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Make ELF reader big-endian compatible
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Converting from integers to char arrays reveals endianness.
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@tautschnig
tautschnig committed Jul 20, 2023
1 parent 7f53078 commit 321dc37
Showing 1 changed file with 100 additions and 0 deletions.
100 changes: 100 additions & 0 deletions src/goto-programs/elf_reader.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,39 @@ Module: Read ELF

#include <istream>

static void u16_to_native_endian_inplace(bool le_input, uint16_t &input)
{
const uint8_t *input_as_bytes = reinterpret_cast<uint8_t *>(&input);
input = (((uint16_t)input_as_bytes[0]) << (le_input ? 0 : 8)) |
(((uint16_t)input_as_bytes[1]) << (le_input ? 8 : 0));
}

static void u32_to_native_endian_inplace(bool le_input, uint32_t &input)
{
const uint8_t *input_as_bytes = reinterpret_cast<uint8_t *>(&input);
input = (((uint32_t)input_as_bytes[0]) << (le_input ? 0 : 24)) |
(((uint32_t)input_as_bytes[1]) << (le_input ? 8 : 16)) |
(((uint32_t)input_as_bytes[2]) << (le_input ? 16 : 8)) |
(((uint32_t)input_as_bytes[3]) << (le_input ? 24 : 0));
}

static void
u64_to_native_endian_inplace(bool le_input, unsigned long long &input)
{
static_assert(
sizeof(unsigned long long) == 8,
"unsigned long long expected to be 8 bytes");
const uint8_t *input_as_bytes = reinterpret_cast<uint8_t *>(&input);
input = (((unsigned long long)input_as_bytes[0]) << (le_input ? 0 : 56)) |
(((unsigned long long)input_as_bytes[1]) << (le_input ? 8 : 48)) |
(((unsigned long long)input_as_bytes[2]) << (le_input ? 16 : 40)) |
(((unsigned long long)input_as_bytes[3]) << (le_input ? 24 : 32)) |
(((unsigned long long)input_as_bytes[4]) << (le_input ? 32 : 24)) |
(((unsigned long long)input_as_bytes[5]) << (le_input ? 40 : 16)) |
(((unsigned long long)input_as_bytes[6]) << (le_input ? 48 : 8)) |
(((unsigned long long)input_as_bytes[7]) << (le_input ? 56 : 0));
}

elf_readert::elf_readert(std::istream &_in):in(_in)
{
// read 32-bit header
Expand Down Expand Up @@ -43,6 +76,20 @@ elf_readert::elf_readert(std::istream &_in):in(_in)
else
throw deserialization_exceptiont("ELF32 header malformed (EI_DATA)");

u16_to_native_endian_inplace(little_endian, elf32_header.e_type);
u16_to_native_endian_inplace(little_endian, elf32_header.e_machine);
u32_to_native_endian_inplace(little_endian, elf32_header.e_version);
u32_to_native_endian_inplace(little_endian, elf32_header.e_entry);
u32_to_native_endian_inplace(little_endian, elf32_header.e_phoff);
u32_to_native_endian_inplace(little_endian, elf32_header.e_shoff);
u32_to_native_endian_inplace(little_endian, elf32_header.e_flags);
u16_to_native_endian_inplace(little_endian, elf32_header.e_ehsize);
u16_to_native_endian_inplace(little_endian, elf32_header.e_phentsize);
u16_to_native_endian_inplace(little_endian, elf32_header.e_phnum);
u16_to_native_endian_inplace(little_endian, elf32_header.e_shentsize);
u16_to_native_endian_inplace(little_endian, elf32_header.e_shnum);
u16_to_native_endian_inplace(little_endian, elf32_header.e_shstrndx);

if(elf32_header.e_version!=1)
throw deserialization_exceptiont("unknown ELF32 version");

Expand All @@ -64,6 +111,26 @@ elf_readert::elf_readert(std::istream &_in):in(_in)
in.read(
reinterpret_cast<char*>(&elf32_section_header_table[i]),
sizeof(Elf32_Shdr));
u32_to_native_endian_inplace(
little_endian, elf32_section_header_table[i].sh_name);
u32_to_native_endian_inplace(
little_endian, elf32_section_header_table[i].sh_type);
u32_to_native_endian_inplace(
little_endian, elf32_section_header_table[i].sh_flags);
u32_to_native_endian_inplace(
little_endian, elf32_section_header_table[i].sh_addr);
u32_to_native_endian_inplace(
little_endian, elf32_section_header_table[i].sh_offset);
u32_to_native_endian_inplace(
little_endian, elf32_section_header_table[i].sh_size);
u32_to_native_endian_inplace(
little_endian, elf32_section_header_table[i].sh_link);
u32_to_native_endian_inplace(
little_endian, elf32_section_header_table[i].sh_info);
u32_to_native_endian_inplace(
little_endian, elf32_section_header_table[i].sh_addralign);
u32_to_native_endian_inplace(
little_endian, elf32_section_header_table[i].sh_entsize);
}

// string table
Expand All @@ -89,6 +156,19 @@ elf_readert::elf_readert(std::istream &_in):in(_in)
little_endian=false;
else
throw deserialization_exceptiont("ELF64 header malformed (EI_DATA)");
u16_to_native_endian_inplace(little_endian, elf64_header.e_type);
u16_to_native_endian_inplace(little_endian, elf64_header.e_machine);
u32_to_native_endian_inplace(little_endian, elf64_header.e_version);
u64_to_native_endian_inplace(little_endian, elf64_header.e_entry);
u64_to_native_endian_inplace(little_endian, elf64_header.e_phoff);
u64_to_native_endian_inplace(little_endian, elf64_header.e_shoff);
u32_to_native_endian_inplace(little_endian, elf64_header.e_flags);
u16_to_native_endian_inplace(little_endian, elf64_header.e_ehsize);
u16_to_native_endian_inplace(little_endian, elf64_header.e_phentsize);
u16_to_native_endian_inplace(little_endian, elf64_header.e_phnum);
u16_to_native_endian_inplace(little_endian, elf64_header.e_shentsize);
u16_to_native_endian_inplace(little_endian, elf64_header.e_shnum);
u16_to_native_endian_inplace(little_endian, elf64_header.e_shstrndx);

if(elf64_header.e_version!=1)
throw deserialization_exceptiont("unknown ELF64 version");
Expand All @@ -111,6 +191,26 @@ elf_readert::elf_readert(std::istream &_in):in(_in)
in.read(
reinterpret_cast<char*>(&elf64_section_header_table[i]),
sizeof(Elf64_Shdr));
u32_to_native_endian_inplace(
little_endian, elf64_section_header_table[i].sh_name);
u32_to_native_endian_inplace(
little_endian, elf64_section_header_table[i].sh_type);
u64_to_native_endian_inplace(
little_endian, elf64_section_header_table[i].sh_flags);
u64_to_native_endian_inplace(
little_endian, elf64_section_header_table[i].sh_addr);
u64_to_native_endian_inplace(
little_endian, elf64_section_header_table[i].sh_offset);
u64_to_native_endian_inplace(
little_endian, elf64_section_header_table[i].sh_size);
u32_to_native_endian_inplace(
little_endian, elf64_section_header_table[i].sh_link);
u32_to_native_endian_inplace(
little_endian, elf64_section_header_table[i].sh_info);
u64_to_native_endian_inplace(
little_endian, elf64_section_header_table[i].sh_addralign);
u64_to_native_endian_inplace(
little_endian, elf64_section_header_table[i].sh_entsize);
}

// string table
Expand Down

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