[ELF] Fix X86 & X86_64 PLT retpoline padding

[andrewng]

Summary

The PLT retpoline support for X86 and X86_64 did not include the padding
when writing the header and entries. This issue was revealed when linker
scripts were used, as this disables the built-in behaviour of filling
the last page of executable segments with trap instructions. This
particular behaviour was hiding the missing padding.

[ruiu]

Instead of doing this, we should fill executable segments with trap instructions even if linker script is in use, shouldn't we?

ELF/Arch/X86.cpp

184 ↗

(On Diff #139128)

I don't like to sprinkle too many asserts in code.

[• espindola]

In D44682#1043455, @ruiu wrote:

Instead of doing this, we should fill executable segments with trap instructions even if linker script is in use, shouldn't we?

The issue with linker scripts is that they force SingleRoRx. This causes text and data to be mixed.

These tests should probably use --no-rosegment instead of linkerscripts.

[ruiu]

In D44682#1043962, @espindola wrote:

In D44682#1043455, @ruiu wrote:

Instead of doing this, we should fill executable segments with trap instructions even if linker script is in use, shouldn't we?

The issue with linker scripts is that they force SingleRoRx. This causes text and data to be mixed.

Hm, then what is the point of this change? We could fill unused .plt bytes with trap instructions, but you still have plenty of bytes that are executable if all data is executable.

[tstellar]

Do we need this fix in 5.0.2 and 6.0.1?

[andrewng]

In D44682#1043455, @ruiu wrote:

Instead of doing this, we should fill executable segments with trap instructions even if linker script is in use, shouldn't we?

The current behaviour is only to fill the last page of executable segments with trap instructions. So even in the non linker script case, there still could be zero rather than trap instruction padding in the PLT. I don't know how big an issue this really is, but it feels better to be padding with trap instructions.

In D44682#1043962, @espindola wrote:

In D44682#1043455, @ruiu wrote:

Instead of doing this, we should fill executable segments with trap instructions even if linker script is in use, shouldn't we?

The issue with linker scripts is that they force SingleRoRx. This causes text and data to be mixed.

These tests should probably use --no-rosegment instead of linkerscripts.

I don't think that this issue is directly related to this behaviour of linker scripts.

ELF/Arch/X86.cpp

184 ↗

(On Diff #139128)

Would you like me to remove all the asserts or just this one?

[• espindola]

> The current behaviour is only to fill the last page of executable segments with trap instructions. So even in the non linker script case, there still could be zero rather than trap instruction padding in the PLT. I don't know how big an issue this really is, but it feels better to be padding with trap instructions.

OK, I think there is a far more general issue at play:

https://bugs.llvm.org/show_bug.cgi?id=36853

We should probably fix the non linkerscript non --no-rosegment case first and see if it covers this too.

[ruiu]

In D44682#1044005, @tstellar wrote:

Do we need this fix in 5.0.2 and 6.0.1?

I don't think so because the feature is "good to have". GNU linkers don't do this.

Do you want it in .0.1 releases?

[andrewng]

I think the PLT writing should handle the padding itself. It certainly feels more correct. It looks though D44775 is heading in that direction too.

[andrewng]

Removed assertions and tidied up white space a little.

[• espindola]

Given the discussion on the other threads I agree. There are two independent issues:

• Space outside of some sections not having traps
• Space inside some synthetic sections not having traps.

