Hi, Le mardi 28 octobre 2014 à 22:34 +0000, One Thousand Gnomes a écrit : > On Sun, 26 Oct 2014 12:25:08 +0000 > "Skidanov, Alexey" <[email protected]> wrote:
> > > Running 32 bit user space needs some work to be done with ioctls. I > > understand that there are two options to implement: > > 1. Use only fixed size types. Pad IOCTLS params to multiple of 64 > > bits - simple; don't know if it covers all compatibility issues; > > 2. 32 bit compatibility layer (through compat_ioctl, just like many > > drivers in kernel implement) - just a little bit simple code with some > > translations; really covers all issues; > > > > Which one is preferred by kernel community? > > You shouldn't need to pad paramters in most cases as platform alignment > rules are usually sane for 32 and 64bit. In most case, except i386 (ia32) vs amd64 (x86_64): u64 are going to be aligned on 4 bytes boundaries for 32bits ABI and 8 bytes boundaries for 64bits ABI. I've tried to explained this issue in a lightning talk[1][2] I'd given at Kernel Recipes[3] this year. [1] http://opteya.com/talks/2014/kernel-recipes/lightning-talk-kernel-userspace-ABI/ [2] https://gitorious.org/opteya/talk-kernel-userspace-abi [3] http://kernel.recipes/ Regards. -- Yann Droneaud OPTEYA -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
