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serenity/Kernel/Coredump.cpp
Liav A 0bb7c8f4c4 Kernel+SystemServer: Don't hardcode coredump directory path 
Instead, allow userspace to decide on the coredump directory path. By
default, SystemServer sets it to the /tmp/coredump directory, but users
can now change this by writing a new path to the sysfs node at
/sys/kernel/variables/coredump_directory, and also to read this node to
check where coredumps are currently generated at.
2022-12-03 05:56:59 -07:00

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/*
* Copyright (c) 2019-2020, Jesse Buhagiar <jooster669@gmail.com>
* Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
* Copyright (c) 2020-2021, Linus Groh <linusg@serenityos.org>
* Copyright (c) 2021, Andreas Kling <klingi@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/ByteBuffer.h>
#include <AK/JsonObjectSerializer.h>
#include <AK/Singleton.h>
#include <Kernel/Coredump.h>
#include <Kernel/FileSystem/Custody.h>
#include <Kernel/FileSystem/OpenFileDescription.h>
#include <Kernel/FileSystem/VirtualFileSystem.h>
#include <Kernel/KLexicalPath.h>
#include <Kernel/Locking/Spinlock.h>
#include <Kernel/Memory/ScopedAddressSpaceSwitcher.h>
#include <Kernel/Process.h>
#include <LibC/elf.h>
#include <LibELF/Core.h>
#define INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS 0
static Singleton<SpinlockProtected<OwnPtr<KString>>> s_coredump_directory_path;
namespace Kernel {
SpinlockProtected<OwnPtr<KString>>& Coredump::directory_path()
{
return s_coredump_directory_path;
}
bool Coredump::FlatRegionData::looks_like_userspace_heap_region() const
{
return name().starts_with("LibJS:"sv) || name().starts_with("malloc:"sv);
}
bool Coredump::FlatRegionData::is_consistent_with_region(Memory::Region const& region) const
{
if (m_access != region.access())
return false;
if (m_page_count != region.page_count() || m_size != region.size())
return false;
if (m_vaddr != region.vaddr())
return false;
return true;
}
ErrorOr<NonnullOwnPtr<Coredump>> Coredump::try_create(NonnullLockRefPtr<Process> process, StringView output_path)
{
if (!process->is_dumpable()) {
dbgln("Refusing to generate coredump for non-dumpable process {}", process->pid().value());
return EPERM;
}
Vector<FlatRegionData> regions;
size_t number_of_regions = process->address_space().with([](auto& space) {
return space->region_tree().regions().size();
});
TRY(regions.try_ensure_capacity(number_of_regions));
TRY(process->address_space().with([&](auto& space) -> ErrorOr<void> {
for (auto& region : space->region_tree().regions())
TRY(regions.try_empend(region, TRY(KString::try_create(region.name()))));
return {};
}));
auto description = TRY(try_create_target_file(process, output_path));
return adopt_nonnull_own_or_enomem(new (nothrow) Coredump(move(process), move(description), move(regions)));
}
Coredump::Coredump(NonnullLockRefPtr<Process> process, NonnullLockRefPtr<OpenFileDescription> description, Vector<FlatRegionData> regions)
: m_process(move(process))
, m_description(move(description))
, m_regions(move(regions))
{
m_num_program_headers = 0;
for (auto& region : m_regions) {
#if !INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS
if (region.looks_like_userspace_heap_region())
continue;
#endif
if (region.access() == Memory::Region::Access::None)