This patch fixes the second one.
Sorry about the confusion on my side.

lld/trunk/ELF/Arch/X86.cpp

const uint8_t Insn[] = {
       0xeb, 0xf9,                               // 17:   jmp loop
       0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, // 19:   int3; .align 16
       0x89, 0x0c, 0x24,                         // 20: next: mov %ecx, (%esp)
       0x8b, 0x4c, 0x24, 0x04,                   // 23:   mov 0x4(%esp), %ecx
       0x89, 0x44, 0x24, 0x04,                   // 27:   mov %eax ,0x4(%esp)
       0x89, 0xc8,                               // 2b:   mov %ecx, %eax
       0x59,                                     // 2d:   pop %ecx
       0xc3,                                     // 2e:   ret
+      0xcc,                                     // 2f:   int3; padding
   };
   memcpy(Buf, Insn, sizeof(Insn));
 
   uint32_t Ebx = InX::Got->getVA() + InX::Got->getSize();
   uint32_t GotPlt = InX::GotPlt->getVA() - Ebx;
   write32le(Buf + 2, GotPlt + 4);
   write32le(Buf + 9, GotPlt + 8);
 }
 
 void RetpolinePic::writePlt(uint8_t *Buf, uint64_t GotPltEntryAddr,
                             uint64_t PltEntryAddr, int32_t Index,
                             unsigned RelOff) const {
   const uint8_t Insn[] = {
-      0x50,                   // pushl %eax
-      0x8b, 0x83, 0, 0, 0, 0, // mov foo@GOT(%ebx), %eax
-      0xe8, 0,    0, 0, 0,    // call plt+0x20
-      0xe9, 0,    0, 0, 0,    // jmp plt+0x12
-      0x68, 0,    0, 0, 0,    // pushl $reloc_offset
-      0xe9, 0,    0, 0, 0,    // jmp plt+0
+      0x50,                            // pushl %eax
+      0x8b, 0x83, 0,    0,    0,    0, // mov foo@GOT(%ebx), %eax
+      0xe8, 0,    0,    0,    0,       // call plt+0x20
+      0xe9, 0,    0,    0,    0,       // jmp plt+0x12
+      0x68, 0,    0,    0,    0,       // pushl $reloc_offset
+      0xe9, 0,    0,    0,    0,       // jmp plt+0
+      0xcc, 0xcc, 0xcc, 0xcc, 0xcc,    // int3; padding
   };
   memcpy(Buf, Insn, sizeof(Insn));
 
   uint32_t Ebx = InX::Got->getVA() + InX::Got->getSize();
   unsigned Off = getPltEntryOffset(Index);
   write32le(Buf + 3, GotPltEntryAddr - Ebx);
   write32le(Buf + 8, -Off - 12 + 32);
   write32le(Buf + 13, -Off - 17 + 18);
   write32le(Buf + 18, RelOff);
   write32le(Buf + 23, -Off - 27);
 }
 
 RetpolineNoPic::RetpolineNoPic() {
   PltHeaderSize = 48;
   PltEntrySize = 32;
 }
 
 void RetpolineNoPic::writeGotPlt(uint8_t *Buf, const Symbol &S) const {
   write32le(Buf, S.getPltVA() + 16);
 }
 
 void RetpolineNoPic::writePltHeader(uint8_t *Buf) const {
-  const uint8_t PltData[] = {
+  const uint8_t Insn[] = {
       0xff, 0x35, 0,    0,    0,    0, // 0:    pushl GOTPLT+4
       0x50,                            // 6:    pushl %eax
       0xa1, 0,    0,    0,    0,       // 7:    mov GOTPLT+8, %eax
       0xe8, 0x0f, 0x00, 0x00, 0x00,    // c:    call next
       0xf3, 0x90,                      // 11: loop: pause
       0x0f, 0xae, 0xe8,                // 13:   lfence
       0xeb, 0xf9,                      // 16:   jmp loop
       0xcc, 0xcc, 0xcc, 0xcc, 0xcc,    // 18:   int3
       0xcc, 0xcc, 0xcc,                // 1f:   int3; .align 16
       0x89, 0x0c, 0x24,                // 20: next: mov %ecx, (%esp)
       0x8b, 0x4c, 0x24, 0x04,          // 23:   mov 0x4(%esp), %ecx
       0x89, 0x44, 0x24, 0x04,          // 27:   mov %eax ,0x4(%esp)
       0x89, 0xc8,                      // 2b:   mov %ecx, %eax
       0x59,                            // 2d:   pop %ecx
       0xc3,                            // 2e:   ret
+      0xcc,                            // 2f:   int3; padding
   };
-  memcpy(Buf, PltData, sizeof(PltData));
+  memcpy(Buf, Insn, sizeof(Insn));
 
