From 683399be81e3dd5d71767eed54f868a5450a1c19 Mon Sep 17 00:00:00 2001
From: Reid Kleckner <rnk@google.com>
Date: Thu, 1 Feb 2018 22:37:22 +0000
Subject: [PATCH 1/2] Merging r323155 in LLD, with modifications to handle int3
fill
Original commit message:
------------------------------------------------------------------------
r323155 | chandlerc | 2018-01-22 14:05:25 -0800 (Mon, 22 Jan 2018) | 133 lines
Introduce the "retpoline" x86 mitigation technique for variant #2 of the speculative execution vulnerabilities disclosed today, specifically identified by CVE-2017-5715, "Branch Target Injection", and is one of the two halves to Spectre..
Summary:
First, we need to explain the core of the vulnerability. Note that this
is a very incomplete description, please see the Project Zero blog post
for details:
https://googleprojectzero.blogspot.com/2018/01/reading-privileged-memory-with-side.html
The basis for branch target injection is to direct speculative execution
of the processor to some "gadget" of executable code by poisoning the
prediction of indirect branches with the address of that gadget. The
gadget in turn contains an operation that provides a side channel for
reading data. Most commonly, this will look like a load of secret data
followed by a branch on the loaded value and then a load of some
predictable cache line. The attacker then uses timing of the processors
cache to determine which direction the branch took *in the speculative
execution*, and in turn what one bit of the loaded value was. Due to the
nature of these timing side channels and the branch predictor on Intel
processors, this allows an attacker to leak data only accessible to
a privileged domain (like the kernel) back into an unprivileged domain.
The goal is simple: avoid generating code which contains an indirect
branch that could have its prediction poisoned by an attacker. In many
cases, the compiler can simply use directed conditional branches and
a small search tree. LLVM already has support for lowering switches in
this way and the first step of this patch is to disable jump-table
lowering of switches and introduce a pass to rewrite explicit indirectbr
sequences into a switch over integers.
However, there is no fully general alternative to indirect calls. We
introduce a new construct we call a "retpoline" to implement indirect
calls in a non-speculatable way. It can be thought of loosely as
a trampoline for indirect calls which uses the RET instruction on x86.
Further, we arrange for a specific call->ret sequence which ensures the
processor predicts the return to go to a controlled, known location. The
retpoline then "smashes" the return address pushed onto the stack by the
call with the desired target of the original indirect call. The result
is a predicted return to the next instruction after a call (which can be
used to trap speculative execution within an infinite loop) and an
actual indirect branch to an arbitrary address.
On 64-bit x86 ABIs, this is especially easily done in the compiler by
using a guaranteed scratch register to pass the target into this device.
For 32-bit ABIs there isn't a guaranteed scratch register and so several
different retpoline variants are introduced to use a scratch register if
one is available in the calling convention and to otherwise use direct
stack push/pop sequences to pass the target address.
This "retpoline" mitigation is fully described in the following blog
post: https://support.google.com/faqs/answer/7625886
We also support a target feature that disables emission of the retpoline
thunk by the compiler to allow for custom thunks if users want them.
These are particularly useful in environments like kernels that
routinely do hot-patching on boot and want to hot-patch their thunk to
different code sequences. They can write this custom thunk and use
`-mretpoline-external-thunk` *in addition* to `-mretpoline`. In this
case, on x86-64 thu thunk names must be:
```
__llvm_external_retpoline_r11
```
or on 32-bit:
```
__llvm_external_retpoline_eax
__llvm_external_retpoline_ecx
__llvm_external_retpoline_edx
__llvm_external_retpoline_push
```
And the target of the retpoline is passed in the named register, or in
the case of the `push` suffix on the top of the stack via a `pushl`
instruction.
There is one other important source of indirect branches in x86 ELF
binaries: the PLT. These patches also include support for LLD to
generate PLT entries that perform a retpoline-style indirection.
The only other indirect branches remaining that we are aware of are from
precompiled runtimes (such as crt0.o and similar). The ones we have
found are not really attackable, and so we have not focused on them
here, but eventually these runtimes should also be replicated for
retpoline-ed configurations for completeness.
For kernels or other freestanding or fully static executables, the
compiler switch `-mretpoline` is sufficient to fully mitigate this
particular attack. For dynamic executables, you must compile *all*
libraries with `-mretpoline` and additionally link the dynamic
executable and all shared libraries with LLD and pass `-z retpolineplt`
(or use similar functionality from some other linker). We strongly
recommend also using `-z now` as non-lazy binding allows the
retpoline-mitigated PLT to be substantially smaller.
