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Message-ID: <20140716114005.GB2021@newbook>
Date: Wed, 16 Jul 2014 04:40:06 -0700
From: Isaac Dunham <ibid.ag@...il.com>
To: musl@...ts.openwall.com
Subject: Re: More MIPS stat.h breakage...?
On Wed, Jul 16, 2014 at 12:15:56AM -0400, Rich Felker wrote:
> I thought all of these issues were addressed a long time ago, but I
> think we still may have at least one bits-header bug on MIPS big
> endian: stat.h. The kernel version of this structure has:
>
> struct stat64 {
> unsigned long st_dev;
> unsigned long st_pad0[3]; /* Reserved for st_dev expansion */
> ...
>
> whereas st_dev needs to be dev_t, which is 64-bit.
>
> We're handling this now simply by using the following definition:
>
> struct stat
> {
> dev_t st_dev;
> long __st_padding1[2];
> ...
>
> i.e. incorporating one of the padding slots into st_dev. But this only
> yields the correct value for little endian. For big endian, I think
> device numbers are appearing in the upper 32 bits rather than the
> lower ones. This renders the major, minor, etc. macros incorrect.
>
> I think the cleanest fix for this is probably to add an arch-specific,
> nop-by-default function __stat_fixup or similar that gets called
> whenever any stat-family syscall succeeds in order to patch up the
> results as needed. Alternatively, we clould do the patchup at the
> syscall level for mips' syscall_arch.h, much like how x32 works.
>
> Anyone have strong opinions on how this should be handled?
I seem to remember some comment about trying to work on kernels that predate
stat64(). __stat_fixup would be a logical way to handle that, should that
still be intended.
The most precise information I can find is that stat64() dates to 2.4.18;
I'm not sure about the accuracy of that.
But I don't have a strong opinion; I just noticed a similarity to an idea
that was mentioned some time back.
Also, I'm not aware of any reasons 2.4.1x might be a major target
for musl. ;-)
Thanks,
Isaac Dunham
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