Rework the R_NEG support on both gas and ld for the PowerPC AIX targets, in order to manage C++ exceptions built with GCC.

bfd	PR binutils/21700
	* reloc.c (BFD_RELOC_PPC_NEG): New relocation.
	* bfd-in2.h: Regenerate.
	* libbfd.h: Regenerate.
	* coff-rs6000.c (_bfd_xcoff_reloc_type_lookup): Add
	BFD_RELOC_PPC_NEG handler.
	(xcoff_reloc_type_neg): Correctly substract addend.
	* coff64-rs6000.c (xcoff64_howto_table): Add R_NEG_32
	howto.
	(xcoff64_rtype2howto): Add handler for R_NEG_32.
	(xcoff64_reloc_type_lookup): Add BFD_RELOC_PPC_NEG handler.
	* xcofflink.c (xcoff_need_ldrel_p): Check output section
	for R_POS-like relocations. New argument added.
	(xcoff_mark): Adapt to new xcoff_need_ldrel_p argument.
	(xcoff_link_input_bfd): Likewise.

gas	* config/tc-ppc.c (ppc_get_csect_to_adjust): New function.
	(ppc_fix_adjustable): Manage fx_subsy part.
	(tc_gen_reloc): Create second relocation when both
	fx_addsy and fx_subsy are provided.
	* config/tc-ppc.h (RELOC_EXPANSION_POSSIBLE): New define.
	(MAX_RELOC_EXPANSION): Likewise.
	(TC_FORCE_RELOCATION_SUB_SAME): Likewise
	(UNDEFINED_DIFFERENCE_OK): Likewise
	* testsuite/gas/all/gas.exp: Skip difference between two
	undefined symbols test.

ld	* testsuite/ld-powerpc/aix52.exp: Add new test.
	* testsuite/ld-powerpc/aix-neg-reloc-32.d: New test.
	* testsuite/ld-powerpc/aix-neg-reloc-64.d: New test.
	* testsuite/ld-powerpc/aix-neg-reloc.ex: New test.
	* testsuite/ld-powerpc/aix-neg-reloc.s: New test.

7 files changed, 56 insertions, 5 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 513d6e9..972311b 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,21 @@
+2021-04-20  Clément Chigot  <clement.chigot@atos.net>
+
+	PR binutils/21700
+	* reloc.c (BFD_RELOC_PPC_NEG): New relocation.
+	* bfd-in2.h: Regenerate.
+	* libbfd.h: Regenerate.
+	* coff-rs6000.c (_bfd_xcoff_reloc_type_lookup): Add
+	BFD_RELOC_PPC_NEG handler.
+	(xcoff_reloc_type_neg): Correctly substract addend.
+	* coff64-rs6000.c (xcoff64_howto_table): Add R_NEG_32
+	howto.
+	(xcoff64_rtype2howto): Add handler for R_NEG_32.
+	(xcoff64_reloc_type_lookup): Add BFD_RELOC_PPC_NEG handler.
+	* xcofflink.c (xcoff_need_ldrel_p): Check output section
+	for R_POS-like relocations. New argument added.
+	(xcoff_mark): Adapt to new xcoff_need_ldrel_p argument.
+	(xcoff_link_input_bfd): Likewise.
+
 2021-04-16  Alan Modra  <amodra@gmail.com>
 
 	PR 27567
diff --git a/bfd/bfd-in2.h b/bfd/bfd-in2.h
index cdfb933..d5780e4 100644
--- a/bfd/bfd-in2.h
+++ b/bfd/bfd-in2.h
@@ -2921,6 +2921,7 @@ instruction.  */
   BFD_RELOC_PPC_VLE_SDAREL_HA16D,
   BFD_RELOC_PPC_16DX_HA,
   BFD_RELOC_PPC_REL16DX_HA,
+  BFD_RELOC_PPC_NEG,
   BFD_RELOC_PPC64_HIGHER,
   BFD_RELOC_PPC64_HIGHER_S,
   BFD_RELOC_PPC64_HIGHEST,
diff --git a/bfd/coff-rs6000.c b/bfd/coff-rs6000.c
index 237c7ed..7cfe404 100644
--- a/bfd/coff-rs6000.c
+++ b/bfd/coff-rs6000.c
@@ -1253,6 +1253,8 @@ _bfd_xcoff_reloc_type_lookup (bfd *abfd ATTRIBUTE_UNUSED,
       return &xcoff_howto_table[0];
     case BFD_RELOC_NONE:
       return &xcoff_howto_table[0xf];
+    case BFD_RELOC_PPC_NEG:
+      return &xcoff_howto_table[0x1];
     case BFD_RELOC_PPC_TLSGD:
       return &xcoff_howto_table[0x20];
     case BFD_RELOC_PPC_TLSIE:
@@ -2985,7 +2987,7 @@ xcoff_reloc_type_neg (bfd *input_bfd ATTRIBUTE_UNUSED,
 		      bfd_vma *relocation,
 		      bfd_byte *contents ATTRIBUTE_UNUSED)
 {
-  *relocation = addend - val;
+  *relocation = - val - addend;
   return true;
 }
 
diff --git a/bfd/coff64-rs6000.c b/bfd/coff64-rs6000.c
index cc671b2..8895340 100644
--- a/bfd/coff64-rs6000.c
+++ b/bfd/coff64-rs6000.c
@@ -1320,7 +1320,21 @@ reloc_howto_type xcoff64_howto_table[] =
 	 MINUS_ONE,		/* dst_mask */
 	 false),		/* pcrel_offset */
 
