[binutils-gdb/binutils-2_34-branch] aarch64: set sh_entsize of .plt to 0

[Szabolcs Nagy]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=e3b314d3a61db4b0b36975fa00eb9043a6142448

commit e3b314d3a61db4b0b36975fa00eb9043a6142448
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Wed Jul 29 15:47:50 2020 +0100

    aarch64: set sh_entsize of .plt to 0
    
    On aarch64 the first PLT entry is 32 bytes, subsequent entries
    are 16 bytes by default but can be 24 bytes with BTI or with
    PAC-PLT.
    
    sh_entsize of .plt was set to the PLT entry size, so in some
    cases sh_size % sh_entsize != 0, which breaks some tools.
    
    Note that PLT0 (and the TLSDESC stub code which is also in the
    PLT) were historically not padded up to meet the sh_size
    requirement, but to ensure that PLT stub code is aligned on
    cache lines. Similar layout is present on other targets too
    which just happens to make sh_size a multiple of sh_entsize and
    it is not expected that sh_entsize of .plt is used for anything.
    
    This patch sets sh_entsize of .plt to 0: the section does not
    hold a table of fixed-size entries so other values are not
    conforming in principle to the ELF spec.
    
    bfd/ChangeLog:
    
            Backport from mainline.
            2020-07-30  Szabolcs Nagy  <szabolcs.nagy@arm.com>
    
            PR ld/26312
            * elfnn-aarch64.c (elfNN_aarch64_init_small_plt0_entry): Set sh_entsize
            to 0.
            (elfNN_aarch64_finish_dynamic_sections): Remove sh_entsize setting.
    
    (cherry picked from commit 4d3bb35620e70d543d438bf21be1307f7ea0f5d0)

Diff:
---
 bfd/ChangeLog       | 10 ++++++++++
 bfd/elfnn-aarch64.c | 11 +++++------
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index ca87f744a3d..ecd099580a4 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,13 @@
+2020-08-11  Szabolcs Nagy  <szabolcs.nagy@arm.com>
+
+	Backport from mainline.
+	2020-07-30  Szabolcs Nagy  <szabolcs.nagy@arm.com>
+
+	PR ld/26312
+	* elfnn-aarch64.c (elfNN_aarch64_init_small_plt0_entry): Set sh_entsize
+	to 0.
+	(elfNN_aarch64_finish_dynamic_sections): Remove sh_entsize setting.
+
 2020-04-21  Tamar Christina  <tamar.christina@arm.com>
 
 	Backport from mainline.
diff --git a/bfd/elfnn-aarch64.c b/bfd/elfnn-aarch64.c
index 5fabcd8f646..0493cbb080a 100644
--- a/bfd/elfnn-aarch64.c
+++ b/bfd/elfnn-aarch64.c
@@ -9571,8 +9571,11 @@ elfNN_aarch64_init_small_plt0_entry (bfd *output_bfd ATTRIBUTE_UNUSED,
 
   memcpy (htab->root.splt->contents, htab->plt0_entry,
 	  htab->plt_header_size);
-  elf_section_data (htab->root.splt->output_section)->this_hdr.sh_entsize =
-    htab->plt_header_size;
+
+  /* PR 26312: Explicitly set the sh_entsize to 0 so that
+     consumers do not think that the section contains fixed
+     sized objects.  */
+  elf_section_data (htab->root.splt->output_section)->this_hdr.sh_entsize = 0;
 
   plt_got_2nd_ent = (htab->root.sgotplt->output_section->vma
 		  + htab->root.sgotplt->output_offset
@@ -9674,10 +9677,6 @@ elfNN_aarch64_finish_dynamic_sections (bfd *output_bfd,
     {
       elfNN_aarch64_init_small_plt0_entry (output_bfd, htab);
 
-      elf_section_data (htab->root.splt->output_section)->
-	this_hdr.sh_entsize = htab->plt_entry_size;
-
-
       if (htab->tlsdesc_plt && !(info->flags & DF_BIND_NOW))
 	{
 	  BFD_ASSERT (htab->dt_tlsdesc_got != (bfd_vma)-1);