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glibc/nptl/allocatestack.c

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/* Copyright (C) 2002-2019 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
The GNU C 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 2.1 of the License, or (at your option) any later version.
The GNU C 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 the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <assert.h>
#include <errno.h>
#include <signal.h>
#include <stdint.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/param.h>
#include <dl-sysdep.h>
#include <dl-tls.h>
#include <tls.h>
#include <list.h>
#include <lowlevellock.h>
#include <futex-internal.h>
#include <kernel-features.h>
#include <stack-aliasing.h>
#ifndef NEED_SEPARATE_REGISTER_STACK
/* Most architectures have exactly one stack pointer. Some have more. */
# define STACK_VARIABLES void *stackaddr = NULL
/* How to pass the values to the 'create_thread' function. */
# define STACK_VARIABLES_ARGS stackaddr
/* How to declare function which gets there parameters. */
# define STACK_VARIABLES_PARMS void *stackaddr
/* How to declare allocate_stack. */
# define ALLOCATE_STACK_PARMS void **stack
/* This is how the function is called. We do it this way to allow
other variants of the function to have more parameters. */
# define ALLOCATE_STACK(attr, pd) allocate_stack (attr, pd, &stackaddr)
#else
/* We need two stacks. The kernel will place them but we have to tell
the kernel about the size of the reserved address space. */
# define STACK_VARIABLES void *stackaddr = NULL; size_t stacksize = 0
/* How to pass the values to the 'create_thread' function. */
# define STACK_VARIABLES_ARGS stackaddr, stacksize
/* How to declare function which gets there parameters. */
# define STACK_VARIABLES_PARMS void *stackaddr, size_t stacksize
/* How to declare allocate_stack. */
# define ALLOCATE_STACK_PARMS void **stack, size_t *stacksize
/* This is how the function is called. We do it this way to allow
other variants of the function to have more parameters. */
# define ALLOCATE_STACK(attr, pd) \
allocate_stack (attr, pd, &stackaddr, &stacksize)
#endif
/* Default alignment of stack. */
#ifndef STACK_ALIGN
# define STACK_ALIGN __alignof__ (long double)
#endif
/* Default value for minimal stack size after allocating thread
descriptor and guard. */
#ifndef MINIMAL_REST_STACK
# define MINIMAL_REST_STACK 4096
#endif
/* Newer kernels have the MAP_STACK flag to indicate a mapping is used for
a stack. Use it when possible. */
#ifndef MAP_STACK
# define MAP_STACK 0
#endif
/* This yields the pointer that TLS support code calls the thread pointer. */
#if TLS_TCB_AT_TP
# define TLS_TPADJ(pd) (pd)
#elif TLS_DTV_AT_TP
# define TLS_TPADJ(pd) ((struct pthread *)((char *) (pd) + TLS_PRE_TCB_SIZE))
#endif
/* Cache handling for not-yet free stacks. */
/* Maximum size in kB of cache. */
static size_t stack_cache_maxsize = 40 * 1024 * 1024; /* 40MiBi by default. */
static size_t stack_cache_actsize;
/* Mutex protecting this variable. */
static int stack_cache_lock = LLL_LOCK_INITIALIZER;
/* List of queued stack frames. */
static LIST_HEAD (stack_cache);
/* List of the stacks in use. */
static LIST_HEAD (stack_used);
/* We need to record what list operations we are going to do so that,
in case of an asynchronous interruption due to a fork() call, we
can correct for the work. */
static uintptr_t in_flight_stack;
/* List of the threads with user provided stacks in use. No need to
initialize this, since it's done in __pthread_initialize_minimal. */
list_t __stack_user __attribute__ ((nocommon));
hidden_data_def (__stack_user)
/* Check whether the stack is still used or not. */
#define FREE_P(descr) ((descr)->tid <= 0)
static void
stack_list_del (list_t *elem)
{
in_flight_stack = (uintptr_t) elem;
atomic_write_barrier ();
list_del (elem);
atomic_write_barrier ();
in_flight_stack = 0;
}
static void
stack_list_add (list_t *elem, list_t *list)
{
in_flight_stack = (uintptr_t) elem | 1;
atomic_write_barrier ();
list_add (elem, list);
atomic_write_barrier ();
in_flight_stack = 0;
}
/* We create a double linked list of all cache entries. Double linked
because this allows removing entries from the end. */
/* Get a stack frame from the cache. We have to match by size since
some blocks might be too small or far too large. */
static struct pthread *
get_cached_stack (size_t *sizep, void **memp)
{
size_t size = *sizep;
struct pthread *result = NULL;
list_t *entry;
lll_lock (stack_cache_lock, LLL_PRIVATE);
/* Search the cache for a matching entry. We search for the
smallest stack which has at least the required size. Note that
in normal situations the size of all allocated stacks is the
same. As the very least there are only a few different sizes.
