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Merge "Add explicit state for heapprofd hooking."

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Florian Mayer 2020-03-12 17:12:17 +00:00 committed by Gerrit Code Review
commit c84d295f7c
1 changed files with 195 additions and 102 deletions
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269
libc/bionic/malloc_heapprofd.cpp
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@ -48,48 +48,104 @@
#include "malloc_heapprofd.h"
#include "malloc_limit.h"
// Installing heapprofd hooks is a multi step process, as outlined below.
//
// The incremental hooking and a dedicated task thread are used since we cannot
// do heavy work within a signal handler, or when blocking a malloc invocation.
//
// +--->+-------------+------------------+
// | +->+kInitialState+----------------+ | malloc functions are not intercepted in any way.
// | | +-------+-----+ | |
// | | | | |
// | | v | |
// | | +-------+----------------+ | | currently installing the ephemeral hooks.
// | | |kInstallingEphemeralHook|<--+ | |
// | | +-------+----------------+ | | |
// | | | | | |
// | | v | | |
// | | +-------+---------------+ | | | ephemeral hooks are installed. on the first call to
// | | |kEphemeralHookInstalled| | | | malloc these hooks spawn a thread that installs the
// | | +-------+---------------+ | | | heapprofd hooks.
// | | | | | |
// | | v | | |
// | | +-------+--------------+ | | | first call to malloc happened. the hooks are reset to
// | +--|kRemovingEphemeralHook| | | | kInitialState.
// | +----------------------+ | | |
// | | | |
// | | | |
// | +---------------+ | | | currently installing the heapprofd hook
// | |kInstallingHook|<-----------|-+ |
// | +-------+-------+ | |
// | | | |
// | v | |
// | +-------+------+ | | heapprofd hooks are installed. these forward calls to
// | |kHookInstalled|-------------+ | malloc / free / etc. to heapprofd_client.so.
// | +-------+------+ |
// | | |
// | v |
// | +-------+---------+ | currently resetting the hooks to default.
// |----+kUninstallingHook| |
// +-----------------+ |
// |
// |
// +------------------+ | malloc debug / malloc hooks are active. these take
// |kIncompatibleHooks+<------------+ precendence over heapprofd, so heapprofd will not get
// +------------------+ enabled. this is a terminal state.
//
enum MallocHeapprofdState : uint8_t {
kInitialState,
kInstallingEphemeralHook,
kEphemeralHookInstalled,
kRemovingEphemeralHook,
kInstallingHook,
kHookInstalled,
kUninstallingHook,
kIncompatibleHooks
};
enum ModifyGlobalsMode {
kWithLock, // all calls to MaybeModifyGlobals with kWithLock will serialise. they can fail
// due to a concurrent call with kWithoutLock.
kWithoutLock // calls to MaybeModifyGlobals with kWithoutLock do not serialise. they can fail
// due to concurrent calls with kWithoutLock or kWithLock.
};
// Provide mutual exclusion so no two threads try to modify the globals at the same time.
template <typename Fn>
bool MaybeModifyGlobals(ModifyGlobalsMode mode, Fn f) {
bool success = false;
if (mode == kWithLock) {
pthread_mutex_lock(&gGlobalsMutateLock);
}
// As we have grabbed the mutex, the following condition should always hold, except
// if we are currently running HandleHeapprofdSignal.
if (!atomic_exchange(&gGlobalsMutating, true)) {
f();
success = true;
atomic_store(&gGlobalsMutating, false);
} else {
error_log("%s: heapprofd client: concurrent modification.", getprogname());
}
if (mode == kWithLock) {
pthread_mutex_unlock(&gGlobalsMutateLock);
}
return success;
}
extern "C" void* MallocInitHeapprofdHook(size_t);
static constexpr char kHeapprofdSharedLib[] = "heapprofd_client.so";
static constexpr char kHeapprofdPrefix[] = "heapprofd";
static constexpr char kHeapprofdPropertyEnable[] = "heapprofd.enable";
// The logic for triggering heapprofd (at runtime) is as follows:
// 1. A reserved profiling signal is received by the process, its si_value
// discriminating between different handlers. For the case of heapprofd,
// HandleHeapprofdSignal is called.
// 2. If the initialization is not already in flight
// (gHeapprofdInitInProgress is false), the malloc hook is set to
// point at InitHeapprofdHook, and gHeapprofdInitInProgress is set to
// true.
// 3. The next malloc call enters InitHeapprofdHook, which removes the malloc
// hook, and spawns a detached pthread to run the InitHeapprofd task.
// (gHeapprofdInitHookInstalled atomic is used to perform this once.)