When manually apply similar transformations to `-mretpoline` to the
Linux kernel we observed very small performance hits to applications
running typical workloads, and relatively minor hits (approximately 2%)
even for extremely syscall-heavy applications. This is largely due to
the small number of indirect branches that occur in performance
sensitive paths of the kernel.
When using these patches on statically linked applications, especially
C++ applications, you should expect to see a much more dramatic
performance hit. For microbenchmarks that are switch, indirect-, or
virtual-call heavy we have seen overheads ranging from 10% to 50%.
However, real-world workloads exhibit substantially lower performance
impact. Notably, techniques such as PGO and ThinLTO dramatically reduce
the impact of hot indirect calls (by speculatively promoting them to
direct calls) and allow optimized search trees to be used to lower
switches. If you need to deploy these techniques in C++ applications, we
*strongly* recommend that you ensure all hot call targets are statically
linked (avoiding PLT indirection) and use both PGO and ThinLTO. Well
tuned servers using all of these techniques saw 5% - 10% overhead from
the use of retpoline.
We will add detailed documentation covering these components in
subsequent patches, but wanted to make the core functionality available
as soon as possible. Happy for more code review, but we'd really like to
get these patches landed and backported ASAP for obvious reasons. We're
planning to backport this to both 6.0 and 5.0 release streams and get
a 5.0 release with just this cherry picked ASAP for distros and vendors.
This patch is the work of a number of people over the past month: Eric, Reid,
Rui, and myself. I'm mailing it out as a single commit due to the time
sensitive nature of landing this and the need to backport it. Huge thanks to
everyone who helped out here, and everyone at Intel who helped out in
discussions about how to craft this. Also, credit goes to Paul Turner (at
Google, but not an LLVM contributor) for much of the underlying retpoline
design.
Reviewers: echristo, rnk, ruiu, craig.topper, DavidKreitzer
Subscribers: sanjoy, emaste, mcrosier, mgorny, mehdi_amini, hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D41723
------------------------------------------------------------------------
git-svn-id: https://llvm.org/svn/llvm-project/lld/branches/release_50@324025 91177308-0d34-0410-b5e6-96231b3b80d8
---
ELF/Arch/X86.cpp | 156 ++++++++++++++++++++++++++++++++++++++-
ELF/Arch/X86_64.cpp | 138 ++++++++++++++++++++++++++++++++--
ELF/Config.h | 1 +
ELF/Driver.cpp | 1 +
test/ELF/i386-retpoline-nopic.s | 81 ++++++++++++++++++++
test/ELF/i386-retpoline-pic.s | 62 ++++++++++++++++
test/ELF/x86-64-retpoline-znow.s | 53 +++++++++++++
test/ELF/x86-64-retpoline.s | 66 +++++++++++++++++
8 files changed, 548 insertions(+), 10 deletions(-)
create mode 100644 test/ELF/i386-retpoline-nopic.s
create mode 100644 test/ELF/i386-retpoline-pic.s