Therefore this loop will exit early most of the time with an
exact match. */
list_for_each (entry, &stack_cache)
{
struct pthread *curr;
curr = list_entry (entry, struct pthread, list);
if (FREE_P (curr) && curr->stackblock_size >= size)
{
if (curr->stackblock_size == size)
{
result = curr;
break;
}
if (result == NULL
|| result->stackblock_size > curr->stackblock_size)
result = curr;
}
}
if (__builtin_expect (result == NULL, 0)
/* Make sure the size difference is not too excessive. In that
case we do not use the block. */
|| __builtin_expect (result->stackblock_size > 4 * size, 0))
{
/* Release the lock. */
lll_unlock (stack_cache_lock, LLL_PRIVATE);
return NULL;
}
/* Don't allow setxid until cloned. */
result->setxid_futex = -1;
/* Dequeue the entry. */
stack_list_del (&result->list);
/* And add to the list of stacks in use. */
stack_list_add (&result->list, &stack_used);
/* And decrease the cache size. */
stack_cache_actsize -= result->stackblock_size;
/* Release the lock early. */
lll_unlock (stack_cache_lock, LLL_PRIVATE);
/* Report size and location of the stack to the caller. */
*sizep = result->stackblock_size;
*memp = result->stackblock;
/* Cancellation handling is back to the default. */
result->cancelhandling = 0;
result->cleanup = NULL;
/* No pending event. */
result->nextevent = NULL;
/* Clear the DTV. */
dtv_t *dtv = GET_DTV (TLS_TPADJ (result));
for (size_t cnt = 0; cnt < dtv[-1].counter; ++cnt)
free (dtv[1 + cnt].pointer.to_free);
memset (dtv, '\0', (dtv[-1].counter + 1) * sizeof (dtv_t));
/* Re-initialize the TLS. */
_dl_allocate_tls_init (TLS_TPADJ (result));
return result;
}
/* Free stacks until cache size is lower than LIMIT. */
static void
free_stacks (size_t limit)
{
/* We reduce the size of the cache. Remove the last entries until
the size is below the limit. */
list_t *entry;
list_t *prev;
/* Search from the end of the list. */
list_for_each_prev_safe (entry, prev, &stack_cache)
{
struct pthread *curr;
curr = list_entry (entry, struct pthread, list);
if (FREE_P (curr))
{
/* Unlink the block. */
stack_list_del (entry);
/* Account for the freed memory. */
stack_cache_actsize -= curr->stackblock_size;
/* Free the memory associated with the ELF TLS. */
_dl_deallocate_tls (TLS_TPADJ (curr), false);
/* Remove this block. This should never fail. If it does
something is really wrong. */
if (__munmap (curr->stackblock, curr->stackblock_size) != 0)
abort ();
/* Maybe we have freed enough. */
if (stack_cache_actsize <= limit)
break;
}
}
}
/* Free all the stacks on cleanup. */
void
__nptl_stacks_freeres (void)
{
free_stacks (0);
}
/* Add a stack frame which is not used anymore to the stack. Must be
called with the cache lock held. */
static inline void
__attribute ((always_inline))
queue_stack (struct pthread *stack)
{
/* We unconditionally add the stack to the list. The memory may
still be in use but it will not be reused until the kernel marks
the stack as not used anymore. */
stack_list_add (&stack->list, &stack_cache);
stack_cache_actsize += stack->stackblock_size;
if (__glibc_unlikely (stack_cache_actsize > stack_cache_maxsize))
free_stacks (stack_cache_maxsize);
}
static int
change_stack_perm (struct pthread *pd
#ifdef NEED_SEPARATE_REGISTER_STACK
, size_t pagemask
#endif
)
{
#ifdef NEED_SEPARATE_REGISTER_STACK
void *stack = (pd->stackblock
+ (((((pd->stackblock_size - pd->guardsize) / 2)
& pagemask) + pd->guardsize) & pagemask));
size_t len = pd->stackblock + pd->stackblock_size - stack;
#elif _STACK_GROWS_DOWN
void *stack = pd->stackblock + pd->guardsize;
size_t len = pd->stackblock_size - pd->guardsize;
#elif _STACK_GROWS_UP
void *stack = pd->stackblock;
size_t len = (uintptr_t) pd - pd->guardsize - (uintptr_t) pd->stackblock;
#else
# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
#endif
if (__mprotect (stack, len, PROT_READ | PROT_WRITE | PROT_EXEC) != 0)
return errno;
return 0;
}
/* Return the guard page position on allocated stack. */
static inline char *
__attribute ((always_inline))
guard_position (void *mem, size_t size, size_t guardsize, struct pthread *pd,
size_t pagesize_m1)
{
#ifdef NEED_SEPARATE_REGISTER_STACK
