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Kernel: Generate a coredump file when a process crashes
When a process crashes, we generate a coredump file and write it in /tmp/coredumps/. The coredump file is an ELF file of type ET_CORE. It contains a segment for every userspace memory region of the process, and an additional PT_NOTE segment that contains the registers state for each thread, and a additional data about memory regions (e.g their name).
This commit is contained in:
Itamar
Andreas Kling
parent
efe4da57df
commit
b4842d33bb
11 changed files with 427 additions and 1 deletions
274
Kernel/CoreDump.cpp
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274
Kernel/CoreDump.cpp
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/*
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* Copyright (c) 2019-2020, Jesse Buhagiar <jooster669@gmail.com>
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* Copyright (c) 2020, Itamar S. <itamar8910@gmail.com>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <AK/ByteBuffer.h>
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#include <Kernel/CoreDump.h>
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#include <Kernel/FileSystem/Custody.h>
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#include <Kernel/FileSystem/FileDescription.h>
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#include <Kernel/FileSystem/VirtualFileSystem.h>
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#include <Kernel/Process.h>
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#include <Kernel/Ptrace.h>
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#include <Kernel/RTC.h>
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#include <Kernel/SpinLock.h>
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#include <Kernel/VM/ProcessPagingScope.h>
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#include <LibELF/CoreDump.h>
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#include <LibELF/exec_elf.h>
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namespace Kernel {
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OwnPtr<CoreDump> CoreDump::create(Process& process)
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{
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auto fd = create_target_file(process);
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if (!fd)
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return nullptr;
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return make<CoreDump>(process, fd.release_nonnull());
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}
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CoreDump::CoreDump(Process& process, NonnullRefPtr<FileDescription>&& fd)
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: m_process(process)
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, m_fd(move(fd))
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, m_num_program_headers(process.m_regions.size() + 1) // +1 for NOTE segment
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{
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}
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CoreDump::~CoreDump()
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{
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}
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RefPtr<FileDescription> CoreDump::create_target_file(const Process& process)
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{
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static constexpr const char* coredumps_directory = "/tmp/coredump";
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if (VFS::the().open_directory(coredumps_directory, VFS::the().root_custody()).is_error()) {
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auto res = VFS::the().mkdir(coredumps_directory, 0777, VFS::the().root_custody());
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if (res.is_error())
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return nullptr;
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}
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auto tmp_dir = VFS::the().open_directory(coredumps_directory, VFS::the().root_custody());
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if (tmp_dir.is_error())
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return nullptr;
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auto fd_or_error = VFS::the().open(
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String::format("%s_%u.core", process.name().characters(), RTC::now()),
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O_CREAT | O_WRONLY | O_EXCL,
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0, // We will enable reading from userspace when we finish generating the coredump file
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*tmp_dir.value(),
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UidAndGid { process.uid(), process.gid() });
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if (fd_or_error.is_error())
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return nullptr;
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return fd_or_error.value();
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}
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void CoreDump::write_elf_header()
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{
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Elf32_Ehdr elf_file_header;
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elf_file_header.e_ident[EI_MAG0] = 0x7f;
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elf_file_header.e_ident[EI_MAG1] = 'E';
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elf_file_header.e_ident[EI_MAG2] = 'L';
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elf_file_header.e_ident[EI_MAG3] = 'F';
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elf_file_header.e_ident[EI_CLASS] = ELFCLASS32;
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elf_file_header.e_ident[EI_DATA] = ELFDATA2LSB;
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elf_file_header.e_ident[EI_VERSION] = EV_CURRENT;
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elf_file_header.e_ident[EI_OSABI] = 0; // ELFOSABI_NONE
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elf_file_header.e_ident[EI_ABIVERSION] = 0;
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elf_file_header.e_ident[EI_PAD + 1] = 0;
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elf_file_header.e_ident[EI_PAD + 2] = 0;
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elf_file_header.e_ident[EI_PAD + 3] = 0;
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elf_file_header.e_ident[EI_PAD + 4] = 0;
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elf_file_header.e_ident[EI_PAD + 5] = 0;
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elf_file_header.e_ident[EI_PAD + 6] = 0;
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elf_file_header.e_ident[EI_NIDENT] = 16;
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elf_file_header.e_type = ET_CORE;
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elf_file_header.e_machine = EM_386;
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elf_file_header.e_version = 1;
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elf_file_header.e_entry = 0;
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elf_file_header.e_phoff = sizeof(Elf32_Ehdr);
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elf_file_header.e_shoff = 0;
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elf_file_header.e_flags = 0;
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elf_file_header.e_ehsize = sizeof(Elf32_Ehdr);
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elf_file_header.e_shentsize = sizeof(Elf32_Shdr);
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elf_file_header.e_phentsize = sizeof(Elf32_Phdr);
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elf_file_header.e_phnum = m_num_program_headers;
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elf_file_header.e_shnum = 0;
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elf_file_header.e_shstrndx = SHN_UNDEF;
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(void)m_fd->write(UserOrKernelBuffer::for_kernel_buffer(reinterpret_cast<uint8_t*>(&elf_file_header)), sizeof(Elf32_Ehdr));
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}
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void CoreDump::write_program_headers(size_t notes_size)
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{
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size_t offset = sizeof(Elf32_Ehdr) + m_num_program_headers * sizeof(Elf32_Phdr);
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for (auto& region : m_process.m_regions) {
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Elf32_Phdr phdr {};
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phdr.p_type = PT_LOAD;
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phdr.p_offset = offset;
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phdr.p_vaddr = reinterpret_cast<uint32_t>(region.vaddr().as_ptr());
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phdr.p_paddr = 0;
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phdr.p_filesz = region.page_count() * PAGE_SIZE;
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phdr.p_memsz = region.page_count() * PAGE_SIZE;
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phdr.p_align = 0;
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phdr.p_flags = region.is_readable() ? PF_R : 0;
