[lld] bf45624 - [ELF][PPC32] Support .got2 in an output section description
Fangrui Song via llvm-commits
llvm-commits at lists.llvm.org
Thu Dec 23 11:32:49 PST 2021
Author: Fangrui Song
Date: 2021-12-23T11:32:44-08:00
New Revision: bf45624ba07f8bd65f38db872c89d8c0e4ffd5fe
URL: https://github.com/llvm/llvm-project/commit/bf45624ba07f8bd65f38db872c89d8c0e4ffd5fe
DIFF: https://github.com/llvm/llvm-project/commit/bf45624ba07f8bd65f38db872c89d8c0e4ffd5fe.diff
LOG: [ELF][PPC32] Support .got2 in an output section description
I added `PPC32Got2Section` D62464 to support .got2 but did not implement .got2
in another output section.
PR52799 has a linker script placing .got2 in .rodata, which causes a null
pointer dereference because a MergeSyntheticSection's file is nullptr.
Add the support.
Added:
lld/test/ELF/linkerscript/ppc32-got2.s
Modified:
lld/ELF/InputFiles.h
lld/ELF/InputSection.cpp
lld/ELF/SyntheticSections.cpp
lld/ELF/Thunks.cpp
lld/test/ELF/ppc32-relocatable-got2.s
Removed:
################################################################################
diff --git a/lld/ELF/InputFiles.h b/lld/ELF/InputFiles.h
index 1fee39371cca5..a031ef94c14da 100644
--- a/lld/ELF/InputFiles.h
+++ b/lld/ELF/InputFiles.h
@@ -41,6 +41,7 @@ namespace elf {
using llvm::object::Archive;
+class InputSection;
class Symbol;
// If --reproduce is specified, all input files are written to this tar archive.
@@ -114,13 +115,13 @@ class InputFile {
SmallVector<Symbol *, 0> symbols;
+ // .got2 in the current file. This is used by PPC32 -fPIC/-fPIE to compute
+ // offsets in PLT call stubs.
+ InputSection *ppc32Got2 = nullptr;
+
// Index of MIPS GOT built for this file.
uint32_t mipsGotIndex = -1;
- // outSecOff of .got2 in the current file. This is used by PPC32 -fPIC/-fPIE
- // to compute offsets in PLT call stubs.
- uint32_t ppc32Got2OutSecOff = 0;
-
// groupId is used for --warn-backrefs which is an optional error
// checking feature. All files within the same --{start,end}-group or
// --{start,end}-lib get the same group ID. Otherwise, each file gets a new
diff --git a/lld/ELF/InputSection.cpp b/lld/ELF/InputSection.cpp
index 56a3510e41bb0..df8cc5f221a0b 100644
--- a/lld/ELF/InputSection.cpp
+++ b/lld/ELF/InputSection.cpp
@@ -474,13 +474,13 @@ void InputSection::copyRelocations(uint8_t *buf, ArrayRef<RelTy> rels) {
else if (config->relocatable && type != target->noneRel)
sec->relocations.push_back({R_ABS, type, rel.r_offset, addend, &sym});
} else if (config->emachine == EM_PPC && type == R_PPC_PLTREL24 &&
- p->r_addend >= 0x8000) {
+ p->r_addend >= 0x8000 && sec->file->ppc32Got2) {
// Similar to R_MIPS_GPREL{16,32}. If the addend of R_PPC_PLTREL24
// indicates that r30 is relative to the input section .got2
// (r_addend>=0x8000), after linking, r30 should be relative to the output
// section .got2 . To compensate for the shift, adjust r_addend by
- // ppc32Got2OutSecOff.
- p->r_addend += sec->file->ppc32Got2OutSecOff;
+ // ppc32Got->outSecOff.
+ p->r_addend += sec->file->ppc32Got2->outSecOff;
}
}
}
diff --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp
index 9bf6118ebc3fd..872dd0e612afc 100644
--- a/lld/ELF/SyntheticSections.cpp
+++ b/lld/ELF/SyntheticSections.cpp
@@ -3620,14 +3620,12 @@ void PPC32Got2Section::finalizeContents() {
// .got2 . This function computes outSecOff of each .got2 to be used in
// PPC32PltCallStub::writeTo(). The purpose of this empty synthetic section is
// to collect input sections named ".got2".
- uint32_t offset = 0;
for (SectionCommand *cmd : getParent()->commands)
if (auto *isd = dyn_cast<InputSectionDescription>(cmd)) {
for (InputSection *isec : isd->sections) {
- if (isec == this)
- continue;
- isec->file->ppc32Got2OutSecOff = offset;
- offset += (uint32_t)isec->getSize();
+ // isec->file may be nullptr for MergeSyntheticSection.
+ if (isec != this && isec->file)
+ isec->file->ppc32Got2 = isec;
}
}
}
diff --git a/lld/ELF/Thunks.cpp b/lld/ELF/Thunks.cpp
index 85a0a67d613ca..38de4db191f45 100644
--- a/lld/ELF/Thunks.cpp
+++ b/lld/ELF/Thunks.cpp
@@ -806,8 +806,9 @@ void elf::writePPC32PltCallStub(uint8_t *buf, uint64_t gotPltVA,
// The stub loads an address relative to r30 (.got2+Addend). Addend is
// almost always 0x8000. The address of .got2 is
diff erent in another object
// file, so a stub cannot be shared.