continue;
++m_num_program_headers;
}
++m_num_program_headers; // +1 for NOTE segment
}
ErrorOr<NonnullLockRefPtr<OpenFileDescription>> Coredump::try_create_target_file(Process const& process, StringView output_path)
{
auto output_directory = KLexicalPath::dirname(output_path);
auto dump_directory = TRY(VirtualFileSystem::the().open_directory(Process::current().credentials(), output_directory, VirtualFileSystem::the().root_custody()));
auto dump_directory_metadata = dump_directory->inode().metadata();
if (dump_directory_metadata.uid != 0 || dump_directory_metadata.gid != 0 || dump_directory_metadata.mode != 040777) {
dbgln("Refusing to put coredump in sketchy directory '{}'", output_directory);
return EINVAL;
}
auto process_credentials = process.credentials();
return TRY(VirtualFileSystem::the().open(
Process::current().credentials(),
KLexicalPath::basename(output_path),
O_CREAT | O_WRONLY | O_EXCL,
S_IFREG, // We will enable reading from userspace when we finish generating the coredump file
*dump_directory,
UidAndGid { process_credentials->uid(), process_credentials->gid() }));
}
ErrorOr<void> Coredump::write_elf_header()
{
ElfW(Ehdr) elf_file_header;
elf_file_header.e_ident[EI_MAG0] = 0x7f;
elf_file_header.e_ident[EI_MAG1] = 'E';
elf_file_header.e_ident[EI_MAG2] = 'L';
elf_file_header.e_ident[EI_MAG3] = 'F';
#if ARCH(I386)
elf_file_header.e_ident[EI_CLASS] = ELFCLASS32;
#elif ARCH(X86_64) || ARCH(AARCH64)
elf_file_header.e_ident[EI_CLASS] = ELFCLASS64;
#else
# error Unknown architecture
#endif
elf_file_header.e_ident[EI_DATA] = ELFDATA2LSB;
elf_file_header.e_ident[EI_VERSION] = EV_CURRENT;
elf_file_header.e_ident[EI_OSABI] = 0; // ELFOSABI_NONE
elf_file_header.e_ident[EI_ABIVERSION] = 0;
elf_file_header.e_ident[EI_PAD + 1] = 0;
elf_file_header.e_ident[EI_PAD + 2] = 0;
elf_file_header.e_ident[EI_PAD + 3] = 0;
elf_file_header.e_ident[EI_PAD + 4] = 0;
elf_file_header.e_ident[EI_PAD + 5] = 0;
elf_file_header.e_ident[EI_PAD + 6] = 0;
elf_file_header.e_type = ET_CORE;
#if ARCH(I386)
elf_file_header.e_machine = EM_386;
#elif ARCH(X86_64)
elf_file_header.e_machine = EM_X86_64;
#elif ARCH(AARCH64)
elf_file_header.e_machine = EM_AARCH64;
#else
# error Unknown architecture
#endif
elf_file_header.e_version = 1;
elf_file_header.e_entry = 0;
elf_file_header.e_phoff = sizeof(ElfW(Ehdr));
elf_file_header.e_shoff = 0;
elf_file_header.e_flags = 0;
elf_file_header.e_ehsize = sizeof(ElfW(Ehdr));
elf_file_header.e_shentsize = sizeof(ElfW(Shdr));
elf_file_header.e_phentsize = sizeof(ElfW(Phdr));
elf_file_header.e_phnum = m_num_program_headers;
elf_file_header.e_shnum = 0;
elf_file_header.e_shstrndx = SHN_UNDEF;
TRY(m_description->write(UserOrKernelBuffer::for_kernel_buffer(reinterpret_cast<uint8_t*>(&elf_file_header)), sizeof(ElfW(Ehdr))));
return {};
}
ErrorOr<void> Coredump::write_program_headers(size_t notes_size)
{
size_t offset = sizeof(ElfW(Ehdr)) + m_num_program_headers * sizeof(ElfW(Phdr));
for (auto& region : m_regions) {
#if !INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS
if (region.looks_like_userspace_heap_region())
continue;
#endif
if (region.access() == Memory::Region::Access::None)
continue;
ElfW(Phdr) phdr {};
phdr.p_type = PT_LOAD;
phdr.p_offset = offset;
phdr.p_vaddr = region.vaddr().get();
phdr.p_paddr = 0;
phdr.p_filesz = region.page_count() * PAGE_SIZE;
