From: Stefan Metzmacher <metze@samba.org>
Date: Wed, 7 Aug 2024 11:01:48 +0000 (+0200)
Subject: lib/replace: add renameat2() replacement
X-Git-Tag: tdb-1.4.13~1314
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f6550e804ea5604b1d7ec67e629fad8baee87f8b;p=thirdparty%2Fsamba.git

lib/replace: add renameat2() replacement

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15693

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
---

diff --git a/lib/replace/replace.c b/lib/replace/replace.c
index 0b4e06d8bd5..359f43352bd 100644
--- a/lib/replace/replace.c
+++ b/lib/replace/replace.c
@@ -1171,3 +1171,63 @@ long rep_openat2(int dirfd, const char *pathname,
 #endif
 }
 #endif /* !HAVE_OPENAT2 */
+
+#ifndef HAVE_RENAMEAT2
+
+/* fallback to wellknown __NR_renameat2 values */
+#ifndef __NR_renameat2
+# if defined(LINUX) && defined(HAVE_SYS_SYSCALL_H)
+#  if defined(__i386__)
+#   define __NR_renameat2 353
+#  elif defined(__x86_64__) && defined(__LP64__)
+#   define __NR_renameat2 316 /* 316 0x13C */
+#  elif defined(__x86_64__) && defined(__ILP32__)
+#   define __NR_renameat2 1073742140 /* 1073742140 0x4000013C */
+#  elif defined(__aarch64__)
+#   define __NR_renameat2 276
+#  elif defined(__arm__)
+#   define __NR_renameat2 382
+#  elif defined(__sparc__)
+#   define __NR_renameat2 345
+#  endif
+# endif /* defined(LINUX) && defined(HAVE_SYS_SYSCALL_H) */
+#endif /* !__NR_renameat2 */
+
+#ifdef DISABLE_OPATH
+/*
+ * systems without O_PATH also don't have renameat2,
+ * so make sure we at a realistic combination.
+ */
+#undef __NR_renameat2
+#endif /* DISABLE_OPATH */
+
+int rep_renameat2(int __oldfd, const char *__old, int __newfd,
+		  const char *__new, unsigned int __flags)
+{
+	if (__flags != 0) {
+#ifdef __NR_renameat2
+		int ret;
+
+		ret = syscall(__NR_renameat2,
+			      __oldfd,
+			      __old,
+			      __newfd,
+			      __new,
+			      __flags);
+		if (ret != -1 || errno != ENOSYS) {
+			/*
+			 * if it's ENOSYS, we fallback
+			 * to EINVAL below, otherwise
+			 * we return what the kernel
+			 * did.
+			 */
+			return ret;
+		}
+#endif
+		errno = EINVAL;
+		return -1;
+	}
+
+	return renameat(__oldfd, __old, __newfd, __new);
+}
+#endif /* ! HAVE_RENAMEAT2 */
diff --git a/lib/replace/system/filesys.h b/lib/replace/system/filesys.h
index 8005b18780f..9738ad52935 100644
--- a/lib/replace/system/filesys.h
+++ b/lib/replace/system/filesys.h
@@ -278,4 +278,33 @@ long rep_openat2(int dirfd, const char *pathname,
 	rep_openat2(dirfd, pathname, how, size)
 #endif /* !HAVE_OPENAT2 */
 
+#ifdef DISABLE_OPATH
+/*
+ * Without O_PATH, the kernel
+ * most likely doesn't have renameat2() too
+ * and we should test the fallback code
+ */
+#undef HAVE_RENAMEAT2
+#endif
+
+#ifndef HAVE_RENAMEAT2
+
+#ifndef RENAME_NOREPLACE
+# define RENAME_NOREPLACE (1 << 0)
+#endif
+
+#ifndef RENAME_EXCHANGE
+# define RENAME_EXCHANGE (1 << 1)
+#endif
+
+#ifndef RENAME_WHITEOUT
+# define RENAME_WHITEOUT (1 << 2)
+#endif
+
+int rep_renameat2(int __oldfd, const char *__old, int __newfd,
+		  const char *__new, unsigned int __flags);
+#define renameat2(__oldfd, __old, __newfd, __new, __flags) \
+	rep_renameat2(__oldfd, __old, __newfd, __new, __flags)
+#endif /* !HAVE_RENAMEAT2 */
+
 #endif
diff --git a/lib/replace/wscript b/lib/replace/wscript
index 77e655bb68b..f5114b69ffc 100644
--- a/lib/replace/wscript
+++ b/lib/replace/wscript
@@ -422,7 +422,7 @@ def configure(conf):
     conf.CHECK_FUNCS('link readlink symlink realpath snprintf vsnprintf')
     conf.CHECK_FUNCS('asprintf vasprintf setenv unsetenv strnlen strtoull __strtoull')
     conf.CHECK_FUNCS('strtouq strtoll __strtoll strtoq memalign posix_memalign')
-    conf.CHECK_FUNCS('fmemopen')
+    conf.CHECK_FUNCS('fmemopen renameat2')
 
     if conf.CONFIG_SET('HAVE_MEMALIGN'):
         conf.CHECK_DECLS('memalign', headers='malloc.h')