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Add a new function dllockinit() for registering thread locking

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functions to be used by the dynamic linker.  This can be called by
threads packages at start-up time.  I will add the call to libc_r
soon.

Also add a default locking method that is used up until dllockinit()
is called.  The default method works by blocking SIGVTALRM, SIGPROF,
and SIGALRM in critical sections.  It is based on the observation
that most user-space threads packages implement thread preemption
with one of these signals (usually SIGVTALRM).

The dynamic linker has never been reentrant, but it became less
reentrant in revision 1.34 of "src/libexec/rtld-elf/rtld.c".
Starting with that revision, multiple threads each doing lazy
binding could interfere with each other.  The usual symptom was
that a symbol was falsely reported as undefined at start-up time.
It was rare but not unseen.  This commit fixes it.
This commit is contained in:
John Polstra 1999-12-27 04:44:04 +00:00
parent fdba49eb7e
commit d3980376e8
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=55122
15 changed files with 640 additions and 46 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
include/dlfcn.h
View File

@ -66,6 +66,13 @@ __BEGIN_DECLS
int dladdr __P((const void *, Dl_info *));
int dlclose __P((void *));
const char *dlerror __P((void));
void dllockinit __P((void *_context,
void *(*_lock_create)(void *_context),
void (*_rlock_acquire)(void *_lock),
void (*_wlock_acquire)(void *_lock),
void (*_lock_release)(void *_lock),
void (*_lock_destroy)(void *_lock),
void (*_context_destroy)(void *_context)));
void *dlopen __P((const char *, int));
void *dlsym __P((void *, const char *));
__END_DECLS

2
lib/libc/gen/Makefile.inc
View File

@ -34,7 +34,7 @@ SRCS+= _rand48.c _spinlock_stub.c alarm.c arc4random.c assert.c \
.if ${LIB} == "c"
MAN3+= alarm.3 arc4random.3 clock.3 \
confstr.3 crypt.3 ctermid.3 daemon.3 \
devname.3 directory.3 dladdr.3 dlopen.3 \
devname.3 directory.3 dladdr.3 dllockinit.3 dlopen.3 \
err.3 exec.3 fnmatch.3 frexp.3 ftok.3 fts.3 \
getbootfile.3 getbsize.3 getcap.3 getcwd.3 \
getdiskbyname.3 getdomainname.3 getfsent.3 \

14
lib/libc/gen/dlfcn.c
View File

@ -78,6 +78,20 @@ dlerror(void)
return sorry;
}
#pragma weak dllockinit
void
dllockinit(void *context,
void *(*lock_create)(void *context),
void (*rlock_acquire)(void *lock),
void (*wlock_acquire)(void *lock),
void (*lock_release)(void *lock),
void (*lock_destroy)(void *lock),
void (*context_destroy)(void *context))
{
if (context_destroy != NULL)
context_destroy(context);
}
#pragma weak dlopen
void *
dlopen(const char *name, int mode)

