elf/x86-64: Subtract __ImageBase for R_AMD64_IMAGEBASE

When linking Windows x86-64 relocatable object files to generate x86-64
ELF executable, we need to subtract __ImageBase, aka __executable_start,
for R_AMD64_IMAGEBASE relocation:

1. Add link_info to struct output_elf_obj_tdata to store linker info and
_bfd_get_link_info() to retrieve it.
2. Add ldelf_set_output_arch to set up link_info.
3. Add pex64_link_add_symbols to create an indirect reference to
__executable_start for __ImageBase to support R_AMD64_IMAGEBASE relocation
when adding symbols from Windows x86-64 relocatable object files to
generate x86-64 ELF executable.
4. Also subtract __ImageBase for R_AMD64_IMAGEBASE when generating x86-64
ELF executable.

bfd/

	PR ld/27425
	PR ld/27432
	* bfd.c (_bfd_get_link_info): New function.
	* elf-bfd.h (output_elf_obj_tdata): Add link_info.
	(elf_link_info): New.
	* libbfd-in.h (_bfd_get_link_info): New prototype.
	* coff-x86_64.c (coff_amd64_reloc): Also subtract __ImageBase for
	R_AMD64_IMAGEBASE when generating x86-64 ELF executable.
	* pe-x86_64.c: Include "coff/internal.h" and "libcoff.h".
	(pex64_link_add_symbols): New function.
	(coff_bfd_link_add_symbols): New macro.
	* libbfd.h: Regenerated.

ld/

	PR ld/27425
	PR ld/27432
	* ldelf.c (ldelf_set_output_arch): New function.
	* ldelf.h (ldelf_set_output_arch): New prototype.
	* emultempl/elf.em (LDEMUL_SET_OUTPUT_ARCH): Default to
	ldelf_set_output_arch.
	* ld-x86-64/pe-x86-64-1.od: Expect __executable_start.
	* testsuite/ld-x86-64/pe-x86-64-2.od: Likewise.
	* testsuite/ld-x86-64/pe-x86-64-3.od: Likewise.
	* testsuite/ld-x86-64/pe-x86-64-4.od: Likewise.
	* testsuite/ld-x86-64/pe-x86-64-5.od: Likewise.
	* testsuite/ld-x86-64/pe-x86-64-5.rd: Likewise.
	* testsuite/ld-x86-64/pe-x86-64-6.obj.bz2: New file.
	* testsuite/ld-x86-64/pe-x86-64-6.od: Likewise.
	* testsuite/ld-x86-64/pe-x86-64.exp: Run ld/27425 test.

7 files changed, 96 insertions, 5 deletions

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index dac602b..a43a3c2 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,18 @@
+2021-03-05  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/27425
+	PR ld/27432
+	* bfd.c (_bfd_get_link_info): New function.
+	* elf-bfd.h (output_elf_obj_tdata): Add link_info.
+	(elf_link_info): New.
+	* libbfd-in.h (_bfd_get_link_info): New prototype.
+	* coff-x86_64.c (coff_amd64_reloc): Also subtract __ImageBase for
+	R_AMD64_IMAGEBASE when generating x86-64 ELF executable.
+	* pe-x86_64.c: Include "coff/internal.h" and "libcoff.h".
+	(pex64_link_add_symbols): New function.
+	(coff_bfd_link_add_symbols): New macro.
+	* libbfd.h: Regenerated.
+
 2021-03-05  Craig Blackmore  <craig.blackmore@embecosm.com>
 	    Andrew Burgess  <andrew.burgess@embecosm.com>
 
diff --git a/bfd/bfd.c b/bfd/bfd.c
index f194433..2c62085 100644
--- a/bfd/bfd.c
+++ b/bfd/bfd.c
@@ -2808,3 +2808,14 @@ bfd_convert_section_contents (bfd *ibfd, sec_ptr isec, bfd *obfd,
   *ptr_size = size;
   return TRUE;
 }
+
+/* Get the linker information.  */
+
+struct bfd_link_info *
+_bfd_get_link_info (bfd *abfd)
+{
+  if (bfd_get_flavour (abfd) != bfd_target_elf_flavour)
+    return NULL;
+
+  return elf_link_info (abfd);
+}
diff --git a/bfd/coff-x86_64.c b/bfd/coff-x86_64.c
index 5b09023..870df2b 100644
--- a/bfd/coff-x86_64.c
+++ b/bfd/coff-x86_64.c
@@ -131,11 +131,38 @@ coff_amd64_reloc (bfd *abfd,
 	diff -= reloc_entry->howto->type - R_AMD64_PCRLONG;
     }
 
-  /* FIXME: How should this case be handled?  */
   if (reloc_entry->howto->type == R_AMD64_IMAGEBASE
-      && output_bfd != NULL
-      && bfd_get_flavour (output_bfd) == bfd_target_coff_flavour)
-    diff -= pe_data (output_bfd)->pe_opthdr.ImageBase;
+      && output_bfd == NULL)
+    {
+      bfd *obfd = input_section->output_section->owner;
+      struct bfd_link_info *link_info;
+      struct bfd_link_hash_entry *h;
+      switch (bfd_get_flavour (obfd))
+	{
+	case bfd_target_coff_flavour:
+	  diff -= pe_data (obfd)->pe_opthdr.ImageBase;
+	  break;
+	case bfd_target_elf_flavour:
+	  /* Subtract __ImageBase.  */
+	  link_info = _bfd_get_link_info (obfd);
+	  if (link_info == NULL)
+	    return bfd_reloc_dangerous;
+	  h = bfd_link_hash_lookup (link_info->hash, "__ImageBase",
+				    FALSE, FALSE, FALSE);
+	  if (h == NULL)
+	    return bfd_reloc_dangerous;
+	  while (h->type == bfd_link_hash_indirect)
+	    h = h->u.i.link;
+	  /* ELF symbols in relocatable files are section relative,
+	     but in nonrelocatable files they are virtual addresses.  */
+	  diff -= (h->u.def.value
+		   + h->u.def.section->output_offset
+		   + h->u.def.section->output_section->vma);
+	  break;
+	default:
+	  break;
+	}
+    }
 #endif
 
