Messages in this thread | | | Date | Wed, 12 Aug 2009 21:00:19 +0800 | Subject | Re: Is compat_sys_ioctl called when both kernel and userland are 64bit ? | From | april <> |
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2009/8/12 Andi Kleen <andi@firstfloor.org>: > april <aapril03@gmail.com> writes: >> >> it seems when a kernel is built to x86_64, whenever a ioctl called >> ,the call flow will be ia32_syscall -->compat_sys_ioctl->compat >> ioctl(if provided) > > Only for syscalls throught int 0x80 (or 32bit SYSCALL/SYSENTER), which normally > only come from 32bit processes. In theory 64bit processes > could use them, but they normally don't. >
so you mean in 64bit process with a 64bit Linux kernel, system call is not through int 0x80 ? I know little about x86_64 arch, so I suppose it still through INT 0x80 can you tell me more about this? or where to get more information abort it?
>> but I have some doubt: >> >> My question is: >> 1. Is compat_sys_ioctl called when both kernel and userland are 64bit >> (suppose I provide those compat ioctl functions)? > > No. > >> If not, how kernel knows the driver is 32bit or 64bit? > > There are no 32bit drivers on a 64bit kernel, all drivers are 64bit. > > For 32bit processes running on a 64bit kernel it depends on the > entry points (int 0x80 or SYSENTER/SYSCALL) > >> 2. when using mmap, the 64bit kernel will return a 64bit address, and >> a userland(32bit) application can only get the lower 32bit, >> it can work when the memory is not large. > > The kernel makes sure to only hand out 32bit addresses to 32bit > processes. > I am using a 64bit kernel ,32bit Ubuntu9.04 which kernel was replaced by a 64bit one, and add some compat ioctl to make drm module work(on VIA platform),X can work well(only 512M ram) I am not test but guess it will has problem is memory is large (for example ,over 4G)
> -Andi > > -- > ak@linux.intel.com -- Speaking for myself only. > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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