create mode 100644 test/ELF/x86-64-retpoline-znow.s
create mode 100644 test/ELF/x86-64-retpoline.s
diff --git a/ELF/Arch/X86.cpp b/ELF/Arch/X86.cpp
index a1e9bca..ac71a9b 100644
--- a/ELF/Arch/X86.cpp
+++ b/ELF/Arch/X86.cpp
@@ -21,7 +21,7 @@ using namespace lld;
using namespace lld::elf;
namespace {
-class X86 final : public TargetInfo {
+class X86 : public TargetInfo {
public:
X86();
RelExpr getRelExpr(uint32_t Type, const SymbolBody &S,
@@ -358,7 +358,157 @@ void X86::relaxTlsLdToLe(uint8_t *Loc, uint32_t Type, uint64_t Val) const {
memcpy(Loc - 2, Inst, sizeof(Inst));
}
+namespace {
+class RetpolinePic : public X86 {
+public:
+ RetpolinePic();
+ void writeGotPlt(uint8_t *Buf, const SymbolBody &S) const override;
+ void writePltHeader(uint8_t *Buf) const override;
+ void writePlt(uint8_t *Buf, uint64_t GotPltEntryAddr, uint64_t PltEntryAddr,
+ int32_t Index, unsigned RelOff) const override;
+};
+
+class RetpolineNoPic : public X86 {
+public:
+ RetpolineNoPic();
+ void writeGotPlt(uint8_t *Buf, const SymbolBody &S) const override;
+ void writePltHeader(uint8_t *Buf) const override;
+ void writePlt(uint8_t *Buf, uint64_t GotPltEntryAddr, uint64_t PltEntryAddr,
+ int32_t Index, unsigned RelOff) const override;
+};
+} // namespace
+
+RetpolinePic::RetpolinePic() {
+ PltHeaderSize = 48;
+ PltEntrySize = 32;
+}
+
+void RetpolinePic::writeGotPlt(uint8_t *Buf, const SymbolBody &S) const {
+ write32le(Buf, S.getPltVA() + 17);
+}
+
+void RetpolinePic::writePltHeader(uint8_t *Buf) const {
+ const uint8_t Insn[] = {
+ 0xff, 0xb3, 0, 0, 0, 0, // 0: pushl GOTPLT+4(%ebx)
+ 0x50, // 6: pushl %eax
+ 0x8b, 0x83, 0, 0, 0, 0, // 7: mov GOTPLT+8(%ebx), %eax
+ 0xe8, 0x0e, 0x00, 0x00, 0x00, // d: call 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
+ 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
+ };
+ memcpy(Buf, Insn, sizeof(Insn));
+ assert(sizeof(Insn) == TargetInfo::PltHeaderSize);
+
+ 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
+ 0xcc, 0xcc, 0xcc, 0xcc, 0xcc,
+ };
+ memcpy(Buf, Insn, sizeof(Insn));
+ assert(sizeof(Insn) == TargetInfo::PltEntrySize);
+
+ uint32_t Ebx = InX::Got->getVA() + InX::Got->getSize();
+ write32le(Buf + 3, GotPltEntryAddr - Ebx);
+ write32le(Buf + 8, -Index * PltEntrySize - PltHeaderSize - 12 + 32);
+ write32le(Buf + 13, -Index * PltEntrySize - PltHeaderSize - 17 + 18);
+ write32le(Buf + 18, RelOff);
+ write32le(Buf + 23, -Index * PltEntrySize - PltHeaderSize - 27);
+}
+
+RetpolineNoPic::RetpolineNoPic() {
+ PltHeaderSize = 64;
+ PltEntrySize = 32;
+}
+
+void RetpolineNoPic::writeGotPlt(uint8_t *Buf, const SymbolBody &S) const {
+ write32le(Buf, S.getPltVA() + 16);
+}
+
+void RetpolineNoPic::writePltHeader(uint8_t *Buf) const {
+ const uint8_t PltData[] = {
+ 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
+ 0xcc, 0xcc, 0xcc, 0xcc,
+ 0xcc, 0xcc, 0xcc, 0xcc,
+ 0xcc, 0xcc, 0xcc, 0xcc,
+ 0xcc, 0xcc, 0xcc, 0xcc,
+ };
+ memcpy(Buf, PltData, sizeof(PltData));
