[lld] r296378 - Add terminator to .eh_frame sections
Rafael Avila de Espindola via llvm-commits
llvm-commits at lists.llvm.org
Tue Feb 28 10:41:35 PST 2017
I am pretty sure this is wrong. Given
.cfi_startproc
nop
.cfi_endproc
bfd and gold produce a .eh_frame that is 0x30 bytes long. We used to do
that too, but now we produce one that is 0x34.
I think that normally the terminator comes from a .o file that gcc/clang
adds to the link.
Rui, could you revert this for now?
Mark, could you provide an example where bfd/gold is adding the
terminator?
Cheers,
Rafael
Rui Ueyama via llvm-commits <llvm-commits at lists.llvm.org> writes:
> Author: ruiu
> Date: Mon Feb 27 14:44:59 2017
> New Revision: 296378
>
> URL: http://llvm.org/viewvc/llvm-project?rev=296378&view=rev
> Log:
> Add terminator to .eh_frame sections
>
> Patch by Mark Kettenis.
>
> Currenlty ld.lld does not add a terminator (a CIE with its length field
> set to zero) to the .eh_frame sections it generates. While the relevant
> standards (the AMD64 SysV ABI and the Linux LSB) are not explicit about
> this, such a terminator is expected by some unwinder implementations and
> seems to be always emitted by ld.bfd. In addition to that, the Linux LSB
>
> https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html#EHFRAME
>
> explicitly says that
>
> The .eh_frame section shall contain 1 or more Call Frame Information
> (CFI) records.
>
> Currently, if the .eh_frame sections of the input files only contain
> terminators, ld.lld emits a zero=sized .eh_frame section
> which clearly doesn't meet that requirement.
>
> The diff makes sure a terminator gets added to each .eh_frame section
> and adjusts all the relevant tests to account for that. An additional
> test isn't needed as these adjustments mean that the existence of the
> terminator is tested for by several tests already.
>
> Differential Revision: https://reviews.llvm.org/D30335
>
> Modified:
> lld/trunk/ELF/SyntheticSections.cpp
> lld/trunk/test/ELF/eh-frame-hdr.s
> lld/trunk/test/ELF/eh-frame-merge.s
> lld/trunk/test/ELF/ehframe-relocation.s
> lld/trunk/test/ELF/invalid-fde-rel.s
> lld/trunk/test/ELF/linkerscript/eh-frame-hdr.s
> lld/trunk/test/ELF/linkerscript/symbols-synthetic.s
> lld/trunk/test/ELF/map-file.s
> lld/trunk/test/ELF/relocatable-eh-frame.s
>
> Modified: lld/trunk/ELF/SyntheticSections.cpp
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/SyntheticSections.cpp?rev=296378&r1=296377&r2=296378&view=diff
> ==============================================================================
> --- lld/trunk/ELF/SyntheticSections.cpp (original)
> +++ lld/trunk/ELF/SyntheticSections.cpp Mon Feb 27 14:44:59 2017
> @@ -540,7 +540,14 @@ template <class ELFT> void EhFrameSectio
> Off += alignTo(Fde->size(), sizeof(uintX_t));
> }
> }
> - this->Size = Off;
> +
> + // Add a CIE record of length 0 as a terminator. While the relevant
> + // standards don't explicitly require such a terminator, ld.bfd and
> + // ld.gold always seem to add one and some unwiders rely on its
> + // presence. It also prevents us from generating a .eh_frame section
> + // with zero Call Frame Information records, which isn't allowed by
> + // the LSB standard.
