[xen staging] x86/build: work around older GNU ld not leaving .got.plt empty

[patchbot@xxxxxxx]

commit a2b8da2574586270207c6eb8e7aa8cd19eb74947
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Tue Mar 22 13:10:59 2022 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Mar 22 13:10:59 2022 +0100

    x86/build: work around older GNU ld not leaving .got.plt empty
    
    The initial three entries in .got.plt are "static", i.e. present
    independent of actual entries allocation of which is triggered by
    respective relocations. When no real entries are needed, halfway recent
    ld discards the "static" portion of the table as well, but older GNU ld
    fails to do so.
    
    Fixes: dedb0aa42c6d ("x86/build: use --orphan-handling linker option if 
available")
    Reported-by: Julien Grall <jgrall@xxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Tested-by: Julien Grall <jgrall@xxxxxxxxxx>
---
 xen/arch/x86/xen.lds.S | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index d33e295320..db2aaf7781 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -497,7 +497,13 @@ ASSERT(IS_ALIGNED(__bss_end,        8), "__bss_end 
misaligned")
 
 #ifndef EFI
 ASSERT(!SIZEOF(.got),      ".got non-empty")
-ASSERT(!SIZEOF(.got.plt),  ".got.plt non-empty")
+/*
+ * At least GNU ld 2.30 and earlier fail to discard the generic part of
+ * .got.plt when no actual entries were allocated. Permit this case alongside
+ * the section being empty.
+ */
+ASSERT(!SIZEOF(.got.plt) || SIZEOF(.got.plt) == 3 * 8,
+       "unexpected .got.plt size")
 ASSERT(!SIZEOF(.igot.plt), ".igot.plt non-empty")
 ASSERT(!SIZEOF(.iplt),     ".iplt non-empty")
 ASSERT(!SIZEOF(.plt),      ".plt non-empty")
--
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