On 02/01/2014 03:59 PM, Andy Lutomirski wrote: > > If it is, indeed, okay to use non-fixed maps on 32-bit, it might > also be okay on 64-bit. If so, it could be useful to implement that, > which would remove a bit of a wart and allow PR_SET_TSC to work > usefully for 64-bit userspace. (This would remove the need for the > VVAR macro and would allow shorter rip-relative address modes.) >
We can't really move the 64-bit legacy vsyscall area, though, as it is an ABI. It can be disabled with vsyscall=none, but Linus has vehemently vetoed removing them. > (Note that those fixmaps are a security problem on native 32-bit if > NX is not available. We may not care.) Not only on native 32 bit... although the amount of 64-bit hardware without NX is quite small, the same is true for anywhere near modern 32-bit hardware. >> >> -#define VDSO_HIGH_BASE 0xffffe000U /* CONFIG_COMPAT_VDSO address */ >> +#define VDSO_HIGH_BASE 0xffffc000U /* CONFIG_COMPAT_VDSO address */ > > This is odd. Can you explain it? > He needs 3 pages instead of 1 after his changes. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/