diff mbox series

[v3] LoongArch: Fix the infinite loop caused by calling undefweak symbol

Message ID 20241129082939.1510203-1-cailulu@loongson.cn
State New
Headers
Series [v3] LoongArch: Fix the infinite loop caused by calling undefweak symbol |

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Commit Message

Lulu Cai Nov. 29, 2024, 8:29 a.m. UTC 
  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.

---
Changes in v3:
  - The call instruction is not deleted but converted to jump address 0.
  - Add b %plt(sym) => jirl $zero,$zero,0.
  - Convert in relocate_section instead of relax_section.

Changes in v2:
  - Pass @var{again} to loongarch_relax_call_undefweak to continue the
    next relax.
v2: https://sourceware.org/pipermail/binutils/2024-November/137744.html

Changes in v1:
  - Convert undefweak calls that do not use plt to nop or delete them.
v1: https://sourceware.org/pipermail/binutils/2024-November/137701.html
---
 bfd/elfnn-loongarch.c                         | 39 +++++++++++++++++++
 .../ld-loongarch-elf/call_undefweak.d         | 26 +++++++++++++
 .../ld-loongarch-elf/call_undefweak.s         | 33 ++++++++++++++++
 .../ld-loongarch-elf/ld-loongarch-elf.exp     | 11 ++++++
 4 files changed, 109 insertions(+)
 create mode 100644 ld/testsuite/ld-loongarch-elf/call_undefweak.d
 create mode 100644 ld/testsuite/ld-loongarch-elf/call_undefweak.s

Comments

Lulu Cheng Nov. 30, 2024, 8:34 a.m. UTC | #1 
Pushed to r15-5819.

在 2024/11/29 下午4:29, Lulu Cai 写道:
> 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.
>
> ---
> Changes in v3:
>    - The call instruction is not deleted but converted to jump address 0.
>    - Add b %plt(sym) => jirl $zero,$zero,0.
>    - Convert in relocate_section instead of relax_section.
>
> Changes in v2:
>    - Pass @var{again} to loongarch_relax_call_undefweak to continue the
>      next relax.
> v2: https://sourceware.org/pipermail/binutils/2024-November/137744.html
>
> Changes in v1:
>    - Convert undefweak calls that do not use plt to nop or delete them.
> v1: https://sourceware.org/pipermail/binutils/2024-November/137701.html
> ---
>   bfd/elfnn-loongarch.c                         | 39 +++++++++++++++++++
>   .../ld-loongarch-elf/call_undefweak.d         | 26 +++++++++++++
>   .../ld-loongarch-elf/call_undefweak.s         | 33 ++++++++++++++++
>   .../ld-loongarch-elf/ld-loongarch-elf.exp     | 11 ++++++
>   4 files changed, 109 insertions(+)
>   create mode 100644 ld/testsuite/ld-loongarch-elf/call_undefweak.d
>   create mode 100644 ld/testsuite/ld-loongarch-elf/call_undefweak.s
>
> diff --git a/bfd/elfnn-loongarch.c b/bfd/elfnn-loongarch.c
> index 8189a23a3a9..7451153270f 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 00000000000..4761651817c
> --- /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 00000000000..cc1405f0625
> --- /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 e1b038cb579..d7c2b311f2f 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-*-*"] {
diff mbox series

Patch

diff --git a/bfd/elfnn-loongarch.c b/bfd/elfnn-loongarch.c
index 8189a23a3a9..7451153270f 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 00000000000..4761651817c
--- /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 00000000000..cc1405f0625
--- /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 e1b038cb579..d7c2b311f2f 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-*-*"] {