+ assert(sizeof(PltData) == TargetInfo::PltHeaderSize);
+
+ 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
+ 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc,
+ };
+ memcpy(Buf, Insn, sizeof(Insn));
+ assert(sizeof(Insn) == TargetInfo::PltEntrySize);
+
+ write32le(Buf + 2, GotPltEntryAddr);
+ write32le(Buf + 7, -Index * PltEntrySize - PltHeaderSize - 11 + 32);
+ write32le(Buf + 12, -Index * PltEntrySize - PltHeaderSize - 16 + 17);
+ write32le(Buf + 17, RelOff);
+ write32le(Buf + 22, -Index * PltEntrySize - PltHeaderSize - 26);
+}
+
TargetInfo *elf::getX86TargetInfo() {
- static X86 Target;
- return &Target;
+ if (Config->ZRetpolineplt) {
+ if (Config->Pic) {
+ static RetpolinePic T;
+ return &T;
+ }
+ static RetpolineNoPic T;
+ return &T;
+ }
+
+ static X86 T;
+ return &T;
}
diff --git a/ELF/Arch/X86_64.cpp b/ELF/Arch/X86_64.cpp
index 10179f5..f06fda7 100644
--- a/ELF/Arch/X86_64.cpp
+++ b/ELF/Arch/X86_64.cpp
@@ -23,7 +23,7 @@ using namespace lld;
using namespace lld::elf;
namespace {
-template <class ELFT> class X86_64 final : public TargetInfo {
+template <class ELFT> class X86_64 : public TargetInfo {
public:
X86_64();
RelExpr getRelExpr(uint32_t Type, const SymbolBody &S,
@@ -462,12 +462,136 @@ void X86_64<ELFT>::relaxGot(uint8_t *Loc, uint64_t Val) const {
write32le(Loc - 1, Val + 1);
}
-TargetInfo *elf::getX32TargetInfo() {
- static X86_64<ELF32LE> Target;
- return &Target;
+namespace {
+template <class ELFT> class Retpoline : public X86_64<ELFT> {
+public:
+ Retpoline();
+ void writeGotPlt(uint8_t *Buf, const SymbolBody &S) const override;
+ void writePltHeader(uint8_t *Buf) const override;
+ void writePlt(uint8_t *Buf, uint64_t GotPltEntryAddr, uint64_t PltEntryAddr,
+ int32_t Index, unsigned RelOff) const override;
+};
+
+template <class ELFT> class RetpolineZNow : public X86_64<ELFT> {
+public:
+ RetpolineZNow();
+ void writeGotPlt(uint8_t *Buf, const SymbolBody &S) const override {}
+ void writePltHeader(uint8_t *Buf) const override;
+ void writePlt(uint8_t *Buf, uint64_t GotPltEntryAddr, uint64_t PltEntryAddr,
+ int32_t Index, unsigned RelOff) const override;
+};
+} // namespace
+
+template <class ELFT> Retpoline<ELFT>::Retpoline() {
+ TargetInfo::PltHeaderSize = 48;
+ TargetInfo::PltEntrySize = 32;
+}
+
+template <class ELFT>
+void Retpoline<ELFT>::writeGotPlt(uint8_t *Buf, const SymbolBody &S) const {
+ write32le(Buf, S.getPltVA() + 17);
+}
+
+template <class ELFT> void Retpoline<ELFT>::writePltHeader(uint8_t *Buf) const {
+ const uint8_t Insn[] = {
+ 0xff, 0x35, 0, 0, 0, 0, // 0: pushq GOTPLT+8(%rip)
+ 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; .align 16
+ 0xcc, 0xcc, 0xcc, 0xcc,
+ };
+ memcpy(Buf, Insn, sizeof(Insn));
+ assert(sizeof(Insn) == TargetInfo::PltHeaderSize);
+
+ 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
+ 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, // int3; .align 16
+ };
+ memcpy(Buf, Insn, sizeof(Insn));
+ assert(sizeof(Insn) == TargetInfo::PltEntrySize);
+
