| From e50de21c6e58dd471a423dbcea360b897aeda51a Mon Sep 17 00:00:00 2001 |
| From: Florian Weimer <fweimer@redhat.com> |
| Date: Wed, 3 Feb 2021 08:55:13 -0300 |
| Subject: [PATCH] linux: Require /dev/shm as the shared memory file system |
| |
| Previously, glibc would pick an arbitrary tmpfs file system from |
| /proc/mounts if /dev/shm was not available. This could lead to |
| an unsuitable file system being picked for the backing storage for |
| shm_open, sem_open, and related functions. |
| |
| This patch introduces a new function, __shm_get_name, which builds |
| the file name under the appropriate (now hard-coded) directory. It is |
| called from the various shm_* and sem_* function. Unlike the |
| SHM_GET_NAME macro it replaces, the callers handle the return values |
| and errno updates. shm-directory.c is moved directly into the posix |
| subdirectory because it can be implemented directly using POSIX |
| functionality. It resides in libc because it is needed by both |
| librt and nptl/htl. |
| |
| In the sem_open implementation, tmpfname is initialized directly |
| from a string constant. This happens to remove one alloca call. |
| |
| Checked on x86_64-linux-gnu. |
| |
| [Adrian: backported to glibc v2.32] |
| Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com> |
| --- |
| htl/Makefile | 2 - |
| htl/Versions | 1 - |
| {sysdeps/nptl => include}/shm-directory.h | 28 +++-- |
| nptl/Makefile | 1 - |
| nptl/Versions | 1 - |
| nptl/nptlfreeres.c | 1 - |
| nptl/pthreadP.h | 1 - |
| nptl/sem_open.c | 34 ++--- |
| nptl/sem_unlink.c | 10 +- |
| posix/Makefile | 3 +- |
| posix/Versions | 1 + |
| {sysdeps/posix => posix}/shm-directory.c | 30 +++-- |
| sysdeps/htl/shm-directory.h | 30 ----- |
| sysdeps/posix/Makefile | 6 - |
| sysdeps/posix/shm-directory.h | 66 ---------- |
| sysdeps/posix/shm_open.c | 10 +- |
| sysdeps/posix/shm_unlink.c | 13 +- |
| sysdeps/unix/sysv/linux/shm-directory.c | 147 ---------------------- |
| 18 files changed, 84 insertions(+), 301 deletions(-) |
| rename {sysdeps/nptl => include}/shm-directory.h (59%) |
| rename {sysdeps/posix => posix}/shm-directory.c (60%) |
| delete mode 100644 sysdeps/htl/shm-directory.h |
| delete mode 100644 sysdeps/posix/shm-directory.h |
| delete mode 100644 sysdeps/unix/sysv/linux/shm-directory.c |
| |
| diff --git a/htl/Makefile b/htl/Makefile |
| index 326a920fb3..86a1e731d1 100644 |
| --- a/htl/Makefile |
| +++ b/htl/Makefile |
| @@ -132,8 +132,6 @@ libpthread-routines := pt-attr pt-attr-destroy pt-attr-getdetachstate \ |
| sem-post sem-timedwait sem-trywait sem-unlink \ |
| sem-wait \ |
| \ |
| - shm-directory \ |
| - \ |
| cancellation \ |
| cthreads-compat \ |
| herrno \ |
| diff --git a/htl/Versions b/htl/Versions |
| index 832cc5d814..1d127266b3 100644 |
| --- a/htl/Versions |
| +++ b/htl/Versions |
| @@ -168,7 +168,6 @@ libpthread { |
| } |
| |
| GLIBC_PRIVATE { |
| - __shm_directory; |
| __pthread_threads; |
| |
| __cthread_detach; |
| diff --git a/sysdeps/nptl/shm-directory.h b/include/shm-directory.h |
| similarity index 59% |
| rename from sysdeps/nptl/shm-directory.h |
| rename to include/shm-directory.h |
| index 3021682fb3..59a5f89c06 100644 |