   uint32_t GotPlt = InX::GotPlt->getVA();
   write32le(Buf + 2, GotPlt + 4);
   write32le(Buf + 8, GotPlt + 8);
 }
 
 void RetpolineNoPic::writePlt(uint8_t *Buf, uint64_t GotPltEntryAddr,
                               uint64_t PltEntryAddr, int32_t Index,
                               unsigned RelOff) const {
   const uint8_t Insn[] = {
-      0x50,             // 0:  pushl %eax
-      0xa1, 0, 0, 0, 0, // 1:  mov foo_in_GOT, %eax
-      0xe8, 0, 0, 0, 0, // 6:  call plt+0x20
-      0xe9, 0, 0, 0, 0, // b:  jmp plt+0x11
-      0x68, 0, 0, 0, 0, // 10: pushl $reloc_offset
-      0xe9, 0, 0, 0, 0, // 15: jmp plt+0
+      0x50,                         // 0:  pushl %eax
+      0xa1, 0,    0,    0,    0,    // 1:  mov foo_in_GOT, %eax
+      0xe8, 0,    0,    0,    0,    // 6:  call plt+0x20
+      0xe9, 0,    0,    0,    0,    // b:  jmp plt+0x11
+      0x68, 0,    0,    0,    0,    // 10: pushl $reloc_offset
+      0xe9, 0,    0,    0,    0,    // 15: jmp plt+0
+      0xcc, 0xcc, 0xcc, 0xcc, 0xcc, // 1a: int3; padding
+      0xcc,                         // 1f: int3; padding
   };
   memcpy(Buf, Insn, sizeof(Insn));
 
   unsigned Off = getPltEntryOffset(Index);
   write32le(Buf + 2, GotPltEntryAddr);
   write32le(Buf + 7, -Off - 11 + 32);
   write32le(Buf + 12, -Off - 16 + 17);
   write32le(Buf + 17, RelOff);

lld/trunk/ELF/Arch/X86_64.cpp

const uint8_t Insn[] = {
       0x4c, 0x8b, 0x1d, 0,    0,    0,    0,    // 6:    mov GOTPLT+16(%rip), %r11
       0xe8, 0x0e, 0x00, 0x00, 0x00,             // d:    callq next
       0xf3, 0x90,                               // 12: loop: pause
       0x0f, 0xae, 0xe8,                         // 14:   lfence
       0xeb, 0xf9,                               // 17:   jmp loop
       0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, // 19:   int3; .align 16
       0x4c, 0x89, 0x1c, 0x24,                   // 20: next: mov %r11, (%rsp)
       0xc3,                                     // 24:   ret
+      0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, // 25:   int3; padding
+      0xcc, 0xcc, 0xcc, 0xcc,                   // 2c:   int3; padding
   };
   memcpy(Buf, Insn, sizeof(Insn));
 
   uint64_t GotPlt = InX::GotPlt->getVA();
   uint64_t Plt = InX::Plt->getVA();
   write32le(Buf + 2, GotPlt - Plt - 6 + 8);
   write32le(Buf + 9, GotPlt - Plt - 13 + 16);
 }
 
