u8 *past = elf_ent_for_offset(shdr->sh_offset + shdr->sh_size, ehdr);
return &next[shdr->sh_entsize] > past ? NULL : next;
}
char *elf_symbol_for_addr(Elf_Addr addr, Elf_Ehdr *ehdr)
{
Elf_Shdr *shdr;
Elf_Sym *sym;
elf_for_each_sym (sym, shdr, ehdr)
if (sym->st_value == addr) {
Elf_Shdr *strhdr =
&elf_first_section(ehdr)[shdr->sh_link];
char *strings =
elf_ent_for_offset(strhdr->sh_offset, ehdr);
return &strings[sym->st_name];
}
return NULL;
}
/**
* elf_identify - does the buffer contain an ELF object?
* @buffer: pointer to data to identify
* @size: size in bytes of buffer
*
* Return: %true if the buffer looks like an ELF object, otherwise %false
*/
bool elf_identify(void *buffer, size_t size)
{
const Elf_Ehdr *ehdr = buffer;
if (size < sizeof(*ehdr))
return false;
return ehdr->e_ident[EI_MAG0] == ELFMAG0 &&
ehdr->e_ident[EI_MAG1] == ELFMAG1 &&
ehdr->e_ident[EI_MAG2] == ELFMAG2 &&
ehdr->e_ident[EI_MAG3] == ELFMAG3 &&
ehdr->e_ident[EI_VERSION] == EV_CURRENT;
}