Re: struct statfs/statfs64 in linux-generic

[Andrew Pinski <pinskia at gmail dot com>]

On Sun, Nov 3, 2013 at 11:18 PM, Chung-Lin Tang <cltang@codesourcery.com> wrote:
> Hi,
>
> I'm currently working on the glibc port for Altera Nios II, and per the
> kernel upstreaming requirements, we're making it a user of linux-generic
> in glibc.
>
> I've come across an issue about struct statfs/statfs64, where I've
> listed the struct definitions in both glibc and the kernel below.
>
> In linux-generic, both struct statfs/statfs64 has some fields as 64-bit
> words, padded properly if need on 32-bit targets. Effectively, they have
> to be same-format, to pass to the statfs64 syscall uniformly.
>
> __SWORD_TYPE appears to be int/long on 32/64-bit targets. This means
> that for 32-bit targets, struct statfs[64] will be made of 32-bit words,
> with a few 64-bit fields embedded in the middle.
>
>
> In the kernel however, the fields of importance in struct statfs is made
> up of entirely '__statfs_word', defined to be 64-bit or 32-bit depending
> on target (putting aside signedness for now).
>
> Notice how that, while this does work for 64-bit targets, 32-bit targets
> cannot properly define a compatible struct statfs[64], at least not with
> simple typedefs.
>
> Chris, as you seem the original developer/maintainer of linux-generic
> and the tile ports (as I observed from the mail archives), I'm curious
> if you saw any similar problems with tilegx -m32? The only users of
> linux-generic appears to be only aarch64 and tile, and nios2 will be
> another 32-bit user.
>
> The exact FAIL I saw was posix/tst-getconf, which I traced to a failed
> statfs64 call in pathconf(), due to a failed sizeof(struct statfs64)
> check inside the kernel syscall code.


Yes I ran into this same issue when I was working on ILP32 for AARCH64.
Attached is the patch which I used.

Thanks,
Andrew Pinski

>
> Thanks,
> Chung-Lin
>
>
> In glibc, ports/sysdeps/unix/sysv/linux/generic/bits/statfs.h:
> struct statfs
>   {
>     __SWORD_TYPE f_type;
>     __SWORD_TYPE f_bsize;
>     __field64(__fsblkcnt_t, __fsblkcnt64_t, f_blocks);
>     __field64(__fsblkcnt_t, __fsblkcnt64_t, f_bfree);
>     __field64(__fsblkcnt_t, __fsblkcnt64_t, f_bavail);
>     __field64(__fsfilcnt_t, __fsfilcnt64_t, f_files);
>     __field64(__fsfilcnt_t, __fsfilcnt64_t, f_ffree);
>     __fsid_t f_fsid;
>     __SWORD_TYPE f_namelen;
>     __SWORD_TYPE f_frsize;
>     __SWORD_TYPE f_flags;
>     __SWORD_TYPE f_spare[4];
>   } __attribute__((__aligned__(8)));
>
> #ifdef __USE_LARGEFILE64
> struct statfs64
>   {
>     __SWORD_TYPE f_type;
>     __SWORD_TYPE f_bsize;
>     __fsblkcnt64_t f_blocks;
>     __fsblkcnt64_t f_bfree;
>     __fsblkcnt64_t f_bavail;
>     __fsfilcnt64_t f_files;
>     __fsfilcnt64_t f_ffree;
>     __fsid_t f_fsid;
>     __SWORD_TYPE f_namelen;
>     __SWORD_TYPE f_frsize;
>     __SWORD_TYPE f_flags;
>     __SWORD_TYPE f_spare[4];
>   } __attribute__((__aligned__(8)));
> #endif
>
>
> In Linux kernel, include/uapi/asm-generic/statfs.h:
>
> #ifndef __statfs_word
> #if __BITS_PER_LONG == 64
> #define __statfs_word long
> #else
> #define __statfs_word __u32
> #endif
> #endif
>
> struct statfs {
>         __statfs_word f_type;
>         __statfs_word f_bsize;
>         __statfs_word f_blocks;
>         __statfs_word f_bfree;
>         __statfs_word f_bavail;
>         __statfs_word f_files;
>         __statfs_word f_ffree;
>         __kernel_fsid_t f_fsid;
>         __statfs_word f_namelen;
>         __statfs_word f_frsize;
>         __statfs_word f_flags;
>         __statfs_word f_spare[4];
> };
>
> #ifndef ARCH_PACK_STATFS64
> #define ARCH_PACK_STATFS64
> #endif
>
> struct statfs64 {
>         __statfs_word f_type;
>         __statfs_word f_bsize;
>         __u64 f_blocks;
>         __u64 f_bfree;
>         __u64 f_bavail;
>         __u64 f_files;
>         __u64 f_ffree;
>         __kernel_fsid_t f_fsid;
>         __statfs_word f_namelen;
>         __statfs_word f_frsize;
>         __statfs_word f_flags;
>         __statfs_word f_spare[4];
> } ARCH_PACK_STATFS64;

Attachment: fixstatfs.diff.txt
Description: Text document