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* [glibc] nptl: Move legacy unwinding implementation into libc
@ 2021-04-21 18:25 Florian Weimer
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From: Florian Weimer @ 2021-04-21 18:25 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f79f2065817e080f65f3c3a2fee966f5a97f1746
commit f79f2065817e080f65f3c3a2fee966f5a97f1746
Author: Florian Weimer <fweimer@redhat.com>
Date: Wed Apr 21 19:49:50 2021 +0200
nptl: Move legacy unwinding implementation into libc
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>
Diff:
---
nptl/Versions | 2 ++
nptl/cleanup_defer_compat.c | 56 ++---------------------------------
nptl/libc-cleanup.c | 64 ++++++++++++++++++++++++++++++++++++++--
nptl/nptl-init.c | 2 --
sysdeps/nptl/libc-lock.h | 59 ++++++++++++++++++------------------
sysdeps/nptl/libc-lockP.h | 26 +---------------
sysdeps/nptl/pthread-functions.h | 4 ---
7 files changed, 97 insertions(+), 116 deletions(-)
diff --git a/nptl/Versions b/nptl/Versions
index 60202b4969..2e5a964b11 100644
--- a/nptl/Versions
+++ b/nptl/Versions
@@ -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;
diff --git a/nptl/cleanup_defer_compat.c b/nptl/cleanup_defer_compat.c
index 49ef53ea60..1957318208 100644
--- a/nptl/cleanup_defer_compat.c
+++ b/nptl/cleanup_defer_compat.c
@@ -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. */
diff --git a/nptl/libc-cleanup.c b/nptl/libc-cleanup.c
index 61f97eceda..14ccfe9285 100644
--- a/nptl/libc-cleanup.c
+++ b/nptl/libc-cleanup.c
@@ -17,11 +17,69 @@
<https://www.gnu.org/licenses/>. */
#include "pthreadP.h"
+#include <tls.h>
+#include <libc-lock.h>
+void
+__libc_cleanup_push_defer (struct _pthread_cleanup_buffer *buffer)
+{
+ 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_routine (struct __pthread_cleanup_frame *f)
+__libc_cleanup_pop_restore (struct _pthread_cleanup_buffer *buffer)
{
- if (f->__do_it)
- f->__cancel_routine (f->__cancel_arg);
+ 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)
diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
index 2c7e2222d4..43e2564e59 100644
--- a/nptl/nptl-init.c
+++ b/nptl/nptl-init.c
@@ -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,
diff --git a/sysdeps/nptl/libc-lock.h b/sysdeps/nptl/libc-lock.h
index dea96121b3..e8a5e68a12 100644
--- a/sysdeps/nptl/libc-lock.h
+++ b/sysdeps/nptl/libc-lock.h
@@ -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
diff --git a/sysdeps/nptl/libc-lockP.h b/sysdeps/nptl/libc-lockP.h
index 63b605dee2..2c928b7a76 100644
--- a/sysdeps/nptl/libc-lockP.h
+++ b/sysdeps/nptl/libc-lockP.h
@@ -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
diff --git a/sysdeps/nptl/pthread-functions.h b/sysdeps/nptl/pthread-functions.h
index 97a5c48939..4268084b66 100644
--- a/sysdeps/nptl/pthread-functions.h
+++ b/sysdeps/nptl/pthread-functions.h
@@ -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 *)
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