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nptl: Move legacy unwinding implementation into libc

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It is still used internally.  Since unwinding is now available
unconditionally, avoid indirect calls through function pointers loaded
from the stack by inlining the non-cancellation cleanup code.  This
avoids a regression in security hardening.

The out-of-line  __libc_cleanup_routine implementation is no longer
needed because the inline definition is now static __always_inline.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Florian Weimer 2021-04-21 19:49:50 +02:00
parent 5715c29e91
commit f79f206581
7 changed files with 98 additions and 117 deletions
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2
nptl/Versions
View file

@ -87,6 +87,8 @@ libc {
__futex_abstimed_wait64;
__futex_abstimed_wait_cancelable64;
__libc_alloca_cutoff;
__libc_cleanup_pop_restore;
__libc_cleanup_push_defer;
__libc_dl_error_tsd;
__libc_pthread_init;
__lll_clocklock_elision;

56
nptl/cleanup_defer_compat.c
View file

@ -17,41 +17,15 @@
<https://www.gnu.org/licenses/>. */
#include "pthreadP.h"
#include <libc-lock.h>
void
_pthread_cleanup_push_defer (struct _pthread_cleanup_buffer *buffer,
void (*routine) (void *), void *arg)
{
struct pthread *self = THREAD_SELF;
buffer->__routine = routine;
buffer->__arg = arg;
buffer->__prev = THREAD_GETMEM (self, cleanup);
int cancelhandling = THREAD_GETMEM (self, cancelhandling);
/* Disable asynchronous cancellation for now. */
if (__glibc_unlikely (cancelhandling & CANCELTYPE_BITMASK))
while (1)
{
int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling,
cancelhandling
& ~CANCELTYPE_BITMASK,
cancelhandling);
if (__glibc_likely (curval == cancelhandling))
/* Successfully replaced the value. */
break;
/* Prepare for the next round. */
cancelhandling = curval;
}
buffer->__canceltype = (cancelhandling & CANCELTYPE_BITMASK
? PTHREAD_CANCEL_ASYNCHRONOUS
: PTHREAD_CANCEL_DEFERRED);
THREAD_SETMEM (self, cleanup, buffer);
__libc_cleanup_push_defer (buffer);
}
strong_alias (_pthread_cleanup_push_defer, __pthread_cleanup_push_defer)
@ -60,31 +34,7 @@ void
_pthread_cleanup_pop_restore (struct _pthread_cleanup_buffer *buffer,
int execute)
{
struct pthread *self = THREAD_SELF;
THREAD_SETMEM (self, cleanup, buffer->__prev);
int cancelhandling;
if (__builtin_expect (buffer->__canceltype != PTHREAD_CANCEL_DEFERRED, 0)
&& ((cancelhandling = THREAD_GETMEM (self, cancelhandling))
& CANCELTYPE_BITMASK) == 0)
{
while (1)
{
int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling,
cancelhandling
| CANCELTYPE_BITMASK,
cancelhandling);
if (__glibc_likely (curval == cancelhandling))
/* Successfully replaced the value. */
break;
/* Prepare for the next round. */
cancelhandling = curval;
}
CANCELLATION_P (self);
}
__libc_cleanup_pop_restore (buffer);
/* If necessary call the cleanup routine after we removed the
current cleanup block from the list. */

