On Thu, Nov 06, 2014 at 04:54:31PM +0000, Will Deacon wrote: > On Thu, Nov 06, 2014 at 04:43:12PM +0000, Catalin Marinas wrote: > > On Fri, Oct 24, 2014 at 02:56:39PM +0100, Mark Rutland wrote: > > > [d] Print different hwcaps dependent on the personality. > > > > > > This would allow for 32-bit and 64-bit applications to function > > > correctly, but for some 32-bit applications the personality would > > > need to be set explicitly by the user. > > > > Which makes this option actually in line with the uname -m behaviour. My > > vote goes for [d] with option [b] as a close alternative. > > > > > [1] arm, v3.17, Versatile Express A15x2 A7x3 coretile > > > Features : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm > > [...] > > > [2] arm64, v3.17, Juno platform > > > Features : fp asimd evtstrm aes pmull sha1 sha2 crc32 > > > > As an exercise, I'm trying to see what option [b] would look like when > > CONFIG_COMPAT is enabled: > > > > Features : fp asimd evtstrm aes pmull sha1 sha2 crc32 half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae > > > > The duplicate strings would only be listed once (evtstrm, aes, pmull, > > sha1, sha2, crc32). New AArch64 features that we may expect to be > > optional on AArch32 could be prefixed with "a64". If they are missing > > entirely from AArch32, (like asimd), no need for the prefix. > > > > The advantage is that we don't need to check the personality but we have > > to assume that scripts would not search for substrings (sane people > > shouldn't do this anyway as the Features string can always be extended). > > And a big disadvantage is that I can imagine AArch64 applications checking > for "neon" instead of "asimd", which will break if they're run under kernels > without COMPAT support enabled. That's because they do stupid things and I they probably deserve to break ;). But I agree, there is a risk. > So I'm inclined to stick with Mark's patch as it is. If we don't hear otherwise, I propose sometime next week we queue Mark's patch for -next. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
