[lkml]   [2010]   [Jul]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [PATCH][GIT PULL][for 2.6.35] tracing: Add alignment to syscall metadata declarations
    On Fri, Jul 09, 2010 at 05:05:50PM -0400, Steven Rostedt wrote:
    > On Fri, 2010-07-09 at 22:53 +0200, Sam Ravnborg wrote:
    > > But in this case we have no control of the value of "." (current address)
    > > when we have processed (_ftrace_events) so it may even be at a 2 byte boundary.
    > > The linker will add padding as needed to satisfy the alignmnet of
    > > __syscalls_metadata - but that padding will be inbetween "." and the first
    > > member in __syscalls_metadata.
    > Fine, but this is a separate issue. I doubt the "ALIGN(8);" would have
    > helped us anyway. Remember what the issue we had:
    > ffffffff8173c438 <__start_syscalls_metadata>:
    > ...
    > ffffffff8173c440 <__syscall_meta__mmap>:
    > __start_syscalls_metadata was already aligned to 8, but for some strange
    > reason, gcc decided to align the first member to 16.

    I found some more info in following bug:

    Jeff Mahoney says:
    GCC 4.5 introduced behavior that forces the alignment of structures to
    use the largest possible value. The default value is 32 bytes, so if
    some structures are defined with a 4-byte alignment and others aren't
    declared with an alignment constraint at all - it will align at 32-bytes.

    So according to this we can rely on 32 byte alignment and
    this is trivial to add in


     \ /
      Last update: 2010-07-10 00:05    [W:0.022 / U:1.244 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site