+ uint64_t Off = TargetInfo::PltHeaderSize + TargetInfo::PltEntrySize * Index;
+
+ write32le(Buf + 3, GotPltEntryAddr - PltEntryAddr - 7);
+ write32le(Buf + 8, -Off - 12 + 32);
+ write32le(Buf + 13, -Off - 17 + 18);
+ write32le(Buf + 18, Index);
+ write32le(Buf + 23, -Off - 27);
+}
+
+template <class ELFT> RetpolineZNow<ELFT>::RetpolineZNow() {
+ TargetInfo::PltHeaderSize = 32;
+ TargetInfo::PltEntrySize = 16;
+}
+
+template <class ELFT>
+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, // 15: int3; .align 16
+ 0xcc, 0xcc, 0xcc, 0xcc, 0xcc,
+ 0xcc, 0xcc, 0xcc, 0xcc, 0xcc,
+ };
+ memcpy(Buf, Insn, sizeof(Insn));
+ assert(sizeof(Insn) == TargetInfo::PltHeaderSize);
}
-TargetInfo *elf::getX86_64TargetInfo() {
- static X86_64<ELF64LE> Target;
- return &Target;
+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
+ 0xcc, 0xcc, 0xcc, 0xcc, // int3; .align 16
+ };
+ memcpy(Buf, Insn, sizeof(Insn));
+ assert(sizeof(Insn) == TargetInfo::PltEntrySize);
+
+ write32le(Buf + 3, GotPltEntryAddr - PltEntryAddr - 7);
+ write32le(Buf + 8,
+ -Index * TargetInfo::PltEntrySize - TargetInfo::PltHeaderSize - 12);
}
+
+template <class ELFT> TargetInfo *getTargetInfo() {
+ if (Config->ZRetpolineplt) {
+ if (Config->ZNow) {
+ static RetpolineZNow<ELFT> T;
+ return &T;
+ }
+ static Retpoline<ELFT> T;
+ return &T;
+ }
+
+ static X86_64<ELFT> T;
+ return &T;
+}
+
+TargetInfo *elf::getX32TargetInfo() { return getTargetInfo<ELF32LE>(); }
+TargetInfo *elf::getX86_64TargetInfo() { return getTargetInfo<ELF64LE>(); }
diff --git a/ELF/Config.h b/ELF/Config.h
index 23627dd..bc8a5ae 100644
--- a/ELF/Config.h
+++ b/ELF/Config.h
@@ -156,6 +156,7 @@ struct Configuration {
bool ZRelro;
bool ZRodynamic;
bool ZText;
+ bool ZRetpolineplt;
bool ExitEarly;
bool ZWxneeded;
DiscardPolicy Discard;
diff --git a/ELF/Driver.cpp b/ELF/Driver.cpp
index 47a50bb..4a6556f 100644
--- a/ELF/Driver.cpp
+++ b/ELF/Driver.cpp
@@ -688,6 +688,7 @@ void LinkerDriver::readConfigs(opt::InputArgList &Args) {
Config->ZNow = hasZOption(Args, "now");
Config->ZOrigin = hasZOption(Args, "origin");
Config->ZRelro = !hasZOption(Args, "norelro");
+ Config->ZRetpolineplt = hasZOption(Args, "retpolineplt");
Config->ZRodynamic = hasZOption(Args, "rodynamic");
Config->ZStackSize = getZOptionValue(Args, "stack-size", 0);
Config->ZText = !hasZOption(Args, "notext");
diff --git a/test/ELF/i386-retpoline-nopic.s b/test/ELF/i386-retpoline-nopic.s
new file mode 100644
index 0000000..4de813e
--- /dev/null
+++ b/test/ELF/i386-retpoline-nopic.s
@@ -0,0 +1,81 @@
+// 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: ld.lld %t1.o %t2.so -o %t.exe -z retpolineplt
+// RUN: llvm-objdump -d -s %t.exe | FileCheck %s
+
+// CHECK: Disassembly of section .plt:
+// CHECK-NEXT: .plt:
+// CHECK-NEXT: 11010: ff 35 04 20 01 00 pushl 73732
+// CHECK-NEXT: 11016: 50 pushl %eax
+// CHECK-NEXT: 11017: a1 08 20 01 00 movl 73736, %eax
+// CHECK-NEXT: 1101c: e8 0f 00 00 00 calll 15 <.plt+0x20>
+// CHECK-NEXT: 11021: f3 90 pause
