10267 ld and GCC disagree about i386 local dynamic TLS

@@ -413,15 +413,26 @@
          * 0x0c
          */
         0x90
 };
 
-static uchar_t tlsinstr_gd_ie_movgs[] = {
+static uchar_t tlsinstr_ld_le_movgs[] = {
         /*
-         *      movl %gs:0x0,%eax
+         * 0x00 movl %gs:0x0,%eax
          */
-        0x65, 0xa1, 0x00, 0x00, 0x00, 00
+        0x65, 0xa1, 0x00, 0x00, 0x00, 0x00,
+};
+
+/*
+ * 0x00 nopl 0(%eax,%eax) -- the intel recommended 5-byte nop
+ * See Intel® 64 and IA-32 Architectures Software Developer’s Manual
+ *    Volume 2B: Instruction Set Reference, M-U
+ *    Table 4-12, Recommended Multi-Byte Sequence of NOP Instruction
+ */
+static uchar_t tlsinstr_nop5[] = {
+
+        0x0f, 0x1f, 0x44, 0x00, 0x00
 };
 
 #define TLS_GD_IE_MOV   0x8b    /* movl opcode */
 #define TLS_GD_IE_POP   0x58    /* popl + reg */
 

@@ -526,11 +537,12 @@
                 return (FIX_RELOC);
 
         case R_386_TLS_GD_PLT:
         case R_386_PLT32:
                 /*
-                 * Fixup done via the TLS_GD relocation
+                 * Fixup done via the TLS_GD/TLS_LDM relocation processing
+                 * and ld_reloc_plt() handling __tls_get_addr().
                  */
                 DBG_CALL(Dbg_reloc_transition(ofl->ofl_lml, M_MACH,
                     R_386_NONE, arsp, ld_reloc_sym_name));
                 return (FIX_DONE);
 

@@ -540,21 +552,14 @@
 
                 /*
                  * Transition:
                  *      call __tls_get_addr()
                  * to:
-                 *      nop
-                 *      nop
-                 *      nop
-                 *      nop
-                 *      nop
-                 */
-                *(offset - 1) = TLS_NOP;
-                *(offset) = TLS_NOP;
-                *(offset + 1) = TLS_NOP;
-                *(offset + 2) = TLS_NOP;
-                *(offset + 3) = TLS_NOP;
+                 *      nopl 0x0(%eax,%eax)
+                 */
+                (void) memcpy(offset - 1, tlsinstr_nop5,
+                    sizeof (tlsinstr_nop5));
                 return (FIX_DONE);
 
         case R_386_TLS_LDM:
                 DBG_CALL(Dbg_reloc_transition(ofl->ofl_lml, M_MACH,
                     R_386_NONE, arsp, ld_reloc_sym_name));

@@ -567,12 +572,21 @@
                  *
                  * to:
                  *
                  *  0x00 movl %gs:0, %eax
                  */
-                (void) memcpy(offset - 2, tlsinstr_gd_ie_movgs,
-                    sizeof (tlsinstr_gd_ie_movgs));
+                (void) memcpy(offset - 2, tlsinstr_ld_le_movgs,
+                    sizeof (tlsinstr_ld_le_movgs));
+
+                /*
+                 *  We implicitly treat this as if a R_386_TLS_LDM_PLT for the
+                 *  __tls_get_addr call followed it as the GNU compiler
+                 *  doesn't generate one.  This is safe, because if one _does_
+                 *  exist we'll just write the nop again.
+                 */
+                (void) memcpy(offset + 4, tlsinstr_nop5,
+                    sizeof (tlsinstr_nop5));
                 return (FIX_DONE);
 
         case R_386_TLS_LDO_32:
                 /*
                  *  Instructions: