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Kernel+LibELF: Move sys$execve()'s loading logic from LibELF to Kernel

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It was really weird that ELF loading was performed by the ELF::Loader
class instead of just being done by the kernel itself. This patch moves
all the layout logic from ELF::Loader over to sys$execve().

The kernel no longer cares about ELF::Loader and instead only uses an
ELF::Image as an interpreting wrapper around executables.
This commit is contained in:
Andreas Kling 2020-12-25 01:22:55 +01:00
parent d7ad082afa
commit 7551a66f73
3 changed files with 90 additions and 134 deletions
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102
Libraries/LibELF/Loader.cpp
View file

@ -29,20 +29,12 @@
#include <AK/Memory.h>
#include <AK/QuickSort.h>
#ifdef KERNEL
# include <Kernel/VM/MemoryManager.h>
# define do_memcpy copy_to_user
#else
# define do_memcpy memcpy
#endif
//#define Loader_DEBUG
namespace ELF {
Loader::Loader(const u8* buffer, size_t size, String&& name, bool verbose_logging)
Loader::Loader(const u8* buffer, size_t size, String&&, bool verbose_logging)
: m_image(buffer, size, verbose_logging)
, m_name(move(name))
{
if (m_image.is_valid())
m_symbol_count = m_image.symbol_count();
@ -52,98 +44,6 @@ Loader::~Loader()
{
}
bool Loader::load()
{
#ifdef Loader_DEBUG
m_image.dump();
#endif
if (!m_image.is_valid())
return false;
if (!layout())
return false;
return true;
}
bool Loader::layout()
{
bool failed = false;
m_image.for_each_program_header([&](const Image::ProgramHeader& program_header) {
if (program_header.type() == PT_TLS) {
#ifdef KERNEL
auto* tls_image = tls_section_hook(program_header.size_in_memory(), program_header.alignment());
if (!tls_image) {
failed = true;
return;
}
if (!m_image.is_within_image(program_header.raw_data(), program_header.size_in_image())) {
dbg() << "Shenanigans! ELF PT_TLS header sneaks outside of executable.";
failed = true;
return;
}
if (!do_memcpy(tls_image, program_header.raw_data(), program_header.size_in_image())) {
failed = false;
return;
}
#endif
return;
}
if (program_header.type() != PT_LOAD)
return;
#ifdef KERNEL
# ifdef Loader_DEBUG
kprintf("PH: V%p %u r:%u w:%u\n", program_header.vaddr().get(), program_header.size_in_memory(), program_header.is_readable(), program_header.is_writable());
# endif
if (program_header.is_writable()) {
auto* allocated_section = alloc_section_hook(
program_header.vaddr(),
program_header.size_in_memory(),
program_header.alignment(),
program_header.is_readable(),
program_header.is_writable(),
String::format("%s-alloc-%s%s", m_name.is_empty() ? "elf" : m_name.characters(), program_header.is_readable() ? "r" : "", program_header.is_writable() ? "w" : ""));
if (!allocated_section) {
failed = true;
return;
}
if (!m_image.is_within_image(program_header.raw_data(), program_header.size_in_image())) {
dbg() << "Shenanigans! Writable ELF PT_LOAD header sneaks outside of executable.";
failed = true;
return;
}
// It's not always the case with PIE executables (and very well shouldn't be) that the
// virtual address in the program header matches the one we end up giving the process.
// In order to copy the data image correctly into memory, we need to copy the data starting at
// the right initial page offset into the pages allocated for the elf_alloc-XX section.
// FIXME: There's an opportunity to munmap, or at least mprotect, the padding space between
// the .text and .data PT_LOAD sections of the executable.
// Accessing it would definitely be a bug.
auto page_offset = program_header.vaddr();
page_offset.mask(~PAGE_MASK);
if (!do_memcpy((u8*)allocated_section + page_offset.get(), program_header.raw_data(), program_header.size_in_image())) {
failed = false;
return;
}
} else {
auto* mapped_section = map_section_hook(
program_header.vaddr(),
program_header.size_in_memory(),
program_header.alignment(),
program_header.offset(),
program_header.is_readable(),
program_header.is_writable(),
program_header.is_executable(),
String::format("%s-map-%s%s%s", m_name.is_empty() ? "elf" : m_name.characters(), program_header.is_readable() ? "r" : "", program_header.is_writable() ? "w" : "", program_header.is_executable() ? "x" : ""));
if (!mapped_section) {
failed = true;
}
}
#endif
});
return !failed;
}
#ifndef KERNEL
Optional<Image::Symbol> Loader::find_symbol(u32 address, u32* out_offset) const
{

11
Libraries/LibELF/Loader.h
View file

@ -48,12 +48,6 @@ public:
static NonnullRefPtr<Loader> create(const u8* data, size_t size, String&& name = String::empty(), bool verbose_logging = true) { return adopt(*new Loader(data, size, move(name), verbose_logging)); }
~Loader();
bool load();
#if defined(KERNEL)
Function<void*(VirtualAddress, size_t, size_t, bool, bool, const String&)> alloc_section_hook;
Function<void*(size_t, size_t)> tls_section_hook;
Function<void*(VirtualAddress, size_t, size_t, size_t, bool r, bool w, bool x, const String&)> map_section_hook;
#endif
VirtualAddress entry() const
{
return m_image.entry();
@ -75,22 +69,17 @@ private:
bool layout();
Image m_image;
String m_name;
size_t m_symbol_count { 0 };
struct SortedSymbol {
u32 address;
StringView name;
#ifndef KERNEL
String demangled_name;
Optional<Image::Symbol> symbol;
#endif
};
#ifndef KERNEL
mutable Vector<SortedSymbol> m_sorted_symbols;
#endif
};
} // end namespace ELF