[PATCH] D90520: [ELF] --emit-relocs: fix st_value of STT_SECTION in the presence of a gap before the first input section
Fangrui Song via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Nov 2 08:37:29 PST 2020
This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG2fc704a0a529: [ELF] --emit-relocs: fix st_value of STT_SECTION in the presence of a gap… (authored by MaskRay).
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D90520/new/
https://reviews.llvm.org/D90520
Files:
lld/ELF/SyntheticSections.cpp
lld/ELF/Writer.cpp
lld/test/ELF/section-symbol-gap.s
Index: lld/test/ELF/section-symbol-gap.s
===================================================================
--- /dev/null
+++ lld/test/ELF/section-symbol-gap.s
@@ -0,0 +1,51 @@
+# REQUIRES: x86
+## Test st_value of the STT_SECTION symbol equals the output section address,
+## instead of the first input section address.
+
+# RUN: split-file %s %t
+# RUN: llvm-mc -filetype=obj -triple=x86_64 %t/asm -o %t.o
+
+# RUN: ld.lld --emit-relocs -T %t/lds %t.o -o %t.out
+# RUN: llvm-readelf -S -r -s %t.out | FileCheck %s --check-prefix=EXE
+
+## In -r mode, section addresses are zeros, hence the st_value fields of
+## STT_SECTION are zeros.
+# RUN: ld.lld -r -T %t/lds %t.o -o %t.ro
+# RUN: llvm-readelf -S -r -s %t.ro | FileCheck %s --check-prefix=RO
+
+# EXE: [Nr] Name Type Address
+# EXE-NEXT: [ 0]
+# EXE-NEXT: [ 1] .text PROGBITS 0000000000000000
+# EXE-NEXT: [ 2] .bss NOBITS 000000000000000a
+
+# EXE: R_X86_64_64 {{.*}} .bss + 1
+
+# EXE: Symbol table '.symtab' contains 4 entries:
+# EXE-NEXT: Num: Value Size Type Bind Vis Ndx Name
+# EXE-NEXT: 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
+# EXE-NEXT: 1: 000000000000000a 0 SECTION LOCAL DEFAULT 2 .bss
+# EXE-NEXT: 2: 0000000000000000 0 SECTION LOCAL DEFAULT 1 .text
+# EXE-NEXT: 3: 0000000000000000 0 SECTION LOCAL DEFAULT 4 .comment
+
+# RO: [Nr] Name Type Address
+# RO-NEXT: [ 0]
+# RO-NEXT: [ 1] .bss NOBITS 0000000000000000
+
+# RO: R_X86_64_64 {{.*}} .bss + 1
+
+# RO: Symbol table '.symtab' contains 3 entries:
+# RO-NEXT: Num: Value Size Type Bind Vis Ndx Name
+# RO-NEXT: 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND
+# RO-NEXT: 1: 0000000000000000 0 SECTION LOCAL DEFAULT 1 .bss
+# RO-NEXT: 2: 0000000000000000 0 SECTION LOCAL DEFAULT 2 .text
+
+#--- asm
+movabsq .bss, %rax
+
+.bss
+.byte 0
+
+#--- lds
+SECTIONS {
+ .bss : { BYTE(0) *(.bss) }
+}
Index: lld/ELF/Writer.cpp
===================================================================
--- lld/ELF/Writer.cpp
+++ lld/ELF/Writer.cpp
@@ -811,9 +811,12 @@
if (isa<SyntheticSection>(isec) && !(isec->flags & SHF_MERGE))
continue;
+ // Set the symbol to be relative to the output section so that its st_value
+ // equals the output section address. Note, there may be a gap between the
+ // start of the output section and isec.
auto *sym =
make<Defined>(isec->file, "", STB_LOCAL, /*stOther=*/0, STT_SECTION,
- /*value=*/0, /*size=*/0, isec);
+ /*value=*/0, /*size=*/0, isec->getOutputSection());
in.symTab->addSymbol(sym);
}
}
Index: lld/ELF/SyntheticSections.cpp
===================================================================
--- lld/ELF/SyntheticSections.cpp
+++ lld/ELF/SyntheticSections.cpp
@@ -2198,9 +2198,8 @@
else
eSym->st_size = sym->getSize();
- // st_value is usually an address of a symbol, but that has a
- // special meaning for uninstantiated common symbols (this can
- // occur if -r is given).
+ // st_value is usually an address of a symbol, but that has a special
+ // meaning for uninstantiated common symbols (--no-define-common).
if (BssSection *commonSec = getCommonSec(ent.sym))
eSym->st_value = commonSec->alignment;
else if (isDefinedHere)
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