+// CHECK-NEXT: 11023: 0f ae e8 lfence
+// CHECK-NEXT: 11026: eb f9 jmp -7 <.plt+0x11>
+// CHECK-NEXT: 11028: cc int3
+// CHECK-NEXT: 11029: cc int3
+// CHECK-NEXT: 1102a: cc int3
+// CHECK-NEXT: 1102b: cc int3
+// CHECK-NEXT: 1102c: cc int3
+// CHECK-NEXT: 1102d: cc int3
+// CHECK-NEXT: 1102e: cc int3
+// CHECK-NEXT: 1102f: cc int3
+// CHECK-NEXT: 11030: 89 0c 24 movl %ecx, (%esp)
+// CHECK-NEXT: 11033: 8b 4c 24 04 movl 4(%esp), %ecx
+// CHECK-NEXT: 11037: 89 44 24 04 movl %eax, 4(%esp)
+// CHECK-NEXT: 1103b: 89 c8 movl %ecx, %eax
+// CHECK-NEXT: 1103d: 59 popl %ecx
+// CHECK-NEXT: 1103e: c3 retl
+// CHECK-NEXT: 1103f: cc int3
+// CHECK-NEXT: 11040: cc int3
+// CHECK-NEXT: 11041: cc int3
+// CHECK-NEXT: 11042: cc int3
+// CHECK-NEXT: 11043: cc int3
+// CHECK-NEXT: 11044: cc int3
+// CHECK-NEXT: 11045: cc int3
+// CHECK-NEXT: 11046: cc int3
+// CHECK-NEXT: 11047: cc int3
+// CHECK-NEXT: 11048: cc int3
+// CHECK-NEXT: 11049: cc int3
+// CHECK-NEXT: 1104a: cc int3
+// CHECK-NEXT: 1104b: cc int3
+// CHECK-NEXT: 1104c: cc int3
+// CHECK-NEXT: 1104d: cc int3
+// CHECK-NEXT: 1104e: cc int3
+// CHECK-NEXT: 1104f: cc int3
+// CHECK-NEXT: 11050: 50 pushl %eax
+// CHECK-NEXT: 11051: a1 0c 20 01 00 movl 73740, %eax
+// CHECK-NEXT: 11056: e8 d5 ff ff ff calll -43 <.plt+0x20>
+// CHECK-NEXT: 1105b: e9 c1 ff ff ff jmp -63 <.plt+0x11>
+// CHECK-NEXT: 11060: 68 00 00 00 00 pushl $0
+// CHECK-NEXT: 11065: e9 a6 ff ff ff jmp -90 <.plt>
+// CHECK-NEXT: 1106a: cc int3
+// CHECK-NEXT: 1106b: cc int3
+// CHECK-NEXT: 1106c: cc int3
+// CHECK-NEXT: 1106d: cc int3
+// CHECK-NEXT: 1106e: cc int3
+// CHECK-NEXT: 1106f: cc int3
+// CHECK-NEXT: 11070: 50 pushl %eax
+// CHECK-NEXT: 11071: a1 10 20 01 00 movl 73744, %eax
+// CHECK-NEXT: 11076: e8 b5 ff ff ff calll -75 <.plt+0x20>
+// CHECK-NEXT: 1107b: e9 a1 ff ff ff jmp -95 <.plt+0x11>
+// CHECK-NEXT: 11080: 68 08 00 00 00 pushl $8
+// CHECK-NEXT: 11085: e9 86 ff ff ff jmp -122 <.plt>
+// CHECK-NEXT: 1108a: cc int3
+// CHECK-NEXT: 1108b: cc int3
+// CHECK-NEXT: 1108c: cc int3
+// CHECK-NEXT: 1108d: cc int3
+// CHECK-NEXT: 1108e: cc int3
+// CHECK-NEXT: 1108f: cc int3
+
+// CHECK: Contents of section .got.plt:
+// CHECK-NEXT: 00300100 00000000 00000000 60100100
+// CHECK-NEXT: 80100100
+
+.global _start
+_start:
+ jmp bar@PLT
+ jmp zed@PLT
diff --git a/test/ELF/i386-retpoline-pic.s b/test/ELF/i386-retpoline-pic.s
new file mode 100644
index 0000000..3555950
--- /dev/null
+++ b/test/ELF/i386-retpoline-pic.s
@@ -0,0 +1,62 @@
+// 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: ld.lld %t1.o %t2.so -o %t.exe -z retpolineplt -pie
+// RUN: llvm-objdump -d -s %t.exe | FileCheck %s
+
+// CHECK: Disassembly of section .plt:
+// CHECK-NEXT: .plt:
+// CHECK-NEXT: 1010: ff b3 04 20 00 00 pushl 8196(%ebx)
+// CHECK-NEXT: 1016: 50 pushl %eax
+// CHECK-NEXT: 1017: 8b 83 08 20 00 00 movl 8200(%ebx), %eax
+// CHECK-NEXT: 101d: e8 0e 00 00 00 calll 14 <.plt+0x20>
+// CHECK-NEXT: 1022: f3 90 pause
+// CHECK-NEXT: 1024: 0f ae e8 lfence
