Date: Mon, 7 Sep 2020 23:58:20 +0200 From: Arnd Bergmann <arnd@...db.de> To: musl@...ts.openwall.com Subject: Re: riscv32 v2 On Mon, Sep 7, 2020 at 11:46 PM Rich Felker <dalias@...c.org> wrote: > On Mon, Sep 07, 2020 at 11:35:45PM +0200, Arnd Bergmann wrote: > > On Mon, Sep 7, 2020 at 8:06 PM Rich Felker <dalias@...c.org> wrote: > > > On Mon, Sep 07, 2020 at 06:47:00AM -0400, Stefan O'Rear wrote: > > > > > > * Copy the IPC_TIME64 bits from arch/arm/bits to trigger the musl code > > > > for fixing time64 IPC_STAT results. I'm not super happy with this, > > > > maybe there should be a new mechanism in musl for fixing IPC_STAT for > > > > unconditionally-time64 architectures. > > > > > > If the riscv32 IPC syscalls don't actually provide in-place time64 but > > > require translation, I think it's fairly appropriate as-is. > > > > > > From the definitions in your patch, it looks like all the time fields > > > are fixed-word-order (little endian) and possibly not aligned, so it > > > seems like they can't be used in-place. Is this correct? > > > > Yes, rv32 uses the generic system call arguments, which are > > unfortunately defined this way. In retrospect I wish I had > > replaced the ipc syscalls with a sane version for time64, but at > > the time time it seemed as easy way out to use the fields that > > had been reserved for this purpose despite the broken > > byte order and alignment. > > Thanks for clarifying. BTW does passing IPC_64 produce an error on > rv32? If so, this is another advantage of keeping the IPC_TIME64 bit > -- it would catch programs bypassing libc and making the syscalls > directly. Yes, this is now the generic behavior for the split IPC syscalls (as opposed to sys_ipc on older architectures). The only architectures that parse the version in the split ipc syscalls are the ones that already had these and were interpreting IPC_64 before linux-5.1: alpha, arm32, microblaze, mips-n32, mips-n64, and xtensa. There are additional architectures that require passing IPC_64 in sys_ipc() but reject it in the split syscalls: m68k, mips-o32, powerpc, s390, sh, sparc, and x86. Arnd
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