Commit Graph

2932 Commits

Author SHA1 Message Date
Fangrui Song 89f7859641 [ELF][test] Improve LTO tests
Add file-level comments
Delete insignificant addresses to make them more tolerant to layout changes
Simplify test output

llvm-svn: 371292
2019-09-07 08:20:09 +00:00
Matthew Voss c177919409 Update lld tests dynamic-list.s and symbol-override.s to use llvm-nm
The following tests failed on Windows bots due to nm not being
available:

  lld/test/ELF/dynamic-list.s
  lld/test/ELF/symbol-override.s

llvm-svn: 371267
2019-09-06 22:51:46 +00:00
Fangrui Song 2682bc3c9d [ELF] Replace error() with errorOrWarn() for the ASSERT command
Summary:
ld.bfd produces an output with --noinhibit-exec when an ASSERT fails.
Use errorOrWarn() so that we can produce an output as well.

An interesting case is that symbol assignments may execute multiple
times, so we probably want to suppress errors for non-final runs.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D67285

llvm-svn: 371225
2019-09-06 16:30:22 +00:00
Fangrui Song 8d30c1dcec Reland D66717 [ELF] Do not ICF two sections with different output sections (by SECTIONS commands)
Recommit r370635 (reverted by r371202), with one change: move addOrphanSections() before ICF.

Before, orphan sections in two different partitions may be folded and
moved to the main partition.

Now, InputSection->OutputSection assignment for orphans happens before
ICF. ICF does not fold input sections with different output sections.

With the PR43241 reproduce,
`llvm-objcopy --extract-partition libvr.so libchrome__combined.so libvr.so` => no error

Updated description:

Fixes PR39418. Complements D47241 (the non-linker-script case).

processSectionCommands() assigns input sections to output sections.
ICF is called before it, so .text.foo and .text.bar may be folded even if
their output sections are made different by SECTIONS commands.

```
markLive<ELFT>()
doIcf<ELFT>()                      // During ICF, we don't know the output sections
writeResult()
  combineEhSections<ELFT>()
  script->processSectionCommands() // InputSection -> OutputSection assignment
```

This patch splits processSectionCommands() into processSectionCommands()
and processSymbolAssignments(), and moves
processSectionCommands()/addOrphanSections() before ICF:

```
markLive<ELFT>()
combineEhSections<ELFT>()
script->processSectionCommands()
script->addOrphanSections();
doIcf<ELFT>()                      // should remove folded input sections
writeResult()
  script->processSymbolAssignments()
```

An alternative approach is to unfold a section `sec` in
processSectionCommands() when we find `sec` and `sec->repl` belong to
different output sections. I feel this patch is superior because this
can fold more sections and the decouple of
SectionCommand/SymbolAssignment gives flexibility:

* An ExprValue can't be evaluated before its section is assigned to an
  output section -> we can delete getOutputSectionVA and simplify
  another place where we had to check if the output section is null.
  Moreover, a case in linkerscript/early-assign-symbol.s can be handled
  now.
* processSectionCommands/processSymbolAssignments can be freely moved
  around.

llvm-svn: 371216
2019-09-06 15:57:44 +00:00
Fangrui Song 5d9f419a2e Revert "Revert r370635, it caused PR43241."
This reverts commit 50d2dca22b3b05d0ee4883b0cbf93d7d15f241fc.

llvm-svn: 371215
2019-09-06 15:57:24 +00:00
Fangrui Song 8f10a5f42d [ELF][test] Simplify and reorganize tests
Add file-level comments
Delete insignificant addresses to make them more tolerant to layout changes
Simplify test output
Delete simple Inputs/*.s files