return mem + (((size - guardsize) / 2) & ~pagesize_m1);
#elif _STACK_GROWS_DOWN
return mem;
#elif _STACK_GROWS_UP
return (char *) (((uintptr_t) pd - guardsize) & ~pagesize_m1);
#endif
}
/* Based on stack allocated with PROT_NONE, setup the required portions with
'prot' flags based on the guard page position. */
static inline int
setup_stack_prot (char *mem, size_t size, char *guard, size_t guardsize,
const int prot)
{
char *guardend = guard + guardsize;
#if _STACK_GROWS_DOWN && !defined(NEED_SEPARATE_REGISTER_STACK)
/* As defined at guard_position, for architectures with downward stack
the guard page is always at start of the allocated area. */
if (__mprotect (guardend, size - guardsize, prot) != 0)
return errno;
#else
size_t mprots1 = (uintptr_t) guard - (uintptr_t) mem;
if (__mprotect (mem, mprots1, prot) != 0)
return errno;
size_t mprots2 = ((uintptr_t) mem + size) - (uintptr_t) guardend;
if (__mprotect (guardend, mprots2, prot) != 0)
return errno;
#endif
return 0;
}
/* Mark the memory of the stack as usable to the kernel. It frees everything
except for the space used for the TCB itself. */
static
#ifndef __LCC__
inline
#endif
void
__always_inline
advise_stack_range (void *mem, size_t size, uintptr_t pd, size_t guardsize)
{
uintptr_t sp = (uintptr_t) CURRENT_STACK_FRAME;
size_t pagesize_m1 = __getpagesize () - 1;
#if _STACK_GROWS_DOWN && !defined(NEED_SEPARATE_REGISTER_STACK)
size_t freesize = (sp - (uintptr_t) mem) & ~pagesize_m1;
assert (freesize < size);
if (freesize > PTHREAD_STACK_MIN)
__madvise (mem, freesize - PTHREAD_STACK_MIN, MADV_DONTNEED);
#else
/* Page aligned start of memory to free (higher than or equal
to current sp plus the minimum stack size). */
uintptr_t freeblock = (sp + PTHREAD_STACK_MIN + pagesize_m1) & ~pagesize_m1;
uintptr_t free_end = (pd - guardsize) & ~pagesize_m1;
if (free_end > freeblock)
{
size_t freesize = free_end - freeblock;
assert (freesize < size);
__madvise ((void*) freeblock, freesize, MADV_DONTNEED);
}
#endif
}
/* Returns a usable stack for a new thread either by allocating a
new stack or reusing a cached stack of sufficient size.
ATTR must be non-NULL and point to a valid pthread_attr.
PDP must be non-NULL. */
static int
allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
ALLOCATE_STACK_PARMS)
{
struct pthread *pd;
size_t size;
size_t pagesize_m1 = __getpagesize () - 1;
assert (powerof2 (pagesize_m1 + 1));
assert (TCB_ALIGNMENT >= STACK_ALIGN);
/* Get the stack size from the attribute if it is set. Otherwise we
use the default we determined at start time. */
if (attr->stacksize != 0)
size = attr->stacksize;
else
{
lll_lock (__default_pthread_attr_lock, LLL_PRIVATE);
size = __default_pthread_attr.stacksize;
lll_unlock (__default_pthread_attr_lock, LLL_PRIVATE);
}
/* Get memory for the stack. */
if (__glibc_unlikely (attr->flags & ATTR_FLAG_STACKADDR))
{
uintptr_t adj;
char *stackaddr = (char *) attr->stackaddr;
/* Assume the same layout as the _STACK_GROWS_DOWN case, with struct
pthread at the top of the stack block. Later we adjust the guard
location and stack address to match the _STACK_GROWS_UP case. */
if (_STACK_GROWS_UP)
stackaddr += attr->stacksize;
/* If the user also specified the size of the stack make sure it
is large enough. */
if (attr->stacksize != 0
&& attr->stacksize < (__static_tls_size + MINIMAL_REST_STACK))
return EINVAL;
/* Adjust stack size for alignment of the TLS block. */
#if TLS_TCB_AT_TP
adj = ((uintptr_t) stackaddr - TLS_TCB_SIZE)
& __static_tls_align_m1;
assert (size > adj + TLS_TCB_SIZE);
#elif TLS_DTV_AT_TP
adj = ((uintptr_t) stackaddr - __static_tls_size)
& __static_tls_align_m1;
assert (size > adj);
#endif
/* The user provided some memory. Let's hope it matches the
size... We do not allocate guard pages if the user provided
the stack. It is the user's responsibility to do this if it
is wanted. */
#if TLS_TCB_AT_TP
pd = (struct pthread *) ((uintptr_t) stackaddr
- TLS_TCB_SIZE - adj);
#elif TLS_DTV_AT_TP
pd = (struct pthread *) ((
#if ! defined __ptr128__
(uintptr_t)
#endif
stackaddr
- __static_tls_size - adj)
- TLS_PRE_TCB_SIZE);
#endif
/* The user provided stack memory needs to be cleared. */