 template <class ELFT>
 void Retpoline<ELFT>::writePlt(uint8_t *Buf, uint64_t GotPltEntryAddr,
                                uint64_t PltEntryAddr, int32_t Index,
                                unsigned RelOff) const {
   const uint8_t Insn[] = {
       0x4c, 0x8b, 0x1d, 0, 0, 0, 0, // 0:  mov foo@GOTPLT(%rip), %r11
-      0xe8, 0,    0,    0, 0,       // 7:  callq plt+0x20
-      0xe9, 0,    0,    0, 0,       // c:  jmp plt+0x12
-      0x68, 0,    0,    0, 0,       // 11: pushq <relocation index>
-      0xe9, 0,    0,    0, 0,       // 16: jmp plt+0
+      0xe8, 0,    0,    0,    0,    // 7:  callq plt+0x20
+      0xe9, 0,    0,    0,    0,    // c:  jmp plt+0x12
+      0x68, 0,    0,    0,    0,    // 11: pushq <relocation index>
+      0xe9, 0,    0,    0,    0,    // 16: jmp plt+0
+      0xcc, 0xcc, 0xcc, 0xcc, 0xcc, // 1b: int3; padding
   };
   memcpy(Buf, Insn, sizeof(Insn));
 
   uint64_t Off = TargetInfo::getPltEntryOffset(Index);
 
   write32le(Buf + 3, GotPltEntryAddr - PltEntryAddr - 7);
   write32le(Buf + 8, -Off - 12 + 32);
   write32le(Buf + 13, -Off - 17 + 18);
void RetpolineZNow<ELFT>::writePltHeader(uint8_t *Buf) const {
   const uint8_t Insn[] = {
       0xe8, 0x0b, 0x00, 0x00, 0x00, // 0:    call next
       0xf3, 0x90,                   // 5:  loop: pause
       0x0f, 0xae, 0xe8,             // 7:    lfence
       0xeb, 0xf9,                   // a:    jmp loop
       0xcc, 0xcc, 0xcc, 0xcc,       // c:    int3; .align 16
       0x4c, 0x89, 0x1c, 0x24,       // 10: next: mov %r11, (%rsp)
       0xc3,                         // 14:   ret
+      0xcc, 0xcc, 0xcc, 0xcc, 0xcc, // 15:   int3; padding
+      0xcc, 0xcc, 0xcc, 0xcc, 0xcc, // 1a:   int3; padding
+      0xcc,                         // 1f:   int3; padding
   };
   memcpy(Buf, Insn, sizeof(Insn));
 }
 
 template <class ELFT>
 void RetpolineZNow<ELFT>::writePlt(uint8_t *Buf, uint64_t GotPltEntryAddr,
                                    uint64_t PltEntryAddr, int32_t Index,
                                    unsigned RelOff) const {
   const uint8_t Insn[] = {
-      0x4c, 0x8b, 0x1d, 0, 0, 0, 0, // mov foo@GOTPLT(%rip), %r11
-      0xe9, 0,    0,    0, 0,       // jmp plt+0
+      0x4c, 0x8b, 0x1d, 0,    0, 0, 0, // mov foo@GOTPLT(%rip), %r11
+      0xe9, 0,    0,    0,    0,       // jmp plt+0
+      0xcc, 0xcc, 0xcc, 0xcc,          // int3; padding
   };
   memcpy(Buf, Insn, sizeof(Insn));
 
   write32le(Buf + 3, GotPltEntryAddr - PltEntryAddr - 7);
   write32le(Buf + 8, -TargetInfo::getPltEntryOffset(Index) - 12);
 }
 
