Adhemerval Zanella
2015-May-06 14:43 UTC
[LLVMdev] [lld] Wrong references for C++ COMDAT groups
Hi,
Checking the llvm test-suite SingleSource/Regression/C++/EH/class_hierarchy
testcase on aarch64 I noted something strange:
Dump of assembler code for function _Z4funcj:
0x0000000000400650 <+0>: stp x22, x21, [sp,#-48]!
0x0000000000400654 <+4>: stp x20, x19, [sp,#16]
0x0000000000400658 <+8>: stp x29, x30, [sp,#32]
0x000000000040065c <+12>: add x29, sp, #0x20
=> 0x0000000000400660 <+16>: .inst 0x2bfffff7 ; undefined
Where it should be:
0000000000000000 <_Z4funcj>:
0: a9bd57f6 stp x22, x21, [sp,#-48]!
4: a9014ff4 stp x20, x19, [sp,#16]
8: a9027bfd stp x29, x30, [sp,#32]
c: 910083fd add x29, sp, #0x20
10: 2a0003f3 mov w19, w0
And there is no relocation (static or dynamic) point to the faulty instruction.
It exist, however, a group section relocation with same offset, but for a
different text segments (the exception handler stub create by clang):
Relocation section '.rela.text' at offset 0xed8 contains 2 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000000010 00480000011b R_AARCH64_CALL26 0000000000000000
_ZNSt9exceptionD2Ev + 0
000000000020 004d0000011a R_AARCH64_JUMP26 0000000000000000 _ZdlPv + 0
Relocation section '.rela.text' at offset 0xf08 contains 2 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000000010 00480000011b R_AARCH64_CALL26 0000000000000000
_ZNSt9exceptionD2Ev + 0
000000000020 004d0000011a R_AARCH64_JUMP26 0000000000000000 _ZdlPv + 0
Relocation section '.rela.text' at offset 0xf38 contains 2 entries:
Offset Info Type Sym. Value Sym. Name + Addend
000000000010 00480000011b R_AARCH64_CALL26 0000000000000000
_ZNSt9exceptionD2Ev + 0
000000000020 004d0000011a R_AARCH64_JUMP26 0000000000000000 _ZdlPv + 0
However seems that LLD is indeed condescending them, but create duplicated
references
for the wrong segments:
Writing atom: _Z4funcj | 1520
Handle relocJump26 - S: 400460 A: 0 P: 400660 result: 3ffff98
Handle relocJump26 - S: 400470 A: 0 P: 400670 result: 3ffff98
The first relocJump26 shouldn't be applied to .text segment 0x400660, but
solely on the
_ZN4BaseD0Ev section. I am trying to debug how lld exactly is generating this
wrong
Reference, but I still can right figure out. Any idea of what is happening
here?
Shankar Easwaran
2015-May-06 21:18 UTC
[LLVMdev] [lld] Wrong references for C++ COMDAT groups
Does this test pass on X86_64 ? Groups are read in the Reader and is documented below :- See http://lld.llvm.org/design.html#linking-steps on Section Groups to get more information. On Wed, May 6, 2015 at 9:43 AM, Adhemerval Zanella < adhemerval.zanella at linaro.org> wrote:> Hi, > > Checking the llvm test-suite SingleSource/Regression/C++/EH/class_hierarchy > testcase on aarch64 I noted something strange: > > Dump of assembler code for function _Z4funcj: > 0x0000000000400650 <+0>: stp x22, x21, [sp,#-48]! > 0x0000000000400654 <+4>: stp x20, x19, [sp,#16] > 0x0000000000400658 <+8>: stp x29, x30, [sp,#32] > 0x000000000040065c <+12>: add x29, sp, #0x20 > => 0x0000000000400660 <+16>: .inst 0x2bfffff7 ; undefined > > Where it should be: > > 0000000000000000 <_Z4funcj>: > 0: a9bd57f6 stp x22, x21, [sp,#-48]! > 4: a9014ff4 stp x20, x19, [sp,#16] > 8: a9027bfd stp x29, x30, [sp,#32] > c: 910083fd add x29, sp, #0x20 > 10: 2a0003f3 mov w19, w0 > > And there is no relocation (static or dynamic) point to the faulty > instruction. > It exist, however, a group section relocation with same offset, but for a > different text segments (the exception handler stub create by clang): > > Relocation section '.rela.text' at offset 0xed8 contains 2 entries: > Offset Info Type Sym. Value Sym. Name + > Addend > 000000000010 00480000011b R_AARCH64_CALL26 0000000000000000 > _ZNSt9exceptionD2Ev + 0 > 000000000020 004d0000011a R_AARCH64_JUMP26 0000000000000000 _ZdlPv + 0 > > Relocation section '.rela.text' at offset 0xf08 contains 2 entries: > Offset Info Type Sym. Value Sym. Name + > Addend > 000000000010 00480000011b R_AARCH64_CALL26 0000000000000000 > _ZNSt9exceptionD2Ev + 0 > 000000000020 004d0000011a R_AARCH64_JUMP26 0000000000000000 _ZdlPv + 0 > > Relocation section '.rela.text' at offset 0xf38 contains 2 entries: > Offset Info Type Sym. Value Sym. Name + > Addend > 000000000010 00480000011b R_AARCH64_CALL26 0000000000000000 > _ZNSt9exceptionD2Ev + 0 > 000000000020 004d0000011a R_AARCH64_JUMP26 0000000000000000 _ZdlPv + 0 > > However seems that LLD is indeed condescending them, but create duplicated > references > for the wrong segments: > > Writing atom: _Z4funcj | 1520 > Handle relocJump26 - S: 400460 A: 0 P: 400660 result: > 3ffff98 > Handle relocJump26 - S: 400470 A: 0 P: 400670 result: > 3ffff98 > > The first relocJump26 shouldn't be applied to .text segment 0x400660, but > solely on the > _ZN4BaseD0Ev section. I am trying to debug how lld exactly is generating > this wrong > Reference, but I still can right figure out. Any idea of what is > happening here? >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20150506/ca13fbf7/attachment.html>
