From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-3.0 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_MED,RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL autolearn=ham autolearn_force=no version=3.4.4 Received: from second.openwall.net (second.openwall.net [193.110.157.125]) by inbox.vuxu.org (Postfix) with SMTP id 3993120EE2 for ; Tue, 23 Apr 2024 17:51:07 +0200 (CEST) Received: (qmail 5425 invoked by uid 550); 23 Apr 2024 15:51:02 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Reply-To: musl@lists.openwall.com Received: (qmail 5374 invoked from network); 23 Apr 2024 15:51:01 -0000 Date: Tue, 23 Apr 2024 11:51:14 -0400 From: Rich Felker To: Tony Ambardar Cc: musl@lists.openwall.com Message-ID: <20240423155114.GN4163@brightrain.aerifal.cx> References: <20240421153640.379015-1-Tony.Ambardar@gmail.com> <20240422224726.GL4163@brightrain.aerifal.cx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Subject: Re: [musl] [PATCH v1] add renameat2 linux syscall wrapper On Mon, Apr 22, 2024 at 09:39:17PM -0700, Tony Ambardar wrote: > On Mon, Apr 22, 2024 at 06:47:26PM -0400, Rich Felker wrote: > > On Sun, Apr 21, 2024 at 08:36:40AM -0700, Tony Ambardar wrote: > > > This syscall is available since Linux 3.15 and also implemented in glibc > > > from version 2.28. It is commonly used in filesystem or security contexts. > > > > > > Defines RENAME_NOREPLACE, RENAME_EXCHANGE, RENAME_WHITEOUT are guarded by > > > _GNU_SOURCE as with glibc. > > > > > > Signed-off-by: Tony Ambardar > > > --- > > > include/stdio.h | 7 +++++++ > > > src/linux/renameat2.c | 8 ++++++++ > > > 2 files changed, 15 insertions(+) > > > create mode 100644 src/linux/renameat2.c > > > > > > diff --git a/include/stdio.h b/include/stdio.h > > > index cb858618..8312c3bf 100644 > > > --- a/include/stdio.h > > > +++ b/include/stdio.h > > > @@ -158,6 +158,13 @@ char *ctermid(char *); > > > #define L_ctermid 20 > > > #endif > > > > > > +#if defined(_GNU_SOURCE) > > > +#define RENAME_NOREPLACE (1 << 0) > > > +#define RENAME_EXCHANGE (1 << 1) > > > +#define RENAME_WHITEOUT (1 << 2) > > > + > > > +int renameat2(int, const char *, int, const char *, unsigned int); > > > +#endif > > > > s/unsigned int/unsigned/ and maybe just write out the constants? I > > think that's the style musl uses most places. > > Right, the constants-by-shift mirrored glibc and I saw these also in musl > e.g. hwcap.h, elf.h, mount.h, syslog.h, etc. I'm not wedded to either but > just wanted to be consistent. Please confirm a preference and I'll update. > > > > > > #if defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) \ > > > || defined(_BSD_SOURCE) > > > diff --git a/src/linux/renameat2.c b/src/linux/renameat2.c > > > new file mode 100644 > > > index 00000000..3062aa15 > > > --- /dev/null > > > +++ b/src/linux/renameat2.c > > > @@ -0,0 +1,8 @@ > > > +#define _GNU_SOURCE > > > +#include > > > +#include "syscall.h" > > > + > > > +int renameat2(int oldfd, const char *old, int newfd, const char *new, unsigned int flags) > > > +{ > > > + return syscall(SYS_renameat2, oldfd, old, newfd, new, flags); > > > +} > > > -- > > > 2.34.1 > > > > This probably at least needs to support flags==0 on kernels without > > SYS_renameat2 by calling renameat in that case. Then I'm not sure if > > ENOSYS should be kept if the new syscall is missing, or just EINVAL or > > whatever is used to report unsupported flags. > > I had wondered about this too and looked at all 'arch/.../syscall.h.in' > files. All arches support SYS_renameat2, but riscv, aarch64, loongarch64 > and or1k are missing SYS_rename and/or SYS_renameat. Also, current code in > stdio/rename.c and unistd/renameat.c may fall back _unconditionally_ to > use SYS_renameat2 in these cases, with the assumption it's always present. > > I think this means we're OK? Or do we allow for old kernels which lack > SYS_renameat2, in which case some existing code would need updating? No, this just means it's unconditionally present on some archs (because they were added after SYS_renameat2 was added), not that it can be assumed to be present in general. Rich