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-rw-r--r--lld/ELF/LinkerScript.cpp32
-rw-r--r--lld/ELF/OutputSections.cpp83
-rw-r--r--lld/ELF/OutputSections.h1
-rw-r--r--lld/test/ELF/incompatible-section-flags.s18
-rw-r--r--lld/test/ELF/incompatible-section-types.s10
-rw-r--r--lld/test/ELF/linkerscript/phdrs.s2
-rw-r--r--lld/test/ELF/linkerscript/sections.s40
-rw-r--r--lld/test/ELF/section-name.s15
-rw-r--r--lld/test/ELF/string-table.s18
9 files changed, 124 insertions, 95 deletions
diff --git a/lld/ELF/LinkerScript.cpp b/lld/ELF/LinkerScript.cpp
index 5057b57a4a5..ccc1059949d 100644
--- a/lld/ELF/LinkerScript.cpp
+++ b/lld/ELF/LinkerScript.cpp
@@ -264,42 +264,12 @@ LinkerScript<ELFT>::createInputSectionList(OutputSectionCommand &OutCmd) {
}
template <class ELFT>
-static SectionKey<ELFT::Is64Bits> createKey(InputSectionBase<ELFT> *C,
- StringRef OutsecName) {
- // When using linker script the merge rules are different.
- // Unfortunately, linker scripts are name based. This means that expressions
- // like *(.foo*) can refer to multiple input sections that would normally be
- // placed in different output sections. We cannot put them in different
- // output sections or we would produce wrong results for
- // start = .; *(.foo.*) end = .; *(.bar)
- // and a mapping of .foo1 and .bar1 to one section and .foo2 and .bar2 to
- // another. The problem is that there is no way to layout those output
- // sections such that the .foo sections are the only thing between the
- // start and end symbols.
-
- // An extra annoyance is that we cannot simply disable merging of the contents
- // of SHF_MERGE sections, but our implementation requires one output section
- // per "kind" (string or not, which size/aligment).
- // Fortunately, creating symbols in the middle of a merge section is not
- // supported by bfd or gold, so we can just create multiple section in that
- // case.
- typedef typename ELFT::uint uintX_t;
- uintX_t Flags = C->Flags & (SHF_MERGE | SHF_STRINGS);
-
- uintX_t Alignment = 0;
- if (isa<MergeInputSection<ELFT>>(C))
- Alignment = std::max<uintX_t>(C->Alignment, C->Entsize);
-
- return SectionKey<ELFT::Is64Bits>{OutsecName, /*Type*/ 0, Flags, Alignment};
-}
-
-template <class ELFT>
void LinkerScript<ELFT>::addSection(OutputSectionFactory<ELFT> &Factory,
InputSectionBase<ELFT> *Sec,
StringRef Name) {
OutputSectionBase *OutSec;
bool IsNew;
- std::tie(OutSec, IsNew) = Factory.create(createKey(Sec, Name), Sec);
+ std::tie(OutSec, IsNew) = Factory.create(Sec, Name);
if (IsNew)
OutputSections->push_back(OutSec);
OutSec->addSection(Sec);
diff --git a/lld/ELF/OutputSections.cpp b/lld/ELF/OutputSections.cpp
index bf7f9c29a29..0ba602060dc 100644
--- a/lld/ELF/OutputSections.cpp
+++ b/lld/ELF/OutputSections.cpp
@@ -537,21 +537,68 @@ static typename ELFT::uint getOutFlags(InputSectionBase<ELFT> *S) {
template <class ELFT>
static SectionKey<ELFT::Is64Bits> createKey(InputSectionBase<ELFT> *C,
StringRef OutsecName) {
+ // The ELF spec just says
+ // ----------------------------------------------------------------
+ // In the first phase, input sections that match in name, type and
+ // attribute flags should be concatenated into single sections.
+ // ----------------------------------------------------------------
+ //
+ // However, it is clear that at least some flags have to be ignored for
+ // section merging. At the very least SHF_GROUP and SHF_COMPRESSED have to be
+ // ignored. We should not have two output .text sections just because one was
+ // in a group and another was not for example.
+ //
+ // It also seems that that wording was a late addition and didn't get the
+ // necessary scrutiny.
+ //
+ // Merging sections with different flags is expected by some users. One
+ // reason is that if one file has
+ //
+ // int *const bar __attribute__((section(".foo"))) = (int *)0;
+ //
+ // gcc with -fPIC will produce a read only .foo section. But if another
+ // file has
+ //
+ // int zed;
+ // int *const bar __attribute__((section(".foo"))) = (int *)&zed;
+ //
+ // gcc with -fPIC will produce a read write section.
+ //
+ // Last but not least, when using linker script the merge rules are forced by
+ // the script. Unfortunately, linker scripts are name based. This means that
+ // expressions like *(.foo*) can refer to multiple input sections with
+ // different flags. We cannot put them in different output sections or we
+ // would produce wrong results for
+ //
+ // start = .; *(.foo.*) end = .; *(.bar)
+ //
+ // and a mapping of .foo1 and .bar1 to one section and .foo2 and .bar2 to
+ // another. The problem is that there is no way to layout those output
+ // sections such that the .foo sections are the only thing between the start
+ // and end symbols.
+ //
+ // Given the above issues, we instead merge sections by name and error on
+ // incompatible types and flags.
+ //
+ // The exception being SHF_MERGE, where we create different output sections
+ // for each alignment. This makes each output section simple. In case of
+ // relocatable object generation we do not try to perform merging and treat
+ // SHF_MERGE sections as regular ones, but also create different output
+ // sections for them to allow merging at final linking stage.
+ //
+ // Fortunately, creating symbols in the middle of a merge section is not
+ // supported by bfd or gold, so the SHF_MERGE exception should not cause
+ // problems with most linker scripts.
+
typedef typename ELFT::uint uintX_t;
- uintX_t Flags = getOutFlags(C);
+ uintX_t Flags = C->Flags & (SHF_MERGE | SHF_STRINGS);
- // For SHF_MERGE we create different output sections for each alignment.
- // This makes each output section simple and keeps a single level mapping from
- // input to output.
- // In case of relocatable object generation we do not try to perform merging
- // and treat SHF_MERGE sections as regular ones, but also create different
- // output sections for them to allow merging at final linking stage.
uintX_t Alignment = 0;
if (isa<MergeInputSection<ELFT>>(C) ||
(Config->Relocatable && (C->Flags & SHF_MERGE)))
Alignment = std::max<uintX_t>(C->Alignment, C->Entsize);
- return SectionKey<ELFT::Is64Bits>{OutsecName, C->Type, Flags, Alignment};
+ return SectionKey<ELFT::Is64Bits>{OutsecName, Flags, Alignment};
}
template <class ELFT>
@@ -562,6 +609,10 @@ OutputSectionFactory<ELFT>::create(InputSectionBase<ELFT> *C,
return create(Key, C);
}
+static uint64_t getIncompatibleFlags(uint64_t Flags) {
+ return Flags & (SHF_ALLOC | SHF_TLS);
+}
+
template <class ELFT>
std::pair<OutputSectionBase *, bool>
OutputSectionFactory<ELFT>::create(const SectionKey<ELFT::Is64Bits> &Key,
@@ -569,6 +620,12 @@ OutputSectionFactory<ELFT>::create(const SectionKey<ELFT::Is64Bits> &Key,
uintX_t Flags = getOutFlags(C);
OutputSectionBase *&Sec = Map[Key];
if (Sec) {
+ if (getIncompatibleFlags(Sec->Flags) != getIncompatibleFlags(C->Flags))
+ error("Section has flags incompatible with others with the same name " +
+ toString(C));
