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Message-ID: <20131230221341.GN24286@brightrain.aerifal.cx>
Date: Mon, 30 Dec 2013 17:13:41 -0500
From: Rich Felker <dalias@...ifal.cx>
To: musl@...ts.openwall.com
Subject: Re: stat64 on mips
On Mon, Dec 30, 2013 at 10:10:59PM +0000, Justin Cormack wrote:
> On Mon, Dec 30, 2013 at 10:03 PM, Rich Felker <dalias@...ifal.cx> wrote:
> > On Mon, Dec 30, 2013 at 10:02:19PM +0000, Justin Cormack wrote:
> >> On Mon, Dec 30, 2013 at 9:29 PM, Rich Felker <dalias@...ifal.cx> wrote:
> >> > On Mon, Dec 30, 2013 at 06:20:46PM +0000, Justin Cormack wrote:
> >> >> MIPS is the most confusing architecture, but as far as I can make out,
> >> >> the definition of struct stat64 that Musl has is probably the right
> >> >> one for mips n32 but wrong for mips o32 which should be
> >> >>
> >> >> struct stat {
> >> >> unsigned long st_dev;
> >> >> unsigned long __st_pad0[3];
> >> >> unsigned long long st_ino;
> >> >> mode_t st_mode;
> >> >> nlink_t st_nlink;
> >> >> uid_t st_uid;
> >> >> gid_t st_gid;
> >> >> unsigned long st_rdev;
> >> >> unsigned long __st_pad1[3];
> >> >> long long st_size;
> >> >> time_t st_atime;
> >> >> unsigned long st_atime_nsec;
> >> >> time_t st_mtime;
> >> >> unsigned long st_mtime_nsec;
> >> >> time_t st_ctime;
> >> >> unsigned long st_ctime_nsec;
> >> >> unsigned long st_blksize;
> >> >> unsigned long __st_pad2;
> >> >> long long st_blocks;
> >> >> };
> >> >>
> >> >> It does appear that the syscalls for the two ABIs differ in this...
> >> >
> >> > This structure is identical to the one in musl except that it has
> >> > 32-bit dev_t plus padding in place of 64-bit dev_t, and the musl
> >> > version has reserved space at the end. Can you check whether the dev_t
> >> > issue is actually a problem (it might be, based on endianness, and if
> >> > so I think it would require ugly fixups in userspace)?
> >>
> >> Ah no, my mistake, you are right, the padding seems correct and I was
> >> getting confused as usual by dev_t. However the 64 bit dev_t is a
> >> problem on bigendian mips.
> >>
> >> (Whats the reason for Musl using 64 bit dev_t? glibc compatibility?)
> >
> > And room for expansion, and consistency of the type between archs.
> > There's no justification for dev_t or similar types to be
> > arch-specific.
>
> But isnt the kernel dev_t 32 bit for all archs?
Yes and no. They have adjacent padding reserved to make it up to
128-bit, despite the fact that intmax_t is 64-bit everywhere and thus
128-bit types can't really be used. I suspect on big-endian the
padding is at the other side to allow for this already, but it might
be misaligned with respect to the 64/128 bit size in musl at present.
Rich
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