[PATCH] bfd: correct relocation handling for objcopy COFF -> ELF

[PATCH] bfd: correct relocation handling for objcopy COFF -> ELF

[Jan Beulich]

While documented to not be reliable, it is still odd for objcopy to
silently produce bad output when converting COFF/PE object files to ELF
ones. The issue there is that relocation addends all are screwed up by
subtracting the symbol's section offset. In the COFF/PE world, to my
knowledge, section contents stores the addends alone, not the result of
symbol value plus addend. Hence the compensation talked about in a
comment ahead of the sole use site of CALC_ADDEND() may need to account
for the VMA (which is always zero for object files anyway), but not for
the symbol value.

The coff-sh.c adjustment is based upon guessing that behavior there is
the same. Note also how coff-aarch64.c short-circuits CALC_ADDEND()
altogether, which may suggest that a much simpler macro might do for the
COFF_WITH_PE case in the three arch-specific files touched here.

For (at least) Arm/WinCE this actually results in more appropriate
objdump output as well, as can be seen in the one testcase which has its
expectations adjusted (the generated binary doesn't change).

--- a/bfd/coff-i386.c
+++ b/bfd/coff-i386.c
@@ -405,7 +405,8 @@ static reloc_howto_type howto_table[] =
       cache_ptr->addend = - coffsym->native->u.syment.n_value;	\
     else if (ptr && bfd_asymbol_bfd (ptr) == abfd		\
 	     && ptr->section != (asection *) NULL)		\
-      cache_ptr->addend = - (ptr->section->vma + ptr->value);	\
+      cache_ptr->addend = - (ptr->section->vma			\
+			     + COFF_PE_ADDEND_BIAS (ptr));	\
     else							\
       cache_ptr->addend = 0;					\
     if (ptr && reloc.r_type < NUM_HOWTOS			\
--- a/bfd/coff-sh.c
+++ b/bfd/coff-sh.c
@@ -544,7 +544,8 @@ sh_coff_reloc_name_lookup (bfd *abfd ATT
       cache_ptr->addend = 0;					\
     else if (ptr && bfd_asymbol_bfd (ptr) == abfd		\
 	     && ptr->section != (asection *) NULL)		\
-      cache_ptr->addend = - (ptr->section->vma + ptr->value);	\
+      cache_ptr->addend = - (ptr->section->vma			\
+			     + COFF_PE_ADDEND_BIAS (ptr));	\
     else							\
       cache_ptr->addend = 0;					\
     if ((reloc).r_type == R_SH_SWITCH8				\
--- a/bfd/coff-x86_64.c
+++ b/bfd/coff-x86_64.c
@@ -542,7 +542,8 @@ static reloc_howto_type howto_table[] =
       cache_ptr->addend = - coffsym->native->u.syment.n_value;	\
     else if (ptr && bfd_asymbol_bfd (ptr) == abfd		\
 	     && ptr->section != NULL)				\
-      cache_ptr->addend = - (ptr->section->vma + ptr->value);	\
+      cache_ptr->addend = - (ptr->section->vma			\
+			     + COFF_PE_ADDEND_BIAS (ptr));	\
     else							\
       cache_ptr->addend = 0;					\
     if (ptr && reloc.r_type < NUM_HOWTOS			\
--- a/bfd/coffcode.h
+++ b/bfd/coffcode.h
@@ -5151,6 +5151,12 @@ SUBSUBSECTION
 	final-linked object.  See @code{CALC_ADDEND}.
 */
 
+#ifdef COFF_WITH_PE
+#define COFF_PE_ADDEND_BIAS(ptr) 0 /* Symbol value not stored in raw data.  */
+#else
+#define COFF_PE_ADDEND_BIAS(ptr) ((ptr)->value)
+#endif
+
 #ifndef CALC_ADDEND
 #define CALC_ADDEND(abfd, ptr, reloc, cache_ptr)		\
   {								\
@@ -5167,7 +5173,8 @@ SUBSUBSECTION
       cache_ptr->addend = 0;					\
     else if (ptr && bfd_asymbol_bfd (ptr) == abfd		\
 	     && ptr->section != NULL)				\
-      cache_ptr->addend = - (ptr->section->vma + ptr->value);	\
+      cache_ptr->addend = - (ptr->section->vma			\
+			     + COFF_PE_ADDEND_BIAS (ptr));	\
     else							\
       cache_ptr->addend = 0;					\
   }
--- a/gas/testsuite/gas/arm/wince.d
+++ b/gas/testsuite/gas/arm/wince.d
@@ -15,11 +15,11 @@ Disassembly of section .text:
 0+008 <global_sym\+0x4> e1a00000 	nop			@ \(mov r0, r0\)
 0+00c <global_sym\+0x8> e1a00000 	nop			@ \(mov r0, r0\)
 0+010 <global_sym\+0xc> eafffffb 	b	f+ff8 <global_sym\+0xf+ff4>
-			10: ARM_26D	global_sym-0x4
+			10: ARM_26D	global_sym
 0+014 <global_sym\+0x10> ebfffffa 	bl	f+ff4 <global_sym\+0xf+ff0>
-			14: ARM_26D	global_sym-0x4
+			14: ARM_26D	global_sym
 0+018 <global_sym\+0x14> 0afffff9 	beq	f+ff0 <global_sym\+0xf+fec>
-			18: ARM_26D	global_sym-0x4
+			18: ARM_26D	global_sym
 0+01c <global_sym\+0x18> eafffff8 	b	0+004 <global_sym>
 0+020 <global_sym\+0x1c> ebfffff7 	bl	0+004 <global_sym>
 0+024 <global_sym\+0x20> 0afffff6 	beq	0+004 <global_sym>