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Kernel: Steer away from heap allocations for ProcFS process data

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Instead, use more static patterns to acquire that sort of data.
This commit is contained in:
Liav A 2021-08-10 20:51:28 +03:00 • committed by Andreas Kling
parent bf1adc2d5d
commit 7ba991dc37
11 changed files with 991 additions and 879 deletions
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147
Kernel/ProcessExposed.cpp
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@ -18,35 +18,77 @@ namespace Kernel {
static SpinLock<u8> s_index_lock;
static InodeIndex s_next_inode_index = 0;
static size_t s_allocate_inode_index()
namespace SegmentedProcFSIndex {
static InodeIndex __build_raw_segmented_index(u32 primary, u16 sub_directory, u32 property)
{
VERIFY(primary < 0x10000000);
VERIFY(property < 0x100000);
// Note: The sub-directory part is already limited to 0xFFFF, so no need to VERIFY it.
return static_cast<u64>((static_cast<u64>(primary) << 36) | (static_cast<u64>(sub_directory) << 20) | property);
}
static InodeIndex build_segmented_index_with_known_pid(ProcessID pid, u16 sub_directory, u32 property)
{
return __build_raw_segmented_index(pid.value() + 1, sub_directory, property);
}
static InodeIndex build_segmented_index_with_unknown_property(ProcessID pid, ProcessSubDirectory sub_directory, unsigned property)
{
return build_segmented_index_with_known_pid(pid, to_underlying(sub_directory), static_cast<u32>(property));
}
InodeIndex build_segmented_index_for_pid_directory(ProcessID pid)
{
return build_segmented_index_with_unknown_property(pid, ProcessSubDirectory::Reserved, to_underlying(MainProcessProperty::Reserved));
}
InodeIndex build_segmented_index_for_sub_directory(ProcessID pid, ProcessSubDirectory sub_directory)
{
return build_segmented_index_with_unknown_property(pid, sub_directory, to_underlying(MainProcessProperty::Reserved));
}
InodeIndex build_segmented_index_for_main_property(ProcessID pid, ProcessSubDirectory sub_directory, MainProcessProperty property)
{
return build_segmented_index_with_known_pid(pid, to_underlying(sub_directory), to_underlying(property));
}
InodeIndex build_segmented_index_for_main_property_in_pid_directory(ProcessID pid, MainProcessProperty property)
{
return build_segmented_index_with_known_pid(pid, to_underlying(ProcessSubDirectory::Reserved), to_underlying(property));
}
InodeIndex build_segmented_index_for_thread_stack(ProcessID pid, ThreadID thread_id)
{
return build_segmented_index_with_unknown_property(pid, ProcessSubDirectory::Stacks, thread_id.value());
}
InodeIndex build_segmented_index_for_file_description(ProcessID pid, unsigned fd)
{
return build_segmented_index_with_unknown_property(pid, ProcessSubDirectory::FileDescriptions, fd);
}
}
static size_t s_allocate_global_inode_index()
{
ScopedSpinLock lock(s_index_lock);
s_next_inode_index = s_next_inode_index.value() + 1;
// Note: Global ProcFS indices must be above 0 and up to maximum of what 36 bit (2 ^ 36 - 1) can represent.
VERIFY(s_next_inode_index > 0);
VERIFY(s_next_inode_index < 0x100000000);
return s_next_inode_index.value();
}
InodeIndex ProcFSComponentRegistry::allocate_inode_index() const
ProcFSExposedComponent::ProcFSExposedComponent()
{
return s_allocate_inode_index();
}
ProcFSExposedComponent::ProcFSExposedComponent(StringView name)
: m_component_index(s_allocate_inode_index())
: m_component_index(s_allocate_global_inode_index())
{
m_name = KString::try_create(name);
}
// Note: This constructor is intended to be used in /proc/pid/fd/* symlinks
// so we preallocated inode index for them so we just need to set it here.