 template <class ELFT> TargetInfo *getTargetInfo() {

lld/trunk/test/ELF/i386-retpoline-nopic-linkerscript.s

+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -triple=i386-unknown-linux %s -o %t1.o
+// RUN: llvm-mc -filetype=obj -triple=i386-unknown-linux %p/Inputs/shared.s -o %t2.o
+// RUN: ld.lld -shared %t2.o -o %t2.so
+
+// RUN: echo "SECTIONS { \
+// RUN:   .text : { *(.text) } \
+// RUN:   .plt : { *(.plt) } \
+// RUN:   .got.plt : { *(.got.plt) } \
+// RUN:   .dynstr : { *(.dynstr) } \
+// RUN: }" > %t.script
+// RUN: ld.lld %t1.o %t2.so -o %t.exe -z retpolineplt --script %t.script
+// RUN: llvm-objdump -d -s %t.exe | FileCheck %s
+
+// CHECK:      Disassembly of section .plt:
+// CHECK-NEXT: .plt:
+// CHECK-NEXT: 10:       ff 35 fc 00 00 00       pushl   252
+// CHECK-NEXT: 16:       50      pushl   %eax
+// CHECK-NEXT: 17:       a1 00 01 00 00  movl    256, %eax
+// CHECK-NEXT: 1c:       e8 0f 00 00 00  calll   15 <.plt+0x20>
+// CHECK-NEXT: 21:       f3 90   pause
+// CHECK-NEXT: 23:       0f ae e8        lfence
+// CHECK-NEXT: 26:       eb f9   jmp     -7 <.plt+0x11>
+// CHECK-NEXT: 28:       cc      int3
+// CHECK-NEXT: 29:       cc      int3
+// CHECK-NEXT: 2a:       cc      int3
+// CHECK-NEXT: 2b:       cc      int3
+// CHECK-NEXT: 2c:       cc      int3
+// CHECK-NEXT: 2d:       cc      int3
+// CHECK-NEXT: 2e:       cc      int3
+// CHECK-NEXT: 2f:       cc      int3
+// CHECK-NEXT: 30:       89 0c 24        movl    %ecx, (%esp)
+// CHECK-NEXT: 33:       8b 4c 24 04     movl    4(%esp), %ecx
+// CHECK-NEXT: 37:       89 44 24 04     movl    %eax, 4(%esp)
+// CHECK-NEXT: 3b:       89 c8   movl    %ecx, %eax
+// CHECK-NEXT: 3d:       59      popl    %ecx
+// CHECK-NEXT: 3e:       c3      retl
+// CHECK-NEXT: 3f:       cc      int3
+// CHECK-NEXT: 40:       50      pushl   %eax
+// CHECK-NEXT: 41:       a1 04 01 00 00  movl    260, %eax
+// CHECK-NEXT: 46:       e8 e5 ff ff ff  calll   -27 <.plt+0x20>
+// CHECK-NEXT: 4b:       e9 d1 ff ff ff  jmp     -47 <.plt+0x11>
+// CHECK-NEXT: 50:       68 00 00 00 00  pushl   $0
+// CHECK-NEXT: 55:       e9 b6 ff ff ff  jmp     -74 <.plt>
+// CHECK-NEXT: 5a:       cc      int3
+// CHECK-NEXT: 5b:       cc      int3
+// CHECK-NEXT: 5c:       cc      int3
+// CHECK-NEXT: 5d:       cc      int3
+// CHECK-NEXT: 5e:       cc      int3
+// CHECK-NEXT: 5f:       cc      int3
+// CHECK-NEXT: 60:       50      pushl   %eax
+// CHECK-NEXT: 61:       a1 08 01 00 00  movl    264, %eax
+// CHECK-NEXT: 66:       e8 c5 ff ff ff  calll   -59 <.plt+0x20>
+// CHECK-NEXT: 6b:       e9 b1 ff ff ff  jmp     -79 <.plt+0x11>
+// CHECK-NEXT: 70:       68 08 00 00 00  pushl   $8
+// CHECK-NEXT: 75:       e9 96 ff ff ff  jmp     -106 <.plt>
+// CHECK-NEXT: 7a:       cc      int3
+// CHECK-NEXT: 7b:       cc      int3
+// CHECK-NEXT: 7c:       cc      int3
+// CHECK-NEXT: 7d:       cc      int3
+// CHECK-NEXT: 7e:       cc      int3
+// CHECK-NEXT: 7f:       cc      int3
+
+.global _start
+_start:
+  jmp bar@PLT
+  jmp zed@PLT

