libc: Extend __libc_freeres framework (Bug 23329).

The __libc_freeres framework does not extend to non-libc.so objects.
This causes problems in general for valgrind and mtrace detecting
unfreed objects in both libdl.so and libpthread.so.  This change is
a pre-requisite to properly moving the malloc hooks out of malloc
since such a move now requires precise accounting of all allocated
data before destructors are run.

This commit adds a proper hook in libc.so.6 for both libdl.so and
for libpthread.so, this ensures that shm-directory.c which uses
freeit () to free memory is called properly.  We also remove the
nptl_freeres hook and fall back to using weak-ref-and-check idiom
for a loaded libpthread.so, thus making this process similar for
all DSOs.

Lastly we follow best practice and use explicit free calls for
both libdl.so and libpthread.so instead of the generic hook process
which has undefined order.

Tested on x86_64 with no regressions.

Signed-off-by: DJ Delorie <dj@redhat.com>
Signed-off-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Carlos O'Donell 2018-06-22 09:28:47 -04:00
parent 37d3d244e1
commit 2827ab990a
26 changed files with 245 additions and 53 deletions

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@ -1,3 +1,51 @@
2018-06-29 DJ Delorie <dj@redhat.com>
Carlos O'Donell <carlos@redhat.com>
[BZ #23329]
* include/libc-symbols.h: Comment the freeres framework.
* include/set-hooks.h: Include libc-symbols.h. Fix comment.
* dlfcn/Makefile (libdl-routines): Add dlfreeres.
* dlfcn/Versions (GLIBC_PRIVATE): Add __libdl_freeres.
* dlfcn/dlerror.c: Include libc-symbols.h
(__dlerror_main_freeres): New function.
* dlfcn/dlfreeres.c: New file.
* dlfcn/sdlfreeres.c: New file.
* include/dlfcn.h: Declare __dlerror_main_freeres.
* malloc/set-freeres.c: Declare __libdl_freeres, and
__libpthread_freeres.
(__libc_subfreeres): Call __libdl_freeres, and __libpthread_freeres if
the releavant libraries are loaded.
* malloc/thread-freeres.c: Add comments.
* nptl/Makefile (libpthread-routines): Add nptlfreeres.
* nptl/Version (GLIBC_PRIVATE): Add __libpthread_freeres.
* nptl/allocatestack.c (__nptl_free_stacks): New function.
(__free_stacks): Rename to...
(free_stacks): ...this. Mark static.
(queue_stack): Call free_stacks.
* nptl/libc_pthread_init.c [SHARED] (freeres_libpthread): Delete.
* nptl/nptl-init.c: Delete delcaration of nptl_freeres.
* sysdeps/nptl/pthread-functions.h (pthread_functions): Remove
ptr_freeres element from struct.
(pthread_functions): Remove .ptr_freeres from struct initializer.
[SHARED] (nptl_freeres): Remove.
* nptl/nptlfreeres.c: New file.
* nptl/pthreadP.h
[IS_IN (libpthread) && SHARED ] (__unwind_freeres): Rename to...
[IS_IN (libpthread)] (__nptl_unwind_freeres): ...this. Mark
attribute_hidden.
(__free_stacks): Rename to...
(__nptl_stacks_freeres): ...this.
(__shm_directory_freeres): Declare.
* nptl/unwind-forcedunwind.c (__unwind_freeres): Rename to...
(__nptl_unwind_freeres): ...this.
* resolv/res-close.c: Add comment.
* resolv/resolv_conf.c: Include libc-symbols.h.
* string/strerror_l.c: Include libc-symbols.h.
* sunrpc/rpc_thread.c: Include libc-symbols.h.
* sysdeps/mach/strerror_l.c: Inlcude libc-symbols.h
* sysdeps/unix/sysv/linux/shm-directory.c (freeit): Rename to...
[IS_IN (libpthread)] (__shm_directory_freeres): ...this.
2018-06-29 Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com>
* stdlib/tst-strfmon_l.c: Add tests for long double.