memset (pd, '\0', sizeof (struct pthread));
/* The first TSD block is included in the TCB. */
pd->specific[0] = pd->specific_1stblock;
/* Remember the stack-related values. */
pd->stackblock = (char *) stackaddr - size;
pd->stackblock_size = size;
/* This is a user-provided stack. It will not be queued in the
stack cache nor will the memory (except the TLS memory) be freed. */
pd->user_stack = true;
/* This is at least the second thread. */
pd->header.multiple_threads = 1;
#ifndef TLS_MULTIPLE_THREADS_IN_TCB
__pthread_multiple_threads = *__libc_multiple_threads_ptr = 1;
#endif
#ifdef NEED_DL_SYSINFO
SETUP_THREAD_SYSINFO (pd);
#endif
/* Don't allow setxid until cloned. */
pd->setxid_futex = -1;
/* Allocate the DTV for this thread. */
if (_dl_allocate_tls (TLS_TPADJ (pd)) == NULL)
{
/* Something went wrong. */
assert (errno == ENOMEM);
return errno;
}
/* Prepare to modify global data. */
lll_lock (stack_cache_lock, LLL_PRIVATE);
/* And add to the list of stacks in use. */
list_add (&pd->list, &__stack_user);
lll_unlock (stack_cache_lock, LLL_PRIVATE);
}
else
{
/* Allocate some anonymous memory. If possible use the cache. */
size_t guardsize;
#if defined __ptr128__
size_t reported_guardsize;
#endif /* defined __ptr128__ */
size_t reqsize;
void *mem;
const int prot = (PROT_READ | PROT_WRITE
| ((GL(dl_stack_flags) & PF_X) ? PROT_EXEC : 0));
/* Adjust the stack size for alignment. */
size &= ~__static_tls_align_m1;
assert (size != 0);
/* Make sure the size of the stack is enough for the guard and
eventually the thread descriptor. */
guardsize = (attr->guardsize + pagesize_m1) & ~pagesize_m1;
if (guardsize < attr->guardsize || size + guardsize < guardsize)
/* Arithmetic overflow. */
return EINVAL;
#if defined __ptr128__
/* Ensure that `pthread_getattr_np ()' sets the value of iattr->guardsize
according to the user's expectations. */
reported_guardsize = guardsize;
/* This stupidly prevents subsequent manipulations with mprotect ()
unworkable in PM due to readonly AP returned by the initial mmap ()
from taking place. */
guardsize = 0;
#endif /* defined __ptr128__ */
size += guardsize;
if (__builtin_expect (size < ((guardsize + __static_tls_size
+ MINIMAL_REST_STACK + pagesize_m1)
& ~pagesize_m1),
0))
/* The stack is too small (or the guard too large). */
return EINVAL;
/* Try to get a stack from the cache. */
reqsize = size;
pd = get_cached_stack (&size, &mem);
if (pd == NULL)
{
/* To avoid aliasing effects on a larger scale than pages we
adjust the allocated stack size if necessary. This way
allocations directly following each other will not have
aliasing problems. */
#if MULTI_PAGE_ALIASING != 0
if ((size % MULTI_PAGE_ALIASING) == 0)
size += pagesize_m1 + 1;
#endif
/* If a guard page is required, avoid committing memory by first
allocate with PROT_NONE and then reserve with required permission
excluding the guard page. */
mem = __mmap (NULL, size, (guardsize == 0) ? prot : PROT_NONE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0);
if (__glibc_unlikely (mem == MAP_FAILED))
return errno;
/* SIZE is guaranteed to be greater than zero.
So we can never get a null pointer back from mmap. */
assert (mem != NULL);
/* Place the thread descriptor at the end of the stack. */
#if TLS_TCB_AT_TP
pd = (struct pthread *) ((((uintptr_t) mem + size)
- TLS_TCB_SIZE)
& ~__static_tls_align_m1);
#elif TLS_DTV_AT_TP
pd = (struct pthread *) ((((uintptr_t) mem + size
- __static_tls_size)
& ~__static_tls_align_m1)
- TLS_PRE_TCB_SIZE);
# if defined __ptr128__
pd = (struct pthread *) ((char *) mem + (unsigned long) pd
- (unsigned long) mem);
# endif
#endif
/* Now mprotect the required region excluding the guard area. */
if (__glibc_likely (guardsize > 0))
{
char *guard = guard_position (mem, size, guardsize, pd,
pagesize_m1);
if (setup_stack_prot (mem, size, guard, guardsize, prot) != 0)
{
__munmap (mem, size);
return errno;
}
}
/* Remember the stack-related values. */
pd->stackblock = mem;
pd->stackblock_size = size;
/* Update guardsize for newly allocated guardsize to avoid
an mprotect in guard resize below. */
pd->guardsize = guardsize;
/* We allocated the first block thread-specific data array.
