[lld] r260460 - ELF: Implement __attribute__((init_priority(N)) support.
Rui Ueyama via llvm-commits
llvm-commits at lists.llvm.org
Wed Feb 10 15:42:17 PST 2016
Are .[cd]tors still in use?
On Wed, Feb 10, 2016 at 3:38 PM, Sean Silva <chisophugis at gmail.com> wrote:
> Did you intend to add .[cd]tors support also? That was part of PR26538.
>
> -- Sean Silva
>
> On Wed, Feb 10, 2016 at 3:20 PM, Rui Ueyama via llvm-commits <
> llvm-commits at lists.llvm.org> wrote:
>
>> Author: ruiu
>> Date: Wed Feb 10 17:20:42 2016
>> New Revision: 260460
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=260460&view=rev
>> Log:
>> ELF: Implement __attribute__((init_priority(N)) support.
>>
>> Added:
>> lld/trunk/test/ELF/init_fini_priority.s
>> Modified:
>> lld/trunk/ELF/OutputSections.cpp
>> lld/trunk/ELF/OutputSections.h
>> lld/trunk/ELF/Writer.cpp
>>
>> Modified: lld/trunk/ELF/OutputSections.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=260460&r1=260459&r2=260460&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/OutputSections.cpp (original)
>> +++ lld/trunk/ELF/OutputSections.cpp Wed Feb 10 17:20:42 2016
>> @@ -750,6 +750,44 @@ void OutputSection<ELFT>::addSection(Inp
>> this->Header.sh_size = Off;
>> }
>>
>> +// If an input string is in the form of "foo.N" where N is a number,
>> +// return N. Otherwise, returns 65536, which is one greater than the
>> +// lowest priority.
>> +static int getPriority(StringRef S) {
>> + size_t Pos = S.rfind('.');
>> + if (Pos == StringRef::npos)
>> + return 65536;
>> + int V;
>> + if (S.substr(Pos + 1).getAsInteger(10, V))
>> + return 65536;
>> + return V;
>> +}
>> +
>> +// Sorts input sections by section name suffixes, so that .foo.N comes
>> +// before .foo.M if N < M. Used to sort .{init,fini}_array.N sections.
>> +// For more detail, read the section of the GCC's manual about
>> init_priority.
>> +template <class ELFT> void OutputSection<ELFT>::sortByPriority() {
>> + // Sort sections by priority.
>> + typedef std::pair<int, InputSection<ELFT> *> Pair;
>> + std::vector<Pair> V;
>> + for (InputSection<ELFT> *S : Sections)
>> + V.push_back({getPriority(S->getSectionName()), S});
>> + std::sort(V.begin(), V.end(),
>> + [](const Pair &A, const Pair &B) { return A.first < B.first;
>> });
>> + Sections.clear();
>> + for (Pair &P : V)
>> + Sections.push_back(P.second);
>> +
>> + // Reassign section addresses.
>> + uintX_t Off = 0;
>> + for (InputSection<ELFT> *S : Sections) {
>> + Off = alignTo(Off, S->getAlign());
>> + S->OutSecOff = Off;
>> + Off += S->getSize();
>> + }
>> + this->Header.sh_size = Off;
>> +}
>> +
>> // Returns a VA which a relocatin RI refers to. Used only for local
>> symbols.
>> // For non-local symbols, use SymbolBody::getVA instead.
>> template <class ELFT, bool IsRela>
>>
>> Modified: lld/trunk/ELF/OutputSections.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.h?rev=260460&r1=260459&r2=260460&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/OutputSections.h (original)
>> +++ lld/trunk/ELF/OutputSections.h Wed Feb 10 17:20:42 2016
>> @@ -279,6 +279,7 @@ public:
>> typedef typename llvm::object::ELFFile<ELFT>::uintX_t uintX_t;
>> OutputSection(StringRef Name, uint32_t sh_type, uintX_t sh_flags);
>> void addSection(InputSectionBase<ELFT> *C) override;
>> + void sortByPriority();
>> void writeTo(uint8_t *Buf) override;
>>
>> private:
>>
>> Modified: lld/trunk/ELF/Writer.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=260460&r1=260459&r2=260460&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/Writer.cpp (original)
>> +++ lld/trunk/ELF/Writer.cpp Wed Feb 10 17:20:42 2016
>> @@ -735,6 +735,10 @@ StringRef Writer<ELFT>::getOutputSection
>> return ".data";
>> if (S.startswith(".bss."))
>> return ".bss";
>> + if (S.startswith(".init_array."))
>> + return ".init_array";
>> + if (S.startswith(".fini_array."))
>> + return ".fini_array";
>> return S;
>> }
>>
>> @@ -915,6 +919,13 @@ template <class ELFT> void Writer<ELFT>:
>> Symtab.addAbsolute("end", ElfSym<ELFT>::End);
>> }
>>
>> +// Sort input sections by section name suffixes for
>> +// __attribute__((init_priority(N))).
>> +template <class ELFT> static void sortByPriority(OutputSectionBase<ELFT>
>> *S) {
>> + if (S)
>> + reinterpret_cast<OutputSection<ELFT> *>(S)->sortByPriority();
>> +}
>> +
>> // Create output section objects and add them to OutputSections.
>> template <class ELFT> bool Writer<ELFT>::createSections() {
>> OutputSections.push_back(Out<ELFT>::ElfHeader);
>> @@ -962,6 +973,10 @@ template <class ELFT> bool Writer<ELFT>:
>> Out<ELFT>::Dynamic->FiniArraySec =
>> Factory.lookup(".fini_array", SHT_FINI_ARRAY, SHF_WRITE |
>> SHF_ALLOC);
>>
>> + // Sort section contents for __attribute__((init_priority(N)).
>> + sortByPriority(Out<ELFT>::Dynamic->InitArraySec);
>> + sortByPriority(Out<ELFT>::Dynamic->FiniArraySec);
>> +
>> // The linker needs to define SECNAME_start, SECNAME_end and
>> SECNAME_stop
>> // symbols for sections, so that the runtime can get the start and end
>> // addresses of each section by section name. Add such symbols.
>>
>> Added: lld/trunk/test/ELF/init_fini_priority.s
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/init_fini_priority.s?rev=260460&view=auto
>>
>> ==============================================================================
>> --- lld/trunk/test/ELF/init_fini_priority.s (added)
>> +++ lld/trunk/test/ELF/init_fini_priority.s Wed Feb 10 17:20:42 2016
>> @@ -0,0 +1,29 @@
>> +// RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
>> +// RUN: ld.lld %t -o %t.exe
>> +// RUN: llvm-objdump -s %t.exe | FileCheck %s
>> +// REQUIRES: x86
>> +
>> +.globl _start
>> +_start:
>> + nop
>> +
>> +.section .init_array, "aw", @init_array
>> + .align 8
>> + .byte 1
>> +.section .init_array.100, "aw", @init_array
>> + .long 2
>> +.section .init_array.5, "aw", @init_array
>> + .byte 3
>> +
>> +.section .fini_array, "aw", @fini_array
>> + .align 8
>> + .byte 4
>> +.section .fini_array.100, "aw", @fini_array
>> + .long 5
>> +.section .fini_array.5, "aw", @fini_array
>> + .byte 6
>> +
>> +// CHECK: Contents of section .init_array:
>> +// CHECK-NEXT: 03020000 00000000 01
>> +// CHECK: Contents of section .fini_array:
>> +// CHECK-NEXT: 06050000 00000000 04
>>
>>
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>
>
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