Adhemerval Zanella
2015-May-07 15:02 UTC
[LLVMdev] [lld] Wrong references for C++ COMDAT groups
Looks like it is also not working on x86_64, using clang/lld I am seeing a segmentation fault: Dump of assembler code for function _Z4funcj: 0x0000000000400590 <+0>: push %rbp 0x0000000000400591 <+1>: push %rbx 0x0000000000400592 <+2>: push %rax 0x0000000000400593 <+3>: mov %edi,%ebp 0x0000000000400595 <+5>: pop %rdx 0x0000000000400596 <+6>: cld => 0x0000000000400597 <+7>: or %esi,0x46(%rdi) 0x000000000040059a <+10>: mov $0xde000018,%edi Where the disassemble should be: Disassembly of section .text: 0000000000000000 <_Z4funcj>: 0: 55 push %rbp 1: 53 push %rbx 2: 50 push %rax 3: 89 fd mov %edi,%ebp 5: 83 fd 09 cmp $0x9,%ebp 8: 77 46 ja 50 <_Z4funcj+0x50> a: bf 18 00 00 00 mov $0x18,%edi f: e8 00 00 00 00 callq 14 <_Z4funcj+0x14> 14: 48 89 c3 mov %rax,%rbx 17: 48 c7 03 00 00 00 00 movq $0x0,(%rbx) 1e: 89 6b 08 mov %ebp,0x8(%rbx) 21: bf 0e 00 00 00 mov $0xe,%edi 26: e8 00 00 00 00 callq 2b <_Z4funcj+0x2b> As for aarch64, x86_64 object shows some relocation in group sections: Relocation section '.rela.text' at offset 0xb48 contains 2 entries: Offset Info Type Sym. Value Sym. Name + Addend 000000000005 003200000002 R_X86_64_PC32 0000000000000000 _ZNSt9exceptionD2Ev - 4 00000000000e 003700000002 R_X86_64_PC32 0000000000000000 _ZdlPv - 4 That should me meant only for the group section text, not the default text segment. On 06-05-2015 18:18, Shankar Easwaran wrote:> Does this test pass on X86_64 ? Groups are read in the Reader and is documented below :- > > See http://lld.llvm.org/design.html#linking-steps on Section Groups to get more information. > > On Wed, May 6, 2015 at 9:43 AM, Adhemerval Zanella <adhemerval.zanella at linaro.org <mailto:adhemerval.zanella at linaro.org>> wrote: > > Hi, > > Checking the llvm test-suite SingleSource/Regression/C++/EH/class_hierarchy > testcase on aarch64 I noted something strange: > > Dump of assembler code for function _Z4funcj: > 0x0000000000400650 <+0>: stp x22, x21, [sp,#-48]! > 0x0000000000400654 <+4>: stp x20, x19, [sp,#16] > 0x0000000000400658 <+8>: stp x29, x30, [sp,#32] > 0x000000000040065c <+12>: add x29, sp, #0x20 > => 0x0000000000400660 <+16>: .inst 0x2bfffff7 ; undefined > > Where it should be: > > 0000000000000000 <_Z4funcj>: > 0: a9bd57f6 stp x22, x21, [sp,#-48]! > 4: a9014ff4 stp x20, x19, [sp,#16] > 8: a9027bfd stp x29, x30, [sp,#32] > c: 910083fd add x29, sp, #0x20 > 10: 2a0003f3 mov w19, w0 > > And there is no relocation (static or dynamic) point to the faulty instruction. > It exist, however, a group section relocation with same offset, but for a > different text segments (the exception handler stub create by clang): > > Relocation section '.rela.text' at offset 0xed8 contains 2 entries: > Offset Info Type Sym. Value Sym. Name + Addend > 000000000010 00480000011b R_AARCH64_CALL26 0000000000000000 _ZNSt9exceptionD2Ev + 0 > 000000000020 004d0000011a R_AARCH64_JUMP26 0000000000000000 _ZdlPv + 0 > > Relocation section '.rela.text' at offset 0xf08 contains 2 entries: > Offset Info Type Sym. Value Sym. Name + Addend > 000000000010 00480000011b R_AARCH64_CALL26 0000000000000000 _ZNSt9exceptionD2Ev + 0 > 000000000020 004d0000011a R_AARCH64_JUMP26 0000000000000000 _ZdlPv + 0 > > Relocation section '.rela.text' at offset 0xf38 contains 2 entries: > Offset Info Type Sym. Value Sym. Name + Addend > 000000000010 00480000011b R_AARCH64_CALL26 0000000000000000 _ZNSt9exceptionD2Ev + 0 > 000000000020 004d0000011a R_AARCH64_JUMP26 0000000000000000 _ZdlPv + 0 > > However seems that LLD is indeed condescending them, but create duplicated references > for the wrong segments: > > Writing atom: _Z4funcj | 1520 > Handle relocJump26 - S: 400460 A: 0 P: 400660 result: 3ffff98 > Handle relocJump26 - S: 400470 A: 0 P: 400670 result: 3ffff98 > > The first relocJump26 shouldn't be applied to .text segment 0x400660, but solely on the > _ZN4BaseD0Ev section. I am trying to debug how lld exactly is generating this wrong > Reference, but I still can right figure out. Any idea of what is happening here? > >