This address will not change for the lifetime of this
descriptor. */
pd->specific[0] = pd->specific_1stblock;
/* This is at least the second thread. */
pd->header.multiple_threads = 1;
#ifndef TLS_MULTIPLE_THREADS_IN_TCB
__pthread_multiple_threads = *__libc_multiple_threads_ptr = 1;
#endif
#ifdef NEED_DL_SYSINFO
SETUP_THREAD_SYSINFO (pd);
#endif
/* Don't allow setxid until cloned. */
pd->setxid_futex = -1;
/* Allocate the DTV for this thread. */
if (_dl_allocate_tls (TLS_TPADJ (pd)) == NULL)
{
/* Something went wrong. */
assert (errno == ENOMEM);
/* Free the stack memory we just allocated. */
(void) __munmap (mem, size);
return errno;
}
/* Prepare to modify global data. */
lll_lock (stack_cache_lock, LLL_PRIVATE);
/* And add to the list of stacks in use. */
stack_list_add (&pd->list, &stack_used);
lll_unlock (stack_cache_lock, LLL_PRIVATE);
/* There might have been a race. Another thread might have
caused the stacks to get exec permission while this new
stack was prepared. Detect if this was possible and
change the permission if necessary. */
if (__builtin_expect ((GL(dl_stack_flags) & PF_X) != 0
&& (prot & PROT_EXEC) == 0, 0))
{
int err = change_stack_perm (pd
#ifdef NEED_SEPARATE_REGISTER_STACK
, ~pagesize_m1
#endif
);
if (err != 0)
{
/* Free the stack memory we just allocated. */
(void) __munmap (mem, size);
return err;
}
}
/* Note that all of the stack and the thread descriptor is
zeroed. This means we do not have to initialize fields
with initial value zero. This is specifically true for
the 'tid' field which is always set back to zero once the
stack is not used anymore and for the 'guardsize' field
which will be read next. */
}
/* Create or resize the guard area if necessary. */
if (__glibc_unlikely (guardsize > pd->guardsize))
{
char *guard = guard_position (mem, size, guardsize, pd,
pagesize_m1);
if (__mprotect (guard, guardsize, PROT_NONE) != 0)
{
mprot_error:
lll_lock (stack_cache_lock, LLL_PRIVATE);
/* Remove the thread from the list. */
stack_list_del (&pd->list);
lll_unlock (stack_cache_lock, LLL_PRIVATE);
/* Get rid of the TLS block we allocated. */
_dl_deallocate_tls (TLS_TPADJ (pd), false);
/* Free the stack memory regardless of whether the size
of the cache is over the limit or not. If this piece
of memory caused problems we better do not use it
anymore. Uh, and we ignore possible errors. There
is nothing we could do. */
(void) __munmap (mem, size);
return errno;
}
pd->guardsize = guardsize;
}
else if (__builtin_expect (pd->guardsize - guardsize > size - reqsize,
0))
{
/* The old guard area is too large. */
#ifdef NEED_SEPARATE_REGISTER_STACK
char *guard = mem + (((size - guardsize) / 2) & ~pagesize_m1);
char *oldguard = mem + (((size - pd->guardsize) / 2) & ~pagesize_m1);
if (oldguard < guard
&& __mprotect (oldguard, guard - oldguard, prot) != 0)
goto mprot_error;
if (__mprotect (guard + guardsize,
oldguard + pd->guardsize - guard - guardsize,
prot) != 0)
goto mprot_error;
#elif _STACK_GROWS_DOWN
if (__mprotect ((char *) mem + guardsize, pd->guardsize - guardsize,
prot) != 0)
goto mprot_error;
#elif _STACK_GROWS_UP
char *new_guard = (char *)(((uintptr_t) pd - guardsize)
& ~pagesize_m1);
char *old_guard = (char *)(((uintptr_t) pd - pd->guardsize)
& ~pagesize_m1);
/* The guard size difference might be > 0, but once rounded
to the nearest page the size difference might be zero. */
if (new_guard > old_guard
&& __mprotect (old_guard, new_guard - old_guard, prot) != 0)
goto mprot_error;
#endif
pd->guardsize = guardsize;
}
/* The pthread_getattr_np() calls need to get passed the size
requested in the attribute, regardless of how large the
actually used guardsize is. */
#if ! defined __ptr128__
pd->reported_guardsize = guardsize;
#else /* defined __ptr128__ */
/* Ensure that `pthread_getattr_np ()' sets the value of iattr->guardsize
according to the user's expectations despite the fact that the actual
guardsize was zeroed out above. */
pd->reported_guardsize = reported_guardsize;
#endif /* defined __ptr128__ */
}
/* Initialize the lock. We have to do this unconditionally since the
stillborn thread could be canceled while the lock is taken. */
pd->lock = LLL_LOCK_INITIALIZER;
/* The robust mutex lists also need to be initialized
unconditionally because the cleanup for the previous stack owner
might have happened in the kernel. */