| --- a/sysdeps/nptl/shm-directory.h |
| +++ b/include/shm-directory.h |
| @@ -18,14 +18,24 @@ |
| |
| #ifndef _SHM_DIRECTORY_H |
| |
| -#include <sysdeps/posix/shm-directory.h> |
| - |
| -/* For NPTL the __shm_directory function lives in libpthread. |
| - We don't want PLT calls from there. But it's also used from |
| - librt, so it cannot just be declared hidden. */ |
| - |
| -#if IS_IN (libpthread) |
| -hidden_proto (__shm_directory) |
| -#endif |
| +#include <limits.h> |
| +#include <paths.h> |
| +#include <stdbool.h> |
| + |
| +/* The directory that contains shared POSIX objects. */ |
| +#define SHMDIR _PATH_DEV "shm/" |
| + |
| +struct shmdir_name |
| +{ |
| + /* The combined prefix/name. The sizeof includes the terminating |
| + NUL byte. 4 bytes are needed for the optional "sem." prefix. */ |
| + char name[sizeof (SHMDIR) + 4 + NAME_MAX]; |
| +}; |
| + |
| +/* Sets RESULT->name to the constructed name and returns 0 on success, |
| + or -1 on failure. Includes the "sem." prefix in the name if |
| + SEM_PREFIX is true. */ |
| +int __shm_get_name (struct shmdir_name *result, const char *name, |
| + bool sem_prefix); |
| |
| #endif /* shm-directory.h */ |
| diff --git a/nptl/Makefile b/nptl/Makefile |
| index 89569c4f46..87fc6b6bc5 100644 |
| --- a/nptl/Makefile |
| +++ b/nptl/Makefile |
| @@ -137,7 +137,6 @@ libpthread-routines = nptl-init nptlfreeres vars events version pt-interp \ |
| pthread_once \ |
| old_pthread_atfork \ |
| pthread_getcpuclockid \ |
| - shm-directory \ |
| sem_init sem_destroy \ |
| sem_open sem_close sem_unlink \ |
| sem_getvalue \ |
| diff --git a/nptl/Versions b/nptl/Versions |
| index aed118e717..7d5644ada1 100644 |
| --- a/nptl/Versions |
| +++ b/nptl/Versions |
| @@ -302,7 +302,6 @@ libpthread { |
| __pthread_clock_gettime; __pthread_clock_settime; |
| __pthread_unwind; __pthread_get_minstack; |
| __pthread_barrier_init; __pthread_barrier_wait; |
| - __shm_directory; |
| __libpthread_freeres; |
| } |
| } |
| diff --git a/nptl/nptlfreeres.c b/nptl/nptlfreeres.c |
| index 07aa34adfa..ef5b765af5 100644 |
| --- a/nptl/nptlfreeres.c |
| +++ b/nptl/nptlfreeres.c |
| @@ -27,6 +27,5 @@ __libpthread_freeres (void) |
| { |
| call_function_static_weak (__default_pthread_attr_freeres); |
| call_function_static_weak (__nptl_stacks_freeres); |
| - call_function_static_weak (__shm_directory_freeres); |
| call_function_static_weak (__nptl_unwind_freeres); |
| } |
| diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h |
| index 6f94d6be31..85dcaa7ec1 100644 |
| --- a/nptl/pthreadP.h |
| +++ b/nptl/pthreadP.h |
| @@ -584,7 +584,6 @@ extern void __nptl_set_robust (struct pthread *self); |
| #endif |
| |
| extern void __nptl_stacks_freeres (void) attribute_hidden; |
| -extern void __shm_directory_freeres (void) attribute_hidden; |
| |
| extern void __wait_lookup_done (void) attribute_hidden; |
| |
| diff --git a/nptl/sem_open.c b/nptl/sem_open.c |
| index b022cbfd9a..bbc62f2e66 100644 |
| --- a/nptl/sem_open.c |
| +++ b/nptl/sem_open.c |
| @@ -62,8 +62,9 @@ int __sem_mappings_lock attribute_hidden = LLL_LOCK_INITIALIZER; |
| |
| /* Search for existing mapping and if possible add the one provided. */ |
| static sem_t * |
