lkml.org 
[lkml]   [2012]   [Aug]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 55/74] lto, workaround: Add workaround for initcall reordering
    >>> On 19.08.12 at 17:01, Andi Kleen <andi@firstfloor.org> wrote:
    > On Sun, Aug 19, 2012 at 09:46:04AM +0100, Jan Beulich wrote:
    >> >>> Andi Kleen <andi@firstfloor.org> 08/19/12 5:05 AM >>>
    >> >Work around a LTO gcc problem: when there is no reference to a variable
    >> >in a module it will be moved to the end of the program. This causes
    >> >reordering of initcalls which the kernel does not like.
    >> >Add a dummy reference function to avoid this. The function is
    >> >deleted by the linker.
    >>
    >> This is not even true on x86, not to speak of generally.
    >
    > Why is it not true ?
    >
    > __initcall is only defined for !MODULE and there __exit discards.

    __exit, on x86 and perhaps other arches, causes the code
    to be discarded at runtime only.

    >> >+#ifdef CONFIG_LTO
    >> >+/* Work around a LTO gcc problem: when there is no reference to a variable
    >> >+ * in a module it will be moved to the end of the program. This causes
    >> >+ * reordering of initcalls which the kernel does not like.
    >> >+ * Add a dummy reference function to avoid this. The function is
    >> >+ * deleted by the linker.
    >> >+ */
    >> >+#define LTO_REFERENCE_INITCALL(x) \
    >> >+ ; /* yes this is needed */ \
    >> >+ static __used __exit void *reference_##x(void) \
    >>
    >> Why not put it into e.g. section .discard.text? That could be expected to be
    >> discarded by the linker without being arch dependent, as long as all arches
    >> use DISCARDS in their linker script.
    >
    >
    > That's what __exit does, doesn't it?

    No - see above. Using .discard.* enforces the discarding at link
    time.

    Jan



    \
     
     \ /
      Last update: 2012-08-20 13:41    [W:4.149 / U:0.088 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site