lld/trunk/test/ELF/i386-retpoline-pic-linkerscript.s

+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -triple=i386-unknown-linux -position-independent %s -o %t1.o
+// RUN: llvm-mc -filetype=obj -triple=i386-unknown-linux -position-independent %p/Inputs/shared.s -o %t2.o
+// RUN: ld.lld -shared %t2.o -o %t2.so
+
+// RUN: echo "SECTIONS { \
+// RUN:   .text : { *(.text) } \
+// RUN:   .plt : { *(.plt) } \
+// RUN:   .got.plt : { *(.got.plt) } \
+// RUN:   .dynstr : { *(.dynstr) } \
+// RUN: }" > %t.script
+// RUN: ld.lld %t1.o %t2.so -o %t.exe -z retpolineplt -pie --script %t.script
+// RUN: llvm-objdump -d -s %t.exe | FileCheck %s
+
+// CHECK:      Disassembly of section .plt:
+// CHECK-NEXT: .plt:
+// CHECK-NEXT: 10:       ff b3 fc 00 00 00       pushl   252(%ebx)
+// CHECK-NEXT: 16:       50      pushl   %eax
+// CHECK-NEXT: 17:       8b 83 00 01 00 00       movl    256(%ebx), %eax
+// CHECK-NEXT: 1d:       e8 0e 00 00 00  calll   14 <.plt+0x20>
+// CHECK-NEXT: 22:       f3 90   pause
+// CHECK-NEXT: 24:       0f ae e8        lfence
+// CHECK-NEXT: 27:       eb f9   jmp     -7 <.plt+0x12>
+// CHECK-NEXT: 29:       cc      int3
+// CHECK-NEXT: 2a:       cc      int3
+// CHECK-NEXT: 2b:       cc      int3
+// CHECK-NEXT: 2c:       cc      int3
+// CHECK-NEXT: 2d:       cc      int3
+// CHECK-NEXT: 2e:       cc      int3
+// CHECK-NEXT: 2f:       cc      int3
+// CHECK-NEXT: 30:       89 0c 24        movl    %ecx, (%esp)
+// CHECK-NEXT: 33:       8b 4c 24 04     movl    4(%esp), %ecx
+// CHECK-NEXT: 37:       89 44 24 04     movl    %eax, 4(%esp)
+// CHECK-NEXT: 3b:       89 c8   movl    %ecx, %eax
+// CHECK-NEXT: 3d:       59      popl    %ecx
+// CHECK-NEXT: 3e:       c3      retl
+// CHECK-NEXT: 3f:       cc      int3
+// CHECK-NEXT: 40:       50      pushl   %eax
+// CHECK-NEXT: 41:       8b 83 04 01 00 00       movl    260(%ebx), %eax
+// CHECK-NEXT: 47:       e8 e4 ff ff ff  calll   -28 <.plt+0x20>
+// CHECK-NEXT: 4c:       e9 d1 ff ff ff  jmp     -47 <.plt+0x12>
+// CHECK-NEXT: 51:       68 00 00 00 00  pushl   $0
+// CHECK-NEXT: 56:       e9 b5 ff ff ff  jmp     -75 <.plt>
+// CHECK-NEXT: 5b:       cc      int3
+// CHECK-NEXT: 5c:       cc      int3
+// CHECK-NEXT: 5d:       cc      int3
+// CHECK-NEXT: 5e:       cc      int3
+// CHECK-NEXT: 5f:       cc      int3
+// CHECK-NEXT: 60:       50      pushl   %eax
+// CHECK-NEXT: 61:       8b 83 08 01 00 00       movl    264(%ebx), %eax
+// CHECK-NEXT: 67:       e8 c4 ff ff ff  calll   -60 <.plt+0x20>
+// CHECK-NEXT: 6c:       e9 b1 ff ff ff  jmp     -79 <.plt+0x12>
+// CHECK-NEXT: 71:       68 08 00 00 00  pushl   $8
+// CHECK-NEXT: 76:       e9 95 ff ff ff  jmp     -107 <.plt>
+// CHECK-NEXT: 7b:       cc      int3
+// CHECK-NEXT: 7c:       cc      int3
+// CHECK-NEXT: 7d:       cc      int3
+// CHECK-NEXT: 7e:       cc      int3
+// CHECK-NEXT: 7f:       cc      int3
+
+.global _start
+_start:
+  jmp bar@PLT
+  jmp zed@PLT