| -check_add_mapping (const char *name, size_t namelen, int fd, sem_t *existing) |
| +check_add_mapping (const char *name, int fd, sem_t *existing) |
| { |
| + size_t namelen = strlen (name); |
| sem_t *result = SEM_FAILED; |
| |
| /* Get the information about the file. */ |
| @@ -150,8 +151,12 @@ sem_open (const char *name, int oflag, ...) |
| return SEM_FAILED; |
| } |
| |
| - /* Create the name of the final file in local variable SHM_NAME. */ |
| - SHM_GET_NAME (EINVAL, SEM_FAILED, SEM_SHM_PREFIX); |
| + struct shmdir_name dirname; |
| + if (__shm_get_name (&dirname, name, true) != 0) |
| + { |
| + __set_errno (EINVAL); |
| + return SEM_FAILED; |
| + } |
| |
| /* Disable asynchronous cancellation. */ |
| #ifdef __libc_ptf_call |
| @@ -164,7 +169,7 @@ sem_open (const char *name, int oflag, ...) |
| if ((oflag & O_CREAT) == 0 || (oflag & O_EXCL) == 0) |
| { |
| try_again: |
| - fd = __libc_open (shm_name, |
| + fd = __libc_open (dirname.name, |
| (oflag & ~(O_CREAT|O_ACCMODE)) | O_NOFOLLOW | O_RDWR); |
| |
| if (fd == -1) |
| @@ -178,13 +183,12 @@ sem_open (const char *name, int oflag, ...) |
| else |
| /* Check whether we already have this semaphore mapped and |
| create one if necessary. */ |
| - result = check_add_mapping (name, namelen, fd, SEM_FAILED); |
| + result = check_add_mapping (name, fd, SEM_FAILED); |
| } |
| else |
| { |
| /* We have to open a temporary file first since it must have the |
| correct form before we can start using it. */ |
| - char *tmpfname; |
| mode_t mode; |
| unsigned int value; |
| va_list ap; |
| @@ -227,16 +231,11 @@ sem_open (const char *name, int oflag, ...) |
| memset ((char *) &sem.initsem + sizeof (struct new_sem), '\0', |
| sizeof (sem_t) - sizeof (struct new_sem)); |
| |
| - tmpfname = __alloca (shm_dirlen + sizeof SEM_SHM_PREFIX + 6); |
| - char *xxxxxx = __mempcpy (tmpfname, shm_dir, shm_dirlen); |
| - |
| + char tmpfname[] = SHMDIR "sem.XXXXXX"; |
| int retries = 0; |
| #define NRETRIES 50 |
| while (1) |
| { |
| - /* Add the suffix for mktemp. */ |
| - strcpy (xxxxxx, "XXXXXX"); |
| - |
| /* We really want to use mktemp here. We cannot use mkstemp |
| since the file must be opened with a specific mode. The |
| mode cannot later be set since then we cannot apply the |
| @@ -254,7 +253,12 @@ sem_open (const char *name, int oflag, ...) |
| if (errno == EEXIST) |
| { |
| if (++retries < NRETRIES) |
| - continue; |
| + { |
| + /* Restore the six placeholder bytes before the |
| + null terminator before the next attempt. */ |
| + memcpy (tmpfname + sizeof (tmpfname) - 7, "XXXXXX", 6); |
| + continue; |
| + } |
| |
| __set_errno (EAGAIN); |
| } |
| @@ -275,7 +279,7 @@ sem_open (const char *name, int oflag, ...) |
| fd, 0)) != MAP_FAILED) |
| { |
| /* Create the file. Don't overwrite an existing file. */ |
| - if (link (tmpfname, shm_name) != 0) |
| + if (link (tmpfname, dirname.name) != 0) |
| { |
| /* Undo the mapping. */ |
| (void) munmap (result, sizeof (sem_t)); |
| @@ -300,7 +304,7 @@ sem_open (const char *name, int oflag, ...) |
| /* Insert the mapping into the search tree. This also |
| determines whether another thread sneaked by and already |