+// CHECK-NEXT: 1027: eb f9 jmp -7 <.plt+0x12>
+// CHECK-NEXT: 1029: cc int3
+// CHECK-NEXT: 102a: cc int3
+// CHECK-NEXT: 102b: cc int3
+// CHECK-NEXT: 102c: cc int3
+// CHECK-NEXT: 102d: cc int3
+// CHECK-NEXT: 102e: cc int3
+// CHECK-NEXT: 102f: cc int3
+// CHECK-NEXT: 1030: 89 0c 24 movl %ecx, (%esp)
+// CHECK-NEXT: 1033: 8b 4c 24 04 movl 4(%esp), %ecx
+// CHECK-NEXT: 1037: 89 44 24 04 movl %eax, 4(%esp)
+// CHECK-NEXT: 103b: 89 c8 movl %ecx, %eax
+// CHECK-NEXT: 103d: 59 popl %ecx
+// CHECK-NEXT: 103e: c3 retl
+// CHECK-NEXT: 103f: cc int3
+// CHECK-NEXT: 1040: 50 pushl %eax
+// CHECK-NEXT: 1041: 8b 83 0c 20 00 00 movl 8204(%ebx), %eax
+// CHECK-NEXT: 1047: e8 e4 ff ff ff calll -28 <.plt+0x20>
+// CHECK-NEXT: 104c: e9 d1 ff ff ff jmp -47 <.plt+0x12>
+// CHECK-NEXT: 1051: 68 00 00 00 00 pushl $0
+// CHECK-NEXT: 1056: e9 b5 ff ff ff jmp -75 <.plt>
+// CHECK-NEXT: 105b: cc int3
+// CHECK-NEXT: 105c: cc int3
+// CHECK-NEXT: 105d: cc int3
+// CHECK-NEXT: 105e: cc int3
+// CHECK-NEXT: 105f: cc int3
+// CHECK-NEXT: 1060: 50 pushl %eax
+// CHECK-NEXT: 1061: 8b 83 10 20 00 00 movl 8208(%ebx), %eax
+// CHECK-NEXT: 1067: e8 c4 ff ff ff calll -60 <.plt+0x20>
+// CHECK-NEXT: 106c: e9 b1 ff ff ff jmp -79 <.plt+0x12>
+// CHECK-NEXT: 1071: 68 08 00 00 00 pushl $8
+// CHECK-NEXT: 1076: e9 95 ff ff ff jmp -107 <.plt>
+// CHECK-NEXT: 107b: cc int3
+// CHECK-NEXT: 107c: cc int3
+// CHECK-NEXT: 107d: cc int3
+// CHECK-NEXT: 107e: cc int3
+// CHECK-NEXT: 107f: cc int3
+
+// CHECK: Contents of section .got.plt:
+// CHECK-NEXT: 2000 00300000 00000000 00000000 51100000
+// CHECK-NEXT: 2010 71100000
+
+.global _start
+_start:
+ jmp bar@PLT
+ jmp zed@PLT
diff --git a/test/ELF/x86-64-retpoline-znow.s b/test/ELF/x86-64-retpoline-znow.s
new file mode 100644
index 0000000..7a4c730
--- /dev/null
+++ b/test/ELF/x86-64-retpoline-znow.s
@@ -0,0 +1,53 @@
+// 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: ld.lld -shared %t1.o %t2.so -o %t.exe -z retpolineplt -z now
+// RUN: llvm-objdump -d -s %t.exe | FileCheck %s
+
+// CHECK: Disassembly of section .plt:
+// CHECK-NEXT: .plt:
+// CHECK-NEXT: 1010: e8 0b 00 00 00 callq 11 <.plt+0x10>
+// CHECK-NEXT: 1015: f3 90 pause
+// CHECK-NEXT: 1017: 0f ae e8 lfence
+// CHECK-NEXT: 101a: eb f9 jmp -7 <.plt+0x5>
+// CHECK-NEXT: 101c: cc int3
+// CHECK-NEXT: 101d: cc int3
+// CHECK-NEXT: 101e: cc int3
+// CHECK-NEXT: 101f: cc int3
+// CHECK-NEXT: 1020: 4c 89 1c 24 movq %r11, (%rsp)
+// CHECK-NEXT: 1024: c3 retq
+// CHECK-NEXT: 1025: cc int3
+// CHECK-NEXT: 1026: cc int3
+// CHECK-NEXT: 1027: cc int3
+// CHECK-NEXT: 1028: cc int3
+// CHECK-NEXT: 1029: cc int3
+// CHECK-NEXT: 102a: cc int3
+// CHECK-NEXT: 102b: cc int3
+// CHECK-NEXT: 102c: cc int3
+// CHECK-NEXT: 102d: cc int3
+// CHECK-NEXT: 102e: cc int3
+// CHECK-NEXT: 102f: cc int3
+// CHECK-NEXT: 1030: 4c 8b 1d b1 10 00 00 movq 4273(%rip), %r11
+// CHECK-NEXT: 1037: e9 d4 ff ff ff jmp -44 <.plt>
+// CHECK-NEXT: 103c: cc int3
+// CHECK-NEXT: 103d: cc int3