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@ -22,7 +22,7 @@ include ../Makeconfig
headers := bits/dlfcn.h dlfcn.h
extra-libs := libdl
libdl-routines := dlopen dlclose dlsym dlvsym dlerror dladdr dladdr1 dlinfo \
dlmopen dlfcn
dlmopen dlfcn dlfreeres
routines := $(patsubst %,s%,$(filter-out dlfcn,$(libdl-routines)))
elide-routines.os := $(routines)

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@ -13,5 +13,6 @@ libdl {
}
GLIBC_PRIVATE {
_dlfcn_hook;
__libdl_freeres;
}
}

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@ -24,6 +24,7 @@
#include <string.h>
#include <libc-lock.h>
#include <ldsodefs.h>
#include <libc-symbols.h>
#if !defined SHARED && IS_IN (libdl)
@ -222,6 +223,19 @@ free_key_mem (void *mem)
# ifdef SHARED
/* Free the dlerror-related resources. */
void
__dlerror_main_freeres (void)
{
void *mem;
/* Free the global memory if used. */
check_free (&last_result);
/* Free the TSD memory if used. */
mem = __libc_getspecific (key);
if (mem != NULL)
free_key_mem (mem);
}
struct dlfcn_hook *_dlfcn_hook __attribute__((nocommon));
libdl_hidden_data_def (_dlfcn_hook)

29
dlfcn/dlfreeres.c Normal file
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@ -0,0 +1,29 @@
/* Clean up allocated libdl memory on demand.
Copyright (C) 2018 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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 <set-hooks.h>
#include <libc-symbols.h>
#include <dlfcn.h>
/* Free libdl.so resources.
Note: Caller ensures we are called only once. */
void
__libdl_freeres (void)
{
call_function_static_weak (__dlerror_main_freeres);
}

1
dlfcn/sdlfreeres.c Normal file
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@ -0,0 +1 @@
#include "dlfreeres.c"

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@ -155,6 +155,8 @@ extern void __libc_register_dl_open_hook (struct link_map *map)
extern void __libc_register_dlfcn_hook (struct link_map *map)
attribute_hidden;
#endif
#endif
extern void __dlerror_main_freeres (void) attribute_hidden;
#endif
#endif

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@ -217,16 +217,6 @@
static const char __evoke_link_warning_##symbol[] \
__attribute__ ((used, section (".gnu.warning." #symbol __sec_comment))) \
= msg;
#define libc_freeres_ptr(decl) \
__make_section_unallocated ("__libc_freeres_ptrs, \"aw\", %nobits") \
decl __attribute__ ((section ("__libc_freeres_ptrs" __sec_comment)))
#define __libc_freeres_fn_section \
__attribute__ ((section ("__libc_freeres_fn")))
#define libc_freeres_fn(name) \
static void name (void) __attribute_used__ __libc_freeres_fn_section; \
text_set_element (__libc_subfreeres, name); \
static void name (void)
/* A canned warning for sysdeps/stub functions. */
#define stub_warning(name) \
@ -244,6 +234,79 @@ requires at runtime the shared libraries from the glibc version used \
for linking")
#endif
/* Resource Freeing Hooks:
Normally a process exits and the OS cleans up any allocated
memory. However, when tooling like mtrace or valgrind is monitoring
the process we need to free all resources that are part of the
process in order to provide the consistency required to track
memory leaks.
A single public API exists and is __libc_freeres(), and this is used
by applications like valgrind to freee resouces.
There are 3 cases:
(a) __libc_freeres
In this case all you need to do is define the freeing routine:
foo.c:
libfoo_freeres_fn (foo_freeres)
{
complex_free (mem);
}
This ensures the function is called at the right point to free
resources.
(b) __libc_freeres_ptr
The framework for (a) iterates over the list of pointers-to-free
in (b) and frees them.
foo.c:
libc_freeres_ptr (static char *foo_buffer);
Freeing these resources alaways happens last and is equivalent
to registering a function that does 'free (foo_buffer)'.
(c) Explicit lists of free routines to call or objects to free.
It is the intended goal to remove (a) and (b) which have some
non-determinism based on link order, and instead use explicit
lists of functions and frees to resolve cleanup ordering issues
and make it easy to debug and maintain.
As of today the following subsystems use (c):
Per-thread cleanup:
* malloc/thread-freeres.c
libdl cleanup:
* dlfcn/dlfreeres.c
libpthread cleanup:
* nptl/nptlfreeres.c
So if you need any shutdown routines to run you should add them
directly to the appropriate subsystem's shutdown list. */
/* Resource pointers to free in libc.so. */
#define libc_freeres_ptr(decl) \
__make_section_unallocated ("__libc_freeres_ptrs, \"aw\", %nobits") \
decl __attribute__ ((section ("__libc_freeres_ptrs" __sec_comment)))
/* Resource freeing functions from libc.so go in this section. */
#define __libc_freeres_fn_section \
__attribute__ ((section ("__libc_freeres_fn")))
/* Resource freeing functions for libc.so. */
#define libc_freeres_fn(name) \
static void name (void) __attribute_used__ __libc_freeres_fn_section; \
text_set_element (__libc_subfreeres, name); \
static void name (void)
/* Declare SYMBOL to be TYPE (`function' or `object') of SIZE bytes
alias to ORIGINAL, when the assembler supports such declarations
(such as in ELF).