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if (region.is_writable())
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phdr.p_flags |= PF_W;
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if (region.is_executable())
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phdr.p_flags |= PF_X;
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offset += phdr.p_filesz;
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(void)m_fd->write(UserOrKernelBuffer::for_kernel_buffer(reinterpret_cast<uint8_t*>(&phdr)), sizeof(Elf32_Phdr));
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}
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Elf32_Phdr notes_pheader {};
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notes_pheader.p_type = PT_NOTE;
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notes_pheader.p_offset = offset;
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notes_pheader.p_vaddr = 0;
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notes_pheader.p_paddr = 0;
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notes_pheader.p_filesz = notes_size;
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notes_pheader.p_memsz = 0;
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notes_pheader.p_align = 0;
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notes_pheader.p_flags = 0;
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(void)m_fd->write(UserOrKernelBuffer::for_kernel_buffer(reinterpret_cast<uint8_t*>(¬es_pheader)), sizeof(Elf32_Phdr));
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}
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void CoreDump::write_regions()
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{
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for (auto& region : m_process.m_regions) {
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if (region.is_kernel())
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continue;
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region.set_readable(true);
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region.remap();
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auto& vmobj = region.vmobject();
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for (size_t i = 0; i < region.page_count(); i++) {
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PhysicalPage* page = vmobj.physical_pages()[region.first_page_index() + i];
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uint8_t zero_buffer[PAGE_SIZE] = {};
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Optional<UserOrKernelBuffer> src_buffer;
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if (page) {
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src_buffer = UserOrKernelBuffer::for_user_buffer(reinterpret_cast<uint8_t*>((region.vaddr().as_ptr() + (i * PAGE_SIZE))), PAGE_SIZE);
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} else {
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// If the current page is not backed by a physical page, we zero it in the coredump file.
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// TODO: Do we want to include the contents of pages that have not been faulted-in in the coredump?
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// (A page may not be backed by a physical page because it has never been faulted in when the process ran).
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src_buffer = UserOrKernelBuffer::for_kernel_buffer(zero_buffer);
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}
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(void)m_fd->write(src_buffer.value(), PAGE_SIZE);
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}
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}
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}
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void CoreDump::write_notes_segment(ByteBuffer& notes_segment)
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{
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(void)m_fd->write(UserOrKernelBuffer::for_kernel_buffer(notes_segment.data()), notes_segment.size());
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}
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ByteBuffer CoreDump::create_notes_threads_data() const
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{
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ByteBuffer threads_data;
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m_process.for_each_thread([&](Thread& thread) {
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ByteBuffer entry_buff;
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ELF::Core::NotesEntry entry {};
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entry.type = ELF::Core::NotesEntry::Type::ThreadInfo;
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ELF::Core::ThreadInfo info {};
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info.tid = thread.tid().value();
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Ptrace::copy_kernel_registers_into_ptrace_registers(info.regs, thread.get_register_dump_from_stack());
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entry_buff.append((void*)&entry, sizeof(entry));
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entry_buff.append((void*)&info, sizeof(info));
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threads_data += entry_buff;
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return IterationDecision::Continue;
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});
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return threads_data;
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}
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ByteBuffer CoreDump::create_notes_regions_data() const
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{
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ByteBuffer regions_data;
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for (size_t region_index = 0; region_index < m_process.m_regions.size(); ++region_index) {
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ELF::Core::NotesEntry entry {};
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entry.type = ELF::Core::NotesEntry::Type::MemoryRegionInfo;
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ByteBuffer memory_region_info_buffer;
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ELF::Core::MemoryRegionInfo info {};
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auto& region = m_process.m_regions[region_index];
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info.region_start = reinterpret_cast<uint32_t>(region.vaddr().as_ptr());
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info.region_end = reinterpret_cast<uint32_t>(region.vaddr().as_ptr() + region.size());
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info.region_start = info.program_header_index;
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memory_region_info_buffer.append((void*)&info, sizeof(info));
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auto name = region.name();
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if (name.is_null())
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name = String::empty();
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memory_region_info_buffer.append(name.characters(), name.length() + 1);
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regions_data.append((void*)&entry, sizeof(entry));
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regions_data += memory_region_info_buffer;
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}
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return regions_data;
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}
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ByteBuffer CoreDump::create_notes_segment_data() const
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{
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ByteBuffer notes_buffer;
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notes_buffer += create_notes_threads_data();
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notes_buffer += create_notes_regions_data();
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ELF::Core::NotesEntry null_entry {};
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null_entry.type = ELF::Core::NotesEntry::Type::Null;
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notes_buffer.append(&null_entry, sizeof(null_entry));
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return notes_buffer;
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}
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void CoreDump::write()
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{
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ProcessPagingScope scope(m_process);
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ByteBuffer notes_segment = create_notes_segment_data();
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write_elf_header();
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write_program_headers(notes_segment.size());
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write_regions();
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write_notes_segment(notes_segment);
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(void)m_fd->chmod(0400); // Make coredump file readable
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}
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}
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