[binutils-gdb] Fix PR 20221 - adjust syms and relocs only if relax shrunk section.

[Denis Chertykov <denisc at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=5c41dbc302c2dd87e201e4fd1d9ae3186f6e51a0

commit 5c41dbc302c2dd87e201e4fd1d9ae3186f6e51a0
Author: Denis Chertykov <chertykov@gmail.com>
Date:   Thu Jun 9 19:17:43 2016 +0300

    Fix PR 20221 - adjust syms and relocs only if relax shrunk section.
    
    This patch fixes an edge case in linker relaxation that causes symbol
    values to be computed incorrectly in the presence of align directives
    in input source code.
    
    bfd/
    	* elf32-avr.c (elf32_avr_relax_delete_bytes): Adjust syms
    	and relocs only if shrinking occurred.
    
    ld/
    	* testsuite/ld-avr/avr-prop-5.d: New.
    	* testsuite/ld-avr/avr-prop-5.s: New.

Diff:
---
 bfd/ChangeLog                    |  6 ++++++
 bfd/elf32-avr.c                  | 21 ++++++++++++++++++---
 ld/ChangeLog                     |  7 +++++++
 ld/testsuite/ld-avr/avr-prop-5.d | 10 ++++++++++
 ld/testsuite/ld-avr/avr-prop-5.s |  7 +++++++
 5 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index d544d02..460e68b 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,9 @@
+2016-06-08  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
+
+	PR ld/20221
+	* elf32-avr.c (elf32_avr_relax_delete_bytes): Adjust syms
+	and relocs only if shrinking occurred.
+
 2016-06-08  H.J. Lu  <hongjiu.lu@intel.com>
 
 	* elf64-i386.c (elf_i386_link_hash_entry): Add tls_get_addr.
diff --git a/bfd/elf32-avr.c b/bfd/elf32-avr.c
index d463d78..b95e251 100644
--- a/bfd/elf32-avr.c
+++ b/bfd/elf32-avr.c
@@ -1828,6 +1828,7 @@ elf32_avr_relax_delete_bytes (bfd *abfd,
   unsigned int symcount;
   struct avr_relax_info *relax_info;
   struct avr_property_record *prop_record = NULL;
+  bfd_boolean did_shrink = FALSE;
 
   symtab_hdr = &elf_tdata (abfd)->symtab_hdr;
   sec_shndx = _bfd_elf_section_from_bfd_section (abfd, sec);
@@ -1863,10 +1864,16 @@ elf32_avr_relax_delete_bytes (bfd *abfd,
 
   /* Actually delete the bytes.  */
   if (toaddr - addr - count > 0)
-    memmove (contents + addr, contents + addr + count,
-             (size_t) (toaddr - addr - count));
+    {
+      memmove (contents + addr, contents + addr + count,
+               (size_t) (toaddr - addr - count));
+      did_shrink = TRUE;
+    }
   if (prop_record == NULL)
-    sec->size -= count;
+    {
+      sec->size -= count;
+      did_shrink = TRUE;
+    }
   else
     {
       /* Use the property record to fill in the bytes we've opened up.  */
@@ -1885,6 +1892,11 @@ elf32_avr_relax_delete_bytes (bfd *abfd,
           prop_record->data.align.preceding_deleted += count;
           break;
         };
+      /* If toaddr == (addr + count), then we didn't delete anything, yet
+         we fill count bytes backwards from toaddr. This is still ok - we
+         end up overwriting the bytes we would have deleted. We just need
+         to remember we didn't delete anything i.e. don't set did_shrink,
+         so that we don't corrupt reloc offsets or symbol values.*/
       memset (contents + toaddr - count, fill, count);
 
       /* Adjust the TOADDR to avoid moving symbols located at the address
@@ -1892,6 +1904,9 @@ elf32_avr_relax_delete_bytes (bfd *abfd,
       toaddr -= count;
     }
 
+  if (!did_shrink)
+    return TRUE;
+
   /* Adjust all the reloc addresses.  */
   for (irel = elf_section_data (sec)->relocs; irel < irelend; irel++)
     {
diff --git a/ld/ChangeLog b/ld/ChangeLog
index cbb98e3..11470c5 100644
--- a/ld/ChangeLog
+++ b/ld/ChangeLog
@@ -1,4 +1,11 @@
+2016-06-08  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>
+
+	PR ld/20221
+	* testsuite/ld-avr/avr-prop-5.d: New.
+	* testsuite/ld-avr/avr-prop-5.s: New.
+
 2016-06-09  Pitchumani Sivanupandi  <pitchumani.s@atmel.com>
+
 	* testsuite/ld-avr/lds-mega.d: New test.
 	* testsuite/ld-avr/lds-mega.s: New test source.
 	* testsuite/ld-avr/lds-tiny.d: New test.
diff --git a/ld/testsuite/ld-avr/avr-prop-5.d b/ld/testsuite/ld-avr/avr-prop-5.d
new file mode 100644
index 0000000..5f62ba3
--- /dev/null
+++ b/ld/testsuite/ld-avr/avr-prop-5.d
@@ -0,0 +1,10 @@
+#name: AVR .avr.prop, single .align proper sym val test.
+#as: -mmcu=avrxmega2 -mlink-relax
+#ld: -mavrxmega2 --relax
+#source: avr-prop-5.s
+#objdump: -S
+#target: avr-*-*
+
+#...
+   0:	00 d0\s+rcall\s+\.\+0\s+; 0x2 <dest>
+#...
\ No newline at end of file
diff --git a/ld/testsuite/ld-avr/avr-prop-5.s b/ld/testsuite/ld-avr/avr-prop-5.s
new file mode 100644
index 0000000..6a3359a
--- /dev/null
+++ b/ld/testsuite/ld-avr/avr-prop-5.s
@@ -0,0 +1,7 @@
+        .text
+        .global _start, dest
+_start:
+        CALL    dest
+        .align  1
+dest:
+        NOP