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@ -22,11 +22,12 @@
#define __need_size_t
#include <stddef.h>
#include <sys/cdefs.h>
#include <libc-symbols.h>
#ifdef symbol_set_define
/* Define a hook variable called NAME. Functions put on this hook take
arguments described by PROTO. Use `text_set_element (NAME, FUNCTION)'
from gnu-stabs.h to add a function to the hook. */
from include/libc-symbols.h to add a function to the hook. */
# define DEFINE_HOOK(NAME, PROTO) \
typedef void __##NAME##_hook_function_t PROTO; \

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@ -26,6 +26,10 @@ DEFINE_HOOK (__libc_subfreeres, (void));
symbol_set_define (__libc_freeres_ptrs);
extern __attribute__ ((weak)) void __libdl_freeres (void);
extern __attribute__ ((weak)) void __libpthread_freeres (void);
void __libc_freeres_fn_section
__libc_freeres (void)
{
@ -39,8 +43,19 @@ __libc_freeres (void)
_IO_cleanup ();
/* We run the resource freeing after IO cleanup. */
RUN_HOOK (__libc_subfreeres, ());
/* Call the libdl list of cleanup functions
(weak-ref-and-check). */
if (&__libdl_freeres != NULL)
__libdl_freeres ();
/* Call the libpthread list of cleanup functions
(weak-ref-and-check). */
if (&__libpthread_freeres != NULL)
__libpthread_freeres ();
for (p = symbol_set_first_element (__libc_freeres_ptrs);
!symbol_set_end_p (__libc_freeres_ptrs, p); ++p)
free (*p);

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@ -24,8 +24,8 @@
/* Thread shutdown function. Note that this function must be called
for threads during shutdown for correctness reasons. Unlike
__libc_subfreeres, skipping calls to it is not a valid
optimization. */
__libc_subfreeres, skipping calls to it is not a valid optimization.
This is called directly from pthread_create as the thread exits. */
void
__libc_thread_freeres (void)
{

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@ -45,7 +45,7 @@ pthread-compat-wrappers = \
sigwait sigsuspend \
recvmsg sendmsg
libpthread-routines = nptl-init vars events version pt-interp \
libpthread-routines = nptl-init nptlfreeres vars events version pt-interp \
pthread_create pthread_exit pthread_detach \
pthread_join pthread_tryjoin pthread_timedjoin \
pthread_join_common \

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@ -271,5 +271,6 @@ libpthread {
__pthread_unwind; __pthread_get_minstack;
__pthread_barrier_init; __pthread_barrier_wait;
__shm_directory;
__libpthread_freeres;
}
}

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@ -251,8 +251,8 @@ get_cached_stack (size_t *sizep, void **memp)
/* Free stacks until cache size is lower than LIMIT. */
void
__free_stacks (size_t 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. */
@ -288,6 +288,12 @@ __free_stacks (size_t limit)
}
}
/* 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. */
@ -302,7 +308,7 @@ queue_stack (struct pthread *stack)
stack_cache_actsize += stack->stackblock_size;
if (__glibc_unlikely (stack_cache_actsize > stack_cache_maxsize))
__free_stacks (stack_cache_maxsize);
free_stacks (stack_cache_maxsize);
}

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@ -77,11 +77,3 @@ __libc_pthread_init (unsigned long int *ptr, void (*reclaim) (void),
return &__libc_multiple_threads;
#endif
}
#ifdef SHARED
libc_freeres_fn (freeres_libptread)
{
if (__libc_pthread_functions_init)
PTHFCT_CALL (ptr_freeres, ());
}
#endif

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@ -78,9 +78,6 @@ extern
void __nptl_set_robust (struct pthread *);
#ifdef SHARED
static void nptl_freeres (void);
static const struct pthread_functions pthread_functions =
{
.ptr_pthread_attr_destroy = __pthread_attr_destroy,
@ -140,8 +137,6 @@ static const struct pthread_functions pthread_functions =
# ifdef SIGSETXID
.ptr__nptl_setxid = __nptl_setxid,
# endif
/* For now only the stack cache needs to be freed. */
.ptr_freeres = nptl_freeres,
.ptr_set_robust = __nptl_set_robust
};
# define ptr_pthread_functions &pthread_functions
@ -151,16 +146,6 @@ static const struct pthread_functions pthread_functions =
#ifdef SHARED
/* This function is called indirectly from the freeres code in libc. */
static void
__libc_freeres_fn_section
nptl_freeres (void)
{
__unwind_freeres ();
__free_stacks (0);
}
static
#endif
void

