Description of symbols is avalable here:
https://docs.oracle.com/cd/E53394_01/html/E54766/u-etext-3c.html
It is said that:
_etext - The address of _etext is the first
location after the last read-only loadable segment.
_edata - The address of _edata is the first
location after the last read-write loadable segment.
_end - If the address of _edata is greater than the address
of _etext, the address of _end is same as the address of _edata.
In real life _end and _edata has different values for that case.
Both gold/bfd set _edata to the end of the last non SHT_NOBITS section.
This patch do the same for consistency.
It should fix the https://llvm.org/bugs/show_bug.cgi?id=26729.
Differential revision: http://reviews.llvm.org/D17601
llvm-svn: 262019
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index b87291f..cbd7853 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -914,20 +914,30 @@
if (!isOutputDynamic())
Symtab.addIgnored("__tls_get_addr");
+ auto Define = [this](StringRef Name, StringRef Alias, Elf_Sym &Sym) {
+ if (Symtab.find(Name))
+ Symtab.addAbsolute(Name, Sym);
+ if (SymbolBody *B = Symtab.find(Alias))
+ if (B->isUndefined())
+ Symtab.addAbsolute(Alias, Sym);
+ };
+
// If the "_end" symbol is referenced, it is expected to point to the address
// right after the data segment. Usually, this symbol points to the end
// of .bss section or to the end of .data section if .bss section is absent.
// We don't know the final address of _end yet, so just add a symbol here,
// and fix ElfSym<ELFT>::End.st_value later.
- if (Symtab.find("_end"))
- Symtab.addAbsolute("_end", ElfSym<ELFT>::End);
-
// Define "end" as an alias to "_end" if it is used but not defined.
// We don't want to define that unconditionally because we don't want to
// break programs that uses "end" as a regular symbol.
- if (SymbolBody *B = Symtab.find("end"))
- if (B->isUndefined())
- Symtab.addAbsolute("end", ElfSym<ELFT>::End);
+ // The similar history with _etext/etext and _edata/edata:
+ // Address of _etext is the first location after the last read-only loadable
+ // segment. Address of _edata points to the end of the last non SHT_NOBITS
+ // section. That is how gold/bfd do. We update the values for these symbols
+ // later, after assigning sections to segments.
+ Define("_end", "end", ElfSym<ELFT>::End);
+ Define("_etext", "etext", ElfSym<ELFT>::Etext);
+ Define("_edata", "edata", ElfSym<ELFT>::Edata);
}
// Sort input sections by section name suffixes for
@@ -1454,6 +1464,17 @@
// Update MIPS _gp absolute symbol so that it points to the static data.
if (Config->EMachine == EM_MIPS)
ElfSym<ELFT>::MipsGp.st_value = getMipsGpAddr<ELFT>();
+
+ // _etext points to location after the last read-only loadable segment.
+ // _edata points to the end of the last non SHT_NOBITS section.
+ for (OutputSectionBase<ELFT> *Sec : OutputSections) {
+ if (!(Sec->getFlags() & SHF_ALLOC))
+ continue;
+ if (!(Sec->getFlags() & SHF_WRITE))
+ ElfSym<ELFT>::Etext.st_value = Sec->getVA() + Sec->getSize();
+ if (Sec->getType() != SHT_NOBITS)
+ ElfSym<ELFT>::Edata.st_value = Sec->getVA() + Sec->getSize();
+ }
}
template <class ELFT> void Writer<ELFT>::writeHeader() {