| added such a mapping despite the fact that we created it. */ |
| - result = check_add_mapping (name, namelen, fd, result); |
| + result = check_add_mapping (name, fd, result); |
| } |
| |
| /* Now remove the temporary name. This should never fail. If |
| diff --git a/nptl/sem_unlink.c b/nptl/sem_unlink.c |
| index 41fbb2c7fd..e10fcf8f65 100644 |
| --- a/nptl/sem_unlink.c |
| +++ b/nptl/sem_unlink.c |
| @@ -27,11 +27,15 @@ |
| int |
| sem_unlink (const char *name) |
| { |
| - /* Construct the filename. */ |
| - SHM_GET_NAME (ENOENT, -1, SEM_SHM_PREFIX); |
| + struct shmdir_name dirname; |
| + if (__shm_get_name (&dirname, name, true) != 0) |
| + { |
| + __set_errno (ENOENT); |
| + return -1; |
| + } |
| |
| /* Now try removing it. */ |
| - int ret = unlink (shm_name); |
| + int ret = unlink (dirname.name); |
| if (ret < 0 && errno == EPERM) |
| __set_errno (EACCES); |
| return ret; |
| diff --git a/posix/Makefile b/posix/Makefile |
| index 605ddbade8..6f41a022d8 100644 |
| --- a/posix/Makefile |
| +++ b/posix/Makefile |
| @@ -65,7 +65,8 @@ routines := \ |
| spawnattr_setsigmask spawnattr_setschedpolicy spawnattr_setschedparam \ |
| posix_madvise \ |
| get_child_max sched_cpucount sched_cpualloc sched_cpufree \ |
| - streams-compat |
| + streams-compat \ |
| + shm-directory |
| |
| aux := init-posix environ |
| tests := test-errno tstgetopt testfnm runtests runptests \ |
| diff --git a/posix/Versions b/posix/Versions |
| index 7d06a6d0c0..cfd3819966 100644 |
| --- a/posix/Versions |
| +++ b/posix/Versions |
| @@ -150,5 +150,6 @@ libc { |
| GLIBC_PRIVATE { |
| __libc_fork; __libc_pread; __libc_pwrite; |
| __nanosleep_nocancel; __pause_nocancel; |
| + __shm_get_name; |
| } |
| } |
| diff --git a/sysdeps/posix/shm-directory.c b/posix/shm-directory.c |
| similarity index 60% |
| rename from sysdeps/posix/shm-directory.c |
| rename to posix/shm-directory.c |
| index 29314f06bb..b4d539d6c9 100644 |
| --- a/sysdeps/posix/shm-directory.c |
| +++ b/posix/shm-directory.c |
| @@ -16,23 +16,31 @@ |
| License along with the GNU C Library; if not, see |
| <https://www.gnu.org/licenses/>. */ |
| |
| -#include <shm-directory.h> |
| #include <unistd.h> |
| |
| #if _POSIX_MAPPED_FILES |
| |
| -# include <paths.h> |
| - |
| -# define SHMDIR (_PATH_DEV "shm/") |
| +#include <alloc_buffer.h> |
| +#include <shm-directory.h> |
| +#include <string.h> |
| |
| -const char * |
| -__shm_directory (size_t *len) |
| +int |
| +__shm_get_name (struct shmdir_name *result, const char *name, bool sem_prefix) |
| { |
| - *len = sizeof SHMDIR - 1; |
| - return SHMDIR; |
| + while (name[0] == '/') |
| + ++name; |
| + size_t namelen = strlen (name); |
| + |
| + struct alloc_buffer buffer |
| + = alloc_buffer_create (result->name, sizeof (result->name)); |
| + alloc_buffer_copy_bytes (&buffer, SHMDIR, strlen (SHMDIR)); |
| + if (sem_prefix) |
| + alloc_buffer_copy_bytes (&buffer, "sem.", strlen ("sem.")); |
| + alloc_buffer_copy_bytes (&buffer, name, namelen + 1); |
| + if (namelen == 0 || memchr (name, '/', namelen) != NULL |
| + || alloc_buffer_has_failed (&buffer)) |
| + return -1; |
| + return 0; |
| } |
| -# if IS_IN (libpthread) |
| -hidden_def (__shm_directory) |
| -# endif |
| |
