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[LLD][RISCV][Zicfilp] Generate unlabeled landing pad-style PLT #145461

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[LLD][RISCV][Zicfilp] Generate unlabeled landing pad-style PLT #145461

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72 changes: 70 additions & 2 deletions lld/ELF/Arch/RISCV.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -27,7 +27,7 @@ using namespace lld::elf;

namespace {

class RISCV final : public TargetInfo {
class RISCV : public TargetInfo {
public:
RISCV(Ctx &);
uint32_t calcEFlags() const override;
Expand Down Expand Up @@ -1065,6 +1065,66 @@ void RISCV::finalizeRelax(int passes) const {
}
}

namespace {

class RISCVCfiLpUnlabeledPLT final : public RISCV {
public:
RISCVCfiLpUnlabeledPLT(Ctx &ctx);
void writePltHeader(uint8_t *buf) const override;
void writePlt(uint8_t *buf, const Symbol &sym,
uint64_t pltEntryAddr) const override;
};

} // namespace

RISCVCfiLpUnlabeledPLT::RISCVCfiLpUnlabeledPLT(Ctx &ctx) : RISCV(ctx) {
pltHeaderSize = 48;
}

void RISCVCfiLpUnlabeledPLT::writePltHeader(uint8_t *buf) const {
// lpad 0
// 1: auipc t2, %pcrel_hi(.got.plt)
// sub t1, t1, t3
// l[wd] t3, %pcrel_lo(1b)(t2); t3 = _dl_runtime_resolve
// addi t1, t1, -pltHeaderSize-16; t1 = &.plt[i] - &.plt[0]
// addi t0, t2, %pcrel_lo(1b)
// srli t1, t1, (rv64?1:2); t1 = &.got.plt[i] - &.got.plt[0]
// l[wd] t0, Wordsize(t0); t0 = link_map
// jr t3
// nop
// nop
// nop
const uint32_t offset =
ctx.in.gotPlt->getVA() - (ctx.in.plt->getVA() + 4 /* offset for lpad */);
const uint32_t load = ctx.arg.is64 ? LD : LW;
write32le(buf + 0, utype(AUIPC, 0, 0)); // lpad 0
write32le(buf + 4, utype(AUIPC, X_T2, hi20(offset)));
write32le(buf + 8, rtype(SUB, X_T1, X_T1, X_T3));
write32le(buf + 12, itype(load, X_T3, X_T2, lo12(offset)));
write32le(buf + 16, itype(ADDI, X_T1, X_T1, -ctx.target->pltHeaderSize - 16));
write32le(buf + 20, itype(ADDI, X_T0, X_T2, lo12(offset)));
write32le(buf + 24, itype(SRLI, X_T1, X_T1, ctx.arg.is64 ? 1 : 2));
write32le(buf + 28, itype(load, X_T0, X_T0, ctx.arg.wordsize));
write32le(buf + 32, itype(JALR, 0, X_T3, 0));
write32le(buf + 36, itype(ADDI, 0, 0, 0)); // nop
write32le(buf + 40, itype(ADDI, 0, 0, 0)); // nop
write32le(buf + 44, itype(ADDI, 0, 0, 0)); // nop
}

void RISCVCfiLpUnlabeledPLT::writePlt(uint8_t *buf, const Symbol &sym,
uint64_t pltEntryAddr) const {
// lpad 0
// 1: auipc t3, %pcrel_hi(f@.got.plt)
// l[wd] t3, %pcrel_lo(1b)(t3)
// jalr t1, t3
const uint32_t offset =
sym.getGotPltVA(ctx) - (pltEntryAddr + 4 /* offset for lpad */);
write32le(buf + 0, utype(AUIPC, 0, 0)); // lpad 0
write32le(buf + 4, utype(AUIPC, X_T3, hi20(offset)));
write32le(buf + 8, itype(ctx.arg.is64 ? LD : LW, X_T3, X_T3, lo12(offset)));
write32le(buf + 12, itype(JALR, X_T1, X_T3, 0));
}

namespace {
// Representation of the merged .riscv.attributes input sections. The psABI
// specifies merge policy for attributes. E.g. if we link an object without an
Expand Down Expand Up @@ -1357,4 +1417,12 @@ void elf::mergeRISCVAttributesSections(Ctx &ctx) {
mergeAttributesSection(ctx, sections));
}

void elf::setRISCVTargetInfo(Ctx &ctx) { ctx.target.reset(new RISCV(ctx)); }
void elf::setRISCVTargetInfo(Ctx &ctx) {
RISCV *target;
if (ctx.arg.andFeatures & GNU_PROPERTY_RISCV_FEATURE_1_CFI_LP_UNLABELED)
target = new RISCVCfiLpUnlabeledPLT(ctx);
else
target = new RISCV(ctx);

ctx.target.reset(target);
}
135 changes: 135 additions & 0 deletions lld/test/ELF/riscv-plt-cfi-lp-unlabeled.s
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Original file line number Diff line number Diff line change
@@ -0,0 +1,135 @@
# REQUIRES: riscv
# RUN: rm -rf %t && split-file %s %t && cd %t