pd->robust_head.futex_offset = (offsetof (pthread_mutex_t, __data.__lock)
- offsetof (pthread_mutex_t,
__data.__list.__next));
pd->robust_head.list_op_pending = NULL;
#if __PTHREAD_MUTEX_HAVE_PREV
pd->robust_prev = &pd->robust_head;
#endif
pd->robust_head.list = &pd->robust_head;
/* We place the thread descriptor at the end of the stack. */
*pdp = pd;
#if _STACK_GROWS_DOWN
void *stacktop;
# if TLS_TCB_AT_TP
/* The stack begins before the TCB and the static TLS block. */
stacktop = ((char *) (pd + 1) - __static_tls_size);
# elif TLS_DTV_AT_TP
stacktop = (char *) (pd - 1);
# endif
# ifdef NEED_SEPARATE_REGISTER_STACK
*stack = pd->stackblock;
*stacksize = stacktop - *stack;
# else
*stack = stacktop;
# endif
#else
*stack = pd->stackblock;
#endif
return 0;
}
void
__deallocate_stack (struct pthread *pd)
{
lll_lock (stack_cache_lock, LLL_PRIVATE);
/* Remove the thread from the list of threads with user defined
stacks. */
stack_list_del (&pd->list);
/* Not much to do. Just free the mmap()ed memory. Note that we do
not reset the 'used' flag in the 'tid' field. This is done by
the kernel. If no thread has been created yet this field is
still zero. */
if (__glibc_likely (! pd->user_stack))
(void) queue_stack (pd);
else
/* Free the memory associated with the ELF TLS. */
_dl_deallocate_tls (TLS_TPADJ (pd), false);
lll_unlock (stack_cache_lock, LLL_PRIVATE);
}
int
__make_stacks_executable (void **stack_endp)
{
/* First the main thread's stack. */
int err = _dl_make_stack_executable (stack_endp);
if (err != 0)
return err;
#ifdef NEED_SEPARATE_REGISTER_STACK
const size_t pagemask = ~(__getpagesize () - 1);
#endif
lll_lock (stack_cache_lock, LLL_PRIVATE);
list_t *runp;
list_for_each (runp, &stack_used)
{
err = change_stack_perm (list_entry (runp, struct pthread, list)
#ifdef NEED_SEPARATE_REGISTER_STACK
, pagemask
#endif
);
if (err != 0)
break;
}
/* Also change the permission for the currently unused stacks. This
might be wasted time but better spend it here than adding a check
in the fast path. */
if (err == 0)
list_for_each (runp, &stack_cache)
{
err = change_stack_perm (list_entry (runp, struct pthread, list)
#ifdef NEED_SEPARATE_REGISTER_STACK
, pagemask
#endif
);
if (err != 0)
break;
}
lll_unlock (stack_cache_lock, LLL_PRIVATE);
return err;
}
/* In case of a fork() call the memory allocation in the child will be
the same but only one thread is running. All stacks except that of
the one running thread are not used anymore. We have to recycle
them. */
void
__reclaim_stacks (void)
{
struct pthread *self = (struct pthread *) THREAD_SELF;
/* No locking necessary. The caller is the only stack in use. But
we have to be aware that we might have interrupted a list
operation. */
if (in_flight_stack != 0)
{
bool add_p = in_flight_stack & 1;
list_t *elem = (list_t *) (in_flight_stack & ~(uintptr_t) 1);
if (add_p)
{
/* We always add at the beginning of the list. So in this case we
only need to check the beginning of these lists to see if the
pointers at the head of the list are inconsistent. */
list_t *l = NULL;
if (stack_used.next->prev != &stack_used)
l = &stack_used;
else if (stack_cache.next->prev != &stack_cache)
l = &stack_cache;
if (l != NULL)
{
assert (l->next->prev == elem);
elem->next = l->next;
elem->prev = l;
l->next = elem;
}
}
else
{
/* We can simply always replay the delete operation. */
elem->next->prev = elem->prev;
elem->prev->next = elem->next;
}
}
/* Mark all stacks except the still running one as free. */
list_t *runp;
list_for_each (runp, &stack_used)
{
struct pthread *curp = list_entry (runp, struct pthread, list);
if (curp != self)
{
/* This marks the stack as free. */
curp->tid = 0;
/* Account for the size of the stack. */
stack_cache_actsize += curp->stackblock_size;
if (curp->specific_used)
{
/* Clear the thread-specific data. */
memset (curp->specific_1stblock, '\0',
sizeof (curp->specific_1stblock));
curp->specific_used = false;
for (size_t cnt = 1; cnt < PTHREAD_KEY_1STLEVEL_SIZE; ++cnt)
if (curp->specific[cnt] != NULL)
{
memset (curp->specific[cnt], '\0',
sizeof (curp->specific_1stblock));
/* We have allocated the block which we do not
free here so re-set the bit. */
curp->specific_used = true;
}
}
}
}
/* Add the stack of all running threads to the cache. */
list_splice (&stack_used, &stack_cache);