109
lib/libc/gen/dllockinit.3 Normal file
View File

@ -0,0 +1,109 @@
.\"
.\" Copyright (c) 1999 John D. Polstra
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd December 26, 1999
.Os FreeBSD
.Dt DLLOCKINIT 3
.Sh NAME
.Nm dllockinit
.Nd register thread locking methods with the dynamic linker
.Sh SYNOPSIS
.Fd #include <dlfcn.h>
.Ft void
.Fn dllockinit "const void *context" "void *(*lock_create)(void *context)" \
"void (*rlock_acquire)(void *lock)" "void (*wlock_acquire)(void *lock)" \
"void (*lock_release)(void *lock)" "void (*lock_destroy)(void *lock)" \
"void (*context_destroy)(void *context)"
.Sh DESCRIPTION
Threads packages can call
.Nm
at initialization time to register locking functions for the dynamic
linker to use. This enables the dynamic linker to prevent multiple
threads from entering its critical sections simultaneously.
.Pp
The
.Fa context
parameter specifies an opaque context for creating locks. The
dynamic linker will pass it to the
.Fa lock_create
function when creating the locks it needs. When the dynamic linker
is permanently finished using the locking functions (e.g., if the
program makes a subsequent call to
.Nm
to register new locking functions) it will call
.Fa context_destroy
to destroy the context.
.Pp
The
.Fa lock_create
parameter specifies a function for creating a read/write lock. It
must return a pointer to the new lock.
.Pp
The
.Fa rlock_acquire
and
.Fa wlock_acquire
parameters specify functions which lock a lock for reading or
writing, respectively. The
.Fa lock_release
parameter specifies a function which unlocks a lock. Each of these
functions is passed a pointer to the lock.
.Pp
The
.Fa lock_destroy
parameter specifies a function to destroy a lock. It may be
.Dv NULL
if locks do not need to be destroyed. The
.Fa context_destroy
specifies a function to destroy the context. It may be
.Dv NULL
if the context does not need to be destroyed.
.Pp
Before
.Nm
is called, the dynamic linker protects its critical sections by
blocking the
.Dv SIGVTALRM ,
.Dv SIGPROF ,
and
.Dv SIGALRM
signals. This is sufficient for many application level threads
packages, which typically use one of these signals to implement
preemption. An application which has registered its own locking
methods with
.Nm
can restore the default locking by calling
.Nm
with all arguments
.Dv NULL .
.Sh SEE ALSO
.Xr rtld 1 ,
.Xr signal 3
.Sh HISTORY
The
.Nm
function first appeared in FreeBSD 4.0.

4
libexec/rtld-elf/Makefile
View File

@ -3,8 +3,8 @@
#
MAINTAINER= jdp
PROG= ld-elf.so.1
SRCS= rtld_start.S rtld.c map_object.c malloc.c xmalloc.c debug.c \
reloc.c
SRCS= rtld_start.S rtld.c lockdflt.c map_object.c malloc.c \
xmalloc.c debug.c reloc.c
NOMAN= true
CFLAGS+= -Wall -DFREEBSD_ELF -I${.CURDIR}/${MACHINE_ARCH} -I${.CURDIR}
LDFLAGS+= -nostdlib -e .rtld_start

94
libexec/rtld-elf/alpha/lockdflt.c Normal file
View File

@ -0,0 +1,94 @@
/*-
* Copyright 1999 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $FreeBSD$
*/
/*
* Default thread locking implementation for the dynamic linker. It
* is used until the client registers a different implementation with
* dllockinit(). The default implementation does mutual exclusion
* by blocking the SIGVTALRM, SIGPROF, and SIGALRM signals. This is
* based on the observation that most userland thread packages use one
* of these signals to support preemption.
*/
#include <dlfcn.h>
#include <signal.h>
#include <stdlib.h>
#include "debug.h"
#include "rtld.h"
typedef struct Struct_LockDflt {
sigset_t lock_mask;
sigset_t old_mask;
int depth;
} LockDflt;
void
lockdflt_acquire(void *lock)
{
LockDflt *l = (LockDflt *)lock;
sigprocmask(SIG_BLOCK, &l->lock_mask, &l->old_mask);
assert(l->depth == 0);
l->depth++;
}
void *
lockdflt_create(void *context)
{
LockDflt *l;
l = NEW(LockDflt);
l->depth = 0;
sigemptyset(&l->lock_mask);
sigaddset(&l->lock_mask, SIGVTALRM);
sigaddset(&l->lock_mask, SIGPROF);
sigaddset(&l->lock_mask, SIGALRM);
return l;
}
void
lockdflt_destroy(void *lock)
{
LockDflt *l = (LockDflt *)lock;
free(l);
}
void
lockdflt_release(void *lock)
{
LockDflt *l = (LockDflt *)lock;
assert(l->depth == 1);
l->depth--;
sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
}
void
lockdflt_init(void)
{
dllockinit(NULL, lockdflt_create, lockdflt_acquire, lockdflt_acquire,
lockdflt_release, lockdflt_destroy, NULL);
}