 #define DOIT(x) \
diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
index c40030b..04785a8 100644
--- a/bfd/elf-bfd.h
+++ b/bfd/elf-bfd.h
@@ -1887,6 +1887,9 @@ struct output_elf_obj_tdata
   /* Used when laying out sections.  */
   file_ptr next_file_pos;
 
+  /* Linker information.  */
+  struct bfd_link_info *link_info;
+
   int num_section_syms;
   unsigned int shstrtab_section, strtab_section;
 
@@ -2064,6 +2067,7 @@ struct elf_obj_tdata
 #define elf_elfsections(bfd)	(elf_tdata(bfd) -> elf_sect_ptr)
 #define elf_numsections(bfd)	(elf_tdata(bfd) -> num_elf_sections)
 #define elf_seg_map(bfd)	(elf_tdata(bfd) -> o->seg_map)
+#define elf_link_info(bfd)	(elf_tdata(bfd) -> o->link_info)
 #define elf_next_file_pos(bfd)	(elf_tdata(bfd) -> o->next_file_pos)
 #define elf_eh_frame_hdr(bfd)	(elf_tdata(bfd) -> o->eh_frame_hdr)
 #define elf_stack_flags(bfd)	(elf_tdata(bfd) -> o->stack_flags)
diff --git a/bfd/libbfd-in.h b/bfd/libbfd-in.h
index 2dc20ec..62b1cee 100644
--- a/bfd/libbfd-in.h
+++ b/bfd/libbfd-in.h
@@ -899,6 +899,8 @@ extern bfd_vma _bfd_safe_read_leb128
 extern bfd_byte * _bfd_write_unsigned_leb128
   (bfd_byte *, bfd_byte *, bfd_vma) ATTRIBUTE_HIDDEN;
 
+extern struct bfd_link_info *_bfd_get_link_info (bfd *);
+
 #if GCC_VERSION >= 7000
 #define _bfd_mul_overflow(a, b, res) __builtin_mul_overflow (a, b, res)
 #else
diff --git a/bfd/libbfd.h b/bfd/libbfd.h
index 7271a2a..3a481ea 100644
--- a/bfd/libbfd.h
+++ b/bfd/libbfd.h
@@ -904,6 +904,8 @@ extern bfd_vma _bfd_safe_read_leb128
 extern bfd_byte * _bfd_write_unsigned_leb128
   (bfd_byte *, bfd_byte *, bfd_vma) ATTRIBUTE_HIDDEN;
 
+extern struct bfd_link_info *_bfd_get_link_info (bfd *);
+
 #if GCC_VERSION >= 7000
 #define _bfd_mul_overflow(a, b, res) __builtin_mul_overflow (a, b, res)
 #else
diff --git a/bfd/pe-x86_64.c b/bfd/pe-x86_64.c
index 5b73444..771651a 100644
--- a/bfd/pe-x86_64.c
+++ b/bfd/pe-x86_64.c
@@ -22,6 +22,8 @@
 
 #include "sysdep.h"
 #include "bfd.h"
+#include "coff/internal.h"
+#include "libcoff.h"
 
 #define TARGET_SYM		x86_64_pe_vec
 #define TARGET_NAME		"pe-x86-64"
@@ -66,5 +68,33 @@ extern bfd_boolean pex64_bfd_print_pdata (bfd *, void *);
 
 #define bfd_pe_print_pdata   pex64_bfd_print_pdata
 
-#include "coff-x86_64.c"
+static bfd_boolean
+pex64_link_add_symbols (bfd *abfd, struct bfd_link_info *info)
+{
+  if (bfd_link_pde (info)
+      && bfd_get_flavour (info->output_bfd) == bfd_target_elf_flavour)
+    {
+      /* NB: When linking Windows x86-64 relocatable object files to
+	 generate ELF executable, create an indirect reference to
+	 __executable_start for __ImageBase to support R_AMD64_IMAGEBASE
+	 relocation which is relative to __ImageBase.  */
+      struct bfd_link_hash_entry *h, *hi;
+      hi = bfd_link_hash_lookup (info->hash, "__ImageBase", TRUE, FALSE,
+				 FALSE);
+      if (hi->type == bfd_link_hash_new
+	  || hi->type == bfd_link_hash_undefined
+	  || hi->type == bfd_link_hash_undefweak)
+	{
+	  h = bfd_link_hash_lookup (info->hash, "__executable_start",
+				    TRUE, FALSE, TRUE);
+	  hi->type = bfd_link_hash_indirect;
+	  hi->u.i.link = h;
+	}
+    }
+
+  return _bfd_coff_link_add_symbols (abfd, info);
+}
 
+#define coff_bfd_link_add_symbols pex64_link_add_symbols
+
+#include "coff-x86_64.c"