// 4. InitHeapprofd, on a dedicated pthread, loads the heapprofd client library,
// installs the full set of heapprofd hooks, and invokes the client's
// initializer. The dedicated pthread then terminates.
// 5. gHeapprofdInitInProgress and gHeapprofdInitHookInstalled are
// reset to false such that heapprofd can be reinitialized. Reinitialization
// means that a new profiling session is started, and any still active is
// torn down.
//
// The incremental hooking and a dedicated task thread are used since we cannot
// do heavy work within a signal handler, or when blocking a malloc invocation.
constexpr char kHeapprofdProgramPropertyPrefix[] = "heapprofd.enable.";
constexpr size_t kHeapprofdProgramPropertyPrefixSize = sizeof(kHeapprofdProgramPropertyPrefix) - 1;
constexpr size_t kMaxCmdlineSize = 512;
// The handle returned by dlopen when previously loading the heapprofd
// hooks. nullptr if shared library has not been already been loaded.
static _Atomic (void*) gHeapprofdHandle = nullptr;
static _Atomic bool gHeapprofdInitInProgress = false;
static _Atomic bool gHeapprofdInitHookInstalled = false;
// Set to true if the process has enabled malloc_debug or malloc_hooks, which
// are incompatible (and take precedence over) heapprofd.
static _Atomic bool gHeapprofdIncompatibleHooks = false;
extern "C" void* MallocInitHeapprofdHook(size_t);
constexpr char kHeapprofdProgramPropertyPrefix[] = "heapprofd.enable.";
constexpr size_t kHeapprofdProgramPropertyPrefixSize = sizeof(kHeapprofdProgramPropertyPrefix) - 1;
constexpr size_t kMaxCmdlineSize = 512;
static _Atomic MallocHeapprofdState gHeapprofdState = kInitialState;
static bool GetHeapprofdProgramProperty(char* data, size_t size) {
if (size < kHeapprofdProgramPropertyPrefixSize) {
@ -157,22 +213,29 @@ static bool GetHeapprofdProgramProperty(char* data, size_t size) {
// Previously installed default dispatch table, if it exists. This is used to
// load heapprofd properly when GWP-ASan was already installed. If GWP-ASan was
// already installed, heapprofd will take over the dispatch table, but will use
// GWP-ASan as the backing dispatch. This variable is atomically protected by
// gHeapprofdInitInProgress.
static const MallocDispatch* gPreviousDefaultDispatchTable = nullptr;
// GWP-ASan as the backing dispatch. Writes to this variable is atomically
// protected by MaybeModifyGlobals.
// Reads are not protected, so this is atomic. We cannot fail the call in
// MallocInitHeapprofdHook.
static _Atomic (const MallocDispatch*) gPreviousDefaultDispatchTable = nullptr;
static MallocDispatch gEphemeralDispatch;
void HandleHeapprofdSignal() {
if (atomic_load_explicit(&gHeapprofdIncompatibleHooks, memory_order_acquire)) {
if (atomic_load(&gHeapprofdState) == kIncompatibleHooks) {
error_log("%s: not enabling heapprofd, malloc_debug/malloc_hooks are enabled.", getprogname());
return;
}
// Checking this variable is only necessary when this could conflict with
// the change to enable the allocation limit. All other places will
// not ever have a conflict modifying the globals.
if (!atomic_exchange(&gGlobalsMutating, true)) {
if (!atomic_exchange(&gHeapprofdInitInProgress, true)) {
// We cannot grab the mutex here, as this is used in a signal handler.
MaybeModifyGlobals(kWithoutLock, [] {
MallocHeapprofdState expected = kInitialState;
// If hooks are already installed, we still want to install ephemeral hooks to retrigger
// heapprofd client initialization.
MallocHeapprofdState expected2 = kHookInstalled;
if (atomic_compare_exchange_strong(&gHeapprofdState, &expected,
kInstallingEphemeralHook) ||
atomic_compare_exchange_strong(&gHeapprofdState, &expected2,
kInstallingEphemeralHook)) {
const MallocDispatch* default_dispatch = GetDefaultDispatchTable();
// Below, we initialize heapprofd lazily by redirecting libc's malloc() to
@ -185,7 +248,7 @@ void HandleHeapprofdSignal() {
// 1. No malloc hooking has been done (heapprofd, GWP-ASan, etc.). In
// this case, everything but malloc() should come from the system
// allocator.
