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Re: [PATCH 2/9] Tilera (and Linux asm-generic) support for glibc
On 11/4/2011 9:51 PM, Joseph S. Myers wrote:
> On Thu, 3 Nov 2011, Chris Metcalf wrote:
>
>> +/* 64-bit libc uses the kernel's 'struct stat', accessed via the
>> + stat() syscall; 32-bit libc uses the kernel's 'struct stat64'
>> + and accesses it via the stat64() syscall. All the various
>> + APIs offered by libc use the kernel shape for their struct stat
>> + structure; the only difference is that 32-bit programs not
>> + using __USE_FILE_OFFSET64 only see the low 32 bits of some
>> + of the fields (specifically st_ino, st_size, and st_blocks). */
> As I understand it, this strategy means that the glibc implementations of
> the 32-bit APIs that fill in a 32-bit "struct stat" - that is, the
> structure where some bits are hidden in padding - need to check that the
> kernel has filled those bits with zeros and return an EOVERFLOW error if
> not, so that users of the 32-bit interfaces do not get unreliable results.
> I don't see any sign of that error handling in this patch.
>
> The same applies to the statfs structure, and to any functions returning
> off_t directly (which includes at least lseek).
Yes, good point. I'll add that to the 32-bit versions for the next patch
submission.
>> diff --git a/sysdeps/unix/sysv/linux/generic/wordsize-32/Versions b/sysdeps/unix/sysv/linux/generic/wordsize-32/Versions
>> new file mode 100644
>> index 0000000..0ba05f9
>> --- /dev/null
>> +++ b/sysdeps/unix/sysv/linux/generic/wordsize-32/Versions
>> @@ -0,0 +1,6 @@
>> +libc {
>> + GLIBC_2.11 {
>> + # Should probably be published in sysdeps/unix/sysv/linux/Versions.
>> + fallocate64;
>> + }
>> +}
> GLIBC_2.11 certainly won't be right for any new port using the generic
> syscall ABI since no such port existed in glibc 2.11. The correct version
> for each architecture would really be the value in that architecture's
> shlib-versions file, making the setting here matter less as long as each
> architecture has an appropriate shlib-versions, but GLIBC_2.15, as the
> version in which generic syscall ABI support is added, is probably the
> best version to put in this file.
OK.
--
Chris Metcalf, Tilera Corp.
http://www.tilera.com