[PATCH v2 1/7] ix86: tighten convert-load-reloc checking

[Jan Beulich]

Just like was done recently for x86-64 (commit 4998f9ea9d35): Even if
the assembler avoids using the relaxable relocation for inapplicable
insns, the relocation type can still appear for other reasons. Be more
thorough in the opcode checking we do, to avoid bogusly altering other
insns.

Furthermore correct an opcode mask (even if with the added condition
that's now fully benign).
---
v2: Add tests.

--- a/bfd/elf32-i386.c
+++ b/bfd/elf32-i386.c
@@ -1453,15 +1453,16 @@ elf_i386_convert_load_reloc (bfd *abfd,
 		  modrm = 0xc0 | (modrm & 0x38) >> 3;
 		  opcode = 0xf7;
 		}
-	      else
+	      else if ((opcode | 0x38) == 0x3b)
 		{
 		  /* Convert "binop foo@GOT(%reg1), %reg2" to
 		     "binop $foo, %reg2".  */
-		  modrm = (0xc0
-			   | (modrm & 0x38) >> 3
-			   | (opcode & 0x3c));
+		  modrm = 0xc0 | ((modrm & 0x38) >> 3) | (opcode & 0x38);
 		  opcode = 0x81;
 		}
+	      else
+		return true;
+
 	      bfd_put_8 (abfd, modrm, contents + roff - 1);
 	      r_type = R_386_32;
 	    }
--- a/ld/testsuite/ld-i386/i386.exp
+++ b/ld/testsuite/ld-i386/i386.exp
@@ -373,6 +373,7 @@ run_dump_test "load5a"
 run_dump_test "load5b"
 run_dump_test "load6"
 run_dump_test "load7"
+run_dump_test "load8"
 run_dump_test "pr19175"
 run_dump_test "pr19615"
 run_dump_test "pr19636-1a"
--- /dev/null
+++ b/ld/testsuite/ld-i386/load8.d
@@ -0,0 +1,14 @@
+#as: --32 -mrelax-relocations=yes
+#ld: -melf_i386 -z noseparate-code
+#objdump: -dw
+
+.*: +file format .*
+
+Disassembly of section .text:
+
+0+8048074 <_start>:
+[ 	]*[a-f0-9]+:	12 05 90 90 04 08    	adc    0x8049090,%al
+[ 	]*[a-f0-9]+:	6b 05 90 90 04 08 01 	imul   \$(0x)?1,0x8049090,%eax
+[ 	]*[a-f0-9]+:	84 35 90 90 04 08    	test   %dh,0x8049090
+[ 	]*[a-f0-9]+:	87 05 90 90 04 08    	xchg   %eax,0x8049090
+#pass
--- /dev/null
+++ b/ld/testsuite/ld-i386/load8.s
@@ -0,0 +1,21 @@
+	.data
+	.type	bar, @object
+bar:
+	.byte	1
+	.size	bar, .-bar
+
+	.text
+	.globl	_start
+	.type	_start, @function
+_start:
+	# Other insns must not be accidentally transformed.
+	adc	0, %al
+	.reloc .-4, R_386_GOT32X, bar
+	imul	$1, 0, %eax
+	.reloc .-5, R_386_GOT32X, bar
+	test	%dh, 0
+	.reloc .-4, R_386_GOT32X, bar
+	xchg	0, %eax
+	.reloc .-4, R_386_GOT32X, bar
+
+	.size	_start, .-_start