+ if (Sec->Type != C->Type)
+ error("Section has different type from others with the same name " +
+ toString(C));
Sec->Flags |= Flags;
return {Sec, false};
}
@@ -591,28 +648,26 @@ OutputSectionFactory<ELFT>::create(const SectionKey<ELFT::Is64Bits> &Key,
template <bool Is64Bits>
typename lld::elf::SectionKey<Is64Bits>
DenseMapInfo<lld::elf::SectionKey<Is64Bits>>::getEmptyKey() {
- return SectionKey<Is64Bits>{DenseMapInfo<StringRef>::getEmptyKey(), 0, 0, 0};
+ return SectionKey<Is64Bits>{DenseMapInfo<StringRef>::getEmptyKey(), 0, 0};
}
template <bool Is64Bits>
typename lld::elf::SectionKey<Is64Bits>
DenseMapInfo<lld::elf::SectionKey<Is64Bits>>::getTombstoneKey() {
- return SectionKey<Is64Bits>{DenseMapInfo<StringRef>::getTombstoneKey(), 0, 0,
- 0};
+ return SectionKey<Is64Bits>{DenseMapInfo<StringRef>::getTombstoneKey(), 0, 0};
}
template <bool Is64Bits>
unsigned
DenseMapInfo<lld::elf::SectionKey<Is64Bits>>::getHashValue(const Key &Val) {
- return hash_combine(Val.Name, Val.Type, Val.Flags, Val.Alignment);
+ return hash_combine(Val.Name, Val.Flags, Val.Alignment);
}
template <bool Is64Bits>
bool DenseMapInfo<lld::elf::SectionKey<Is64Bits>>::isEqual(const Key &LHS,
const Key &RHS) {
return DenseMapInfo<StringRef>::isEqual(LHS.Name, RHS.Name) &&
- LHS.Type == RHS.Type && LHS.Flags == RHS.Flags &&
- LHS.Alignment == RHS.Alignment;
+ LHS.Flags == RHS.Flags && LHS.Alignment == RHS.Alignment;
}
namespace llvm {
diff --git a/lld/ELF/OutputSections.h b/lld/ELF/OutputSections.h
index 978b1f8191e..c603eacffeb 100644
--- a/lld/ELF/OutputSections.h
+++ b/lld/ELF/OutputSections.h
@@ -220,7 +220,6 @@ template <class ELFT> struct Out {
template <bool Is64Bits> struct SectionKey {
typedef typename std::conditional<Is64Bits, uint64_t, uint32_t>::type uintX_t;
StringRef Name;
- uint32_t Type;
uintX_t Flags;
uintX_t Alignment;
};
diff --git a/lld/test/ELF/incompatible-section-flags.s b/lld/test/ELF/incompatible-section-flags.s
new file mode 100644
index 00000000000..efca31bb9a8
--- /dev/null
+++ b/lld/test/ELF/incompatible-section-flags.s
@@ -0,0 +1,18 @@
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+// RUN: not ld.lld -shared %t.o -o %t 2>&1 | FileCheck %s
+
+// CHECK: error: Section has flags incompatible with others with the same name {{.*}}incompatible-section-flags.s.tmp.o:(.foo)
+// CHECK: error: Section has flags incompatible with others with the same name {{.*}}incompatible-section-flags.s.tmp.o:(.bar)
+
+.section .foo, "awT", @progbits, unique, 1
+.quad 0
+
+.section .foo, "aw", @progbits, unique, 2
+.quad 0
+
+
+.section .bar, "aw", @progbits, unique, 3
+.quad 0
+
+.section .bar, "awT", @progbits, unique, 4
+.quad 0
diff --git a/lld/test/ELF/incompatible-section-types.s b/lld/test/ELF/incompatible-section-types.s
new file mode 100644
index 00000000000..0d075aca068
--- /dev/null
+++ b/lld/test/ELF/incompatible-section-types.s
@@ -0,0 +1,10 @@
+// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+// RUN: not ld.lld -shared %t.o -o %t 2>&1 | FileCheck %s
+
+// CHECK: error: Section has different type from others with the same name {{.*}}incompatible-section-types.s.tmp.o:(.foo)
+
+.section .foo, "aw", @progbits, unique, 1
+.quad 0
+
+.section .foo, "aw", @nobits, unique, 2
+.quad 0
diff --git a/lld/test/ELF/linkerscript/phdrs.s b/lld/test/ELF/linkerscript/phdrs.s
