[lld] 8dbea47 - [PowerPC] Support for R_PPC64_REL24_NOTOC calls where the caller has no TOC and the callee is not DSO local
Victor Huang via llvm-commits
llvm-commits at lists.llvm.org
Wed Jul 29 12:50:58 PDT 2020
Author: Victor Huang
Date: 2020-07-29T19:49:28Z
New Revision: 8dbea4785c107aa975b6671025a3cea7829b8370
URL: https://github.com/llvm/llvm-project/commit/8dbea4785c107aa975b6671025a3cea7829b8370
DIFF: https://github.com/llvm/llvm-project/commit/8dbea4785c107aa975b6671025a3cea7829b8370.diff
LOG: [PowerPC] Support for R_PPC64_REL24_NOTOC calls where the caller has no TOC and the callee is not DSO local
This patch supports the situation where caller does not have a valid TOC and
calls using the R_PPC64_REL24_NOTOC relocation and the callee is not DSO local.
In this case the call cannot be made directly since the callee may or may not
require a valid TOC pointer. As a result this situation require a PC-relative
plt stub to set up r12.
Reviewed By: sfertile, MaskRay, stefanp
Differential Revision: https://reviews.llvm.org/D83669
Added:
lld/test/ELF/ppc64-pcrel-call-to-extern.s
Modified:
lld/ELF/Arch/PPC64.cpp
lld/ELF/Thunks.cpp
llvm/include/llvm/Object/ELF.h
Removed:
################################################################################
diff --git a/lld/ELF/Arch/PPC64.cpp b/lld/ELF/Arch/PPC64.cpp
index da0b510d96a1..c1ad72eaa2c9 100644
--- a/lld/ELF/Arch/PPC64.cpp
+++ b/lld/ELF/Arch/PPC64.cpp
@@ -1035,11 +1035,6 @@ bool PPC64::needsThunk(RelExpr expr, RelType type, const InputFile *file,
type != R_PPC64_REL24_NOTOC)
return false;
- // FIXME: Remove the fatal error once the call protocol is implemented.
- if (type == R_PPC64_REL24_NOTOC && s.isInPlt())
- fatal("unimplemented feature: external function call with the reltype"
- " R_PPC64_REL24_NOTOC");
-
// If a function is in the Plt it needs to be called with a call-stub.
if (s.isInPlt())
return true;
diff --git a/lld/ELF/Thunks.cpp b/lld/ELF/Thunks.cpp
index 091a291b26cd..cbdb286557f8 100644
--- a/lld/ELF/Thunks.cpp
+++ b/lld/ELF/Thunks.cpp
@@ -305,6 +305,21 @@ class PPC64R12SetupStub final : public Thunk {
void addSymbols(ThunkSection &isec) override;
};
+// PPC64 PC-relative PLT Stub
+// When a caller that does not maintain a toc-pointer performs an extern call
+// then this stub is needed for:
+// 1) Loading the target functions address from the procedure linkage table into
+// r12 for use by the target functions global entry point, and into the count
+// register with pc-relative instructions.
+// 2) Transferring control to the target function through an indirect branch.
+class PPC64PCRelPLTStub final : public Thunk {
+public:
+ PPC64PCRelPLTStub(Symbol &dest) : Thunk(dest, 0) {}
+ uint32_t size() override { return 16; }
+ void writeTo(uint8_t *buf) override;
+ void addSymbols(ThunkSection &isec) override;
+};
+
// A bl instruction uses a signed 24 bit offset, with an implicit 4 byte
// alignment. This gives a possible 26 bits of 'reach'. If the call offset is
// larger then that we need to emit a long-branch thunk. The target address
@@ -880,6 +895,23 @@ void PPC64R12SetupStub::addSymbols(ThunkSection &isec) {
isec);
}
+void PPC64PCRelPLTStub::writeTo(uint8_t *buf) {
+ int64_t offset = destination.getGotPltVA() - getThunkTargetSym()->getVA();
+ if (!isInt<34>(offset))
+ fatal("offset must fit in 34 bits to encode in the instruction");
+ uint64_t pld =
+ PLD_R12_NO_DISP | (((offset >> 16) & 0x3ffff) << 32) | (offset & 0xffff);
+
+ writePrefixedInstruction(buf + 0, pld); // pld r12, func at plt@pcrel
+ write32(buf + 8, MTCTR_R12); // mtctr r12
+ write32(buf + 12, BCTR); // bctr
+}
+
+void PPC64PCRelPLTStub::addSymbols(ThunkSection &isec) {
+ addSymbol(saver.save("__plt_pcrel_" + destination.getName()), STT_FUNC, 0,
+ isec);
+}
+
void PPC64LongBranchThunk::writeTo(uint8_t *buf) {
int64_t offset = in.ppc64LongBranchTarget->getEntryVA(&destination, addend) -
getPPC64TocBase();
@@ -1007,7 +1039,8 @@ static Thunk *addThunkPPC64(RelType type, Symbol &s, int64_t a) {
type == R_PPC64_REL24_NOTOC) &&
"unexpected relocation type for thunk");
if (s.isInPlt())
- return make<PPC64PltCallStub>(s);
+ return type == R_PPC64_REL24_NOTOC ? (Thunk *)make<PPC64PCRelPLTStub>(s)
+ : (Thunk *)make<PPC64PltCallStub>(s);
// This check looks at the st_other bits of the callee. If the value is 1
// then the callee clobbers the TOC and we need an R2 save stub.
diff --git a/lld/test/ELF/ppc64-pcrel-call-to-extern.s b/lld/test/ELF/ppc64-pcrel-call-to-extern.s
new file mode 100644
index 000000000000..ab2eaf09a6ac
--- /dev/null
+++ b/lld/test/ELF/ppc64-pcrel-call-to-extern.s
@@ -0,0 +1,131 @@
+# REQUIRES: ppc
+# RUN: echo 'SECTIONS { \
+# RUN: .text_caller1 0x10010000 : { *(.text_caller1) } \
+# RUN: .text_caller2 0x10020000 : { *(.text_caller2) } \
+# RUN: .text_caller3 0x10030000 : { *(.text_caller3) } \
+# RUN: }' > %t.script
+
+# RUN: llvm-mc -filetype=obj -triple=powerpc64le --defsym AUX=1 %s -o %t1.o
+# RUN: llvm-mc -filetype=obj -triple=powerpc64le %s -o %t2.o
+# RUN: ld.lld --shared %t2.o -o %t2.so
+# RUN: ld.lld -T %t.script %t1.o %t2.so -o %t
+# RUN: llvm-readelf -s %t | FileCheck %s --check-prefix=SYMBOL
+# RUN: llvm-readelf -S -d %t | FileCheck %s --check-prefix=SEC
+# RUN: llvm-readobj -r %t | FileCheck %s --check-prefix=REL
+# RUN: llvm-objdump -d --no-show-raw-insn --mcpu=pwr10 %t | FileCheck %s
+
+# RUN: llvm-mc -filetype=obj -triple=powerpc64 --defsym AUX=1 %s -o %t1.o
+# RUN: llvm-mc -filetype=obj -triple=powerpc64 %s -o %t2.o
+# RUN: ld.lld --shared %t2.o -o %t2.so
+# RUN: ld.lld -T %t.script %t1.o %t2.so -o %t
+# RUN: llvm-readelf -s %t | FileCheck %s --check-prefix=SYMBOL
+# RUN: llvm-readelf -S -d %t | FileCheck %s --check-prefix=SEC
+# RUN: llvm-readobj -r %t | FileCheck %s --check-prefix=REL
+# RUN: llvm-objdump -d --no-show-raw-insn --mcpu=pwr10 %t | FileCheck %s
+
+## The test is created to check that when a function without TOC access an
+## external function, a r12 setup stub is inserted.
+
+# SYMBOL: Symbol table '.dynsym' contains 4 entries:
+# SYMBOL: 1: 0000000000000000 0 NOTYPE GLOBAL DEFAULT [<other: 0x60>] UND callee_global_TOC
+# SYMBOL-NEXT: 2: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND callee_global_stother0
+# SYMBOL-NEXT: 3: 0000000000000000 0 NOTYPE GLOBAL DEFAULT [<other: 0x20>] UND callee_global_stother1
+
+# SYMBOL: Symbol table '.symtab' contains 12 entries:
+# SYMBOL: 2: 0000000010010000 0 NOTYPE LOCAL DEFAULT [<other: 0x20>] 6 caller1
+# SYMBOL-NEXT: 3: 0000000010020000 0 NOTYPE LOCAL DEFAULT [<other: 0x20>] 7 caller2
+# SYMBOL-NEXT: 4: 0000000010030000 0 NOTYPE LOCAL DEFAULT [<other: 0x20>] 8 caller3
+# SYMBOL: 6: 0000000010010008 16 FUNC LOCAL DEFAULT 6 __plt_pcrel_callee_global_stother0
+# SYMBOL-NEXT: 7: 0000000010020008 16 FUNC LOCAL DEFAULT 7 __plt_pcrel_callee_global_stother1
+# SYMBOL-NEXT: 8: 0000000010030008 16 FUNC LOCAL DEFAULT 8 __plt_pcrel_callee_global_TOC
+# SYMBOL-NEXT: 9: 0000000000000000 0 NOTYPE GLOBAL DEFAULT [<other: 0x60>] UND callee_global_TOC
+# SYMBOL-NEXT: 10: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND callee_global_stother0
+# SYMBOL-NEXT: 11: 0000000000000000 0 NOTYPE GLOBAL DEFAULT [<other: 0x20>] UND callee_global_stother1
+
+## DT_PLTGOT points to .plt
+# SEC: .plt NOBITS 0000000010030140 040140 000028 00 WA 0 0 8
+# SEC: 0x0000000000000003 (PLTGOT) 0x10030140
+
+## The first 2 entries in the .plt are reserved for the dynamic linkers
+## usage. The JMP_SLOT relocations are stored at .plt[2], .plt[3], .plt[4].
+## Check that we emit 3 R_PPC64_JMP_SLOT in .rela.plt.
+# REL: .rela.plt {
+# REL-NEXT: 0x10030150 R_PPC64_JMP_SLOT callee_global_stother0 0x0
+# REL-NEXT: 0x10030158 R_PPC64_JMP_SLOT callee_global_stother1 0x0
+# REL-NEXT: 0x10030160 R_PPC64_JMP_SLOT callee_global_TOC 0x0
+# REL-NEXT: }
+
+# CHECK-LABEL: <caller1>:
+# CHECK: 10010000: bl 0x10010008
+# CHECK-NEXT: 10010004: blr
+
+## .plt[2] - 0x10010008 = 0x10030150 - 0x10010008 = 0x20148 = 131400
+# CHECK-LABEL: <__plt_pcrel_callee_global_stother0>:
+# CHECK: 10010008: pld 12, 131400(0), 1
+# CHECK-NEXT: 10010010: mtctr 12
+# CHECK-NEXT: 10010014: bctr
+
+# CHECK-LABEL: <caller2>:
+# CHECK: 10020000: bl 0x10020008
+# CHECK-NEXT: 10020004: blr
+
+## .plt[3] - 0x10020008 = 0x10030158 - 0x10020008 = 0x10150 = 65872
+# CHECK-LABEL: <__plt_pcrel_callee_global_stother1>:
+# CHECK: 10020008: pld 12, 65872(0), 1
+# CHECK-NEXT: 10020010: mtctr 12
+# CHECK-NEXT: 10020014: bctr
+
+# CHECK-LABEL: <caller3>:
+# CHECK: 10030000: bl 0x10030008
+# CHECK-NEXT: 10030004: blr
+
+## .plt[4] - 0x10030008 = 0x10030160 - 0x10030008 = 0x158 = 344
+# CHECK-LABEL: <__plt_pcrel_callee_global_TOC>:
+# CHECK: 10030008: pld 12, 344(0), 1
+# CHECK-NEXT: 10030010: mtctr 12
+# CHECK-NEXT: 10030014: bctr
+
+.ifdef AUX
+.section .text_caller1, "ax", %progbits
+caller1:
+ .localentry caller1, 1
+ bl callee_global_stother0 at notoc
+ blr
+.section .text_caller2, "ax", %progbits
+caller2:
+ .localentry caller2, 1
+ bl callee_global_stother1 at notoc
+ blr
+
+.section .text_caller3, "ax", %progbits
+caller3:
+ .localentry caller3, 1
+ bl callee_global_TOC at notoc
+ blr
+
+.else
+func_extern:
+ blr
+.globl callee_global_stother0
+callee_global_stother0:
+ blr
+.globl callee_global_stother1
+callee_global_stother1:
+ .localentry callee_global_stother1, 1
+ ## nop is not needed after bl for R_PPC64_REL24_NOTOC
+ bl func_extern at notoc
+ blr
+.globl callee_global_TOC
+callee_global_TOC:
+.Lfunc_gep1:
+ addis 2, 12, .TOC.-.Lfunc_gep1 at ha
+ addi 2, 2, .TOC.-.Lfunc_gep1 at l
+.Lfunc_lep1:
+ .localentry callee_global_TOC, .Lfunc_lep1-.Lfunc_gep1
+ addis 4, 2, global at toc@ha
+ lwz 3, global at toc@l(4)
+ blr
+global:
+ .long 0
+ .size global, 4
+.endif
diff --git a/llvm/include/llvm/Object/ELF.h b/llvm/include/llvm/Object/ELF.h
index 3dab0471a239..0080d0ba58f3 100644
--- a/llvm/include/llvm/Object/ELF.h
+++ b/llvm/include/llvm/Object/ELF.h
@@ -50,6 +50,7 @@ static inline Error createError(const Twine &Err) {
enum PPCInstrMasks : uint64_t {
PADDI_R12_NO_DISP = 0x0610000039800000,
+ PLD_R12_NO_DISP = 0x04100000E5800000,
MTCTR_R12 = 0x7D8903A6,
BCTR = 0x4E800420,
};
More information about the llvm-commits
mailing list