[PATCH v2 1/5] mips: Do not malloc on getdents64 fallback

[Joseph Myers]

On Tue, 8 Oct 2019, Adhemerval Zanella wrote:

> +      memcpy (((char *)(dp) + offsetof (struct dirent64, d_ino)),
> +	      DP_MEMBER (kdp, struct kernel_dirent, d_ino),
> +	      sizeof ((struct dirent64){0}.d_ino));
> +      memcpy (((char *)(dp) + offsetof (struct dirent64, d_off)),
> +	      DP_MEMBER (kdp, struct kernel_dirent, d_ino),
> +	      sizeof ((struct dirent64){0}.d_ino));

(This is slightly different from the version of the code that ended up 
getting committed.)

GCC mainline now gives a rather cryptic error about this code:

../sysdeps/unix/sysv/linux/mips/mips64/getdents64.c: In function '__getdents64':
../sysdeps/unix/sysv/linux/mips/mips64/getdents64.c:121:7: error: 'memcpy' forming offset [4, 7] is out of the bounds [0, 4] [-Werror=array-bounds]
  121 |       memcpy (((char *) dp + offsetof (struct dirent64, d_ino)),
      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  122 |               KDP_MEMBER (kdp, d_ino), sizeof ((struct dirent64){0}.d_ino));
      |               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../sysdeps/unix/sysv/linux/mips/mips64/getdents64.c:123:7: error: 'memcpy' forming offset [4, 7] is out of the bounds [0, 4] [-Werror=array-bounds]
  123 |       memcpy (((char *) dp + offsetof (struct dirent64, d_off)),
      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  124 |               KDP_MEMBER (kdp, d_off), sizeof ((struct dirent64){0}.d_off));
      |               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I think what this error is pointing out is that the field in 
kernel_dirent, for non-n64, is 32-bit, while this is using memcpy to copy 
64 bits from it into the glibc dirent64, which obviously doesn't work.

-- 
Joseph S. Myers
joseph@codesourcery.com