9
libexec/rtld-elf/alpha/reloc.c
View File

@ -47,15 +47,6 @@
#include "debug.h"
#include "rtld.h"
/*
* Debugging support.
*/
#define assert(cond) ((cond) ? (void) 0 :\
(msg("oops: " __XSTRING(__LINE__) "\n"), abort()))
#define msg(s) (write(1, s, strlen(s)))
#define trace() msg("trace: " __XSTRING(__LINE__) "\n");
extern Elf_Dyn _DYNAMIC;
/* Relocate a non-PLT object with addend. */

94
libexec/rtld-elf/amd64/lockdflt.c Normal file
View File

@ -0,0 +1,94 @@
/*-
* Copyright 1999 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $FreeBSD$
*/
/*
* Default thread locking implementation for the dynamic linker. It
* is used until the client registers a different implementation with
* dllockinit(). The default implementation does mutual exclusion
* by blocking the SIGVTALRM, SIGPROF, and SIGALRM signals. This is
* based on the observation that most userland thread packages use one
* of these signals to support preemption.
*/
#include <dlfcn.h>
#include <signal.h>
#include <stdlib.h>
#include "debug.h"
#include "rtld.h"
typedef struct Struct_LockDflt {
sigset_t lock_mask;
sigset_t old_mask;
int depth;
} LockDflt;
void
lockdflt_acquire(void *lock)
{
LockDflt *l = (LockDflt *)lock;
sigprocmask(SIG_BLOCK, &l->lock_mask, &l->old_mask);
assert(l->depth == 0);
l->depth++;
}
void *
lockdflt_create(void *context)
{
LockDflt *l;
l = NEW(LockDflt);
l->depth = 0;
sigemptyset(&l->lock_mask);
sigaddset(&l->lock_mask, SIGVTALRM);
sigaddset(&l->lock_mask, SIGPROF);
sigaddset(&l->lock_mask, SIGALRM);
return l;
}
void
lockdflt_destroy(void *lock)
{
LockDflt *l = (LockDflt *)lock;
free(l);
}
void
lockdflt_release(void *lock)
{
LockDflt *l = (LockDflt *)lock;
assert(l->depth == 1);
l->depth--;
sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
}
void
lockdflt_init(void)
{
dllockinit(NULL, lockdflt_create, lockdflt_acquire, lockdflt_acquire,
lockdflt_release, lockdflt_destroy, NULL);
}

9
libexec/rtld-elf/amd64/reloc.c
View File

@ -47,15 +47,6 @@
#include "debug.h"
#include "rtld.h"
/*
* Debugging support.
*/
#define assert(cond) ((cond) ? (void) 0 :\
(msg("oops: " __XSTRING(__LINE__) "\n"), abort()))
#define msg(s) (write(1, s, strlen(s)))
#define trace() msg("trace: " __XSTRING(__LINE__) "\n");
/*
* Process the special R_386_COPY relocations in the main program. These
* copy data from a shared object into a region in the main program's BSS

9
libexec/rtld-elf/debug.h
View File

@ -38,6 +38,9 @@
#include <sys/cdefs.h>
#include <string.h>
#include <unistd.h>
extern void debug_printf(const char *, ...) __printflike(1, 2);
extern int debug;
@ -47,4 +50,10 @@ extern int debug;
#define dbg(format, args...) ((void) 0)
#endif
#define assert(cond) ((cond) ? (void) 0 : \
(msg("ld-elf.so.1: assert failed: " __FILE__ ":" \
__XSTRING(__LINE__) "\n"), abort()))
#define msg(s) write(1, s, strlen(s))
#define trace() msg("ld-elf.so.1: " __XSTRING(__LINE__) "\n")
#endif /* DEBUG_H */