> + this->Size = Off + 4;
> }
>
> template <class ELFT> static uint64_t readFdeAddr(uint8_t *Buf, int Size) {
>
> Modified: lld/trunk/test/ELF/eh-frame-hdr.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/eh-frame-hdr.s?rev=296378&r1=296377&r2=296378&view=diff
> ==============================================================================
> --- lld/trunk/test/ELF/eh-frame-hdr.s (original)
> +++ lld/trunk/test/ELF/eh-frame-hdr.s Mon Feb 27 14:44:59 2017
> @@ -84,7 +84,7 @@ _start:
> // HDR-NEXT: ]
> // HDR-NEXT: Address: 0x200180
> // HDR-NEXT: Offset: 0x180
> -// HDR-NEXT: Size: 96
> +// HDR-NEXT: Size: 100
> // HDR-NEXT: Link: 0
> // HDR-NEXT: Info: 0
> // HDR-NEXT: AddressAlignment: 8
> @@ -96,6 +96,7 @@ _start:
> // HDR-NEXT: 0030: 14000000 34000000 490E0000 01000000
> // HDR-NEXT: 0040: 00000000 00000000 14000000 4C000000
> // HDR-NEXT: 0050: 320E0000 01000000 00000000 00000000
> +// HDR-NEXT: 0060: 00000000
> // HDR-NEXT: )
> // CIE: 14000000 00000000 017A5200 01781001 1B0C0708 90010000
> // FDE(1): 14000000 1C000000 600E0000 01000000 00000000 00000000
>
> Modified: lld/trunk/test/ELF/eh-frame-merge.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/eh-frame-merge.s?rev=296378&r1=296377&r2=296378&view=diff
> ==============================================================================
> --- lld/trunk/test/ELF/eh-frame-merge.s (original)
> +++ lld/trunk/test/ELF/eh-frame-merge.s Mon Feb 27 14:44:59 2017
> @@ -27,7 +27,7 @@
> // CHECK-NEXT: ]
> // CHECK-NEXT: Address:
> // CHECK-NEXT: Offset:
> -// CHECK-NEXT: Size: 96
> +// CHECK-NEXT: Size: 100
> // CHECK-NEXT: Link: 0
> // CHECK-NEXT: Info: 0
> // CHECK-NEXT: AddressAlignment: 8
> @@ -39,6 +39,7 @@
> // CHECK-NEXT: 0030: 14000000 34000000 D20D0000 02000000 |
> // CHECK-NEXT: 0040: 00000000 00000000 14000000 4C000000 |
> // CHECK-NEXT: 0050: B90D0000 01000000 00000000 00000000 |
> +// CHECK-NEXT: 0060: 00000000 |
> // CHECK-NEXT: )
>
> // CHECK: Name: foo
>
> Modified: lld/trunk/test/ELF/ehframe-relocation.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/ehframe-relocation.s?rev=296378&r1=296377&r2=296378&view=diff
> ==============================================================================
> --- lld/trunk/test/ELF/ehframe-relocation.s (original)
> +++ lld/trunk/test/ELF/ehframe-relocation.s Mon Feb 27 14:44:59 2017
> @@ -12,7 +12,7 @@
> // CHECK-NEXT: ]
> // CHECK-NEXT: Address: 0x200120
> // CHECK-NEXT: Offset:
> -// CHECK-NEXT: Size: 48
> +// CHECK-NEXT: Size: 52
> // CHECK-NOT: .eh_frame
>
> // 0x200120 = 2097440
>
> Modified: lld/trunk/test/ELF/invalid-fde-rel.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/invalid-fde-rel.s?rev=296378&r1=296377&r2=296378&view=diff
> ==============================================================================
> --- lld/trunk/test/ELF/invalid-fde-rel.s (original)
> +++ lld/trunk/test/ELF/invalid-fde-rel.s Mon Feb 27 14:44:59 2017
> @@ -33,4 +33,4 @@
> .long 0x0
> .long 0x0
>
> -// CHECK: 1 .eh_frame 00000018
> +// CHECK: 1 .eh_frame 0000001c
>
> Modified: lld/trunk/test/ELF/linkerscript/eh-frame-hdr.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/linkerscript/eh-frame-hdr.s?rev=296378&r1=296377&r2=296378&view=diff