# RUN: llvm-mc -filetype=obj -triple=riscv32 rv32-foo.s -o foo32.o
# RUN: ld.lld -shared foo32.o -soname=libfoo32.so -z zicfilp-unlabeled-report=error --fatal-warnings -o libfoo32.so
# RUN: llvm-mc -filetype=obj -triple=riscv32 rv32-start.s -o start32.o
# RUN: ld.lld start32.o libfoo32.so -z zicfilp-unlabeled-report=error --fatal-warnings -o out32
# RUN: llvm-readelf -S out32 | FileCheck --check-prefix=SEC32 %s
# RUN: llvm-objdump -d --no-show-raw-insn --mattr=+experimental-zicfilp out32 | FileCheck --check-prefixes=DIS,DIS32 %s

# RUN: llvm-mc -filetype=obj -triple=riscv64 rv64-foo.s -o foo64.o
# RUN: ld.lld -shared foo64.o -soname=libfoo64.so -z zicfilp-unlabeled-report=error --fatal-warnings -o libfoo64.so
# RUN: llvm-mc -filetype=obj -triple=riscv64 rv64-start.s -o start64.o
# RUN: ld.lld start64.o libfoo64.so -z zicfilp-unlabeled-report=error --fatal-warnings -o out64
# RUN: llvm-readelf -S out64 | FileCheck --check-prefix=SEC64 %s
# RUN: llvm-objdump -d --no-show-raw-insn --mattr=+experimental-zicfilp out64 | FileCheck --check-prefixes=DIS,DIS64 %s

# SEC32: .plt PROGBITS {{0*}}00011210
# SEC32: .got.plt PROGBITS {{0*}}000132b8

# SEC64: .plt PROGBITS {{0*}}00011330
# SEC64: .got.plt PROGBITS {{0*}}00013440

# DIS: Disassembly of section .plt:
# DIS: <.plt>:
# DIS-NEXT: lpad 0x0
# DIS-NEXT: auipc t2, 0x2
# DIS-NEXT: sub t1, t1, t3
# DIS32-NEXT: lw t3, 0xa4(t2)
# DIS64-NEXT: ld t3, 0x10c(t2)
# DIS-NEXT: addi t1, t1, -0x40
# DIS32-NEXT: addi t0, t2, 0xa4
# DIS64-NEXT: addi t0, t2, 0x10c
# DIS32-NEXT: srli t1, t1, 0x2
# DIS64-NEXT: srli t1, t1, 0x1
# DIS32-NEXT: lw t0, 0x4(t0)
# DIS64-NEXT: ld t0, 0x8(t0)
# DIS-NEXT: jr t3
# DIS-NEXT: nop
# DIS-NEXT: nop
# DIS-NEXT: nop

# DIS: lpad 0x0
# DIS-NEXT: auipc t3, 0x2
# DIS32-NEXT: lw t3, 0x7c(t3)
# DIS64-NEXT: ld t3, 0xec(t3)
# DIS-NEXT: jalr t1, t3

#--- rv32-start.s

.section ".note.gnu.property", "a"
.balign 4
.4byte 4
.4byte (ndesc_end - ndesc_begin)
.4byte 0x5 // NT_GNU_PROPERTY_TYPE_0
.asciz "GNU"
ndesc_begin:
.balign 4
.4byte 0xc0000000 // GNU_PROPERTY_RISCV_FEATURE_1_AND
.4byte 4
.4byte 1 // GNU_PROPERTY_RISCV_FEATURE_1_CFI_LP_UNLABELED
.balign 4
ndesc_end:

.text
.global _start, foo

_start:
call foo@plt

#--- rv32-foo.s

.section ".note.gnu.property", "a"
.balign 4
.4byte 4
.4byte (ndesc_end - ndesc_begin)
.4byte 0x5 // NT_GNU_PROPERTY_TYPE_0
.asciz "GNU"
ndesc_begin:
.balign 4
.4byte 0xc0000000 // GNU_PROPERTY_RISCV_FEATURE_1_AND
.4byte 4
.4byte 1 // GNU_PROPERTY_RISCV_FEATURE_1_CFI_LP_UNLABELED
.balign 4
ndesc_end:

.text
.global foo
.type foo, @function
foo:
ret

#--- rv64-start.s

.section ".note.gnu.property", "a"
.balign 8
.4byte 4
.4byte (ndesc_end - ndesc_begin)
.4byte 0x5 // NT_GNU_PROPERTY_TYPE_0
.asciz "GNU"
ndesc_begin:
.balign 8
.4byte 0xc0000000 // GNU_PROPERTY_RISCV_FEATURE_1_AND
.4byte 4
.4byte 1 // GNU_PROPERTY_RISCV_FEATURE_1_CFI_LP_UNLABELED
.balign 8
ndesc_end:

.text
.global _start, foo

_start:
call foo@plt

#--- rv64-foo.s

.section ".note.gnu.property", "a"
.balign 8
.4byte 4
.4byte (ndesc_end - ndesc_begin)
.4byte 0x5 // NT_GNU_PROPERTY_TYPE_0
.asciz "GNU"
ndesc_begin:
.balign 8
.4byte 0xc0000000 // GNU_PROPERTY_RISCV_FEATURE_1_AND
.4byte 4
.4byte 1 // GNU_PROPERTY_RISCV_FEATURE_1_CFI_LP_UNLABELED
.balign 8
ndesc_end:

.text
.global foo
.type foo, @function
foo:
ret
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