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xen-ppc-devel
Re: [XenPPC] PHDR link failure testcase
On Mon, Aug 14, 2006 at 07:17:37PM -0400, Amos Waterland wrote:
> Using a `powerpc64-linux-gcc (GCC) 4.1.1 ()' x86->ppc toolchain, if I do this:
>
> diff -r 9563f5c9ab19 xen/include/asm-powerpc/config.h
<snip>
> /usr/powerpc64/lib/gcc/powerpc64-linux/4.1.1/../../../../powerpc64-linux/bin/ld:
> /home/apw/devel/xen/xen.hg/xen/xen-syms: Not enough room for program
> headers (allocated 2, need 3)
I believe the root cause for this is the fact that the .data.percpu
section is becoming large. As it's empty the linker decides to start a
3rd segment rather than waste disk space. 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.
I have 2 solutions to this problem.
1) Explicitly add 3 segmnets in the linker script and manually map
sections to segments.
2) Use the linker script to manually place a bogus data element in the
.data.percpu section, which results in the linker doign the right
thing.
I'm not in a position to judge which is better over the longer term but
"option 2" is a gross hack.
Option 1; Looks like:
------
diff -r 9563f5c9ab19 xen/arch/powerpc/xen.lds.S
--- a/xen/arch/powerpc/xen.lds.S Mon Aug 14 15:22:22 2006 -0500
+++ b/xen/arch/powerpc/xen.lds.S Tue Aug 15 16:28:59 2006 +1000
@@ -10,11 +10,17 @@ 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;
+ data PT_LOAD;
+ extra PT_LOAD;
+}
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) }
@@ -105,13 +111,13 @@ SECTIONS
{
*(.data .data.* .gnu.linkonce.d.*)
SORT(CONSTRUCTORS)
- }
+ } :data
/* Xen addition */
. = ALIGN(32);
__setup_start = .;
- .setup.init : { *(.setup.init) }
+ .setup.init : { *(.setup.init) } :text
__setup_end = .;
__initcall_start = .;
.initcall.init : { *(.initcall.init) }
@@ -121,7 +127,7 @@ 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);
@@ -129,7 +135,7 @@ SECTIONS
/* end Xen addition */
- .data1 : { *(.data1) }
+ .data1 : { *(.data1) } :extra
.tdata : { *(.tdata .tdata.* .gnu.linkonce.td.*) }
.tbss : { *(.tbss .tbss.* .gnu.linkonce.tb.*) *(.tcommon) }
.eh_frame : { KEEP (*(.eh_frame)) }
------
Option 2; Looks like:
------
diff -r 9563f5c9ab19 xen/arch/powerpc/xen.lds.S
--- a/xen/arch/powerpc/xen.lds.S Mon Aug 14 15:22:22 2006 -0500
+++ b/xen/arch/powerpc/xen.lds.S Tue Aug 15 16:34:27 2006 +1000
@@ -121,11 +121,12 @@ 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);
+ . = __per_cpu_start + (NR_CPUS << PERCPU_SHIFT) - 4;
+ LONG(0);
. = ALIGN(STACK_SIZE);
- __per_cpu_end = .;
+ __per_cpu_end = .; }
/* end Xen addition */
------
Both have been compiled and boot on the JS20 here. Neither of these 2 patches
is suggested for inclusion ATM. I wanted some feedback on which seems
better.
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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