-  EMPTY_HOWTO(0x26),
+  /* 0x26: 32 bit relocation, but store negative value.  */
+  HOWTO (R_NEG,			/* type */
+	 0,			/* rightshift */
+	 -2,			/* size (0 = byte, 1 = short, 2 = long) */
+	 32,			/* bitsize */
+	 false,			/* pc_relative */
+	 0,			/* bitpos */
+	 complain_overflow_bitfield, /* complain_on_overflow */
+	 0,			/* special_function */
+	 "R_NEG_32",		/* name */
+	 true,			/* partial_inplace */
+	 MINUS_ONE,		/* src_mask */
+	 MINUS_ONE,		/* dst_mask */
+	 false),		/* pcrel_offset */
+
   EMPTY_HOWTO(0x27),
   EMPTY_HOWTO(0x28),
   EMPTY_HOWTO(0x29),
@@ -1386,6 +1400,9 @@ xcoff64_rtype2howto (arelent *relent, struct internal_reloc *internal)
     {
       if (R_POS == internal->r_type)
 	relent->howto = &xcoff64_howto_table[0x1c];
+
+      if (R_NEG == internal->r_type)
+	relent->howto = &xcoff64_howto_table[0x26];
     }
 
   /* The r_size field of an XCOFF reloc encodes the bitsize of the
@@ -1426,6 +1443,8 @@ xcoff64_reloc_type_lookup (bfd *abfd ATTRIBUTE_UNUSED,
       return &xcoff64_howto_table[0];
     case BFD_RELOC_NONE:
       return &xcoff64_howto_table[0xf];
+    case BFD_RELOC_PPC_NEG:
+      return &xcoff64_howto_table[0x1];
     case BFD_RELOC_PPC64_TLSGD:
       return &xcoff64_howto_table[0x20];
     case BFD_RELOC_PPC64_TLSIE:
diff --git a/bfd/libbfd.h b/bfd/libbfd.h
index f1d25d0..bee1a1f 100644
--- a/bfd/libbfd.h
+++ b/bfd/libbfd.h
@@ -1510,6 +1510,7 @@ static const char *const bfd_reloc_code_real_names[] = { "@@uninitialized@@",
   "BFD_RELOC_PPC_VLE_SDAREL_HA16D",
   "BFD_RELOC_PPC_16DX_HA",
   "BFD_RELOC_PPC_REL16DX_HA",
+  "BFD_RELOC_PPC_NEG",
   "BFD_RELOC_PPC64_HIGHER",
   "BFD_RELOC_PPC64_HIGHER_S",
   "BFD_RELOC_PPC64_HIGHEST",
diff --git a/bfd/reloc.c b/bfd/reloc.c
index 2eb0758a..674b075 100644
--- a/bfd/reloc.c
+++ b/bfd/reloc.c
@@ -2833,6 +2833,8 @@ ENUMX
 ENUMX
   BFD_RELOC_PPC_REL16DX_HA
 ENUMX
+  BFD_RELOC_PPC_NEG
+ENUMX
   BFD_RELOC_PPC64_HIGHER
 ENUMX
   BFD_RELOC_PPC64_HIGHER_S
diff --git a/bfd/xcofflink.c b/bfd/xcofflink.c
index f0e0fe7..1607cd5 100644
--- a/bfd/xcofflink.c
+++ b/bfd/xcofflink.c
@@ -2653,7 +2653,7 @@ xcoff_auto_export_p (struct bfd_link_info *info,
 
 static bool
 xcoff_need_ldrel_p (struct bfd_link_info *info, struct internal_reloc *rel,
-		    struct xcoff_link_hash_entry *h)
+		    struct xcoff_link_hash_entry *h, asection *ssec)
 {
   if (!xcoff_hash_table (info)->loader_section)
     return false;
@@ -2701,6 +2701,14 @@ xcoff_need_ldrel_p (struct bfd_link_info *info, struct internal_reloc *rel,
 		  && bfd_is_abs_section (sec->output_section)))
 	    return false;
 	}
+
+      /* Absolute relocations from read-only sections are forbidden
+	 by AIX loader. However, they can appear in their section's
+         relocations.  */
+      if (ssec != NULL
+	  && (ssec->output_section->flags & SEC_READONLY) != 0)
+	return false;
+
       return true;
 
     case R_TLS:
@@ -2989,7 +2997,7 @@ xcoff_mark (struct bfd_link_info *info, asection *sec)
 
 	      /* See if this reloc needs to be copied into the .loader
 		 section.  */
-	      if (xcoff_need_ldrel_p (info, rel, h))
+	      if (xcoff_need_ldrel_p (info, rel, h, sec))
 		{
 		  ++xcoff_hash_table (info)->ldrel_count;
 		  if (h != NULL)
@@ -4982,7 +4990,7 @@ xcoff_link_input_bfd (struct xcoff_final_link_info *flinfo,
 		}
 
 	      if ((o->flags & SEC_DEBUGGING) == 0
-		  && xcoff_need_ldrel_p (flinfo->info, irel, h))
+		  && xcoff_need_ldrel_p (flinfo->info, irel, h, o))
 		{
 		  asection *sec;