Delete version-script-copy-rel.s - covered by verdef-defaultver.s
Delete version-wildcard.test - covered by version-script-glob.s

llvm-svn: 371213
2019-09-06 15:10:31 +00:00
Nico Weber 8455294f2a Revert r370635, it caused PR43241.
llvm-svn: 371202
2019-09-06 13:23:42 +00:00
Fangrui Song 70e002b50b [ELF][test] Update test after r371185
llvm-svn: 371189
2019-09-06 09:39:48 +00:00
Simon Atanasyan ff2172c9f4 [mips] Make another set of test cases more tolerant to exact symbol addresses. NFC
llvm-svn: 371174
2019-09-06 07:23:02 +00:00
Fangrui Song a2028f73c2 Update SHT_LLVM_PART_EHDR test after r371157
llvm-svn: 371160
2019-09-06 01:18:01 +00:00
Simon Atanasyan 2172f3f49d [mips] Make a few test cases more tolerant to exact symbol addresses. NFC
llvm-svn: 371065
2019-09-05 13:37:16 +00:00
Rui Ueyama e99dc4ba57 Align output segments correctly
Previously, segments were aligned according to their first section's
alignment requirements. That was not correct, but segments are also
aligned to a page boundary, and a page boundary is usually much larger
than a section alignment requirement, so no one noticed this bug before.

Now, lld has --nmagic option which sets maxPageSize to 1 to effectively
disable page alignment, which reveals the issue.

Fixes https://bugs.llvm.org/show_bug.cgi?id=43212

Differential Revision: https://reviews.llvm.org/D67152

llvm-svn: 371013
2019-09-05 05:30:24 +00:00
Fangrui Song 7afffb54ea [ELF] Don't shrink RelrSection
Fixes PR43214.

The size of SHT_RELR may oscillate between 2 numbers (see D53003 for a
similar --pack-dyn-relocs=android issue). This can happen if the shrink
of SHT_RELR causes it to take more words to encode relocation offsets
(this can happen with thunks or segments with overlapping p_offset
ranges), and the expansion of SHT_RELR causes it to take fewer words to
encode relocation offsets.

To avoid the issue, add padding 1s to the end of the relocation section
if its size would decrease. Trailing 1s do not decode to more relocations.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D67164

llvm-svn: 370923
2019-09-04 16:27:35 +00:00
Fangrui Song b4745fad24 [ELF] Add a spell corrector for "undefined symbol" diagnostics
Non-undefined symbols with Levenshtein distance 1 or a transposition are
suggestion candidates. This is probably good enough and it can suggest
some missing/superfluous qualifiers: const, restrict, volatile, & and &&
ref-qualifier, e.g.

   error: undefined symbol: foo(int*)
   >>> referenced by b.o:(.text+0x1)
  +>>> did you mean: foo(int const*)
  +>>> defined in: a.o

   error: undefined symbol: foo(int*&)
   >>> referenced by b.o:(.text+0x1)
  +>>> did you mean: foo(int*)
  +>>> defined in: b.o

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D67039

llvm-svn: 370853
2019-09-04 09:04:26 +00:00
Fangrui Song d8bc6a48ea [ELF] Do not ICF two sections with different output sections (by SECTIONS commands)
Fixes PR39418. Complements D47241 (the non-linker-script case).

processSectionCommands() assigns input sections to output sections.
ICF is called before it, so .text.foo and .text.bar may be folded even if
their output sections are made different by SECTIONS commands.

```
markLive<ELFT>()
doIcf<ELFT>()                      // During ICF, we don't know the output sections
writeResult()
  combineEhSections<ELFT>()
  script->processSectionCommands() // InputSection -> OutputSection assignment
```

This patch splits processSectionCommands() into processSectionCommands() and
processSymbolAssignments(), and moves processSectionCommands() before ICF:

```
markLive<ELFT>()
combineEhSections<ELFT>()
script->processSectionCommands()
doIcf<ELFT>()                      // should remove folded input sections
writeResult()
  script->processSymbolAssignments()
```

An alternative approach is to unfold a section `sec` in
processSectionCommands() when we find `sec` and `sec->repl` belong to
different output sections. I feel this patch is superior because this
can fold more sections and the decouple of
SectionCommand/SymbolAssignment gives flexibility:

* An ExprValue can't be evaluated before its section is assigned to an
  output section -> we can delete getOutputSectionVA and simplify
  another place where we had to check if the output section is null.
  Moreover, a case in linkerscript/early-assign-symbol.s can be handled
  now.
* processSectionCommands/processSymbolAssignments can be freely moved
  around.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D66717

llvm-svn: 370635
2019-09-02 10:33:58 +00:00
Fangrui Song 4514ac7cfb [ELF] Align SHT_LLVM_PART_EHDR to a maximum page size boundary
Fixes https://bugs.chromium.org/p/chromium/issues/detail?id=998712

SHT_LLVM_PART_EHDR marks the start of a partition. The partition
sections will be extracted to a separate file. Align to the next maximum
page size boundary so that we can find the ELF header at the start. We
cannot benefit from overlapping p_offset ranges with the previous
segment anyway.

It seems we lack some llvm-objcopy --extract-main-partition and
--extract-partition sanity checks. It may place EHDR at the start
even if p_offset if non zero. Anyway, the lld change is justified for
the reasons above.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D67032

llvm-svn: 370629
2019-09-02 08:49:50 +00:00
Fangrui Song 688183ec54 [ELF] Set `referenced` bit of Undefined created by BitcodeFile
D64136 and D65584, while fixing STB_WEAK issues and improving our
compatibility with ld.bfd, can cause another STB_WEAK problem related to
LTO:

If %tundef.o has an undefined reference on f,
and %tweakundef.o has a weak undefined reference on f,
%tdef.o has a definition of f

```
ld.lld %tundef.o %tweakundef.o --start-lib %tdef.o --end-lib
```

1) `%tundef.o` doesn't set the `referenced` bit.
2) `%weakundef.o` changes the binding from STB_GLOBAL to STB_WEAK
3) `%tdef.o` is not fetched because the binding is weak.

Step (1) is incorrect. This patch sets the `referenced` bit of Undefined
created by bitcode files.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D66992

llvm-svn: 370437
2019-08-30 07:10:30 +00:00
Nico Weber 3c1996a489 lld: Make a test not fail if "repro" is part of the build directory name
r268231 made it so that the name of the --reproduce archive
is no longer listed in the response file. Previously, with
"--reproduce repro.tar" the response file would contain

  repro/home/.../llvm-build-dir/.../foo.o

but after that change it contained

  home/.../llvm-build-dir/.../foo.o

instead. The test added for this in r268231 checked that
the response file doesn't contain the string "repro", but
if the build dir is named e.g. "llvm-build-repro" then the
test fails because of that.

Change the assert to check that "repro" doesn't exist at the
beginning of the line instead. I verified that the test
still fails with r268231 reverted.

The test technically still fails if someone builds llvm in a directory
'/repro' below the root directory. Don't do that :)

llvm-svn: 370211
2019-08-28 14:33:35 +00:00
Fangrui Song 523f999acf [ELF][RISCV] Allow PT_LOAD to have overlapping p_offset ranges on EM_RISCV
Port the D64906 technique to RISC-V. It deletes 3 alignments at
PT_LOAD boundaries for the default case: the size of a RISC-V binary
decreases by at most 12kb.

llvm-svn: 370192
2019-08-28 12:06:06 +00:00
Fangrui Song 54a6f6839b [ELF][AMDGPU][SPARC] Allow PT_LOAD to have overlapping p_offset ranges on EM_AMDGPU and EM_SPARCV9
llvm-svn: 370180
2019-08-28 09:45:06 +00:00
Fangrui Song 8fbe81fb29 [ELF][RISCV] Assign st_shndx of __global_pointer$ to 1 if .sdata does not exist
This essentially reverts the code change of D63132 and switches to a simpler approach.

In an executable/shared object, st_shndx of a symbol can be:

1) SHN_UNDEF: undefined symbol (or canonical PLT)
2) SHN_ABS: absolute symbol
3) any other value (usually a regular section index) represents a relative symbol.
  The actual value does not matter.