| #endif |
| diff --git a/sysdeps/htl/shm-directory.h b/sysdeps/htl/shm-directory.h |
| deleted file mode 100644 |
| index a9742b3fd2..0000000000 |
| --- a/sysdeps/htl/shm-directory.h |
| +++ /dev/null |
| @@ -1,30 +0,0 @@ |
| -/* Header for directory for shm/sem files. libpthread version. |
| - Copyright (C) 2014-2020 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 _SHM_DIRECTORY_H |
| - |
| -#include <sysdeps/posix/shm-directory.h> |
| - |
| -/* For libpthread the __shm_directory function lives in libpthread. |
| - We don't want PLT calls from there. But it's also used from |
| - librt, so it cannot just be declared hidden. */ |
| - |
| -#if IS_IN (libpthread) |
| -hidden_proto (__shm_directory) |
| -#endif |
| -#endif /* shm-directory.h */ |
| diff --git a/sysdeps/posix/Makefile b/sysdeps/posix/Makefile |
| index 52f20f5d97..b58aa6aadb 100644 |
| --- a/sysdeps/posix/Makefile |
| +++ b/sysdeps/posix/Makefile |
| @@ -3,9 +3,3 @@ L_tmpnam = 20 |
| TMP_MAX = 238328 |
| L_ctermid = 9 |
| L_cuserid = 9 |
| - |
| -ifeq ($(subdir)|$(have-thread-library),rt|no) |
| -# With NPTL, this lives in libpthread so it can be used for sem_open too. |
| -# Without NPTL, it's just private in librt. |
| -librt-routines += shm-directory |
| -endif |
| diff --git a/sysdeps/posix/shm-directory.h b/sysdeps/posix/shm-directory.h |
| deleted file mode 100644 |
| index 9172d9f637..0000000000 |
| --- a/sysdeps/posix/shm-directory.h |
| +++ /dev/null |
| @@ -1,66 +0,0 @@ |
| -/* Header for directory for shm/sem files. |
| - Copyright (C) 2014-2020 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 _SHM_DIRECTORY_H |
| - |
| -#include <errno.h> |
| -#include <limits.h> |
| -#include <stdbool.h> |
| -#include <stdlib.h> |
| -#include <string.h> |
| - |
| -extern const char *__shm_directory (size_t *len); |
| - |
| -/* This defines local variables SHM_DIR and SHM_DIRLEN, giving the |
| - directory prefix (with trailing slash) and length (not including '\0' |
| - terminator) of the directory used for shm files. If that cannot be |
| - determined, it sets errno to ENOSYS and returns RETVAL_FOR_INVALID. |
| - |
| - This uses the local variable NAME as an lvalue, and increments it past |
| - any leading slashes. It then defines the local variable NAMELEN, giving |
| - strlen (NAME) + 1. If NAME is invalid, it sets errno to |
| - ERRNO_FOR_INVALID and returns RETVAL_FOR_INVALID. Finally, it defines |
| - the local variable SHM_NAME, giving the absolute file name of the shm |
| - file corresponding to NAME. PREFIX is a string constant used as a |
| - prefix on NAME. */ |
| - |
| -#define SHM_GET_NAME(errno_for_invalid, retval_for_invalid, prefix) \ |
| - size_t shm_dirlen; \ |
| - const char *shm_dir = __shm_directory (&shm_dirlen); \ |
| - /* If we don't know what directory to use, there is nothing we can do. */ \ |
| - if (__glibc_unlikely (shm_dir == NULL)) \ |
| - { \ |
| - __set_errno (ENOSYS); \ |
| - return retval_for_invalid; \ |
| - } \ |
| - /* Construct the filename. */ \ |
| - while (name[0] == '/') \ |
| - ++name; \ |
| - size_t namelen = strlen (name) + 1; \ |
| - /* Validate the filename. */ \ |
| - if (namelen == 1 || namelen >= NAME_MAX || strchr (name, '/') != NULL) \ |