phdr.p_memsz = region.page_count() * PAGE_SIZE;
phdr.p_align = 0;
phdr.p_flags = region.is_readable() ? PF_R : 0;
if (region.is_writable())
phdr.p_flags |= PF_W;
if (region.is_executable())
phdr.p_flags |= PF_X;
offset += phdr.p_filesz;
[[maybe_unused]] auto rc = m_description->write(UserOrKernelBuffer::for_kernel_buffer(reinterpret_cast<uint8_t*>(&phdr)), sizeof(ElfW(Phdr)));
}
ElfW(Phdr) notes_pheader {};
notes_pheader.p_type = PT_NOTE;
notes_pheader.p_offset = offset;
notes_pheader.p_vaddr = 0;
notes_pheader.p_paddr = 0;
notes_pheader.p_filesz = notes_size;
notes_pheader.p_memsz = notes_size;
notes_pheader.p_align = 0;
notes_pheader.p_flags = 0;
TRY(m_description->write(UserOrKernelBuffer::for_kernel_buffer(reinterpret_cast<uint8_t*>(&notes_pheader)), sizeof(ElfW(Phdr))));
return {};
}
ErrorOr<void> Coredump::write_regions()
{
u8 zero_buffer[PAGE_SIZE] = {};
for (auto& region : m_regions) {
VERIFY(!region.is_kernel());
#if !INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS
if (region.looks_like_userspace_heap_region())
continue;
#endif
if (region.access() == Memory::Region::Access::None)
continue;
auto buffer = TRY(KBuffer::try_create_with_size("Coredump Region Copy Buffer"sv, region.page_count() * PAGE_SIZE));
TRY(m_process->address_space().with([&](auto& space) -> ErrorOr<void> {
auto* real_region = space->region_tree().regions().find(region.vaddr().get());
if (!real_region)
return Error::from_string_view("Failed to find matching region in the process"sv);
if (!region.is_consistent_with_region(*real_region))
return Error::from_string_view("Found region does not match stored metadata"sv);
// If we crashed in the middle of mapping in Regions, they do not have a page directory yet, and will crash on a remap() call
if (!real_region->is_mapped())
return {};
real_region->set_readable(true);
real_region->remap();
for (size_t i = 0; i < region.page_count(); i++) {
auto page = real_region->physical_page(i);
auto src_buffer = [&]() -> ErrorOr<UserOrKernelBuffer> {
if (page)
return UserOrKernelBuffer::for_user_buffer(reinterpret_cast<uint8_t*>((region.vaddr().as_ptr() + (i * PAGE_SIZE))), PAGE_SIZE);
// If the current page is not backed by a physical page, we zero it in the coredump file.
return UserOrKernelBuffer::for_kernel_buffer(zero_buffer);
}();
TRY(src_buffer.value().read(buffer->bytes().slice(i * PAGE_SIZE, PAGE_SIZE)));
}
return {};
}));
TRY(m_description->write(UserOrKernelBuffer::for_kernel_buffer(buffer->data()), buffer->size()));
}
return {};
}
ErrorOr<void> Coredump::write_notes_segment(ReadonlyBytes notes_segment)
{
TRY(m_description->write(UserOrKernelBuffer::for_kernel_buffer(const_cast<u8*>(notes_segment.data())), notes_segment.size()));
return {};
}
ErrorOr<void> Coredump::create_notes_process_data(auto& builder) const
{
ELF::Core::ProcessInfo info {};
info.header.type = ELF::Core::NotesEntryHeader::Type::ProcessInfo;
TRY(builder.append_bytes(ReadonlyBytes { (void*)&info, sizeof(info) }));
{
auto process_obj = TRY(JsonObjectSerializer<>::try_create(builder));
TRY(process_obj.add("pid"sv, m_process->pid().value()));
TRY(process_obj.add("termination_signal"sv, m_process->termination_signal()));
TRY(process_obj.add("executable_path"sv, m_process->executable() ? TRY(m_process->executable()->try_serialize_absolute_path())->view() : ""sv));
