Re: 64bit support on netbsd

[Guy Harris <guy () alum mit edu>]

On Feb 9, 2012, at 7:04 PM, Guy Harris wrote:

> *However*, that's not the only place where structures involving times get passed between the kernel and userland.  
> They *also* get passed in the BIOCGRTIMEOUT and BIOCSRTIMEOUT ioctls, the argument to which is a pointer to a struct 
> timeval.  This being a BSD-flavored OS, the ioctl cookie includes the size of the structure, so an ioctl with a 
> 32-bit struct timeval will have a different ioctl cookie from an ioctl with a 64-bit struct timeval.
>
> From a quick look at the top of the trunk, _BSD_TIME_T_ is always defined as __int64_t and _BSD_SUSECONDS_T_ is 
> always defined as int, so struct timeval would, *modulo padding at the end* (I presume that's the "48bits for i386 
> and 64bits for amd64" - presumably meaning "48 bits for 32-bit platforms and 64 bits for 64-bit platforms"), be laid 
> out the same, so that should work as well.

Except that the padding means that the ioctl cookies will be different, so 32-bit code that attempts a BIOCSRTIMEOUT on 
a 64-bit kernel will succeed only if the kernel has a case in the switch statement to handle the 32-bit version of the 
BIOCSRTIMEOUT cookie.  Given that struct timeval50 is

struct timeval50 {
        long    tv_sec;         /* seconds */
        long    tv_usec;        /* and microseconds */
};

BIOCSORTIMEOUT is *NOT* the 32-bit BIOCSRTIMEOUT cookie, so it appears that a 64-bit kernel will *NOT* handle a 
BIOCSRTIMEOUT from 32-bit userland, so any 32-bit program that uses a libpcap built 32-bit on NetBSD with a 64-bit 
time_t will not work (that includes, but is not necessarily limited to, tcpdump).

Fixing that will require defining, on a 64-bit kernel, an ioctl cookie with the codes for BIOCSRTIMEOUT and with the 
size of a 48-bit struct timeval, and putting into bpf_ioctl() a case for that cookie that handles the 48-bit struct 
timeval argument.  (The same should be done for BIOCGRTIMEOUT; with the possible exception of BIOCGETIF and BIOCSETIF, 
it looks as if the other BPF ioctls have the same in-memory arguments in 32-bit and 64-bit mode.)-
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