66
nptl/libc-cleanup.c
View file

@ -17,11 +17,69 @@
<https://www.gnu.org/licenses/>. */
#include "pthreadP.h"
#include <tls.h>
#include <libc-lock.h>
void
__libc_cleanup_routine (struct __pthread_cleanup_frame *f)
__libc_cleanup_push_defer (struct _pthread_cleanup_buffer *buffer)
{
if (f->__do_it)
f->__cancel_routine (f->__cancel_arg);
struct pthread *self = THREAD_SELF;
buffer->__prev = THREAD_GETMEM (self, cleanup);
int cancelhandling = THREAD_GETMEM (self, cancelhandling);
/* Disable asynchronous cancellation for now. */
if (__glibc_unlikely (cancelhandling & CANCELTYPE_BITMASK))
while (1)
{
int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling,
cancelhandling
& ~CANCELTYPE_BITMASK,
cancelhandling);
if (__glibc_likely (curval == cancelhandling))
/* Successfully replaced the value. */
break;
/* Prepare for the next round. */
cancelhandling = curval;
}
buffer->__canceltype = (cancelhandling & CANCELTYPE_BITMASK
? PTHREAD_CANCEL_ASYNCHRONOUS
: PTHREAD_CANCEL_DEFERRED);
THREAD_SETMEM (self, cleanup, buffer);
}
libc_hidden_def (__libc_cleanup_push_defer)
void
__libc_cleanup_pop_restore (struct _pthread_cleanup_buffer *buffer)
{
struct pthread *self = THREAD_SELF;
THREAD_SETMEM (self, cleanup, buffer->__prev);
int cancelhandling;
if (__builtin_expect (buffer->__canceltype != PTHREAD_CANCEL_DEFERRED, 0)
&& ((cancelhandling = THREAD_GETMEM (self, cancelhandling))
& CANCELTYPE_BITMASK) == 0)
{
while (1)
{
int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling,
cancelhandling
| CANCELTYPE_BITMASK,
cancelhandling);
if (__glibc_likely (curval == cancelhandling))
/* Successfully replaced the value. */
break;
/* Prepare for the next round. */
cancelhandling = curval;
}
CANCELLATION_P (self);
}
}
libc_hidden_def (__libc_cleanup_pop_restore)

2
nptl/nptl-init.c
View file

@ -95,8 +95,6 @@ static const struct pthread_functions pthread_functions =
.ptr___pthread_key_create = __pthread_key_create,
.ptr___pthread_getspecific = __pthread_getspecific,
.ptr___pthread_setspecific = __pthread_setspecific,
.ptr__pthread_cleanup_push_defer = __pthread_cleanup_push_defer,
.ptr__pthread_cleanup_pop_restore = __pthread_cleanup_pop_restore,
.ptr_nthreads = &__nptl_nthreads,
.ptr___pthread_unwind = &__pthread_unwind,
.ptr__nptl_deallocate_tsd = __nptl_deallocate_tsd,

59
sysdeps/nptl/libc-lock.h
View file

@ -143,39 +143,40 @@ typedef struct __libc_lock_recursive_opaque__ __libc_lock_recursive_t;
__libc_maybe_call (__pthread_mutex_unlock, (&(NAME).mutex), 0)
#endif
/* Note that for I/O cleanup handling we are using the old-style
cancel handling. It does not have to be integrated with C++ since
no C++ code is called in the middle. The old-style handling is
faster and the support is not going away. */
extern void _pthread_cleanup_push_defer (struct _pthread_cleanup_buffer *buffer,
void (*routine) (void *), void *arg);
extern void _pthread_cleanup_pop_restore (struct _pthread_cleanup_buffer *buffer,
int execute);
/* Put the unwind buffer BUFFER on the per-thread callback stack. The
caller must fill BUFFER->__routine and BUFFER->__arg before calling
this function. */
void __libc_cleanup_push_defer (struct _pthread_cleanup_buffer *buffer);
libc_hidden_proto (__libc_cleanup_push_defer)
/* Remove BUFFER from the unwind callback stack. The caller must invoke
the callback if desired. */
void __libc_cleanup_pop_restore (struct _pthread_cleanup_buffer *buffer);
libc_hidden_proto (__libc_cleanup_pop_restore)
/* Start critical region with cleanup. */
#define __libc_cleanup_region_start(DOIT, FCT, ARG) \
{ struct _pthread_cleanup_buffer _buffer; \
int _avail; \
if (DOIT) { \
_avail = PTFAVAIL (_pthread_cleanup_push_defer); \
if (_avail) { \
__libc_ptf_call_always (_pthread_cleanup_push_defer, (&_buffer, FCT, \
ARG)); \
} else { \
_buffer.__routine = (FCT); \
_buffer.__arg = (ARG); \
} \
} else { \
_avail = 0; \
}
#define __libc_cleanup_region_start(DOIT, FCT, ARG) \
{ bool _cleanup_start_doit; \
struct _pthread_cleanup_buffer _buffer; \
/* Non-addressable copy of FCT, so that we avoid indirect calls on \
the non-unwinding path. */ \
void (*_cleanup_routine) (void *) = (FCT); \
_buffer.__arg = (ARG); \
if (DOIT) \
{ \
_cleanup_start_doit = true; \
_buffer.__routine = _cleanup_routine; \
__libc_cleanup_push_defer (&_buffer); \
} \
else \
_cleanup_start_doit = false;
/* End critical region with cleanup. */
#define __libc_cleanup_region_end(DOIT) \
if (_avail) { \
__libc_ptf_call_always (_pthread_cleanup_pop_restore, (&_buffer, DOIT));\
} else if (DOIT) \
_buffer.__routine (_buffer.__arg); \
}
#define __libc_cleanup_region_end(DOIT) \
if (_cleanup_start_doit) \
__libc_cleanup_pop_restore (&_buffer); \
if (DOIT) \
_cleanup_routine (_buffer.__arg); \
} /* matches __libc_cleanup_region_start */
/* Hide the definitions which are only supposed to be used inside libc in