31
nptl/nptlfreeres.c Normal file
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@ -0,0 +1,31 @@
/* Clean up allocated libpthread memory on demand.
Copyright (C) 2018 Free Software Foundation, Inc.
This file is part of the GNU C Library.
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 <set-hooks.h>
#include <libc-symbols.h>
#include <pthreadP.h>
/* Free libpthread.so resources.
Note: Caller ensures we are called only once. */
void
__libpthread_freeres (void)
{
call_function_static_weak (__nptl_stacks_freeres);
call_function_static_weak (__shm_directory_freeres);
call_function_static_weak (__nptl_unwind_freeres);
}

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@ -279,8 +279,8 @@ hidden_proto (__pthread_register_cancel)
hidden_proto (__pthread_unregister_cancel)
# ifdef SHARED
extern void attribute_hidden pthread_cancel_init (void);
extern void __unwind_freeres (void);
# endif
extern void __nptl_unwind_freeres (void) attribute_hidden;
#endif
@ -597,7 +597,8 @@ extern int __nptl_setxid (struct xid_command *cmdp) attribute_hidden;
extern void __nptl_set_robust (struct pthread *self);
#endif
extern void __free_stacks (size_t limit) attribute_hidden;
extern void __nptl_stacks_freeres (void) attribute_hidden;
extern void __shm_directory_freeres (void) attribute_hidden;
extern void __wait_lookup_done (void) attribute_hidden;

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@ -140,4 +140,5 @@ __res_thread_freeres (void)
/* Make sure we do a full re-initialization the next time. */
_res.options = 0;
}
/* Also must be called when the main thread exits. */
text_set_element (__libc_subfreeres, __res_thread_freeres);

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@ -23,6 +23,7 @@
#include <libc-lock.h>
#include <resolv-internal.h>
#include <sys/stat.h>
#include <libc-symbols.h>
/* _res._u._ext.__glibc_extension_index is used as an index into a
struct resolv_conf_array object. The intent of this construction

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@ -21,7 +21,7 @@
#include <stdlib.h>
#include <string.h>
#include <sys/param.h>
#include <libc-symbols.h>
static __thread char *last_value;
@ -56,7 +56,6 @@ strerror_l (int errnum, locale_t loc)
return (char *) translate (_sys_errlist_internal[errnum], loc);
}
void
__strerror_thread_freeres (void)
{

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@ -5,6 +5,7 @@
#include <libc-lock.h>
#include <libc-tsd.h>
#include <shlib-compat.h>
#include <libc-symbols.h>
/* Variable used in non-threaded applications or for the first thread. */

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@ -24,6 +24,7 @@
#include <mach/error.h>
#include <errorlib.h>
#include <sys/param.h>
#include <libc-symbols.h>
static __thread char *last_value;
@ -86,7 +87,7 @@ strerror_l (int errnum, locale_t loc)
return (char *) translate (es->subsystem[sub].codes[code], loc);
}
/* This is called when a thread is exiting to free the last_value string. */
void
__strerror_thread_freeres (void)
{

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@ -94,7 +94,6 @@ struct pthread_functions
__attribute ((noreturn)) __cleanup_fct_attribute;
void (*ptr__nptl_deallocate_tsd) (void);
int (*ptr__nptl_setxid) (struct xid_command *);
void (*ptr_freeres) (void);
void (*ptr_set_robust) (struct pthread *);
};

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@ -79,9 +79,9 @@ pthread_cancel_init (void)
libgcc_s_handle = handle;
}
/* Register for cleanup in libpthread.so. */
void
__libc_freeres_fn_section
__unwind_freeres (void)
__nptl_unwind_freeres (void)
{
void *handle = libgcc_s_handle;
if (handle != NULL)

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@ -135,13 +135,13 @@ __shm_directory (size_t *len)
}
#if IS_IN (libpthread)
hidden_def (__shm_directory)
#endif
/* Make sure the table is freed if we want to free everything before
exiting. */
libc_freeres_fn (freeit)
void
__shm_directory_freeres (void)
{
if (mountpoint.dir != defaultdir)
free (mountpoint.dir);
}
#endif