gPreviousDefaultDispatchTable = nullptr;
atomic_store(&gPreviousDefaultDispatchTable, nullptr);
gEphemeralDispatch = *NativeAllocatorDispatch();
} else if (DispatchIsGwpAsan(default_dispatch)) {
// 2. GWP-ASan was installed. We should use GWP-ASan for everything but
@ -193,7 +256,7 @@ void HandleHeapprofdSignal() {
// installed. After heapprofd is finished installing, we will use
// GWP-ASan as heapprofd's backing allocator to allow heapprofd and
// GWP-ASan to coexist.
gPreviousDefaultDispatchTable = default_dispatch;
atomic_store(&gPreviousDefaultDispatchTable, default_dispatch);
gEphemeralDispatch = *default_dispatch;
} else {
// 3. It may be possible at this point in time that heapprofd is
@ -203,7 +266,7 @@ void HandleHeapprofdSignal() {
// We've checked that no other malloc interceptors are being used by
// validating `gHeapprofdIncompatibleHooks` above, so we don't need to
// worry about that case here.
gPreviousDefaultDispatchTable = nullptr;
atomic_store(&gPreviousDefaultDispatchTable, nullptr);
gEphemeralDispatch = *NativeAllocatorDispatch();
}
@ -218,9 +281,12 @@ void HandleHeapprofdSignal() {
atomic_store(&globals->current_dispatch_table, &gEphemeralDispatch);
}
});
atomic_store(&gHeapprofdState, kEphemeralHookInstalled);
} else {
error_log("%s: heapprofd: failed to transition kInitialState -> kInstallingEphemeralHook. "
"current state (possible race): %d", getprogname(), expected2);
}
atomic_store(&gGlobalsMutating, false);
}
});
// Otherwise, we're racing against malloc_limit's enable logic (at most once
// per process, and a niche feature). This is highly unlikely, so simply give
// up if it does happen.
@ -250,7 +316,7 @@ bool HeapprofdShouldLoad() {
}
void HeapprofdRememberHookConflict() {
atomic_store_explicit(&gHeapprofdIncompatibleHooks, true, memory_order_release);
atomic_store(&gHeapprofdState, kIncompatibleHooks);
}
static void CommonInstallHooks(libc_globals* globals) {
@ -268,68 +334,81 @@ static void CommonInstallHooks(libc_globals* globals) {
// Before we set the new default_dispatch_table in FinishInstallHooks, save
// the previous dispatch table. If DispatchReset() gets called later, we want
// to be able to restore the dispatch. We're still under
// gHeapprofdInitInProgress locks at this point.
gPreviousDefaultDispatchTable = GetDefaultDispatchTable();
// MaybeModifyGlobals locks at this point.
atomic_store(&gPreviousDefaultDispatchTable, GetDefaultDispatchTable());
if (FinishInstallHooks(globals, nullptr, kHeapprofdPrefix)) {
atomic_store(&gHeapprofdHandle, impl_handle);
} else if (!reusing_handle) {
dlclose(impl_handle);
}
atomic_store(&gHeapprofdInitInProgress, false);
}
void HeapprofdInstallHooksAtInit(libc_globals* globals) {
if (atomic_exchange(&gHeapprofdInitInProgress, true)) {
return;
}
MaybeModifyGlobals(kWithoutLock, [globals] {
MallocHeapprofdState expected = kInitialState;
if (atomic_compare_exchange_strong(&gHeapprofdState, &expected, kInstallingHook)) {
CommonInstallHooks(globals);
atomic_store(&gHeapprofdState, kHookInstalled);
} else {
error_log("%s: heapprofd: failed to transition kInitialState -> kInstallingHook. "
"current state (possible race): %d", getprogname(), expected);
}
});
}
static void* InitHeapprofd(void*) {
pthread_mutex_lock(&gGlobalsMutateLock);
MaybeModifyGlobals(kWithLock, [] {
MallocHeapprofdState expected = kInitialState;
if (atomic_compare_exchange_strong(&gHeapprofdState, &expected, kInstallingHook)) {
__libc_globals.mutate([](libc_globals* globals) {
CommonInstallHooks(globals);
});
pthread_mutex_unlock(&gGlobalsMutateLock);
// Allow to install hook again to re-initialize heap profiling after the
// current session finished.