26
sysdeps/nptl/libc-lockP.h
View file

@ -251,32 +251,12 @@ _Static_assert (LLL_LOCK_INITIALIZER == 0, "LLL_LOCK_INITIALIZER != 0");
/* Get once control variable. */
#define __libc_once_get(ONCE_CONTROL) ((ONCE_CONTROL) != PTHREAD_ONCE_INIT)
/* Note that for I/O cleanup handling we are using the old-style
cancel handling. It does not have to be integrated with C++ snce
no C++ code is called in the middle. The old-style handling is
faster and the support is not going away. */
extern void _pthread_cleanup_push (struct _pthread_cleanup_buffer *buffer,
void (*routine) (void *), void *arg);
extern void _pthread_cleanup_pop (struct _pthread_cleanup_buffer *buffer,
int execute);
extern void _pthread_cleanup_push_defer (struct _pthread_cleanup_buffer *buffer,
void (*routine) (void *), void *arg);
extern void _pthread_cleanup_pop_restore (struct _pthread_cleanup_buffer *buffer,
int execute);
/* Sometimes we have to exit the block in the middle. */
#define __libc_cleanup_end(DOIT) \
if (_avail) { \
__libc_ptf_call_always (_pthread_cleanup_pop_restore, (&_buffer, DOIT));\
} else if (DOIT) \
_buffer.__routine (_buffer.__arg)
/* __libc_cleanup_push and __libc_cleanup_pop depend on exception
handling and stack unwinding. */
#ifdef __EXCEPTIONS
/* Normal cleanup handling, based on C cleanup attribute. */
__extern_inline void
static __always_inline void
__libc_cleanup_routine (struct __pthread_cleanup_frame *f)
{
if (f->__do_it)
@ -388,8 +368,6 @@ weak_extern (__pthread_once)
weak_extern (__pthread_initialize)
weak_extern (__pthread_atfork)
weak_extern (__pthread_setcancelstate)
weak_extern (_pthread_cleanup_push_defer)
weak_extern (_pthread_cleanup_pop_restore)
# else
# pragma weak __pthread_mutex_init
# pragma weak __pthread_mutex_destroy
@ -412,8 +390,6 @@ weak_extern (_pthread_cleanup_pop_restore)
# pragma weak __pthread_initialize
# pragma weak __pthread_atfork
# pragma weak __pthread_setcancelstate
# pragma weak _pthread_cleanup_push_defer
# pragma weak _pthread_cleanup_pop_restore
# endif
#endif

4
sysdeps/nptl/pthread-functions.h
View file

@ -57,10 +57,6 @@ struct pthread_functions
int (*ptr___pthread_key_create) (pthread_key_t *, void (*) (void *));
void *(*ptr___pthread_getspecific) (pthread_key_t);
int (*ptr___pthread_setspecific) (pthread_key_t, const void *);
void (*ptr__pthread_cleanup_push_defer) (struct _pthread_cleanup_buffer *,
void (*) (void *), void *);
void (*ptr__pthread_cleanup_pop_restore) (struct _pthread_cleanup_buffer *,
int);
#define HAVE_PTR_NTHREADS
unsigned int *ptr_nthreads;
void (*ptr___pthread_unwind) (__pthread_unwind_buf_t *)