From: Yu Watanabe <watanabe.yu+github@gmail.com>
Date: Mon, 3 Mar 2025 18:11:58 +0000 (+0900)
Subject: dirent-util: introduce simple wrapper of posix_getdents()
X-Git-Tag: v258-rc1~1195^2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F36565%2Fhead;p=thirdparty%2Fsystemd.git

dirent-util: introduce simple wrapper of posix_getdents()

glibc exports getdents64 syscall as is, but musl exports it as
posix_getdents(). Let's introduce a simple wrapper of posix_getdents().

Note, our baseline for glibc is 2.31. Hence, we can assume getdents64()
always defined when building with glibc.
---

diff --git a/meson.build b/meson.build
index 6ef51069d9f..fdad63fd298 100644
--- a/meson.build
+++ b/meson.build
@@ -577,7 +577,7 @@ endforeach
 foreach ident : [
         ['set_mempolicy',     '''#include <sys/syscall.h>'''],  # declared at numaif.h provided by libnuma, which we do not use
         ['get_mempolicy',     '''#include <sys/syscall.h>'''],  # declared at numaif.h provided by libnuma, which we do not use
-        ['getdents64',        '''#include <dirent.h>'''],       # since glibc-2.30, but check it for musl
+        ['posix_getdents',    '''#include <dirent.h>'''],       # glibc does not implement it, but musl does
         ['strerrorname_np',   '''#include <string.h>'''],       # since glibc-2.32
         ['mallinfo',          '''#include <malloc.h>'''],       # deprecated since glibc-2.33, but check it for musl
         ['mallinfo2',         '''#include <malloc.h>'''],       # since glibc-2.33
diff --git a/src/basic/dirent-util.h b/src/basic/dirent-util.h
index 0a2fcbf957a..816b28e04fe 100644
--- a/src/basic/dirent-util.h
+++ b/src/basic/dirent-util.h
@@ -30,6 +30,14 @@ struct dirent *readdir_no_dot(DIR *dirp);
                      continue;                                          \
              else
 
+/* Musl provides posix_getdents(). But glibc does not, and provides their own implementation as getdents64().
+ * Let's introduce a simple wrapper. */
+#if !HAVE_POSIX_GETDENTS
+static inline ssize_t posix_getdents(int fd, void *buf, size_t nbyte, int flags) {
+        return getdents64(fd, buf, nbyte);
+}
+#endif
+
 /* Maximum space one dirent structure might require at most */
 #define DIRENT_SIZE_MAX CONST_MAX(sizeof(struct dirent), offsetof(struct dirent, d_name) + NAME_MAX + 1)
 
diff --git a/src/basic/missing_syscall.h b/src/basic/missing_syscall.h
index 53dcd69d9e4..aae07a3f37d 100644
--- a/src/basic/missing_syscall.h
+++ b/src/basic/missing_syscall.h
@@ -212,16 +212,6 @@ static inline int missing_close_range(unsigned first_fd, unsigned end_fd, unsign
 
 /* ======================================================================= */
 
-#if !HAVE_GETDENTS64
-static inline ssize_t missing_getdents64(int fd, void *buffer, size_t length) {
-        return syscall(__NR_getdents64, fd, buffer, length);
-}
-
-#  define getdents64 missing_getdents64
-#endif
-
-/* ======================================================================= */
-
 #if !HAVE_SCHED_SETATTR
 /* since kernel 3.14 (e6cfc0295c7d51b008999a8b13a44fb43f8685ea) */
 static inline ssize_t missing_sched_setattr(pid_t pid, struct sched_attr *attr, unsigned int flags) {
diff --git a/src/basic/recurse-dir.c b/src/basic/recurse-dir.c
index 9612b7c6a50..31d19aef71b 100644
--- a/src/basic/recurse-dir.c
+++ b/src/basic/recurse-dir.c
@@ -5,7 +5,6 @@
 #include "fd-util.h"
 #include "fileio.h"
 #include "fs-util.h"
-#include "missing_syscall.h"
 #include "mountpoint-util.h"
 #include "recurse-dir.h"
 #include "sort-util.h"
@@ -51,7 +50,7 @@ int readdir_all(int dir_fd, RecurseDirFlags flags, DirectoryEntries **ret) {
                 bs = MIN(MALLOC_SIZEOF_SAFE(de) - offsetof(DirectoryEntries, buffer), (size_t) SSIZE_MAX);
                 assert(bs > de->buffer_size);
 
-                n = getdents64(dir_fd, (uint8_t*) de->buffer + de->buffer_size, bs - de->buffer_size);
+                n = posix_getdents(dir_fd, (uint8_t*) de->buffer + de->buffer_size, bs - de->buffer_size, /* flags = */ 0);
                 if (n < 0)
                         return -errno;
                 if (n == 0)
diff --git a/src/basic/stat-util.c b/src/basic/stat-util.c
index 8ae588e2e11..f328f4a78c8 100644
--- a/src/basic/stat-util.c
+++ b/src/basic/stat-util.c
@@ -19,7 +19,6 @@
 #include "macro.h"
 #include "missing_fs.h"
 #include "missing_magic.h"
-#include "missing_syscall.h"
 #include "mountpoint-util.h"
 #include "nulstr-util.h"
 #include "parse-util.h"
@@ -172,7 +171,7 @@ int dir_is_empty_at(int dir_fd, const char *path, bool ignore_hidden_or_backup)
                 struct dirent *de;
                 ssize_t n;
 
-                n = getdents64(fd, buf, m);
+                n = posix_getdents(fd, buf, m, /* flags = */ 0);
                 if (n < 0)
                         return -errno;
                 if (n == 0)