LoongArch: Fix the infinite loop caused by calling undefweak symbol

The undefweak symbol value of non-default visibility is 0 and does
not use plt entry, and will not be relocated in the relocate_secion
function. As a result, an infinite loop is generated because
bl %plt(sym) => bl 0.

Fix this by converting the call into a jump address 0.

4 files changed, 109 insertions, 0 deletions

diff --git a/bfd/elfnn-loongarch.c b/bfd/elfnn-loongarch.c
index 8189a23..7451153 100644
--- a/bfd/elfnn-loongarch.c
+++ b/bfd/elfnn-loongarch.c
@@ -222,6 +222,10 @@ loongarch_elf_new_section_hook (bfd *abfd, asection *sec)
    || (R_TYPE) == R_LARCH_TLS_LE64_LO20	  \
    || (R_TYPE) == R_LARCH_TLS_LE64_HI12)
 
+#define IS_CALL_RELOC(R_TYPE)	  \
+  ((R_TYPE) == R_LARCH_B26	  \
+   ||(R_TYPE) == R_LARCH_CALL36)
+
 /* If TLS GD/IE need dynamic relocations, INDX will be the dynamic indx,
    and set NEED_RELOC to true used in allocate_dynrelocs and
    loongarch_elf_relocate_section for TLS GD/IE.  */
@@ -4015,9 +4019,44 @@ loongarch_elf_relocate_section (bfd *output_bfd, struct bfd_link_info *info,
 	case R_LARCH_B26:
 	case R_LARCH_CALL36:
 	  unresolved_reloc = false;
+	  bool via_plt =
+	    plt != NULL && h != NULL && h->plt.offset != (bfd_vma) - 1;
+
 	  if (is_undefweak)
 	    {
 	      relocation = 0;
+
+	      /* A call to an undefined weak symbol is converted to 0.  */
+	      if (!via_plt && IS_CALL_RELOC (r_type))
+		{
+		  /* call36 fn1 => pcaddu18i $ra,0+jirl $ra,$zero,0
+		     tail36 $t0,fn1 => pcaddi18i $t0,0+jirl $zero,$zero,0  */
+		  if (R_LARCH_CALL36 == r_type)
+		    {
+		      uint32_t jirl = bfd_get (32, input_bfd,
+					  contents + rel->r_offset + 4);
+		      uint32_t rd = LARCH_GET_RD (jirl);
+		      jirl = LARCH_OP_JIRL | rd;
+
+		      bfd_put (32, input_bfd, jirl,
+			       contents + rel->r_offset + 4);
+		    }
+		  else
+		    {
+		      uint32_t b_bl = bfd_get (32, input_bfd,
+					       contents + rel->r_offset);
+		      /* b %plt(fn1) => jirl $zero,zero,0.  */
+		      if (LARCH_INSN_B (b_bl))
+			bfd_put (32, input_bfd, LARCH_OP_JIRL,
+				 contents + rel->r_offset);
+		      else
+		      /* bl %plt(fn1) => jirl $ra,zero,0.  */
+		      bfd_put (32, input_bfd, LARCH_OP_JIRL | 0x1,
+			       contents + rel->r_offset);
+		    }
+		  r = bfd_reloc_continue;
+		  break;
+		}
 	    }
 
 	  if (resolved_local)
diff --git a/ld/testsuite/ld-loongarch-elf/call_undefweak.d b/ld/testsuite/ld-loongarch-elf/call_undefweak.d
new file mode 100644
index 0000000..4761651
--- /dev/null
+++ b/ld/testsuite/ld-loongarch-elf/call_undefweak.d
@@ -0,0 +1,26 @@
+#...
+Disassembly of section \.plt:
+#...
+0+1200004d0 <fn2@plt>:
+   1200004d0:	1c00010f 	pcaddu12i   	\$t3, 8
+   1200004d4:	28ed01ef 	ld.d        	\$t3, \$t3, -1216
+   1200004d8:	4c0001ed 	jirl        	\$t1, \$t3, 0
+   1200004dc:	03400000 	nop
+
+Disassembly of section \.text:
+#...
+0+120000668 <main>:
+   120000668:	4c000000 	jr          	\$zero
+   12000066c:	53fe67ff 	b           	-412	# 1200004d0 <fn2@plt>
+   120000670:	4c000001 	jirl        	\$ra, \$zero, 0
+   120000674:	57fe5fff 	bl          	-420	# 1200004d0 <fn2@plt>
+
+0+120000678 <medium_call_nop>:
+   120000678:	1e000001 	pcaddu18i   	\$ra, 0
+   12000067c:	4c000001 	jirl        	\$ra, \$zero, 0
+   120000680:	1e000001 	pcaddu18i   	\$ra, 0
+   120000684:	4ffe5021 	jirl        	\$ra, \$ra, -432
+   120000688:	1e00000c 	pcaddu18i   	\$t0, 0
+   12000068c:	4c000000 	jr          	\$zero
+   120000690:	1e00000c 	pcaddu18i   	\$t0, 0
+   120000694:	4ffe4180 	jirl        	\$zero, \$t0, -448
diff --git a/ld/testsuite/ld-loongarch-elf/call_undefweak.s b/ld/testsuite/ld-loongarch-elf/call_undefweak.s
new file mode 100644
index 0000000..cc1405f
--- /dev/null
+++ b/ld/testsuite/ld-loongarch-elf/call_undefweak.s
@@ -0,0 +1,33 @@
+	.text
+	.align  2
+	.globl  main
+	.type   main, @function
+main:
+	# undefweak symbol with .hidden and .protected
+	# do not need plt entry, Calls to these symbols
+	# are converted to jump to 0.
+nornal_call_nop:
+	b   %plt(fn1)
+	b   %plt(fn2)
+
+	bl  %plt(fn1)
+	bl  %plt(fn2)
+
+	# Medium call.
+medium_call_nop:
+	.option norelax
+	# call36
+	pcaddu18i $r1,%call36(fn1)
+	jirl      $r1,$r1,0
+	pcaddu18i $r1,%call36(fn2)
+	jirl      $r1,$r1,0
+	# tail36
+	pcaddu18i $r12,%call36(fn1)
+	jirl      $r0,$r12,0
+	pcaddu18i $r12,%call36(fn2)
+	jirl      $r0,$r12,0
+
+	.weak   fn1
+	.hidden fn1
+
+	.weak   fn2
diff --git a/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp b/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
index e1b038c..d7c2b31 100644
--- a/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
+++ b/ld/testsuite/ld-loongarch-elf/ld-loongarch-elf.exp
@@ -143,6 +143,17 @@ if [istarget "loongarch64-*-*"] {
 	    "abs-global.out" \
 	] \
     ]
+
+  run_cc_link_tests [list \
+      [list \
+	  "call undefweak symbol" \
+	  "" "" \
+	  {call_undefweak.s} \
+	  {{objdump {-d} call_undefweak.d}} \
+	  "call_undefweak" \
+      ] \
+  ]
+
 }
 
 if [istarget "loongarch64-*-*"] {