index a7476e80234..025ced95b30 100644
--- a/lld/test/ELF/linkerscript/phdrs.s
+++ b/lld/test/ELF/linkerscript/phdrs.s
@@ -93,7 +93,7 @@
## Check the numetic values for PHDRS.
# RUN: echo "PHDRS {text PT_LOAD FILEHDR PHDRS; foo 0x11223344; } \
-# RUN: SECTIONS { . = SIZEOF_HEADERS; .foo : { *(.*) } : text : foo}" > %t1.script
+# RUN: SECTIONS { . = SIZEOF_HEADERS; .foo : { *(.foo* .text*) } : text : foo}" > %t1.script
# RUN: ld.lld -o %t2 --script %t1.script %t
# RUN: llvm-readobj -program-headers %t2 | FileCheck --check-prefix=INT-PHDRS %s
diff --git a/lld/test/ELF/linkerscript/sections.s b/lld/test/ELF/linkerscript/sections.s
index 416e77346a5..2cb9395e669 100644
--- a/lld/test/ELF/linkerscript/sections.s
+++ b/lld/test/ELF/linkerscript/sections.s
@@ -20,11 +20,10 @@
# SEC-DEFAULT: 2 .data 00000020 {{[0-9a-f]*}} DATA
# SEC-DEFAULT: 3 other 00000003 {{[0-9a-f]*}} DATA
# SEC-DEFAULT: 4 .bss 00000002 {{[0-9a-f]*}} BSS
-# SEC-DEFAULT: 5 .shstrtab 00000002 {{[0-9a-f]*}}
-# SEC-DEFAULT: 6 .comment 00000008 {{[0-9a-f]*}}
-# SEC-DEFAULT: 7 .symtab 00000030 {{[0-9a-f]*}}
-# SEC-DEFAULT: 8 .shstrtab 0000003b {{[0-9a-f]*}}
-# SEC-DEFAULT: 9 .strtab 00000008 {{[0-9a-f]*}}
+# SEC-DEFAULT: 5 .comment 00000008 {{[0-9a-f]*}}
+# SEC-DEFAULT: 6 .symtab 00000030 {{[0-9a-f]*}}
+# SEC-DEFAULT: 7 .shstrtab 0000003b {{[0-9a-f]*}}
+# SEC-DEFAULT: 8 .strtab 00000008 {{[0-9a-f]*}}
# Sections are put in order specified in linker script, other than alloc
# sections going first.
@@ -43,12 +42,11 @@
# Idx Name Size
# SEC-ORDER: 1 .bss 00000002 {{[0-9a-f]*}} BSS
# SEC-ORDER: 2 other 00000003 {{[0-9a-f]*}} DATA
-# SEC-ORDER: 3 .shstrtab 00000002 {{[0-9a-f]*}}
-# SEC-ORDER: 4 .shstrtab 0000003b {{[0-9a-f]*}}
-# SEC-ORDER: 5 .symtab 00000030 {{[0-9a-f]*}}
-# SEC-ORDER: 6 .strtab 00000008 {{[0-9a-f]*}}
-# SEC-ORDER: 7 .data 00000020 {{[0-9a-f]*}} DATA
-# SEC-ORDER: 8 .text 0000000e {{[0-9a-f]*}} TEXT DATA
+# SEC-ORDER: 3 .shstrtab 0000003b {{[0-9a-f]*}}
+# SEC-ORDER: 4 .symtab 00000030 {{[0-9a-f]*}}
+# SEC-ORDER: 5 .strtab 00000008 {{[0-9a-f]*}}
+# SEC-ORDER: 6 .data 00000020 {{[0-9a-f]*}} DATA
+# SEC-ORDER: 7 .text 0000000e {{[0-9a-f]*}} TEXT DATA
# .text and .data have swapped names but proper sizes and types.
# RUN: echo "SECTIONS { \
@@ -63,11 +61,10 @@
# SEC-SWAP-NAMES: 2 .text 00000020 {{[0-9a-f]*}} DATA
# SEC-SWAP-NAMES: 3 other 00000003 {{[0-9a-f]*}} DATA
# SEC-SWAP-NAMES: 4 .bss 00000002 {{[0-9a-f]*}} BSS
-# SEC-SWAP-NAMES: 5 .shstrtab 00000002 {{[0-9a-f]*}}
-# SEC-SWAP-NAMES: 6 .comment 00000008 {{[0-9a-f]*}}
-# SEC-SWAP-NAMES: 7 .symtab 00000030 {{[0-9a-f]*}}
-# SEC-SWAP-NAMES: 8 .shstrtab 0000003b {{[0-9a-f]*}}
-# SEC-SWAP-NAMES: 9 .strtab 00000008 {{[0-9a-f]*}}
+# SEC-SWAP-NAMES: 5 .comment 00000008 {{[0-9a-f]*}}