/* Remove the entry for the current thread to from the cache list
and add it to the list of running threads. Which of the two
lists is decided by the user_stack flag. */
stack_list_del (&self->list);
/* Re-initialize the lists for all the threads. */
INIT_LIST_HEAD (&stack_used);
INIT_LIST_HEAD (&__stack_user);
if (__glibc_unlikely (THREAD_GETMEM (self, user_stack)))
list_add (&self->list, &__stack_user);
else
list_add (&self->list, &stack_used);
/* There is one thread running. */
__nptl_nthreads = 1;
in_flight_stack = 0;
/* Initialize locks. */
stack_cache_lock = LLL_LOCK_INITIALIZER;
__default_pthread_attr_lock = LLL_LOCK_INITIALIZER;
}
#if HP_TIMING_AVAIL
# undef __find_thread_by_id
/* Find a thread given the thread ID. */
attribute_hidden
struct pthread *
__find_thread_by_id (pid_t tid)
{
struct pthread *result = NULL;
lll_lock (stack_cache_lock, LLL_PRIVATE);
/* Iterate over the list with system-allocated threads first. */
list_t *runp;
list_for_each (runp, &stack_used)
{
struct pthread *curp;
curp = list_entry (runp, struct pthread, list);
if (curp->tid == tid)
{
result = curp;
goto out;
}
}
/* Now the list with threads using user-allocated stacks. */
list_for_each (runp, &__stack_user)
{
struct pthread *curp;
curp = list_entry (runp, struct pthread, list);
if (curp->tid == tid)
{
result = curp;
goto out;
}
}
out:
lll_unlock (stack_cache_lock, LLL_PRIVATE);
return result;
}
#endif
#ifdef SIGSETXID
static void
setxid_mark_thread (struct xid_command *cmdp, struct pthread *t)
{
int ch;
/* Wait until this thread is cloned. */
if (t->setxid_futex == -1
&& ! atomic_compare_and_exchange_bool_acq (&t->setxid_futex, -2, -1))
do
futex_wait_simple (&t->setxid_futex, -2, FUTEX_PRIVATE);
while (t->setxid_futex == -2);
/* Don't let the thread exit before the setxid handler runs. */
t->setxid_futex = 0;
do
{
ch = t->cancelhandling;
/* If the thread is exiting right now, ignore it. */
if ((ch & EXITING_BITMASK) != 0)
{
/* Release the futex if there is no other setxid in
progress. */
if ((ch & SETXID_BITMASK) == 0)
{
t->setxid_futex = 1;
futex_wake (&t->setxid_futex, 1, FUTEX_PRIVATE);
}
return;
}
}
while (atomic_compare_and_exchange_bool_acq (&t->cancelhandling,
ch | SETXID_BITMASK, ch));
}
static void
setxid_unmark_thread (struct xid_command *cmdp, struct pthread *t)
{
int ch;
do
{
ch = t->cancelhandling;
if ((ch & SETXID_BITMASK) == 0)
return;
}
while (atomic_compare_and_exchange_bool_acq (&t->cancelhandling,
ch & ~SETXID_BITMASK, ch));
/* Release the futex just in case. */
t->setxid_futex = 1;
futex_wake (&t->setxid_futex, 1, FUTEX_PRIVATE);
}
static int
setxid_signal_thread (struct xid_command *cmdp, struct pthread *t)
{
if ((t->cancelhandling & SETXID_BITMASK) == 0)
return 0;
int val;
pid_t pid = __getpid ();
INTERNAL_SYSCALL_DECL (err);
val = INTERNAL_SYSCALL_CALL (tgkill, err, pid, t->tid, SIGSETXID);
/* If this failed, it must have had not started yet or else exited. */
if (!INTERNAL_SYSCALL_ERROR_P (val, err))
{
atomic_increment (&cmdp->cntr);
return 1;
}
else
return 0;
}
/* Check for consistency across set*id system call results. The abort
should not happen as long as all privileges changes happen through
the glibc wrappers. ERROR must be 0 (no error) or an errno
code. */
void
attribute_hidden
__nptl_setxid_error (struct xid_command *cmdp, int error)
{
do
{
int olderror = cmdp->error;
if (olderror == error)
break;
if (olderror != -1)
{
/* Mismatch between current and previous results. Save the
error value to memory so that is not clobbered by the
abort function and preserved in coredumps. */
volatile int xid_err __attribute__((unused)) = error;
abort ();
}
}
while (atomic_compare_and_exchange_bool_acq (&cmdp->error, error, -1));
}
int
attribute_hidden
__nptl_setxid (struct xid_command *cmdp)
{
int signalled;
int result;
lll_lock (stack_cache_lock, LLL_PRIVATE);
__xidcmd = cmdp;
cmdp->cntr = 0;
cmdp->error = -1;
struct pthread *self = THREAD_SELF;
/* Iterate over the list with system-allocated threads first. */
list_t *runp;
list_for_each (runp, &stack_used)
{
struct pthread *t = list_entry (runp, struct pthread, list);
if (t == self)
continue;
setxid_mark_thread (cmdp, t);
}
/* Now the list with threads using user-allocated stacks. */
list_for_each (runp, &__stack_user)
{
struct pthread *t = list_entry (runp, struct pthread, list);
if (t == self)
continue;