- offset = gotPltVA - (in.ppc32Got2->getParent()->getVA() +
- file->ppc32Got2OutSecOff + addend);
+ offset = gotPltVA -
+ (in.ppc32Got2->getParent()->getVA() +
+ (file->ppc32Got2 ? file->ppc32Got2->outSecOff : 0) + addend);
} else {
// The stub loads an address relative to _GLOBAL_OFFSET_TABLE_ (which is
// currently the address of .got).
diff --git a/lld/test/ELF/linkerscript/ppc32-got2.s b/lld/test/ELF/linkerscript/ppc32-got2.s
new file mode 100644
index 0000000000000..1e232fa2c3c45
--- /dev/null
+++ b/lld/test/ELF/linkerscript/ppc32-got2.s
@@ -0,0 +1,59 @@
+# REQUIRES: ppc
+## Test .got2 placed in a
diff erent output section.
+
+# RUN: rm -rf %t && split-file %s %t
+# RUN: llvm-mc -filetype=obj -triple=powerpc %t/a.s -o %t/a.o
+# RUN: llvm-mc -filetype=obj -triple=powerpc %t/b.s -o %t/b.o
+# RUN: ld.lld -shared -T %t/t %t/a.o %t/b.o -o %t/a.so
+# RUN: llvm-readobj -r %t/a.so | FileCheck --check-prefix=RELOC %s
+# RUN: llvm-readelf -S %t/a.so | FileCheck --check-prefix=SEC %s
+
+# RELOC: .rela.plt {
+# RELOC-NEXT: 0x1A4 R_PPC_JMP_SLOT f 0x0
+# RELOC-NEXT: }
+
+# SEC: .got PROGBITS 0000018c
+# SEC-NEXT: .rodata PROGBITS 00000198
+
+## .got2+0x8000-0xb0 = .rodata+4+0x8000-0xb0 = 0x198+4+0x8000-0xb0 = 65536*1-32532
+# CHECK: <_start>:
+# CHECK-NEXT: bcl 20, 31, 0x
+# CHECK-NEXT: b0: mflr 30
+# CHECK-NEXT: addis 30, 30, 1
+# CHECK-NEXT: addi 30, 30, -32532
+# CHECK-NEXT: bl {{.*}} <00008000.got2.plt_pic32.f>
+
+## &.got[2] - (.got2+0x8000) = &.got[2] - (.rodata+4+0x8000) = 0x1A4 - (0x198+4+0x8000) = -32760
+# CHECK: <00008000.got2.plt_pic32.f>:
+# CHECK-NEXT: lwz 11, -32760(30)
+# CHECK-NEXT: mtctr 11
+# CHECK-NEXT: bctr
+# CHECK-NEXT: nop
+
+#--- a.s
+.section .rodata.cst4,"aM", at progbits,4
+.long 1
+
+.section .got2,"aw"
+.long f
+
+.text
+.globl _start, f, g
+_start:
+ bcl 20,31,.L
+.L:
+ mflr 30
+ addis 30, 30, .got2+0x8000-.L at ha
+ addi 30, 30, .got2+0x8000-.L at l
+ bl f+0x8000 at plt
+
+#--- b.s
+.section .got2,"aw"
+.globl f
+f:
+ bl f+0x8000 at plt
+
+#--- t
+SECTIONS {
+ .rodata : { *(.rodata .rodata.*) *(.got2) }
+}
diff --git a/lld/test/ELF/ppc32-relocatable-got2.s b/lld/test/ELF/ppc32-relocatable-got2.s
index 06ccb39b6a4aa..85a0764ffe5af 100644
--- a/lld/test/ELF/ppc32-relocatable-got2.s
+++ b/lld/test/ELF/ppc32-relocatable-got2.s
@@ -3,10 +3,11 @@
## If r_addend indicates .got2, adjust it by the local .got2's output section offset.
# RUN: llvm-mc -filetype=obj -triple=powerpc %s -o %t.o
-# RUN: ld.lld -r %t.o %t.o -o %t
+# RUN: echo 'bl f+0x8000 at plt' | llvm-mc -filetype=obj -triple=powerpc - -o %t2.o
+# RUN: ld.lld -r %t.o %t.o %t2.o -o %t
# RUN: llvm-readobj -r %t | FileCheck %s
-# RUN: ld.lld -shared --emit-relocs %t.o %t.o -o %t.so
+# RUN: ld.lld -shared --emit-relocs %t.o %t.o %t2.o -o %t.so
# RUN: llvm-readobj -r %t.so | FileCheck %s
# CHECK: .rela.adjust {
@@ -23,6 +24,11 @@
# CHECK-NEXT: R_PPC_PLTREL24 foo 0x0
# CHECK-NEXT: R_PPC_PLTREL24 foo 0x0
# CHECK-NEXT: }
+## %t2.o has an invalid relocation with r_addend=0x8000. Test we don't crash.
+## The addend doesn't matter.
+# CHECK-NEXT: .rela.text {
+# CHECK-NEXT: R_PPC_PLTREL24 f 0x8000
+# CHECK-NEXT: }
.section .got2,"aw"
.long 0
More information about the llvm-commits
mailing list