lkml.org 
[lkml]   [2018]   [Jan]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    SubjectRE: [PATCH] x86/retpoline/entry: Disable the entire SYSCALL64 fast path with retpolines on
    Date
    From: Will Deacon
    > Sent: 29 January 2018 13:20
    ...
    > Another issue with this style of macro definition exists on architectures
    > where the calling convention needs you to carry state around depending on
    > how you packed the previous parameters. For example, on 32-bit ARM, 64-bit
    > values are passed in adjacent pairs of registers but the low numbered
    > register needs to be even. This is what stopped me from trying to use
    > existing helpers such as syscall_get_arguments to unpack the pt_regs
    > and it generally means that anything that says "get me argument n" is going
    > to require constructing arguments 0..n-1 first.
    >
    > To do this properly I think we'll either need to pass back the size and
    > current register offset to the arch code, or just allow the thing to be
    > overridden per syscall (the case above isn't especially frequent).

    If you generate a structure from the argument list that might work
    'by magic'.
    Certainly you can add explicit pads to any structure.

    David



    \
     
     \ /
      Last update: 2018-01-29 16:23    [W:3.352 / U:0.008 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site