94
libexec/rtld-elf/i386/lockdflt.c Normal file
View File

@ -0,0 +1,94 @@
/*-
* Copyright 1999 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $FreeBSD$
*/
/*
* Default thread locking implementation for the dynamic linker. It
* is used until the client registers a different implementation with
* dllockinit(). The default implementation does mutual exclusion
* by blocking the SIGVTALRM, SIGPROF, and SIGALRM signals. This is
* based on the observation that most userland thread packages use one
* of these signals to support preemption.
*/
#include <dlfcn.h>
#include <signal.h>
#include <stdlib.h>
#include "debug.h"
#include "rtld.h"
typedef struct Struct_LockDflt {
sigset_t lock_mask;
sigset_t old_mask;
int depth;
} LockDflt;
void
lockdflt_acquire(void *lock)
{
LockDflt *l = (LockDflt *)lock;
sigprocmask(SIG_BLOCK, &l->lock_mask, &l->old_mask);
assert(l->depth == 0);
l->depth++;
}
void *
lockdflt_create(void *context)
{
LockDflt *l;
l = NEW(LockDflt);
l->depth = 0;
sigemptyset(&l->lock_mask);
sigaddset(&l->lock_mask, SIGVTALRM);
sigaddset(&l->lock_mask, SIGPROF);
sigaddset(&l->lock_mask, SIGALRM);
return l;
}
void
lockdflt_destroy(void *lock)
{
LockDflt *l = (LockDflt *)lock;
free(l);
}
void
lockdflt_release(void *lock)
{
LockDflt *l = (LockDflt *)lock;
assert(l->depth == 1);
l->depth--;
sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
}
void
lockdflt_init(void)
{
dllockinit(NULL, lockdflt_create, lockdflt_acquire, lockdflt_acquire,
lockdflt_release, lockdflt_destroy, NULL);
}

9
libexec/rtld-elf/i386/reloc.c
View File

@ -47,15 +47,6 @@
#include "debug.h"
#include "rtld.h"
/*
* Debugging support.
*/
#define assert(cond) ((cond) ? (void) 0 :\
(msg("oops: " __XSTRING(__LINE__) "\n"), abort()))
#define msg(s) (write(1, s, strlen(s)))
#define trace() msg("trace: " __XSTRING(__LINE__) "\n");
/*
* Process the special R_386_COPY relocations in the main program. These
* copy data from a shared object into a region in the main program's BSS

94
libexec/rtld-elf/lockdflt.c Normal file
View File

@ -0,0 +1,94 @@
/*-
* Copyright 1999 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $FreeBSD$
*/
/*
* Default thread locking implementation for the dynamic linker. It
* is used until the client registers a different implementation with
* dllockinit(). The default implementation does mutual exclusion
* by blocking the SIGVTALRM, SIGPROF, and SIGALRM signals. This is
* based on the observation that most userland thread packages use one
* of these signals to support preemption.
*/
#include <dlfcn.h>
#include <signal.h>
#include <stdlib.h>
#include "debug.h"
#include "rtld.h"
typedef struct Struct_LockDflt {
sigset_t lock_mask;
sigset_t old_mask;
int depth;
} LockDflt;
void
lockdflt_acquire(void *lock)
{
LockDflt *l = (LockDflt *)lock;
sigprocmask(SIG_BLOCK, &l->lock_mask, &l->old_mask);
assert(l->depth == 0);
l->depth++;
}
void *
lockdflt_create(void *context)
{
LockDflt *l;
l = NEW(LockDflt);
l->depth = 0;
sigemptyset(&l->lock_mask);
sigaddset(&l->lock_mask, SIGVTALRM);
sigaddset(&l->lock_mask, SIGPROF);
sigaddset(&l->lock_mask, SIGALRM);
return l;
}
void
lockdflt_destroy(void *lock)
{
LockDflt *l = (LockDflt *)lock;
free(l);
}
void
lockdflt_release(void *lock)
{
LockDflt *l = (LockDflt *)lock;
assert(l->depth == 1);
l->depth--;
sigprocmask(SIG_SETMASK, &l->old_mask, NULL);
}
void
lockdflt_init(void)
{
dllockinit(NULL, lockdflt_create, lockdflt_acquire, lockdflt_acquire,
lockdflt_release, lockdflt_destroy, NULL);
}

