Messages in this thread | | | Date | Tue, 16 Dec 2008 12:02:09 -0500 | From | Kyle McMartin <> | Subject | Re: [PATCH v3 0/3] preadv & pwritev syscalls. |
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On Tue, Dec 16, 2008 at 05:48:58PM +0100, Gerd Hoffmann wrote: > i.e. the ordering of the splitted argument depends on the os endianness? > What is the reason for this? >
Eh? The splitting will occur at the C ABI level, not as a result of glibc (though, it could be done that way if you really wanted, but then you're just moving the wrapper up the chain.)
A 64-bit value on a 32-bit machine will look like, in a register pair, like it looks in memory, with MSB/LSB ordering.
> I'd prefer to have the ordering coded explicitly instead, like this: > > asmlinkage int compat_sys_pwritev(unsigned long fd, > const struct compat_iovec __user *vec, unsigned long vlen, > unsigned pos_low, unsigned pos_high) > { > loff_t pos = pos_low | (loff_t)pos_high << 32; > [ ... ] >
Sadly this isn't possible without a wrapper unless you can guarantee it was passed low high instead of high low. Unless you munge it in userspace, you can't.
regards, Kyle
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