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LibELF: Call mmap() before constructing the DynamicLoader object

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Refactor DynamicLoader construction with a try_create() helper so that
we can call mmap() before making a loader. This way the loader doesn't
need to have an "mmap failed" state.

This patch also takes care of determining the ELF file size in
try_create() instead of expecting callers to provide it.
This commit is contained in:
Andreas Kling 2021-01-31 10:13:23 +01:00
parent d71bfb9614
commit 68576bcf1b
4 changed files with 54 additions and 71 deletions
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72
Userland/Libraries/LibELF/DynamicLoader.cpp
View file

@ -30,13 +30,13 @@
#include <AK/StringBuilder.h>
#include <LibELF/DynamicLoader.h>
#include <LibELF/Validation.h>
#include <assert.h>
#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#ifndef __serenity__
static void* mmap_with_name(void* addr, size_t length, int prot, int flags, int fd, off_t offset, const char*)
@ -51,38 +51,45 @@ namespace ELF {
static bool s_always_bind_now = false;
NonnullRefPtr<DynamicLoader> DynamicLoader::construct(const char* filename, int fd, size_t size)
RefPtr<DynamicLoader> DynamicLoader::try_create(int fd, String filename)
{
return adopt(*new DynamicLoader(filename, fd, size));
}
void* DynamicLoader::do_mmap(int fd, size_t size, const String& name)
{
if (size < sizeof(Elf32_Ehdr))
return MAP_FAILED;
String file_mmap_name = String::formatted("ELF_DYN: {}", name);
return mmap_with_name(nullptr, size, PROT_READ, MAP_PRIVATE, fd, 0, file_mmap_name.characters());
}
DynamicLoader::DynamicLoader(const char* filename, int fd, size_t size)
: m_filename(filename)
, m_file_size(size)
, m_image_fd(fd)
, m_file_mapping(do_mmap(m_image_fd, m_file_size, m_filename))
, m_elf_image((u8*)m_file_mapping, m_file_size)
{
if (m_file_mapping == MAP_FAILED) {
m_valid = false;
return;
struct stat stat;
if (fstat(fd, &stat) < 0) {
perror("DynamicLoader::try_create fstat");
return {};
}
m_tls_size = calculate_tls_size();
ASSERT(stat.st_size >= 0);
size_t size = static_cast<size_t>(stat.st_size);
if (size < sizeof(Elf32_Ehdr))
return {};
String file_mmap_name = String::formatted("ELF_DYN: {}", filename);
auto* data = mmap_with_name(nullptr, size, PROT_READ, MAP_PRIVATE, fd, 0, file_mmap_name.characters());
if (data == MAP_FAILED) {
perror("DynamicLoader::try_create mmap");
return {};
}
return adopt(*new DynamicLoader(fd, move(filename), data, size));
}
DynamicLoader::DynamicLoader(int fd, String filename, void* data, size_t size)
: m_filename(move(filename))
, m_file_size(size)
, m_image_fd(fd)
, m_file_data(data)
, m_elf_image((u8*)m_file_data, m_file_size)
{
m_tls_size = calculate_tls_size();
m_valid = validate();
}
DynamicLoader::~DynamicLoader()
{
munmap(m_file_data, m_file_size);
}
const DynamicObject& DynamicLoader::dynamic_object() const
{
if (!m_cached_dynamic_object) {
@ -115,15 +122,8 @@ size_t DynamicLoader::calculate_tls_size() const
bool DynamicLoader::validate()
{
auto* elf_header = (Elf32_Ehdr*)m_file_mapping;
return validate_elf_header(*elf_header, m_file_size) && validate_program_headers(*elf_header, m_file_size, (u8*)m_file_mapping, m_file_size, &m_program_interpreter);
}
DynamicLoader::~DynamicLoader()
{
if (MAP_FAILED != m_file_mapping)
munmap(m_file_mapping, m_file_size);
close(m_image_fd);
auto* elf_header = (Elf32_Ehdr*)m_file_data;
return validate_elf_header(*elf_header, m_file_size) && validate_program_headers(*elf_header, m_file_size, (u8*)m_file_data, m_file_size, &m_program_interpreter);
}
void* DynamicLoader::symbol_for_name(const char* name)
@ -338,7 +338,7 @@ void DynamicLoader::load_program_headers()
else
data_segment_start = data_region.value().desired_load_address();
memcpy(data_segment_start.as_ptr(), (u8*)m_file_mapping + data_region.value().offset(), data_region.value().size_in_image());
memcpy(data_segment_start.as_ptr(), (u8*)m_file_data + data_region.value().offset(), data_region.value().size_in_image());
// FIXME: Initialize the values in the TLS section. Currently, it is zeroed.
}