-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 06/20/11 08:33, H. Peter Anvin wrote: > On 06/20/2011 07:01 AM, H.J. Lu wrote: >> On Mon, Jun 20, 2011 at 6:53 AM, Bernd Schmidt <ber...@codesourcery.com> >> wrote: >>> On 06/20/2011 03:51 PM, H.J. Lu wrote: >>>> Promote pointers to Pmode when passing/returning in registers is >>>> a security concern. > > No. Promoting *NON*-pointers (or rather, requiring non-pointers to > having already been zero extended) is a security concern. I thought I'd > made that point clear already. This is a hideously critical distinction. > >> Peter, do you think it is safe to assume upper 32bits are zero in >> user space for x32? Kernel isn't a problem since pointer is 64bit >> in kernel and we don't pass pointers on stack to kernel. > > As I have already stated, if we *cannot* require pointers to be > zero-extended on entry to the kernel, we're going to have to have > special entry points for all the x32 system calls except the ones that > don't take pointers.asdfasfd BTW (and feel free to respond off-list), what's the rationale behind zero-extending values in x32 from 32 bits to 64 bits rather than the more traditional sign-extending?
If it's already been discussed, feel free to point me at the thread. It's not hugely important, but I get this nagging feeling I'm missing something. jeff -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJN/1vpAAoJEBRtltQi2kC7XEUH/0XkfWpqjp3ry/GHsLEYn+8/ bKbd8x5gcrdBKenxkqKrDOqhTGUvttRxN4JClafzWSGFdrDiYxIwJAR4NAvuyYWa rRzSgMRl7VBmPAO+CmEyy2LZ7zEHn4j+iGPWrVQLToAjkIxlSO91Tu/8bimXocC6 FymxVe1Zj9+sCDTmirQnc+TtwnQwVIsNfXWk1e1tKO2bXaUQzfX3YaUKW/B1jw1V 5Xfong0y6XTCDAZQ4sNkCqVYaQBZuMfCLHVX8WP/kA0jMRycvgHWM823YFfFEU+P UHGgrVQeJX5GS1yoCXNrvvBLtDLIbnyYSAjosCIgje7hskBIqKqSdr146q1CTfY= =lUfw -----END PGP SIGNATURE-----