lld/trunk/test/ELF/x86-64-retpoline-linkerscript.s

+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1.o
+// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/shared.s -o %t2.o
+// RUN: ld.lld -shared %t2.o -o %t2.so
+
+// RUN: echo "SECTIONS { \
+// RUN:   .text : { *(.text) } \
+// RUN:   .plt : { *(.plt) } \
+// RUN:   .got.plt : { *(.got.plt) } \
+// RUN:   .dynstr : { *(.dynstr) } \
+// RUN: }" > %t.script
+// RUN: ld.lld -shared %t1.o %t2.so -o %t.exe -z retpolineplt --script %t.script
+// RUN: llvm-objdump -d -s %t.exe | FileCheck %s
+
+// CHECK:      Disassembly of section .plt:
+// CHECK-NEXT: .plt:
+// CHECK-NEXT: 10:       ff 35 4a 01 00 00       pushq   330(%rip)
+// CHECK-NEXT: 16:       4c 8b 1d 4b 01 00 00    movq    331(%rip), %r11
+// CHECK-NEXT: 1d:       e8 0e 00 00 00  callq   14 <.plt+0x20>
+// CHECK-NEXT: 22:       f3 90   pause
+// CHECK-NEXT: 24:       0f ae e8        lfence
+// CHECK-NEXT: 27:       eb f9   jmp     -7 <.plt+0x12>
+// CHECK-NEXT: 29:       cc      int3
+// CHECK-NEXT: 2a:       cc      int3
+// CHECK-NEXT: 2b:       cc      int3
+// CHECK-NEXT: 2c:       cc      int3
+// CHECK-NEXT: 2d:       cc      int3
+// CHECK-NEXT: 2e:       cc      int3
+// CHECK-NEXT: 2f:       cc      int3
+// CHECK-NEXT: 30:       4c 89 1c 24     movq    %r11, (%rsp)
+// CHECK-NEXT: 34:       c3      retq
+// CHECK-NEXT: 35:       cc      int3
+// CHECK-NEXT: 36:       cc      int3
+// CHECK-NEXT: 37:       cc      int3
+// CHECK-NEXT: 38:       cc      int3
+// CHECK-NEXT: 39:       cc      int3
+// CHECK-NEXT: 3a:       cc      int3
+// CHECK-NEXT: 3b:       cc      int3
+// CHECK-NEXT: 3c:       cc      int3
+// CHECK-NEXT: 3d:       cc      int3
+// CHECK-NEXT: 3e:       cc      int3
+// CHECK-NEXT: 3f:       cc      int3
+// CHECK-NEXT: 40:       4c 8b 1d 29 01 00 00    movq    297(%rip), %r11
+// CHECK-NEXT: 47:       e8 e4 ff ff ff  callq   -28 <.plt+0x20>
+// CHECK-NEXT: 4c:       e9 d1 ff ff ff  jmp     -47 <.plt+0x12>
+// CHECK-NEXT: 51:       68 00 00 00 00  pushq   $0
+// CHECK-NEXT: 56:       e9 b5 ff ff ff  jmp     -75 <.plt>
+// CHECK-NEXT: 5b:       cc      int3
+// CHECK-NEXT: 5c:       cc      int3
+// CHECK-NEXT: 5d:       cc      int3
+// CHECK-NEXT: 5e:       cc      int3
+// CHECK-NEXT: 5f:       cc      int3
+// CHECK-NEXT: 60:       4c 8b 1d 11 01 00 00    movq    273(%rip), %r11
+// CHECK-NEXT: 67:       e8 c4 ff ff ff  callq   -60 <.plt+0x20>
+// CHECK-NEXT: 6c:       e9 b1 ff ff ff  jmp     -79 <.plt+0x12>
+// CHECK-NEXT: 71:       68 01 00 00 00  pushq   $1
+// CHECK-NEXT: 76:       e9 95 ff ff ff  jmp     -107 <.plt>
+// CHECK-NEXT: 7b:       cc      int3
+// CHECK-NEXT: 7c:       cc      int3
+// CHECK-NEXT: 7d:       cc      int3
+// CHECK-NEXT: 7e:       cc      int3
+// CHECK-NEXT: 7f:       cc      int3
+
+.global _start
+_start:
+  jmp bar@PLT
+  jmp zed@PLT