ProcFSExposedComponent::ProcFSExposedComponent(StringView name, InodeIndex preallocated_index)
: m_component_index(preallocated_index.value())
{
VERIFY(preallocated_index.value() != 0);
VERIFY(preallocated_index <= s_next_inode_index);
m_name = KString::try_create(name);
}
ProcFSExposedDirectory::ProcFSExposedDirectory(StringView name)
: ProcFSExposedComponent(name)
{
@ -62,16 +104,6 @@ ProcFSExposedLink::ProcFSExposedLink(StringView name)
: ProcFSExposedComponent(name)
{
}
ProcFSExposedLink::ProcFSExposedLink(StringView name, InodeIndex preallocated_index)
: ProcFSExposedComponent(name, preallocated_index)
{
}
struct ProcFSInodeData : public FileDescriptionData {
OwnPtr<KBuffer> buffer;
};
KResultOr<size_t> ProcFSGlobalInformation::read_bytes(off_t offset, size_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
{
dbgln_if(PROCFS_DEBUG, "ProcFSGlobalInformation @ {}: read_bytes offset: {} count: {}", name(), offset, count);
@ -121,71 +153,6 @@ KResult ProcFSGlobalInformation::refresh_data(FileDescription& description) cons
return KSuccess;
}
KResultOr<size_t> ProcFSProcessInformation::read_bytes(off_t offset, size_t count, UserOrKernelBuffer& buffer, FileDescription* description) const
{
dbgln_if(PROCFS_DEBUG, "ProcFSProcessInformation @ {}: read_bytes offset: {} count: {}", name(), offset, count);
VERIFY(offset >= 0);
VERIFY(buffer.user_or_kernel_ptr());
if (!description)
return KResult(EIO);
if (!description->data()) {
dbgln("ProcFSGlobalInformation: Do not have cached data!");
return KResult(EIO);
}
MutexLocker locker(m_refresh_lock);
auto& typed_cached_data = static_cast<ProcFSInodeData&>(*description->data());
auto& data_buffer = typed_cached_data.buffer;
if (!data_buffer || (size_t)offset >= data_buffer->size())
return 0;
ssize_t nread = min(static_cast<off_t>(data_buffer->size() - offset), static_cast<off_t>(count));
if (!buffer.write(data_buffer->data() + offset, nread))
return KResult(EFAULT);
return nread;
}
KResult ProcFSProcessInformation::refresh_data(FileDescription& description) const
{
// For process-specific inodes, hold the process's ptrace lock across refresh
// and refuse to load data if the process is not dumpable.
// Without this, files opened before a process went non-dumpable could still be used for dumping.
auto parent_directory = const_cast<ProcFSProcessInformation&>(*this).m_parent_directory.strong_ref();
if (parent_directory.is_null())
return KResult(EINVAL);
auto process = parent_directory->associated_process();
if (!process)
return KResult(ESRCH);
process->ptrace_lock().lock();
if (!process->is_dumpable()) {
process->ptrace_lock().unlock();
return EPERM;
}
ScopeGuard guard = [&] {
process->ptrace_lock().unlock();
};
MutexLocker locker(m_refresh_lock);
auto& cached_data = description.data();
if (!cached_data) {
cached_data = adopt_own_if_nonnull(new (nothrow) ProcFSInodeData);
if (!cached_data)
return ENOMEM;
}
KBufferBuilder builder;
if (!const_cast<ProcFSProcessInformation&>(*this).output(builder))
return ENOENT;
auto& typed_cached_data = static_cast<ProcFSInodeData&>(*cached_data);
typed_cached_data.buffer = builder.build();
if (!typed_cached_data.buffer)
return ENOMEM;
return KSuccess;
}
KResultOr<size_t> ProcFSExposedLink::read_bytes(off_t offset, size_t count, UserOrKernelBuffer& buffer, FileDescription*) const
{
VERIFY(offset == 0);
@ -210,7 +177,7 @@ NonnullRefPtr<Inode> ProcFSExposedLink::to_inode(const ProcFS& procfs_instance)
NonnullRefPtr<Inode> ProcFSExposedComponent::to_inode(const ProcFS& procfs_instance) const
{
return ProcFSInode::create(procfs_instance, *this);
return ProcFSGlobalInode::create(procfs_instance, *this);
}
NonnullRefPtr<Inode> ProcFSExposedDirectory::to_inode(const ProcFS& procfs_instance) const