diff options
Diffstat (limited to 'dlfcn')
| -rw-r--r-- | dlfcn/Makefile | 3 | ||||
| -rw-r--r-- | dlfcn/Versions | 6 | ||||
| -rw-r--r-- | dlfcn/dlerror.c | 305 | ||||
| -rw-r--r-- | dlfcn/dlerror.h | 92 | ||||
| -rw-r--r-- | dlfcn/dlfreeres.c | 29 | ||||
| -rw-r--r-- | dlfcn/libc_dlerror_result.c | 39 |
6 files changed, 265 insertions, 209 deletions
diff --git a/dlfcn/Makefile b/dlfcn/Makefile index d51fd08..994a3af 100644 --- a/dlfcn/Makefile +++ b/dlfcn/Makefile @@ -22,9 +22,10 @@ include ../Makeconfig headers := bits/dlfcn.h dlfcn.h extra-libs := libdl libdl-routines := dlopen dlclose dlsym dlvsym dlerror dladdr dladdr1 dlinfo \ - dlmopen dlfcn dlfreeres + dlmopen dlfcn routines := $(patsubst %,s%,$(filter-out dlfcn,$(libdl-routines))) elide-routines.os := $(routines) +routines += libc_dlerror_result extra-libs-others := libdl diff --git a/dlfcn/Versions b/dlfcn/Versions index 1df6925..f07cb92 100644 --- a/dlfcn/Versions +++ b/dlfcn/Versions @@ -1,3 +1,8 @@ +libc { + GLIBC_PRIVATE { + __libc_dlerror_result; + } +} libdl { GLIBC_2.0 { dladdr; dlclose; dlerror; dlopen; dlsym; @@ -13,6 +18,5 @@ libdl { } GLIBC_PRIVATE { _dlfcn_hook; - __libdl_freeres; } } diff --git a/dlfcn/dlerror.c b/dlfcn/dlerror.c index 947b7c1..7db70a2 100644 --- a/dlfcn/dlerror.c +++ b/dlfcn/dlerror.c @@ -25,6 +25,8 @@ #include <libc-lock.h> #include <ldsodefs.h> #include <libc-symbols.h> +#include <assert.h> +#include <dlerror.h> #if !defined SHARED && IS_IN (libdl) @@ -36,92 +38,75 @@ dlerror (void) #else -/* Type for storing results of dynamic loading actions. */ -struct dl_action_result - { - int errcode; - int returned; - bool malloced; - const char *objname; - const char *errstring; - }; -static struct dl_action_result last_result; -static struct dl_action_result *static_buf; - -/* This is the key for the thread specific memory. */ -static __libc_key_t key; -__libc_once_define (static, once); - -/* Destructor for the thread-specific data. */ -static void init (void); -static void free_key_mem (void *mem); - - char * __dlerror (void) { - char *buf = NULL; - struct dl_action_result *result; - # ifdef SHARED if (!rtld_active ()) return _dlfcn_hook->dlerror (); # endif - /* If we have not yet initialized the buffer do it now. */ - __libc_once (once, init); + struct dl_action_result *result = __libc_dlerror_result; - /* Get error string. */ - if (static_buf != NULL) - result = static_buf; - else + /* No libdl function has been called. No error is possible. */ + if (result == NULL) + return NULL; + + /* For an early malloc failure, clear the error flag and return the + error message. This marks the error as delivered. */ + if (result == dl_action_result_malloc_failed) { - /* init () has been run and we don't use the static buffer. - So we have a valid key. */ - result = (struct dl_action_result *) __libc_getspecific (key); - if (result == NULL) - result = &last_result; + __libc_dlerror_result = NULL; + return (char *) "out of memory"; } - /* Test whether we already returned the string. */ - if (result->returned != 0) + /* Placeholder object. This can be observed in a recursive call, + e.g. from an ELF constructor. */ + if (result->errstring == NULL) + return NULL; + + /* If we have already reported the error, we can free the result and + return NULL. See __libc_dlerror_result_free. */ + if (result->returned) { - /* We can now free the string. */ - if (result->errstring != NULL) - { - if (strcmp (result->errstring, "out of memory") != 0) - free ((char *) result->errstring); - result->errstring = NULL; - } + __libc_dlerror_result = NULL; + dl_action_result_errstring_free (result); + free (result); + return NULL; } - else if (result->errstring != NULL) - { - buf = (char *) result->errstring; - int n; - if (result->errcode == 0) - n = __asprintf (&buf, "%s%s%s", - result->objname, - result->objname[0] == '\0' ? "" : ": ", - _(result->errstring)); - else - n = __asprintf (&buf, "%s%s%s: %s", - result->objname, - result->objname[0] == '\0' ? "" : ": ", - _(result->errstring), - strerror (result->errcode)); - if (n != -1) - { - /* We don't need the error string anymore. */ - if (strcmp (result->errstring, "out of memory") != 0) - free ((char *) result->errstring); - result->errstring = buf; - } - /* Mark the error as returned. */ - result->returned = 1; - } + assert (result->errstring != NULL); + + /* Create the combined error message. */ + char *buf; + int n; + if (result->errcode == 0) + n = __asprintf (&buf, "%s%s%s", + result->objname, + result->objname[0] == '\0' ? "" : ": ", + _(result->errstring)); + else + n = __asprintf (&buf, "%s%s%s: %s", + result->objname, + result->objname[0] == '\0' ? "" : ": ", + _(result->errstring), + strerror (result->errcode)); - return buf; + /* Mark the error as delivered. */ + result->returned = true; + + if (n >= 