| - { \ |
| - __set_errno (errno_for_invalid); \ |
| - return retval_for_invalid; \ |
| - } \ |
| - char *shm_name = __alloca (shm_dirlen + sizeof prefix - 1 + namelen); \ |
| - __mempcpy (__mempcpy (__mempcpy (shm_name, shm_dir, shm_dirlen), \ |
| - prefix, sizeof prefix - 1), \ |
| - name, namelen) |
| - |
| -#endif /* shm-directory.h */ |
| diff --git a/sysdeps/posix/shm_open.c b/sysdeps/posix/shm_open.c |
| index 6ca80cd4e4..d8881e6b82 100644 |
| --- a/sysdeps/posix/shm_open.c |
| +++ b/sysdeps/posix/shm_open.c |
| @@ -24,6 +24,7 @@ |
| |
| #else |
| |
| +# include <errno.h> |
| # include <fcntl.h> |
| # include <pthread.h> |
| # include <shm-directory.h> |
| @@ -33,7 +34,12 @@ |
| int |
| shm_open (const char *name, int oflag, mode_t mode) |
| { |
| - SHM_GET_NAME (EINVAL, -1, ""); |
| + struct shmdir_name dirname; |
| + if (__shm_get_name (&dirname, name, false) != 0) |
| + { |
| + __set_errno (EINVAL); |
| + return -1; |
| + } |
| |
| oflag |= O_NOFOLLOW | O_CLOEXEC; |
| |
| @@ -41,7 +47,7 @@ shm_open (const char *name, int oflag, mode_t mode) |
| int state; |
| pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &state); |
| |
| - int fd = open (shm_name, oflag, mode); |
| + int fd = open (dirname.name, oflag, mode); |
| if (fd == -1 && __glibc_unlikely (errno == EISDIR)) |
| /* It might be better to fold this error with EINVAL since |
| directory names are just another example for unsuitable shared |
| diff --git a/sysdeps/posix/shm_unlink.c b/sysdeps/posix/shm_unlink.c |
| index d95cad9d15..c7caebe74c 100644 |
| --- a/sysdeps/posix/shm_unlink.c |
| +++ b/sysdeps/posix/shm_unlink.c |
| @@ -25,16 +25,21 @@ |
| |
| #include <errno.h> |
| #include <string.h> |
| -#include "shm-directory.h" |
| +#include <shm-directory.h> |
| |
| |
| /* Remove shared memory object. */ |
| int |
| shm_unlink (const char *name) |
| { |
| - SHM_GET_NAME (ENOENT, -1, ""); |
| - |
| - int result = unlink (shm_name); |
| + struct shmdir_name dirname; |
| + if (__shm_get_name (&dirname, name, false) != 0) |
| + { |
| + __set_errno (ENOENT); |
| + return -1; |
| + } |
| + |
| + int result = unlink (dirname.name); |
| if (result < 0 && errno == EPERM) |
| __set_errno (EACCES); |
| return result; |
| diff --git a/sysdeps/unix/sysv/linux/shm-directory.c b/sysdeps/unix/sysv/linux/shm-directory.c |
| deleted file mode 100644 |
| index 43f044d77c..0000000000 |
| --- a/sysdeps/unix/sysv/linux/shm-directory.c |
| +++ /dev/null |
| @@ -1,147 +0,0 @@ |
| -/* Determine directory for shm/sem files. Linux version. |
| - Copyright (C) 2000-2020 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 "shm-directory.h" |
| - |
| -#include <errno.h> |
| -#include <mntent.h> |
| -#include <paths.h> |
| -#include <stdio.h> |
| -#include <string.h> |
| -#include <sys/statfs.h> |
| -#include <libc-lock.h> |
| -#include "linux_fsinfo.h" |
| - |
| - |
| -/* Mount point of the shared memory filesystem. */ |
| -static struct |
| -{ |
| - char *dir; |
| - size_t dirlen; |
| -} mountpoint; |
| - |
| -/* This is the default directory. */ |
| -static const char defaultdir[] = "/dev/shm/"; |
| - |
| -/* Protect the `mountpoint' variable above. */ |