> ==============================================================================
> --- lld/trunk/test/ELF/linkerscript/eh-frame-hdr.s (original)
> +++ lld/trunk/test/ELF/linkerscript/eh-frame-hdr.s Mon Feb 27 14:44:59 2017
> @@ -7,7 +7,7 @@
> # RUN: ld.lld -o %t1 --eh-frame-hdr --script %t.script %t
> # RUN: llvm-objdump -s -section=".eh_frame_hdr" %t1 | FileCheck %s
>
> -# CHECK: 011b033b 14000000 01000000 49000000
> +# CHECK: 011b033b 14000000 01000000 4d000000
> # CHECK-NEXT: 30000000
>
> .global _start
>
> Modified: lld/trunk/test/ELF/linkerscript/symbols-synthetic.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/linkerscript/symbols-synthetic.s?rev=296378&r1=296377&r2=296378&view=diff
> ==============================================================================
> --- lld/trunk/test/ELF/linkerscript/symbols-synthetic.s (original)
> +++ lld/trunk/test/ELF/linkerscript/symbols-synthetic.s Mon Feb 27 14:44:59 2017
> @@ -60,7 +60,7 @@
> # SIMPLE: 0000000000000128 .foo 00000000 .hidden _end_sec
> # SIMPLE-NEXT: 0000000000000120 .foo 00000000 _begin_sec
> # SIMPLE-NEXT: 0000000000000128 *ABS* 00000000 _end_sec_abs
> -# SIMPLE-NEXT: 0000000000001048 .text 00000000 _start
> +# SIMPLE-NEXT: 000000000000104c .text 00000000 _start
> # SIMPLE-NEXT: 0000000000000120 .foo 00000000 begin_foo
> # SIMPLE-NEXT: 0000000000000128 .foo 00000000 end_foo
> # SIMPLE-NEXT: 0000000000000008 *ABS* 00000000 size_foo_1
>
> Modified: lld/trunk/test/ELF/map-file.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/map-file.s?rev=296378&r1=296377&r2=296378&view=diff
> ==============================================================================
> --- lld/trunk/test/ELF/map-file.s (original)
> +++ lld/trunk/test/ELF/map-file.s Mon Feb 27 14:44:59 2017
> @@ -27,8 +27,8 @@ local:
> .comm common,4,16
>
> // CHECK: Address Size Align Out In File Symbol
> -// CHECK-NEXT: 0000000000200158 0000000000000030 8 .eh_frame
> -// CHECK-NEXT: 0000000000200158 0000000000000030 8 .eh_frame
> +// CHECK-NEXT: 0000000000200158 0000000000000034 8 .eh_frame
> +// CHECK-NEXT: 0000000000200158 0000000000000034 8 .eh_frame
> // CHECK-NEXT: 0000000000201000 0000000000000015 4 .text
> // CHECK-NEXT: 0000000000201000 000000000000000e 4 .text
> // CHECK-NEXT: 0000000000201000 000000000000000e 4 {{.*}}{{/|\\}}map-file.s.tmp1.o
>
> Modified: lld/trunk/test/ELF/relocatable-eh-frame.s
> URL: http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/relocatable-eh-frame.s?rev=296378&r1=296377&r2=296378&view=diff
> ==============================================================================
> --- lld/trunk/test/ELF/relocatable-eh-frame.s (original)
> +++ lld/trunk/test/ELF/relocatable-eh-frame.s Mon Feb 27 14:44:59 2017
> @@ -5,7 +5,7 @@
> # RUN: ld.lld %t -o %t.so -shared
> # RUN: llvm-objdump -h %t.so | FileCheck --check-prefix=DSO %s
>
> -# DSO: .eh_frame 00000030
> +# DSO: .eh_frame 00000034
>
> # CHECK: Relocations [
> # CHECK-NEXT: Section ({{.*}}) .rela.eh_frame {
>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
More information about the llvm-commits
mailing list