{
auto arguments_array = TRY(process_obj.add_array("arguments"sv));
for (auto const& argument : m_process->arguments())
TRY(arguments_array.add(argument.view()));
TRY(arguments_array.finish());
}
{
auto environment_array = TRY(process_obj.add_array("environment"sv));
for (auto const& variable : m_process->environment())
TRY(environment_array.add(variable.view()));
TRY(environment_array.finish());
}
TRY(process_obj.finish());
}
TRY(builder.append('\0'));
return {};
}
ErrorOr<void> Coredump::create_notes_threads_data(auto& builder) const
{
for (auto const& thread : m_process->threads_for_coredump({})) {
ELF::Core::ThreadInfo info {};
info.header.type = ELF::Core::NotesEntryHeader::Type::ThreadInfo;
info.tid = thread.tid().value();
if (thread.current_trap())
copy_kernel_registers_into_ptrace_registers(info.regs, thread.get_register_dump_from_stack());
TRY(builder.append_bytes(ReadonlyBytes { &info, sizeof(info) }));
}
return {};
}
ErrorOr<void> Coredump::create_notes_regions_data(auto& builder) const
{
size_t region_index = 0;
for (auto const& region : m_regions) {
#if !INCLUDE_USERSPACE_HEAP_MEMORY_IN_COREDUMPS
if (region.looks_like_userspace_heap_region())
continue;
#endif
if (region.access() == Memory::Region::Access::None)
continue;
ELF::Core::MemoryRegionInfo info {};
info.header.type = ELF::Core::NotesEntryHeader::Type::MemoryRegionInfo;
info.region_start = region.vaddr().get();
info.region_end = region.vaddr().offset(region.size()).get();
info.program_header_index = region_index++;
TRY(builder.append_bytes(ReadonlyBytes { (void*)&info, sizeof(info) }));
// NOTE: The region name *is* null-terminated, so the following is ok:
auto name = region.name();
if (name.is_empty())
TRY(builder.append('\0'));
else
TRY(builder.append(name.characters_without_null_termination(), name.length() + 1));
}
return {};
}
ErrorOr<void> Coredump::create_notes_metadata_data(auto& builder) const
{
ELF::Core::Metadata metadata {};
metadata.header.type = ELF::Core::NotesEntryHeader::Type::Metadata;
TRY(builder.append_bytes(ReadonlyBytes { (void*)&metadata, sizeof(metadata) }));
{
auto metadata_obj = TRY(JsonObjectSerializer<>::try_create(builder));
TRY(m_process->for_each_coredump_property([&](auto& key, auto& value) -> ErrorOr<void> {
TRY(metadata_obj.add(key.view(), value.view()));
return {};
}));
TRY(metadata_obj.finish());
}
TRY(builder.append('\0'));
return {};
}
ErrorOr<void> Coredump::create_notes_segment_data(auto& builder) const
{
TRY(create_notes_process_data(builder));
TRY(create_notes_threads_data(builder));
TRY(create_notes_regions_data(builder));
TRY(create_notes_metadata_data(builder));
ELF::Core::NotesEntryHeader null_entry {};
null_entry.type = ELF::Core::NotesEntryHeader::Type::Null;
TRY(builder.append(ReadonlyBytes { &null_entry, sizeof(null_entry) }));
return {};
}
ErrorOr<void> Coredump::write()
{
ScopedAddressSpaceSwitcher switcher(m_process);
auto builder = TRY(KBufferBuilder::try_create());
TRY(create_notes_segment_data(builder));
TRY(write_elf_header());
TRY(write_program_headers(builder.bytes().size()));
TRY(write_regions());
TRY(write_notes_segment(builder.bytes()));
return m_description->chmod(Process::current().credentials(), 0600); // Make coredump file read/writable
}
}
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