| -__libc_once_define (static, once); |
| - |
| - |
| -/* Determine where the shmfs is mounted (if at all). */ |
| -static void |
| -where_is_shmfs (void) |
| -{ |
| - char buf[512]; |
| - struct statfs f; |
| - struct mntent resmem; |
| - struct mntent *mp; |
| - FILE *fp; |
| - |
| - /* The canonical place is /dev/shm. This is at least what the |
| - documentation tells everybody to do. */ |
| - if (__statfs (defaultdir, &f) == 0 && (f.f_type == SHMFS_SUPER_MAGIC |
| - || f.f_type == RAMFS_MAGIC)) |
| - { |
| - /* It is in the normal place. */ |
| - mountpoint.dir = (char *) defaultdir; |
| - mountpoint.dirlen = sizeof (defaultdir) - 1; |
| - |
| - return; |
| - } |
| - |
| - /* OK, do it the hard way. Look through the /proc/mounts file and if |
| - this does not exist through /etc/fstab to find the mount point. */ |
| - fp = __setmntent ("/proc/mounts", "r"); |
| - if (__glibc_unlikely (fp == NULL)) |
| - { |
| - fp = __setmntent (_PATH_MNTTAB, "r"); |
| - if (__glibc_unlikely (fp == NULL)) |
| - /* There is nothing we can do. Blind guesses are not helpful. */ |
| - return; |
| - } |
| - |
| - /* Now read the entries. */ |
| - while ((mp = __getmntent_r (fp, &resmem, buf, sizeof buf)) != NULL) |
| - /* The original name is "shm" but this got changed in early Linux |
| - 2.4.x to "tmpfs". */ |
| - if (strcmp (mp->mnt_type, "tmpfs") == 0 |
| - || strcmp (mp->mnt_type, "shm") == 0) |
| - { |
| - /* Found it. There might be more than one place where the |
| - filesystem is mounted but one is enough for us. */ |
| - size_t namelen; |
| - |
| - /* First make sure this really is the correct entry. At least |
| - some versions of the kernel give wrong information because |
| - of the implicit mount of the shmfs for SysV IPC. */ |
| - if (__statfs (mp->mnt_dir, &f) != 0 || (f.f_type != SHMFS_SUPER_MAGIC |
| - && f.f_type != RAMFS_MAGIC)) |
| - continue; |
| - |
| - namelen = strlen (mp->mnt_dir); |
| - |
| - if (namelen == 0) |
| - /* Hum, maybe some crippled entry. Keep on searching. */ |
| - continue; |
| - |
| - mountpoint.dir = (char *) malloc (namelen + 2); |
| - if (mountpoint.dir != NULL) |
| - { |
| - char *cp = __mempcpy (mountpoint.dir, mp->mnt_dir, namelen); |
| - if (cp[-1] != '/') |
| - *cp++ = '/'; |
| - *cp = '\0'; |
| - mountpoint.dirlen = cp - mountpoint.dir; |
| - } |
| - |
| - break; |
| - } |
| - |
| - /* Close the stream. */ |
| - __endmntent (fp); |
| -} |
| - |
| - |
| -const char * |
| -__shm_directory (size_t *len) |
| -{ |
| - /* Determine where the shmfs is mounted. */ |
| - __libc_once (once, where_is_shmfs); |
| - |
| - /* If we don't know the mount points there is nothing we can do. Ever. */ |
| - if (__glibc_unlikely (mountpoint.dir == NULL)) |
| - { |
| - __set_errno (ENOSYS); |
| - return NULL; |
| - } |
| - |
| - *len = mountpoint.dirlen; |
| - return mountpoint.dir; |
| -} |
| -#if IS_IN (libpthread) |
| -hidden_def (__shm_directory) |
| - |
| -/* Make sure the table is freed if we want to free everything before |
| - exiting. */ |
| -void |
| -__shm_directory_freeres (void) |
| -{ |
| - if (mountpoint.dir != defaultdir) |
| - free (mountpoint.dir); |
| -} |
| -#endif |
| -- |
| 2.32.0 |
| |