On 04/28/2016 08:18 AM, Christopher Covington wrote: > Please take a look at the following prototype of sharing the PowerPC > VDSO unmap and remap code with other architectures. I've only hooked > up arm64 to begin with. If folks think this is a reasonable approach I > can work on 32 bit ARM as well. Not hearing back from an earlier > request for guidance [1], I simply dove in and started hacking. > Laurent's test case [2][3] is a compelling illustration of whether VDSO > remap works or not on a given architecture. I think there's a much nicer way: https://lkml.kernel.org/r/1461584223-9418-1-git-send-email-dsafonov@xxxxxxxxxxxxx Could arm64 and ppc use this approach? These arch_xyz hooks are gross. Also, at some point, possibly quite soon, x86 will want a way for user code to ask the kernel to map a specific vdso variant at a specific address. Could we perhaps add a new pair of syscalls: struct vdso_info { unsigned long space_needed_before; unsigned long space_needed_after; unsigned long alignment; }; long vdso_get_info(unsigned int vdso_type, struct vdso_info *info); long vdso_remap(unsigned int vdso_type, unsigned long addr, unsigned int flags); #define VDSO_X86_I386 0 #define VDSO_X86_64 1 #define VDSO_X86_X32 2 // etc. vdso_remap will map the vdso of the chosen type such at AT_SYSINFO_EHDR lines up with addr. It will use up to space_needed_before bytes before that address and space_needed_after after than address. It will also unmap the old vdso (or maybe only do that if some flag is set). On x86, mremap is *not* sufficient for everything that's needed, because some programs will need to change the vdso type. --Andy -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>