mirror of
https://github.com/oxen-io/lokinet.git
synced 2024-11-05 21:20:38 +00:00
175 lines
6.9 KiB
C++
175 lines
6.9 KiB
C++
//
|
|
// Copyright 2018 The Abseil Authors.
|
|
//
|
|
// Licensed under the Apache License, Version 2.0 (the "License");
|
|
// you may not use this file except in compliance with the License.
|
|
// You may obtain a copy of the License at
|
|
//
|
|
// http://www.apache.org/licenses/LICENSE-2.0
|
|
//
|
|
// Unless required by applicable law or agreed to in writing, software
|
|
// distributed under the License is distributed on an "AS IS" BASIS,
|
|
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
// See the License for the specific language governing permissions and
|
|
// limitations under the License.
|
|
|
|
#include "absl/debugging/internal/stack_consumption.h"
|
|
|
|
#ifdef ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
|
|
|
|
#include <signal.h>
|
|
#include <sys/mman.h>
|
|
#include <unistd.h>
|
|
|
|
#include <string.h>
|
|
|
|
#include "absl/base/attributes.h"
|
|
#include "absl/base/internal/raw_logging.h"
|
|
|
|
namespace absl {
|
|
inline namespace lts_2018_12_18 {
|
|
namespace debugging_internal {
|
|
namespace {
|
|
|
|
// This code requires that we know the direction in which the stack
|
|
// grows. It is commonly believed that this can be detected by putting
|
|
// a variable on the stack and then passing its address to a function
|
|
// that compares the address of this variable to the address of a
|
|
// variable on the function's own stack. However, this is unspecified
|
|
// behavior in C++: If two pointers p and q of the same type point to
|
|
// different objects that are not members of the same object or
|
|
// elements of the same array or to different functions, or if only
|
|
// one of them is null, the results of p<q, p>q, p<=q, and p>=q are
|
|
// unspecified. Therefore, instead we hardcode the direction of the
|
|
// stack on platforms we know about.
|
|
#if defined(__i386__) || defined(__x86_64__) || defined(__ppc__)
|
|
constexpr bool kStackGrowsDown = true;
|
|
#else
|
|
#error Need to define kStackGrowsDown
|
|
#endif
|
|
|
|
// To measure the stack footprint of some code, we create a signal handler
|
|
// (for SIGUSR2 say) that exercises this code on an alternate stack. This
|
|
// alternate stack is initialized to some known pattern (0x55, 0x55, 0x55,
|
|
// ...). We then self-send this signal, and after the signal handler returns,
|
|
// look at the alternate stack buffer to see what portion has been touched.
|
|
//
|
|
// This trick gives us the the stack footprint of the signal handler. But the
|
|
// signal handler, even before the code for it is exercised, consumes some
|
|
// stack already. We however only want the stack usage of the code inside the
|
|
// signal handler. To measure this accurately, we install two signal handlers:
|
|
// one that does nothing and just returns, and the user-provided signal
|
|
// handler. The difference between the stack consumption of these two signals
|
|
// handlers should give us the stack foorprint of interest.
|
|
|
|
void EmptySignalHandler(int) {}
|
|
|
|
// This is arbitrary value, and could be increase further, at the cost of
|
|
// memset()ting it all to known sentinel value.
|
|
constexpr int kAlternateStackSize = 64 << 10; // 64KiB
|
|
|
|
constexpr int kSafetyMargin = 32;
|
|
constexpr char kAlternateStackFillValue = 0x55;
|
|
|
|
// These helper functions look at the alternate stack buffer, and figure
|
|
// out what portion of this buffer has been touched - this is the stack
|
|
// consumption of the signal handler running on this alternate stack.
|
|
// This function will return -1 if the alternate stack buffer has not been
|
|
// touched. It will abort the program if the buffer has overflowed or is about
|
|
// to overflow.
