[lld] r260460 - ELF: Implement __attribute__((init_priority(N)) support.
Sean Silva via llvm-commits
llvm-commits at lists.llvm.org
Wed Feb 10 16:07:14 PST 2016
On Wed, Feb 10, 2016 at 3:42 PM, Rui Ueyama <ruiu at google.com> wrote:
> Are .[cd]tors still in use?
>
.[cd]tors are the default on most places I think. E.g. clang uses them on
x86_64-unknown-linux and x86_64-scei-ps4. (haven't tried on other
architectures).
-- Sean Silva
>
> 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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