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Message-ID: <366548c1a0d9749e42c0d0c993414a353c9b0b02.camel@physik.fu-berlin.de> Date: Fri, 21 Jun 2024 10:44:39 +0200 From: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de> To: Arnd Bergmann <arnd@...nel.org>, linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org Cc: Arnd Bergmann <arnd@...db.de>, Thomas Bogendoerfer <tsbogend@...ha.franken.de>, linux-mips@...r.kernel.org, Helge Deller <deller@....de>, linux-parisc@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, Andreas Larsson <andreas@...sler.com>, sparclinux@...r.kernel.org, Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>, Christophe Leroy <christophe.leroy@...roup.eu>, "Naveen N . Rao" <naveen.n.rao@...ux.ibm.com>, linuxppc-dev@...ts.ozlabs.org, Brian Cain <bcain@...cinc.com>, linux-hexagon@...r.kernel.org, Guo Ren <guoren@...nel.org>, linux-csky@...r.kernel.org, Heiko Carstens <hca@...ux.ibm.com>, linux-s390@...r.kernel.org, Rich Felker <dalias@...c.org>, linux-sh@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>, Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, linux-fsdevel@...r.kernel.org, libc-alpha@...rceware.org, musl@...ts.openwall.com, ltp@...ts.linux.it, stable@...r.kernel.org Subject: Re: [PATCH 09/15] sh: rework sync_file_range ABI Hi Arnd, thanks for your patch! On Thu, 2024-06-20 at 18:23 +0200, Arnd Bergmann wrote: > From: Arnd Bergmann <arnd@...db.de> > > The unusual function calling conventions on superh ended up causing ^^^^^^ It's spelled SuperH > sync_file_range to have the wrong argument order, with the 'flags' > argument getting sorted before 'nbytes' by the compiler. > > In userspace, I found that musl, glibc, uclibc and strace all expect the > normal calling conventions with 'nbytes' last, so changing the kernel > to match them should make all of those work. > > In order to be able to also fix libc implementations to work with existing > kernels, they need to be able to tell which ABI is used. An easy way > to do this is to add yet another system call using the sync_file_range2 > ABI that works the same on all architectures. > > Old user binaries can now work on new kernels, and new binaries can > try the new sync_file_range2() to work with new kernels or fall back > to the old sync_file_range() version if that doesn't exist. > > Cc: stable@...r.kernel.org > Fixes: 75c92acdd5b1 ("sh: Wire up new syscalls.") > Signed-off-by: Arnd Bergmann <arnd@...db.de> > --- > arch/sh/kernel/sys_sh32.c | 11 +++++++++++ > arch/sh/kernel/syscalls/syscall.tbl | 3 ++- > 2 files changed, 13 insertions(+), 1 deletion(-) > > diff --git a/arch/sh/kernel/sys_sh32.c b/arch/sh/kernel/sys_sh32.c > index 9dca568509a5..d5a4f7c697d8 100644 > --- a/arch/sh/kernel/sys_sh32.c > +++ b/arch/sh/kernel/sys_sh32.c > @@ -59,3 +59,14 @@ asmlinkage int sys_fadvise64_64_wrapper(int fd, u32 offset0, u32 offset1, > (u64)len0 << 32 | len1, advice); > #endif > } > + > +/* > + * swap the arguments the way that libc wants it instead of I think "swap the arguments to the order that libc wants them" would be easier to understand here. > + * moving flags ahead of the 64-bit nbytes argument > + */ > +SYSCALL_DEFINE6(sh_sync_file_range6, int, fd, SC_ARG64(offset), > + SC_ARG64(nbytes), unsigned int, flags) > +{ > + return ksys_sync_file_range(fd, SC_VAL64(loff_t, offset), > + SC_VAL64(loff_t, nbytes), flags); > +} > diff --git a/arch/sh/kernel/syscalls/syscall.tbl b/arch/sh/kernel/syscalls/syscall.tbl > index bbf83a2db986..c55fd7696d40 100644 > --- a/arch/sh/kernel/syscalls/syscall.tbl > +++ b/arch/sh/kernel/syscalls/syscall.tbl > @@ -321,7 +321,7 @@ > 311 common set_robust_list sys_set_robust_list > 312 common get_robust_list sys_get_robust_list > 313 common splice sys_splice > -314 common sync_file_range sys_sync_file_range > +314 common sync_file_range sys_sh_sync_file_range6 ^^^^^^ Why the suffix 6 here? > 315 common tee sys_tee > 316 common vmsplice sys_vmsplice > 317 common move_pages sys_move_pages > @@ -395,6 +395,7 @@ > 385 common pkey_alloc sys_pkey_alloc > 386 common pkey_free sys_pkey_free > 387 common rseq sys_rseq > +388 common sync_file_range2 sys_sync_file_range2 > # room for arch specific syscalls > 393 common semget sys_semget > 394 common semctl sys_semctl I wonder how you discovered this bug. Did you look up the calling convention on SuperH and compare the argument order for the sys_sync_file_range system call documented there with the order in the kernel? Did you also check what order libc uses? I would expect libc on SuperH misordering the arguments as well unless I am missing something. Or do we know that the code is actually currently broken? Thanks, Adrian -- .''`. John Paul Adrian Glaubitz : :' : Debian Developer `. `' Physicist `- GPG: 62FF 8A75 84E0 2956 9546 0006 7426 3B37 F5B5 F913
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