134
libexec/rtld-elf/rtld.c
View File

@ -52,21 +52,23 @@
#include "debug.h"
#include "rtld.h"
/*
* Debugging support.
*/
#define assert(cond) ((cond) ? (void) 0 :\
(msg("oops: " __XSTRING(__LINE__) "\n"), abort()))
#define msg(s) (write(1, s, strlen(s)))
#define trace() msg("trace: " __XSTRING(__LINE__) "\n");
#define END_SYM "_end"
#define PATH_RTLD "/usr/libexec/ld-elf.so.1"
/* Types. */
typedef void (*func_ptr_type)();
typedef struct Struct_LockInfo {
void *context; /* Client context for creating locks */
void *thelock; /* The one big lock */
/* Methods */
void (*rlock_acquire)(void *lock);
void (*wlock_acquire)(void *lock);
void (*lock_release)(void *lock);
void (*lock_destroy)(void *lock);
void (*context_destroy)(void *context);
} LockInfo;
/*
* Function declarations.
*/
@ -88,6 +90,7 @@ static void linkmap_delete(Obj_Entry *);
static int load_needed_objects(Obj_Entry *);
static int load_preload_objects(void);
static Obj_Entry *load_object(char *);
static void lock_nop(void *);
static Obj_Entry *obj_from_addr(const void *);
static void objlist_add(Objlist *, Obj_Entry *);
static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *);
@ -128,6 +131,8 @@ static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */
static Objlist list_main = /* Objects loaded at program startup */
STAILQ_HEAD_INITIALIZER(list_main);
static LockInfo lockinfo;
static Elf_Sym sym_zero; /* For resolving undefined weak refs. */
#define GDB_STATE(s) r_debug.r_state = s; r_debug_state();
@ -147,6 +152,7 @@ static func_ptr_type exports[] = {
(func_ptr_type) &dlopen,
(func_ptr_type) &dlsym,
(func_ptr_type) &dladdr,
(func_ptr_type) &dllockinit,
NULL
};
@ -157,6 +163,24 @@ static func_ptr_type exports[] = {
char *__progname;
char **environ;
static __inline void
rlock_acquire(void)
{
lockinfo.rlock_acquire(lockinfo.thelock);
}
static __inline void
wlock_acquire(void)
{
lockinfo.wlock_acquire(lockinfo.thelock);
}
static __inline void
lock_release(void)
{
lockinfo.lock_release(lockinfo.thelock);
}
/*
* Main entry point for dynamic linking. The first argument is the
* stack pointer. The stack is expected to be laid out as described
@ -322,6 +346,9 @@ _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : "");
set_program_var("environ", env);
dbg("initializing default locks");
dllockinit(NULL, NULL, NULL, NULL, NULL, NULL, NULL);
r_debug_state(); /* say hello to gdb! */
dbg("calling _init functions");
@ -344,6 +371,7 @@ _rtld_bind(Obj_Entry *obj, Elf_Word reloff)
Elf_Addr *where;
Elf_Addr target;
wlock_acquire();
if (obj->pltrel)
rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff);
else
@ -361,6 +389,7 @@ _rtld_bind(Obj_Entry *obj, Elf_Word reloff)
(void *)target, basename(defobj->path));
reloc_jmpslot(where, target);
lock_release();
return target;
}
@ -1058,6 +1087,11 @@ load_object(char *path)
return obj;
}
static void
lock_nop(void *lock)
{
}
static Obj_Entry *
obj_from_addr(const void *addr)
{
@ -1223,16 +1257,21 @@ search_library_path(const char *name, const char *path)
int
dlclose(void *handle)
{
Obj_Entry *root = dlcheck(handle);
Obj_Entry *root;
if (root == NULL)
wlock_acquire();
root = dlcheck(handle);
if (root == NULL) {
lock_release();
return -1;
}
GDB_STATE(RT_DELETE);
unload_object(root, true);
root->dl_refcount--;
GDB_STATE(RT_CONSISTENT);
lock_release();
return 0;
}
@ -1244,14 +1283,67 @@ dlerror(void)
return msg;
}
void
dllockinit(void *context,
void *(*lock_create)(void *context),
void (*rlock_acquire)(void *lock),