0) + { + /* Replace the error string with the newly allocated one. */ + dl_action_result_errstring_free (result); + result->errstring = buf; + result->errstring_source = dl_action_result_errstring_local; + return buf; + } + else + /* We could not create the combined error message, so use the + existing string as a fallback. */ + return result->errstring; } # ifdef SHARED strong_alias (__dlerror, dlerror) @@ -130,130 +115,94 @@ strong_alias (__dlerror, dlerror) int _dlerror_run (void (*operate) (void *), void *args) { - struct dl_action_result *result; - - /* If we have not yet initialized the buffer do it now. */ - __libc_once (once, init); - - /* Get error string and number. */ - if (static_buf != NULL) - result = static_buf; - else + struct dl_action_result *result = __libc_dlerror_result; + if (result != NULL) { - /* We don't use the static buffer and so we have a key. Use it - to get the thread-specific buffer. */ - result = __libc_getspecific (key); - if (result == NULL) + if (result == dl_action_result_malloc_failed) { - result = (struct dl_action_result *) calloc (1, sizeof (*result)); - if (result == NULL) - /* We are out of memory. Since this is no really critical - situation we carry on by using the global variable. - This might lead to conflicts between the threads but - they soon all will have memory problems. */ - result = &last_result; - else - /* Set the tsd. */ - __libc_setspecific (key, result); + /* Clear the previous error. */ + __libc_dlerror_result = NULL; + result = NULL; + } + else + { + /* There is an existing object. Free its error string, but + keep the object. */ + dl_action_result_errstring_free (result); + /* Mark the object as not containing an error. This ensures + that call to dlerror from, for example, an ELF + constructor will not notice this result object. */ + result->errstring = NULL; } } - if (result->errstring != NULL) - { - /* Free the error string from the last failed command. This can - happen if `dlerror' was not run after an error was found. */ - if (result->malloced) - free ((char *) result->errstring); - result->errstring = NULL; - } - - result->errcode = GLRO (dl_catch_error) (&result->objname, - &result->errstring, - &result->malloced, - operate, args); - - /* If no error we mark that no error string is available. */ - result->returned = result->errstring == NULL; + const char *objname; + const char *errstring; + bool malloced; + int errcode = GLRO (dl_catch_error) (&objname, &errstring, &malloced, + operate, args); - return result->errstring != NULL; -} + /* ELF constructors or destructors may have indirectly altered the + value of __libc_dlerror_result, therefore reload it. */ + result = __libc_dlerror_result; - -/* Initialize buffers for results. */ -static void -init (void) -{ - if (__libc_key_create (&key, free_key_mem)) - /* Creating the key failed. This means something really went - wrong. In any case use a static buffer which is better than - nothing. */ - static_buf = &last_result; -} - - -static void -check_free (struct dl_action_result *rec) -{ - if (rec->errstring != NULL - && strcmp (rec->errstring, "out of memory") != 0) + if (errstring == NULL) { - /* We can free the string only if the allocation happened in the - C library used by the dynamic linker. This means, it is - always the C library in the base namespace. When we're statically - linked, the dynamic linker is part of the program and so always - uses the same C library we use here. */ -#ifdef SHARED - struct link_map *map = NULL; - Dl_info info; - if (_dl_addr (check_free, &info, &map, NULL) != 0 && map->l_ns == 0) -#endif + /* There is no error. We no longer need the result object if it + does not contain an error. However, a recursive call may + have added an error even if this call did not cause it. Keep + the other error. */ + if (result != NULL && result->errstring == NULL) { - free ((char *) rec->errstring); - rec->errstring = NULL; + __libc_dlerror_result = NULL; + free (result); } + return 0; } -} - - -static void -__attribute__ ((destructor)) -fini (void) -{ - check_free (&last_result); -} - - -/* Free the thread specific data, this is done if a thread terminates. */ -static void -free_key_mem (void *mem) -{ - check_free ((struct dl_action_result *) mem); + else + { + /* A new error occurred. Check if a result object has to be + allocated. */ + if (result == NULL || result == dl_action_result_malloc_failed) + { + /* Allocating storage for the error message after the fact + is not ideal. But this avoids an infinite recursion in + case malloc itself calls libdl functions (without + triggering errors). */ + result = malloc (sizeof (*result)); + if (result == NULL) + { + /* Assume that the dlfcn failure was due to a malloc + failure, too. */ + if (malloced) + dl_error_free ((char *) errstring); + __libc_dlerror_result = dl_action_result_malloc_failed; + return 1; + } + __libc_dlerror_result = result; + } + else + /* Deallocate the existing error message from a recursive + call, but reuse the result object. */ + dl_action_result_errstring_free (result); + + result->errcode = errcode; + result->objname = objname; + result->errstring = (char *) errstring; + result->returned = false; + /* In case of an error, the malloced flag indicates whether the + error string is constant or not. */ + if (malloced) + result->errstring_source = dl_action_result_errstring_rtld; + else + result->errstring_source = dl_action_result_errstring_constant; - free (mem); - __libc_setspecific (key, NULL); + return 1; + } } # ifdef SHARED -/* Free the dlerror-related resources. */ -void -__dlerror_main_freeres (void) -{ - /* Free the global memory if used. */ - check_free (&last_result); - - if (__libc_once_get (once) && static_buf == NULL) - { - /* init () has been run and we don't use the static buffer. - So we have a valid key. */ - void *mem; - /* 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) diff --git a/dlfcn/dlerror.h b/dlfcn/dlerror.h new file mode 100644 index 0000000..cb9a9ce --- /dev/null +++ b/dlfcn/dlerror.h @@ -0,0 +1,92 @@ +/* Memory management for dlerror messages. + Copyright (C) 2021 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 + <https://www.gnu.org/licenses/>. */ + +#ifndef _DLERROR_H +#define _DLERROR_H + +#include <dlfcn.h> +#include <ldsodefs.h> +#include <stdbool.h> +#include <stdint.h> +#include <stdlib.h> + +/* Source of the errstring member in struct dl_action_result, for + finding the right deallocation routine. */ +enum dl_action_result_errstring_source + { + dl_action_result_errstring_constant, /* String literal, no deallocation. */ + dl_action_result_errstring_rtld, /* libc in the primary namespace. */ + dl_action_result_errstring_local, /* libc in the current namespace. */ + }; + +struct dl_action_result +{ + int errcode; + char errstring_source; + bool returned; + const char *objname; + char *errstring; +}; + +/* Used to free the errstring member of struct dl_action_result in the + dl_action_result_errstring_rtld case. */ +static inline void +dl_error_free (void *ptr) +{ +#ifdef SHARED + /* In the shared case, ld.so may use a different malloc than this + namespace. */ + GLRO (dl_error_free (ptr)); +#else + /* Call the implementation directly. It still has to check for + pointers which cannot be freed, so do not call free directly + here. */ + _dl_error_free (ptr); +#endif +} + +/* Deallocate RESULT->errstring, leaving *RESULT itself allocated. */ +static inline void +dl_action_result_errstring_free (struct dl_action_result *result) +{ + switch (result->errstring_source) + { + case dl_action_result_errstring_constant: + break; + case dl_action_result_errstring_rtld: + dl_error_free (result->errstring); + break; + case dl_action_result_errstring_local: + free (result->errstring); + break; + } +} + +/* Stand-in for an error result object whose allocation failed. No + precise message can be reported for this, but an error must still + be signaled. */ +static struct dl_action_result *const dl_action_result_malloc_failed + __attribute__ ((unused)) = (struct dl_action_result *) (intptr_t) -1; + +/* Thread-local variable for storing dlfcn failures for subsequent + reporting via dlerror. */ +extern __thread struct dl_action_result *__libc_dlerror_result + attribute_tls_model_ie; +void __libc_dlerror_result_free (void) attribute_hidden; + +#endif /* _DLERROR_H */ diff --git a/dlfcn/dlfreeres.c b/dlfcn/dlfreeres.c deleted file mode 100644 index 856b764..0000000 --- a/dlfcn/dlfreeres.c +++ /dev/null @@ -1,29 +0,0 @@ -/* Clean up allocated libdl memory on demand. - Copyright (C) 2018-2021 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 - <https://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); -} diff --git a/dlfcn/libc_dlerror_result.c b/dlfcn/libc_dlerror_result.c new file mode 100644 index 0000000..9974718 --- /dev/null +++ b/dlfcn/libc_dlerror_result.c @@ -0,0 +1,39 @@ +/* Thread-local variable holding the dlerror result. + Copyright (C) 2021 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 <dlerror.h> + +/* This pointer is either NULL, dl_action_result_malloc_failed (), or + has been allocated using malloc by the namespace that also contains + this instance of the thread-local variable. */ +__thread struct dl_action_result *__libc_dlerror_result attribute_tls_model_ie; + +/* Called during thread shutdown to free resources. */ +void +__libc_dlerror_result_free (void) +{ + if (__libc_dlerror_result != NULL) + { + if (__libc_dlerror_result != dl_action_result_malloc_failed) + { + dl_action_result_errstring_free (__libc_dlerror_result); + free (__libc_dlerror_result); + } + __libc_dlerror_result = NULL; + } +} |