|
|
int GetStackConsumption(const void* const altstack) {
|
|
const char* begin;
|
|
int increment;
|
|
if (kStackGrowsDown) {
|
|
begin = reinterpret_cast<const char*>(altstack);
|
|
increment = 1;
|
|
} else {
|
|
begin = reinterpret_cast<const char*>(altstack) + kAlternateStackSize - 1;
|
|
increment = -1;
|
|
}
|
|
|
|
for (int usage_count = kAlternateStackSize; usage_count > 0; --usage_count) {
|
|
if (*begin != kAlternateStackFillValue) {
|
|
ABSL_RAW_CHECK(usage_count <= kAlternateStackSize - kSafetyMargin,
|
|
"Buffer has overflowed or is about to overflow");
|
|
return usage_count;
|
|
}
|
|
begin += increment;
|
|
}
|
|
|
|
ABSL_RAW_LOG(FATAL, "Unreachable code");
|
|
return -1;
|
|
}
|
|
|
|
} // namespace
|
|
|
|
int GetSignalHandlerStackConsumption(void (*signal_handler)(int)) {
|
|
// The alt-signal-stack cannot be heap allocated because there is a
|
|
// bug in glibc-2.2 where some signal handler setup code looks at the
|
|
// current stack pointer to figure out what thread is currently running.
|
|
// Therefore, the alternate stack must be allocated from the main stack
|
|
// itself.
|
|
void* altstack = mmap(nullptr, kAlternateStackSize, PROT_READ | PROT_WRITE,
|
|
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
|
|
ABSL_RAW_CHECK(altstack != MAP_FAILED, "mmap() failed");
|
|
|
|
// Set up the alt-signal-stack (and save the older one).
|
|
stack_t sigstk;
|
|
memset(&sigstk, 0, sizeof(sigstk));
|
|
stack_t old_sigstk;
|
|
sigstk.ss_sp = altstack;
|
|
sigstk.ss_size = kAlternateStackSize;
|
|
sigstk.ss_flags = 0;
|
|
ABSL_RAW_CHECK(sigaltstack(&sigstk, &old_sigstk) == 0,
|
|
"sigaltstack() failed");
|
|
|
|
// Set up SIGUSR1 and SIGUSR2 signal handlers (and save the older ones).
|
|
struct sigaction sa;
|
|
memset(&sa, 0, sizeof(sa));
|
|
struct sigaction old_sa1, old_sa2;
|
|
sigemptyset(&sa.sa_mask);
|
|
sa.sa_flags = SA_ONSTACK;
|
|
|
|
// SIGUSR1 maps to EmptySignalHandler.
|
|
sa.sa_handler = EmptySignalHandler;
|
|
ABSL_RAW_CHECK(sigaction(SIGUSR1, &sa, &old_sa1) == 0, "sigaction() failed");
|
|
|
|
// SIGUSR2 maps to signal_handler.
|
|
sa.sa_handler = signal_handler;
|
|
ABSL_RAW_CHECK(sigaction(SIGUSR2, &sa, &old_sa2) == 0, "sigaction() failed");
|
|
|
|
// Send SIGUSR1 signal and measure the stack consumption of the empty
|
|
// signal handler.
|
|
// The first signal might use more stack space. Run once and ignore the
|
|
// results to get that out of the way.
|
|
ABSL_RAW_CHECK(kill(getpid(), SIGUSR1) == 0, "kill() failed");
|
|
|
|
memset(altstack, kAlternateStackFillValue, kAlternateStackSize);
|
|
ABSL_RAW_CHECK(kill(getpid(), SIGUSR1) == 0, "kill() failed");
|
|
int base_stack_consumption = GetStackConsumption(altstack);
|
|
|
|
// Send SIGUSR2 signal and measure the stack consumption of signal_handler.
|
|
ABSL_RAW_CHECK(kill(getpid(), SIGUSR2) == 0, "kill() failed");
|
|
int signal_handler_stack_consumption = GetStackConsumption(altstack);
|
|
|
|
// Now restore the old alt-signal-stack and signal handlers.
|
|
ABSL_RAW_CHECK(sigaltstack(&old_sigstk, nullptr) == 0,
|
|
"sigaltstack() failed");
|
|
ABSL_RAW_CHECK(sigaction(SIGUSR1, &old_sa1, nullptr) == 0,
|
|
"sigaction() failed");
|
|
ABSL_RAW_CHECK(sigaction(SIGUSR2, &old_sa2, nullptr) == 0,
|
|
"sigaction() failed");
|
|
|
|
ABSL_RAW_CHECK(munmap(altstack, kAlternateStackSize) == 0, "munmap() failed");
|
|
if (signal_handler_stack_consumption != -1 && base_stack_consumption != -1) {
|
|
return signal_handler_stack_consumption - base_stack_consumption;
|
|
}
|
|
return -1;
|
|
}
|
|
|
|
} // namespace debugging_internal
|
|
} // inline namespace lts_2018_12_18
|
|
} // namespace absl
|
|
|
|
#endif // ABSL_INTERNAL_HAVE_DEBUGGING_STACK_CONSUMPTION
|