void (*wlock_acquire)(void *lock),
void (*lock_release)(void *lock),
void (*lock_destroy)(void *lock),
void (*context_destroy)(void *context))
{
/* NULL arguments mean reset to the built-in locks. */
if (lock_create == NULL) {
context = NULL;
lock_create = lockdflt_create;
rlock_acquire = wlock_acquire = lockdflt_acquire;
lock_release = lockdflt_release;
lock_destroy = lockdflt_destroy;
context_destroy = NULL;
}
/* Temporarily set locking methods to no-ops. */
lockinfo.rlock_acquire = lock_nop;
lockinfo.wlock_acquire = lock_nop;
lockinfo.lock_release = lock_nop;
/* Release any existing locks and context. */
if (lockinfo.lock_destroy != NULL)
lockinfo.lock_destroy(lockinfo.thelock);
if (lockinfo.context_destroy != NULL)
lockinfo.context_destroy(lockinfo.context);
/*
* Allocate the locks we will need and call all the new locking
* methods, to accomplish any needed lazy binding for the methods
* themselves.
*/
lockinfo.thelock = lock_create(lockinfo.context);
rlock_acquire(lockinfo.thelock);
lock_release(lockinfo.thelock);
wlock_acquire(lockinfo.thelock);
lock_release(lockinfo.thelock);
/* Record the new method information. */
lockinfo.context = context;
lockinfo.rlock_acquire = rlock_acquire;
lockinfo.wlock_acquire = wlock_acquire;
lockinfo.lock_release = lock_release;
lockinfo.lock_destroy = lock_destroy;
lockinfo.context_destroy = context_destroy;
}
void *
dlopen(const char *name, int mode)
{
Obj_Entry **old_obj_tail = obj_tail;
Obj_Entry *obj = NULL;
Obj_Entry **old_obj_tail;
Obj_Entry *obj;
wlock_acquire();
GDB_STATE(RT_ADD);
old_obj_tail = obj_tail;
obj = NULL;
if (name == NULL) {
obj = obj_main;
obj->refcount++;
@ -1280,7 +1372,7 @@ dlopen(const char *name, int mode)
}
GDB_STATE(RT_CONSISTENT);
lock_release();
return obj;
}
@ -1296,12 +1388,14 @@ dlsym(void *handle, const char *name)
def = NULL;
defobj = NULL;
wlock_acquire();
if (handle == NULL || handle == RTLD_NEXT) {
void *retaddr;
retaddr = __builtin_return_address(0); /* __GNUC__ only */
if ((obj = obj_from_addr(retaddr)) == NULL) {
_rtld_error("Cannot determine caller's shared object");
lock_release();
return NULL;
}
if (handle == NULL) { /* Just the caller's shared object. */
@ -1316,8 +1410,10 @@ dlsym(void *handle, const char *name)
}
}
} else {
if ((obj = dlcheck(handle)) == NULL)
if ((obj = dlcheck(handle)) == NULL) {
lock_release();
return NULL;
}
if (obj->mainprog) {
/* Search main program and all libraries loaded by it. */
@ -1333,10 +1429,13 @@ dlsym(void *handle, const char *name)
}
}
if (def != NULL)
if (def != NULL) {
lock_release();
return defobj->relocbase + def->st_value;
}
_rtld_error("Undefined symbol \"%s\"", name);
lock_release();
return NULL;
}
@ -1348,9 +1447,11 @@ dladdr(const void *addr, Dl_info *info)
void *symbol_addr;
unsigned long symoffset;
wlock_acquire();
obj = obj_from_addr(addr);
if (obj == NULL) {
_rtld_error("No shared object contains address");
lock_release();
return 0;
}
info->dli_fname = obj->path;
@ -1389,6 +1490,7 @@ dladdr(const void *addr, Dl_info *info)
if (info->dli_saddr == addr)
break;
}
lock_release();
return 1;
}

4
libexec/rtld-elf/rtld.h
View File

@ -157,6 +157,10 @@ unsigned long elf_hash(const char *);
const Elf_Sym *find_symdef(unsigned long, Obj_Entry *, const Obj_Entry **,
bool);
void init_pltgot(Obj_Entry *);
void lockdflt_acquire(void *);
void *lockdflt_create(void *);
void lockdflt_destroy(void *);
void lockdflt_release(void *);
void obj_free(Obj_Entry *);
Obj_Entry *obj_new(void);
int reloc_non_plt(Obj_Entry *, Obj_Entry *);