+# SEC-SWAP-NAMES: 6 .symtab 00000030 {{[0-9a-f]*}}
+# SEC-SWAP-NAMES: 7 .shstrtab 0000003b {{[0-9a-f]*}}
+# SEC-SWAP-NAMES: 8 .strtab 00000008 {{[0-9a-f]*}}
# .shstrtab from the input object file is discarded.
# RUN: echo "SECTIONS { \
@@ -102,11 +99,10 @@
# SEC-MULTI: 1 .text 0000000e {{[0-9a-f]*}} TEXT DATA
# SEC-MULTI: 2 .data 00000023 {{[0-9a-f]*}} DATA
# SEC-MULTI: 3 .bss 00000002 {{[0-9a-f]*}} BSS
-# SEC-MULTI: 4 .shstrtab 00000002 {{[0-9a-f]*}}
-# SEC-MULTI: 5 .comment 00000008 {{[0-9a-f]*}}
-# SEC-MULTI: 6 .symtab 00000030 {{[0-9a-f]*}}
-# SEC-MULTI: 7 .shstrtab 00000035 {{[0-9a-f]*}}
-# SEC-MULTI: 8 .strtab 00000008 {{[0-9a-f]*}}
+# SEC-MULTI: 4 .comment 00000008 {{[0-9a-f]*}}
+# SEC-MULTI: 5 .symtab 00000030 {{[0-9a-f]*}}
+# SEC-MULTI: 6 .shstrtab 00000035 {{[0-9a-f]*}}
+# SEC-MULTI: 7 .strtab 00000008 {{[0-9a-f]*}}
.globl _start
_start:
@@ -118,7 +114,5 @@ _start:
.section other,"aw"
.short 10
.byte 20
-.section .shstrtab,""
-.short 20
.section .bss,"",@nobits
.short 0
diff --git a/lld/test/ELF/section-name.s b/lld/test/ELF/section-name.s
index 53f0e536f3d..06d741b2ea7 100644
--- a/lld/test/ELF/section-name.s
+++ b/lld/test/ELF/section-name.s
@@ -19,9 +19,9 @@ _start:
.byte 0
.section .data,"aw"
.byte 0
-.section .bss.a,"",@nobits
+.section .bss.a,"aw",@nobits
.byte 0
-.section .bss,"",@nobits
+.section .bss,"aw",@nobits
.byte 0
.section .foo.a,"aw"
.byte 0
@@ -51,9 +51,8 @@ _start:
// CHECK: 7 .data 00000002
// CHECK: 8 .foo.a 00000001
// CHECK: 9 .foo 00000001
-// CHECK: 10 .bss 00000001
-// CHECK: 11 .bss 00000001
-// CHECK: 12 .comment 00000008
-// CHECK: 13 .symtab 00000060
-// CHECK: 14 .shstrtab 00000075
-// CHECK: 15 .strtab 0000001d
+// CHECK: 10 .bss 00000002
+// CHECK: 11 .comment 00000008
+// CHECK: 12 .symtab 00000060
+// CHECK: 13 .shstrtab 00000075
+// CHECK: 14 .strtab 0000001d
diff --git a/lld/test/ELF/string-table.s b/lld/test/ELF/string-table.s
index 92b8345976d..490c4d574cf 100644
--- a/lld/test/ELF/string-table.s
+++ b/lld/test/ELF/string-table.s
@@ -6,10 +6,7 @@
.global _start
_start:
-.section foobar,"",@progbits,unique,1
-.section foobar,"T",@progbits,unique,2
-.section foobar,"",@nobits,unique,3
-.section foobar,"",@nobits,unique,4
+.section foobar,"",@progbits
.section bar, "a"
@@ -27,17 +24,4 @@ _start:
// CHECK-NEXT: ]
// CHECK-NEXT: Address: 0x0
-// CHECK: Name: foobar
-// CHECK-NEXT: Type: SHT_PROGBITS
-// CHECK-NEXT: Flags [
-// CHECK-NEXT: SHF_TLS
-// CHECK-NEXT: ]
-// CHECK-NEXT: Address: 0x0
-
-// CHECK: Name: foobar
-// CHECK-NEXT: Type: SHT_NOBITS
-// CHECK-NEXT: Flags [
-// CHECK-NEXT: ]
-// CHECK-NEXT: Address: 0x0
-
// CHECK-NOT: Name: foobar
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