lld/trunk/test/ELF/x86-64-retpoline-znow-linkerscript.s

+// REQUIRES: x86
+// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1.o
+// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/shared.s -o %t2.o
+// RUN: ld.lld -shared %t2.o -o %t2.so
+
+// RUN: echo "SECTIONS { \
+// RUN:   .text : { *(.text) } \
+// RUN:   .plt : { *(.plt) } \
+// RUN:   .got.plt : { *(.got.plt) } \
+// RUN:   .dynstr : { *(.dynstr) } \
+// RUN: }" > %t.script
+// RUN: ld.lld -shared %t1.o %t2.so -o %t.exe -z retpolineplt -z now --script %t.script
+// RUN: llvm-objdump -d -s %t.exe | FileCheck %s
+
+// CHECK:      Disassembly of section .plt:
+// CHECK-NEXT: .plt:
+// CHECK-NEXT: 10:  e8 0b 00 00 00  callq 11 <.plt+0x10>
+// CHECK-NEXT: 15:  f3 90   pause
+// CHECK-NEXT: 17:  0f ae e8  lfence
+// CHECK-NEXT: 1a:  eb f9   jmp -7 <.plt+0x5>
+// CHECK-NEXT: 1c:  cc  int3
+// CHECK-NEXT: 1d:  cc  int3
+// CHECK-NEXT: 1e:  cc  int3
+// CHECK-NEXT: 1f:  cc  int3
+// CHECK-NEXT: 20:  4c 89 1c 24   movq  %r11, (%rsp)
+// CHECK-NEXT: 24:  c3  retq
+// CHECK-NEXT: 25:  cc  int3
+// CHECK-NEXT: 26:  cc  int3
+// CHECK-NEXT: 27:  cc  int3
+// CHECK-NEXT: 28:  cc  int3
+// CHECK-NEXT: 29:  cc  int3
+// CHECK-NEXT: 2a:  cc  int3
+// CHECK-NEXT: 2b:  cc  int3
+// CHECK-NEXT: 2c:  cc  int3
+// CHECK-NEXT: 2d:  cc  int3
+// CHECK-NEXT: 2e:  cc  int3
+// CHECK-NEXT: 2f:  cc  int3
+// CHECK-NEXT: 30:  4c 8b 1d 09 01 00 00  movq  265(%rip), %r11
+// CHECK-NEXT: 37:  e9 d4 ff ff ff  jmp -44 <.plt>
+// CHECK-NEXT: 3c:  cc  int3
+// CHECK-NEXT: 3d:  cc  int3
+// CHECK-NEXT: 3e:  cc  int3
+// CHECK-NEXT: 3f:  cc  int3
+// CHECK-NEXT: 40: 4c 8b 1d 01 01 00 00   movq  257(%rip), %r11
+// CHECK-NEXT: 47:  e9 c4 ff ff ff  jmp -60 <.plt>
+// CHECK-NEXT: 4c:  cc  int3
+// CHECK-NEXT: 4d:  cc  int3
+// CHECK-NEXT: 4e:  cc  int3
+// CHECK-NEXT: 4f:  cc  int3
+
+.global _start
+_start:
+  jmp bar@PLT
+  jmp zed@PLT