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/*
* Copyright (C) 2003-2019 Apple Inc. All rights reserved.
* Copyright (C) 2007 Eric Seidel <eric@webkit.org>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
#include "config.h"
#include <wtf/StackBounds.h>
#if OS(DARWIN)
#include <pthread.h>
#elif OS(WINDOWS)
#include <windows.h>
#elif OS(UNIX) || OS(HAIKU)
#include <pthread.h>
#if HAVE(PTHREAD_NP_H)
#include <pthread_np.h>
#endif
#if OS(LINUX)
#include <sys/resource.h>
#include <sys/syscall.h>
#include <unistd.h>
#endif
#if OS(QNX)
#include <sys/storage.h>
#endif
#endif
namespace WTF {
#if OS(DARWIN)
StackBounds StackBounds::newThreadStackBounds(PlatformThreadHandle thread)
{
void* origin = pthread_get_stackaddr_np(thread);
rlim_t size = pthread_get_stacksize_np(thread);
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
void* bound = static_cast<char*>(origin) - size;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
return StackBounds { origin, bound };
}
StackBounds StackBounds::currentThreadStackBoundsInternal()
{
if (pthread_main_np()) {
// FIXME: <rdar://problem/13741204>
// pthread_get_size lies to us when we're the main thread, use get_rlimit instead
void* origin = pthread_get_stackaddr_np(pthread_self());
rlimit limit;
getrlimit(RLIMIT_STACK, &limit);
rlim_t size = limit.rlim_cur;
if (size == RLIM_INFINITY)
size = 8 * MB;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
void* bound = static_cast<char*>(origin) - size;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
return StackBounds { origin, bound };
}
return newThreadStackBounds(pthread_self());
}
#elif OS(QNX)
StackBounds StackBounds::currentThreadStackBoundsInternal()
{
struct _thread_local_storage* tls = __tls();
void* bound = tls->__stackaddr;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
void* origin = static_cast<char*>(bound) + tls->__stacksize;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
return StackBounds { origin, bound };
}
#elif OS(UNIX) || OS(HAIKU)
#if OS(OPENBSD)
StackBounds StackBounds::newThreadStackBounds(PlatformThreadHandle thread)
{
stack_t stack;
pthread_stackseg_np(thread, &stack);
void* origin = stack.ss_sp;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
void* bound = static_cast<char*>(origin) - stack.ss_size;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
return StackBounds { origin, bound };
}
#else // !OS(OPENBSD)
StackBounds StackBounds::newThreadStackBounds(PlatformThreadHandle thread)
{
void* bound = nullptr;
size_t stackSize = 0;
pthread_attr_t sattr;
pthread_attr_init(&sattr);
#if HAVE(PTHREAD_NP_H) || OS(NETBSD)
// e.g. on FreeBSD 5.4, neundorf@kde.org
pthread_attr_get_np(thread, &sattr);
#else
// FIXME: this function is non-portable; other POSIX systems may have different np alternatives
pthread_getattr_np(thread, &sattr);
#endif
int rc = pthread_attr_getstack(&sattr, &bound, &stackSize);
UNUSED_PARAM(rc);
ASSERT(bound);
pthread_attr_destroy(&sattr);
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
void* origin = static_cast<char*>(bound) + stackSize;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
// pthread_attr_getstack's bound is the lowest accessible pointer of the stack.
return StackBounds { origin, bound };
}
#endif // OS(OPENBSD)
StackBounds StackBounds::currentThreadStackBoundsInternal()
{
auto ret = newThreadStackBounds(pthread_self());
#if OS(LINUX)
// on glibc, pthread_attr_getstack will generally return the limit size (minus a guard page)
// for the main thread; this is however not necessarily always true on every libc - for example
// on musl, it will return the currently reserved size - since the stack bounds are expected to
// be constant (and they are for every thread except main, which is allowed to grow), check
// resource limits and use that as the boundary instead (and prevent stack overflows in JSC)
if (getpid() == static_cast<pid_t>(syscall(SYS_gettid))) {
void* origin = ret.origin();
rlimit limit;
getrlimit(RLIMIT_STACK, &limit);
rlim_t size = limit.rlim_cur;
if (size == RLIM_INFINITY)
size = 8 * MB;
// account for a guard page
size -= static_cast<rlim_t>(sysconf(_SC_PAGESIZE));
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
void* bound = static_cast<char*>(origin) - size;
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
static char** oldestEnviron = environ;
// In 32bit architecture, it is possible that environment variables are having a characters which looks like a pointer,
// and conservative GC will find it as a live pointer. We would like to avoid that to precisely exclude non user stack
// data region from this stack bounds. As the article (https://lwn.net/Articles/631631/) and the elf loader implementation
// explain how Linux main thread stack is organized, environment variables vector is placed on the stack, so we can exclude
// environment variables if we use `environ` global variable as a origin of the stack.
// But `setenv` / `putenv` may alter `environ` variable's content. So we record the oldest `environ` variable content, and use it.
StackBounds stackBounds { origin, bound };
if (stackBounds.contains(oldestEnviron))
stackBounds = { oldestEnviron, bound };
return stackBounds;
}
#endif
return ret;
}
#elif OS(WINDOWS)
// GetCurrentThreadStackLimits returns OS-maintained stack limits that are:
// - Independent of guard page state
// - Independent of VirtualQuery results
// - Accurate regardless of stack memory layout
//
// This replaces the previous VirtualQuery-based implementation which assumed
// a 3-layer stack structure (uncommitted -> guard -> committed). That approach
// could fail when:
// - Guard pages were consumed by other threads
// - Security software interfered with memory scanning
// - Stacks were fully committed with no uncommitted region
// - Embedded scenarios (e.g., Ruby Bug #11438)
//
// Reference:
// https://learn.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-getcurrentthreadstacklimits
StackBounds StackBounds::currentThreadStackBoundsInternal()
{
ULONG_PTR lowLimit = 0;
ULONG_PTR highLimit = 0;
GetCurrentThreadStackLimits(&lowLimit, &highLimit);
void* origin = reinterpret_cast<void*>(highLimit);
void* bound = reinterpret_cast<void*>(lowLimit);
return StackBounds { origin, bound };
}
#else
#error Need a way to get the stack bounds on this platform
#endif
} // namespace WTF
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