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

[Jan Beulich <jbeulich@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=67694446f772ae95d330419eb6d01e38e6d24612

commit 67694446f772ae95d330419eb6d01e38e6d24612
Author: Jan Beulich <jbeulich@suse.com>
Date:   Fri Aug 25 14:56:44 2023 +0200

    bfd: correct relocation handling for objcopy COFF -> ELF
    
    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).

Diff:
---
 bfd/coff-i386.c               | 3 ++-
 bfd/coff-sh.c                 | 3 ++-
 bfd/coff-x86_64.c             | 3 ++-
 bfd/coffcode.h                | 9 ++++++++-
 gas/testsuite/gas/arm/wince.d | 6 +++---
 5 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/bfd/coff-i386.c b/bfd/coff-i386.c
index 24a05d3aa65..71516066da8 100644
--- 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			\
diff --git a/bfd/coff-sh.c b/bfd/coff-sh.c
index 14f502e3638..a20c01127b6 100644
--- a/bfd/coff-sh.c
+++ b/bfd/coff-sh.c
@@ -544,7 +544,8 @@ sh_coff_reloc_name_lookup (bfd *abfd ATTRIBUTE_UNUSED,
       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				\
diff --git a/bfd/coff-x86_64.c b/bfd/coff-x86_64.c
index 9a3f85cd1e5..57b975c2eed 100644
--- 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			\
diff --git a/bfd/coffcode.h b/bfd/coffcode.h
index e3f4afd389f..27927039a34 100644
--- a/bfd/coffcode.h
+++ b/bfd/coffcode.h
@@ -5192,6 +5192,12 @@ 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)		\
   {								\
@@ -5208,7 +5214,8 @@ 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;					\
   }
diff --git a/gas/testsuite/gas/arm/wince.d b/gas/testsuite/gas/arm/wince.d
index e5bac1de9c6..e7afbedbbf5 100644
--- 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>