[binutils-gdb] x86: check reloc types for relaxable branches

[Jan Beulich]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=496e01123d85e3a8c3d8fabae11867206e15cc1e

commit 496e01123d85e3a8c3d8fabae11867206e15cc1e
Author: Jan Beulich <jbeulich@suse.com>
Date:   Fri Sep 5 08:33:27 2025 +0200

    x86: check reloc types for relaxable branches
    
    Bypassing _reloc() isn't a good idea, as there are various errors
    checked for there. For example 16-bit JMP or Jcc may not use the @plt
    form (resulting in a 32-bit relocation to be emitted for a 16-bit
    field), which so far we only reject for 16-bit CALL. In exchange this
    allows simplifying the setting up of the "reloc_type" local variable.

Diff:
---
 gas/config/tc-i386.c             | 27 +++++++++++++++------------
 gas/testsuite/gas/i386/i386.exp  |  1 +
 gas/testsuite/gas/i386/reloc16.l |  4 ++++
 gas/testsuite/gas/i386/reloc16.s |  6 ++++++
 4 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/gas/config/tc-i386.c b/gas/config/tc-i386.c
index e758fa393c9..fefd587ac7f 100644
--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -16154,18 +16154,15 @@ md_estimate_size_before_relax (fragS *fragP, segT segment)
       int old_fr_fix;
       fixS *fixP = NULL;
 
-      if (fragP->fr_var != NO_RELOC)
-	reloc_type = (enum bfd_reloc_code_real) fragP->fr_var;
-      else if (size == 2)
-	reloc_type = BFD_RELOC_16_PCREL;
+      reloc_type = (enum bfd_reloc_code_real) fragP->fr_var;
 #ifdef OBJ_ELF
-      else if (fragP->tc_frag_data.code == CODE_64BIT
-	       && fragP->fr_offset == 0
-	       && need_plt32_p (fragP->fr_symbol))
+      if (reloc_type == NO_RELOC
+	  && size != 2
+	  && fragP->tc_frag_data.code == CODE_64BIT
+	  && fragP->fr_offset == 0
+	  && need_plt32_p (fragP->fr_symbol))
 	reloc_type = BFD_RELOC_X86_64_PLT32;
 #endif
-      else
-	reloc_type = BFD_RELOC_32_PCREL;
 
       old_fr_fix = fragP->fr_fix;
       opcode = (unsigned char *) fragP->fr_opcode;
@@ -16179,7 +16176,9 @@ md_estimate_size_before_relax (fragS *fragP, segT segment)
 	  fixP = fix_new (fragP, old_fr_fix, size,
 			  fragP->fr_symbol,
 			  fragP->fr_offset, 1,
-			  reloc_type);
+			  _reloc (size, 1, 1, reloc_type,
+				  fragP->tc_frag_data.code == CODE_64BIT,
+				  fragP->fr_file, fragP->fr_line));
 	  break;
 
 	case COND_JUMP86:
@@ -16198,7 +16197,9 @@ md_estimate_size_before_relax (fragS *fragP, segT segment)
 	      fix_new (fragP, old_fr_fix + 2, 2,
 		       fragP->fr_symbol,
 		       fragP->fr_offset, 1,
-		       reloc_type);
+		       _reloc (size, 1, 1, reloc_type,
+			       fragP->tc_frag_data.code == CODE_64BIT,
+			       fragP->fr_file, fragP->fr_line));
 	      break;
 	    }
 	  /* Fall through.  */
@@ -16224,7 +16225,9 @@ md_estimate_size_before_relax (fragS *fragP, segT segment)
 	  fixP = fix_new (fragP, old_fr_fix + 1, size,
 			  fragP->fr_symbol,
 			  fragP->fr_offset, 1,
-			  reloc_type);
+			  _reloc (size, 1, 1, reloc_type,
+				  fragP->tc_frag_data.code == CODE_64BIT,
+				  fragP->fr_file, fragP->fr_line));
 	  break;
 
 	default:
diff --git a/gas/testsuite/gas/i386/i386.exp b/gas/testsuite/gas/i386/i386.exp
index b068b327af3..137c1002073 100644
--- a/gas/testsuite/gas/i386/i386.exp
+++ b/gas/testsuite/gas/i386/i386.exp
@@ -881,6 +881,7 @@ if {[is_elf_format] || [istarget "*-*-vxworks*"]} then {
     }
 
     run_dump_test "code16-2"
+    run_list_test "reloc16"
 
     if {![istarget "*-*-dragonfly*"]
 	&& ![istarget "*-*-gnu*"]
diff --git a/gas/testsuite/gas/i386/reloc16.l b/gas/testsuite/gas/i386/reloc16.l
new file mode 100644
index 00000000000..9abe379f4d6
--- /dev/null
+++ b/gas/testsuite/gas/i386/reloc16.l
@@ -0,0 +1,4 @@
+.*: Assembler messages:
+.*:4: Error: .*4-byte reloc.*2-byte field.*
+.*:5: Error: .*4-byte reloc.*2-byte field.*
+.*:6: Error: .*4-byte reloc.*2-byte field.*
diff --git a/gas/testsuite/gas/i386/reloc16.s b/gas/testsuite/gas/i386/reloc16.s
new file mode 100644
index 00000000000..c5da920c1f2
--- /dev/null
+++ b/gas/testsuite/gas/i386/reloc16.s
@@ -0,0 +1,6 @@
+	.code16
+	.text
+plt:
+	call	func@plt
+	jz	func@plt
+	jmp	func@plt