atomic_store(&gHeapprofdInitHookInstalled, false);
atomic_store(&gHeapprofdState, kHookInstalled);
} else {
error_log("%s: heapprofd: failed to transition kInitialState -> kInstallingHook. "
"current state (possible race): %d", getprogname(), expected);
}
});
return nullptr;
}
extern "C" void* MallocInitHeapprofdHook(size_t bytes) {
if (!atomic_exchange(&gHeapprofdInitHookInstalled, true)) {
pthread_mutex_lock(&gGlobalsMutateLock);
MaybeModifyGlobals(kWithLock, [] {
MallocHeapprofdState expected = kEphemeralHookInstalled;
if (atomic_compare_exchange_strong(&gHeapprofdState, &expected, kRemovingEphemeralHook)) {
__libc_globals.mutate([](libc_globals* globals) {
atomic_store(&globals->default_dispatch_table, gPreviousDefaultDispatchTable);
const MallocDispatch* previous_dispatch = atomic_load(&gPreviousDefaultDispatchTable);
atomic_store(&globals->default_dispatch_table, previous_dispatch);
if (!MallocLimitInstalled()) {
atomic_store(&globals->current_dispatch_table, gPreviousDefaultDispatchTable);
atomic_store(&globals->current_dispatch_table, previous_dispatch);
}
});
pthread_mutex_unlock(&gGlobalsMutateLock);
atomic_store(&gHeapprofdState, kInitialState);
pthread_t thread_id;
if (pthread_create(&thread_id, nullptr, InitHeapprofd, nullptr) != 0) {
error_log("%s: heapprofd: failed to pthread_create.", getprogname());
} else if (pthread_setname_np(thread_id, "heapprofdinit") != 0) {
error_log("%s: heapprod: failed to pthread_setname_np", getprogname());
} else if (pthread_detach(thread_id) != 0) {
error_log("%s: heapprofd: failed to pthread_detach", getprogname());
}
if (pthread_setname_np(thread_id, "heapprofdinit") != 0) {
error_log("%s: heapprod: failed to pthread_setname_np", getprogname());
}
} else {
warning_log("%s: heapprofd: could not transition kEphemeralHookInstalled -> "
"kRemovingEphemeralHook. current state (possible race): %d. this can be benign "
"if two threads try this transition at the same time", getprogname(),
expected);
}
});
// If we had a previous dispatch table, use that to service the allocation,
// otherwise fall back to the native allocator.
// `gPreviousDefaultDispatchTable` won't change underneath us, as it's
// protected by the `gHeapProfdInitInProgress` lock (which we currently hold).
// The lock was originally taken by our caller in `HandleHeapprofdSignal()`,
// and will be released by `CommonInstallHooks()` via. our `InitHeapprofd()`
// thread that we just created.
if (gPreviousDefaultDispatchTable) {
return gPreviousDefaultDispatchTable->malloc(bytes);
// This could be modified by a concurrent HandleHeapprofdSignal, but that is
// benign as we will dispatch to the ephemeral handler, which will then dispatch
// to the underlying one.
const MallocDispatch* previous_dispatch = atomic_load(&gPreviousDefaultDispatchTable);
if (previous_dispatch) {
return previous_dispatch->malloc(bytes);
}
return NativeAllocatorDispatch()->malloc(bytes);
}
@ -345,20 +424,34 @@ bool HeapprofdInitZygoteChildProfiling() {
}
static bool DispatchReset() {
if (!atomic_exchange(&gHeapprofdInitInProgress, true)) {
pthread_mutex_lock(&gGlobalsMutateLock);
__libc_globals.mutate([](libc_globals* globals) {
atomic_store(&globals->default_dispatch_table, gPreviousDefaultDispatchTable);
if (!MallocLimitInstalled()) {
atomic_store(&globals->current_dispatch_table, gPreviousDefaultDispatchTable);
}
});
pthread_mutex_unlock(&gGlobalsMutateLock);
atomic_store(&gHeapprofdInitInProgress, false);
if (atomic_load(&gHeapprofdState) == kInitialState) {
return true;
}
bool success = false;
MaybeModifyGlobals(kWithLock, [&success] {
MallocHeapprofdState expected = kHookInstalled;
if(atomic_compare_exchange_strong(&gHeapprofdState, &expected, kUninstallingHook)){
__libc_globals.mutate([](libc_globals* globals) {
const MallocDispatch* previous_dispatch = atomic_load(&gPreviousDefaultDispatchTable);
atomic_store(&globals->default_dispatch_table, previous_dispatch);
if (!MallocLimitInstalled()) {
atomic_store(&globals->current_dispatch_table, previous_dispatch);
}
});
atomic_store(&gHeapprofdState, kInitialState);
success = true;
} else {
error_log("%s: heapprofd: failed to transition kHookInstalled -> kUninstallingHook. "
"current state (possible race): %d", getprogname(),
expected);
}
});
if (!success) {
errno = EAGAIN;
return false;
}
return success;
}
bool HeapprofdMallopt(int opcode, void* arg, size_t arg_size) {