Re: [XenPPC] PHDR link failure testcase

[Tony Breeds <tony@xxxxxxxxxxxxxxxxxx>]

On Wed, Aug 16, 2006 at 08:10:20AM -0400, Jimi Xenidis wrote:

> Thanks for getting to the bottom of this Tony.
> 
> >As it's empty the linker decides to start a
> >3rd segment rather than waste disk space.
> 
> Hmm, what is "empty"?

By empty I mean "filled with 0s", which I believe is because all the
per_cpu variables are initialised at runtime.
 
> >  Initially the linker guessed
> >it would need 2 segments, but due to this decision it actually uses 3,
> >causeing the abort.
> >
> >Aparently the newer (read current CVS) tools don't abort here but do
> >the right thing.
> 
> What _is_ the "right thing"?

Use 3 PHDRS.

> Perhaps, this is just mythology/warm-n-fuzzy for me, but I really  
> like having 1 PHDR.
> Lemmy collect my thoughts and come up with a rational reason.

Sure.  Wouldn't that mean that everything will end up being in a 
read/write/execute PHDR.  Do we care about that?

Placing everything in one PHDR would look like:

---
diff -r 279843441136 xen/arch/powerpc/xen.lds.S
--- a/xen/arch/powerpc/xen.lds.S        Wed Aug 16 17:19:38 2006 -0500
+++ b/xen/arch/powerpc/xen.lds.S        Thu Aug 17 11:30:50 2006 +1000
@@ -10,11 +10,15 @@ SEARCH_DIR("=/usr/local/lib64"); SEARCH_
 SEARCH_DIR("=/usr/local/lib64"); SEARCH_DIR("=/lib64"); 
SEARCH_DIR("=/usr/lib64"); SEARCH_DIR("=/usr/local/lib"); SEARCH_DIR("=/lib"); 
SEARCH_DIR("=/usr/lib");
 /* Do we need any of these for elf?
    __DYNAMIC = 0;    */
+PHDRS
+{
+  text PT_LOAD FILEHDR PHDRS;
+}
 SECTIONS
 {
   /* Read-only sections, merged into text segment: */
   PROVIDE (__executable_start = 0x10000000); . = 0x10000000 + SIZEOF_HEADERS;
-  .interp         : { *(.interp) }
+  .interp         : { *(.interp) } :text
   .hash           : { *(.hash) }
   .dynsym         : { *(.dynsym) }
   .dynstr         : { *(.dynstr) }
@@ -121,7 +125,7 @@ SECTIONS
   __inithcall_end = .;
 
   __per_cpu_start = .;
-  .data.percpu : { *(.data.percpu) } :text
+  .data.percpu : { *(.data.percpu) }
   __per_cpu_data_end = .;
   . = __per_cpu_start + (NR_CPUS << PERCPU_SHIFT);
   . = ALIGN(STACK_SIZE);

Yours Tony

   linux.conf.au       http://linux.conf.au/ || http://lca2007.linux.org.au/
   Jan 15-20 2007      The Australian Linux Technical Conference!


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