+// CHECK-NEXT: 103e: cc int3
+// CHECK-NEXT: 103f: cc int3
+// CHECK-NEXT: 1040: 4c 8b 1d a9 10 00 00 movq 4265(%rip), %r11
+// CHECK-NEXT: 1047: e9 c4 ff ff ff jmp -60 <.plt>
+// CHECK-NEXT: 104c: cc int3
+// CHECK-NEXT: 104d: cc int3
+// CHECK-NEXT: 104e: cc int3
+// CHECK-NEXT: 104f: cc int3
+
+// CHECK: Contents of section .got.plt:
+// CHECK-NEXT: 20d0 00200000 00000000 00000000 00000000
+// CHECK-NEXT: 20e0 00000000 00000000 00000000 00000000
+// CHECK-NEXT: 20f0 00000000 00000000
+
+.global _start
+_start:
+ jmp bar@PLT
+ jmp zed@PLT
diff --git a/test/ELF/x86-64-retpoline.s b/test/ELF/x86-64-retpoline.s
new file mode 100644
index 0000000..535f565
--- /dev/null
+++ b/test/ELF/x86-64-retpoline.s
@@ -0,0 +1,66 @@
+// 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: ld.lld -shared %t1.o %t2.so -o %t.exe -z retpolineplt
+// RUN: llvm-objdump -d -s %t.exe | FileCheck %s
+
+// CHECK: Disassembly of section .plt:
+// CHECK-NEXT: .plt:
+// CHECK-NEXT: 1010: ff 35 f2 0f 00 00 pushq 4082(%rip)
+// CHECK-NEXT: 1016: 4c 8b 1d f3 0f 00 00 movq 4083(%rip), %r11
+// CHECK-NEXT: 101d: e8 0e 00 00 00 callq 14 <.plt+0x20>
+// CHECK-NEXT: 1022: f3 90 pause
+// CHECK-NEXT: 1024: 0f ae e8 lfence
+// CHECK-NEXT: 1027: eb f9 jmp -7 <.plt+0x12>
+// CHECK-NEXT: 1029: cc int3
+// CHECK-NEXT: 102a: cc int3
+// CHECK-NEXT: 102b: cc int3
+// CHECK-NEXT: 102c: cc int3
+// CHECK-NEXT: 102d: cc int3
+// CHECK-NEXT: 102e: cc int3
+// CHECK-NEXT: 102f: cc int3
+// CHECK-NEXT: 1030: 4c 89 1c 24 movq %r11, (%rsp)
+// CHECK-NEXT: 1034: c3 retq
+// CHECK-NEXT: 1035: cc int3
+// CHECK-NEXT: 1036: cc int3
+// CHECK-NEXT: 1037: cc int3
+// CHECK-NEXT: 1038: cc int3
+// CHECK-NEXT: 1039: cc int3
+// CHECK-NEXT: 103a: cc int3
+// CHECK-NEXT: 103b: cc int3
+// CHECK-NEXT: 103c: cc int3
+// CHECK-NEXT: 103d: cc int3
+// CHECK-NEXT: 103e: cc int3
+// CHECK-NEXT: 103f: cc int3
+// CHECK-NEXT: 1040: 4c 8b 1d d1 0f 00 00 movq 4049(%rip), %r11
+// CHECK-NEXT: 1047: e8 e4 ff ff ff callq -28 <.plt+0x20>
+// CHECK-NEXT: 104c: e9 d1 ff ff ff jmp -47 <.plt+0x12>
+// CHECK-NEXT: 1051: 68 00 00 00 00 pushq $0
+// CHECK-NEXT: 1056: e9 b5 ff ff ff jmp -75 <.plt>
+// CHECK-NEXT: 105b: cc int3
+// CHECK-NEXT: 105c: cc int3
+// CHECK-NEXT: 105d: cc int3
+// CHECK-NEXT: 105e: cc int3
+// CHECK-NEXT: 105f: cc int3
+// CHECK-NEXT: 1060: 4c 8b 1d b9 0f 00 00 movq 4025(%rip), %r11
+// CHECK-NEXT: 1067: e8 c4 ff ff ff callq -60 <.plt+0x20>
+// CHECK-NEXT: 106c: e9 b1 ff ff ff jmp -79 <.plt+0x12>
+// CHECK-NEXT: 1071: 68 01 00 00 00 pushq $1
+// CHECK-NEXT: 1076: e9 95 ff ff ff jmp -107 <.plt>
+// CHECK-NEXT: 107b: cc int3
+// CHECK-NEXT: 107c: cc int3
+// CHECK-NEXT: 107d: cc int3
+// CHECK-NEXT: 107e: cc int3
+// CHECK-NEXT: 107f: cc int3
+
+// CHECK: Contents of section .got.plt:
+// CHECK-NEXT: 2000 00300000 00000000 00000000 00000000
+// CHECK-NEXT: 2010 00000000 00000000 51100000 00000000
+// CHECK-NEXT: 2020 71100000 00000000
+
+.global _start
+_start:
+ jmp bar@PLT
+ jmp zed@PLT
--
1.8.3.1