setxid_mark_thread (cmdp, t);
}
/* Iterate until we don't succeed in signalling anyone. That means
we have gotten all running threads, and their children will be
automatically correct once started. */
do
{
signalled = 0;
list_for_each (runp, &stack_used)
{
struct pthread *t = list_entry (runp, struct pthread, list);
if (t == self)
continue;
signalled += setxid_signal_thread (cmdp, t);
}
list_for_each (runp, &__stack_user)
{
struct pthread *t = list_entry (runp, struct pthread, list);
if (t == self)
continue;
signalled += setxid_signal_thread (cmdp, t);
}
int cur = cmdp->cntr;
while (cur != 0)
{
futex_wait_simple ((unsigned int *) &cmdp->cntr, cur,
FUTEX_PRIVATE);
cur = cmdp->cntr;
}
}
while (signalled != 0);
/* Clean up flags, so that no thread blocks during exit waiting
for a signal which will never come. */
list_for_each (runp, &stack_used)
{
struct pthread *t = list_entry (runp, struct pthread, list);
if (t == self)
continue;
setxid_unmark_thread (cmdp, t);
}
list_for_each (runp, &__stack_user)
{
struct pthread *t = list_entry (runp, struct pthread, list);
if (t == self)
continue;
setxid_unmark_thread (cmdp, t);
}
/* This must be last, otherwise the current thread might not have
permissions to send SIGSETXID syscall to the other threads. */
INTERNAL_SYSCALL_DECL (err);
result = INTERNAL_SYSCALL_NCS (cmdp->syscall_no, err, 3,
cmdp->id[0], cmdp->id[1], cmdp->id[2]);
int error = 0;
if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (result, err)))
{
error = INTERNAL_SYSCALL_ERRNO (result, err);
__set_errno (error);
result = -1;
}
__nptl_setxid_error (cmdp, error);
lll_unlock (stack_cache_lock, LLL_PRIVATE);
return result;
}
#endif /* SIGSETXID. */
static inline void __attribute__((always_inline))
init_one_static_tls (struct pthread *curp, struct link_map *map)
{
# if TLS_TCB_AT_TP
void *dest = (char *) curp - map->l_tls_offset;
# elif TLS_DTV_AT_TP
void *dest = (char *) curp + map->l_tls_offset + TLS_PRE_TCB_SIZE;
# else
# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
# endif
/* Initialize the memory. */
memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
'\0', map->l_tls_blocksize - map->l_tls_initimage_size);
}
void
attribute_hidden
__pthread_init_static_tls (struct link_map *map)
{
lll_lock (stack_cache_lock, LLL_PRIVATE);
/* Iterate over the list with system-allocated threads first. */
list_t *runp;
list_for_each (runp, &stack_used)
init_one_static_tls (list_entry (runp, struct pthread, list), map);
/* Now the list with threads using user-allocated stacks. */
list_for_each (runp, &__stack_user)
init_one_static_tls (list_entry (runp, struct pthread, list), map);
lll_unlock (stack_cache_lock, LLL_PRIVATE);
}
void
attribute_hidden
__wait_lookup_done (void)
{
lll_lock (stack_cache_lock, LLL_PRIVATE);
struct pthread *self = THREAD_SELF;
/* Iterate over the list with system-allocated threads first. */
list_t *runp;
list_for_each (runp, &stack_used)
{
struct pthread *t = list_entry (runp, struct pthread, list);
if (t == self || t->header.gscope_flag == THREAD_GSCOPE_FLAG_UNUSED)
continue;
int *const gscope_flagp = &t->header.gscope_flag;
/* We have to wait until this thread is done with the global
scope. First tell the thread that we are waiting and
possibly have to be woken. */
if (atomic_compare_and_exchange_bool_acq (gscope_flagp,
THREAD_GSCOPE_FLAG_WAIT,
THREAD_GSCOPE_FLAG_USED))
continue;
do
futex_wait_simple ((unsigned int *) gscope_flagp,
THREAD_GSCOPE_FLAG_WAIT, FUTEX_PRIVATE);
while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT);
}
/* Now the list with threads using user-allocated stacks. */
list_for_each (runp, &__stack_user)
{
struct pthread *t = list_entry (runp, struct pthread, list);
if (t == self || t->header.gscope_flag == THREAD_GSCOPE_FLAG_UNUSED)
continue;
int *const gscope_flagp = &t->header.gscope_flag;
/* We have to wait until this thread is done with the global
scope. First tell the thread that we are waiting and
possibly have to be woken. */
if (atomic_compare_and_exchange_bool_acq (gscope_flagp,
THREAD_GSCOPE_FLAG_WAIT,
THREAD_GSCOPE_FLAG_USED))
continue;
do
futex_wait_simple ((unsigned int *) gscope_flagp,
THREAD_GSCOPE_FLAG_WAIT, FUTEX_PRIVATE);
while (*gscope_flagp == THREAD_GSCOPE_FLAG_WAIT);
}
lll_unlock (stack_cache_lock, LLL_PRIVATE);
}
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