Many ld.so (musl, all archs except MIPS of FreeBSD rtld-elf) even treat 2) and 3)
the same. If .sdata does not exist, it does not matter what value/section
__global_pointer$ has, as long as it is relative (otherwise there will be a pedantic
lld error. See D63132). Just set the st_shndx arbitrarily to 1.

Dummy st_shndx=1 may be used by __rela_iplt_start, linker-script-defined symbols outside a section, __dso_handle, etc.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D66798

llvm-svn: 370172
2019-08-28 09:01:03 +00:00
Vlad Tsyrklevich 57076d3199 Revert "Change the X86 datalayout to add three address spaces for 32 bit signed,"
This reverts commit r370083 because it caused check-lld failures on
sanitizer-x86_64-linux-fast.

llvm-svn: 370142
2019-08-28 01:08:54 +00:00
Amy Huang 1299945b81 Change the X86 datalayout to add three address spaces for 32 bit signed,
32 bit unsigned, and 64 bit pointers.

llvm-svn: 370083
2019-08-27 17:46:53 +00:00
Fangrui Song 024bf27ddf [ELF][ARM] Allow PT_LOAD to have overlapping p_offset ranges on EM_ARM
Port the D64906 technique to ARM. It deletes 3 alignments at
PT_LOAD boundaries for the default case: the size of an arm binary
decreases by at most 12kb.

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D66749

llvm-svn: 370049
2019-08-27 11:52:36 +00:00
Fangrui Song fdbc2bd2aa [ELF][ARM] Add --no-show-raw-insn and -soname to some ARM tests
Delete some insignificant addresses to make it simpler for layout
changes.

llvm-svn: 370048
2019-08-27 11:50:27 +00:00
Richard Trieu f837bb4a34 Copy test data so tests don't traverse test directories. NFC
llvm-svn: 369984
2019-08-26 22:41:05 +00:00
Fangrui Song debcac9fef [ELF] Make LinkerScript::assignAddresses iterative
PR42990. For `SECTIONS { b = a; . = 0xff00 + (a >> 8); a = .; }`,
we currently set st_value(a)=0xff00 while st_value(b)=0xffff.

The following call tree demonstrates the problem:

```
link<ELF64LE>(Args);
  Script->declareSymbols(); // insert a and b as absolute Defined
  Writer<ELFT>().run();
    Script->processSectionCommands();
      addSymbol(cmd);       // a and b are re-inserted. LinkerScript::getSymbolValue
                            // is lazily called by subsequent evaluation
    finalizeSections();
      forEachRelSec(scanRelocations<ELFT>);
        processRelocAux     // another problem PR42506, not affected by this patch
      finalizeAddressDependentContent(); // loop executed once
        script->assignAddresses(); // a = 0, b = 0xff00
    script->assignAddresses(); // a = 0xff00, _end = 0xffff
```

We need another assignAddresses() to finalize the value of `a`.

This patch

1) modifies assignAddress() to track the original section/value of each
  symbol and return a symbol whose section/value has changed.
2) moves the post-finalizeSections assignAddress() inside the loop
  of finalizeAddressDependentContent() and makes it iterative.
  Symbol assignment may not converge so we make a few attempts before
  bailing out.

Note, assignAddresses() must be called at least twice. The penultimate
call finalized section addresses while the last finalized symbol values.
It is somewhat obscure and there was no comment.
linkerscript/addr-zero.test tests this.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D66279

llvm-svn: 369889
2019-08-26 10:23:31 +00:00
Fangrui Song 8e5184af71 [ELF] Error if --strip-all and --emit-relocs are used together
--strip-all suppresses the creation of in.symtab
This can cause a null pointer dereference in OutputSection::finalize()

  // --emit-relocs => copyRelocs is true
  if (!config->copyRelocs || (type != SHT_RELA && type != SHT_REL))
    return;
  ...
  link = in.symTab->getParent()->sectionIndex; // in.symTab is null

Let's just disallow the combination. In some cases the combination can
cause GNU linkers to fail:

* ld.bfd: final link failed: invalid operation
* gold: internal error in set_no_output_symtab_entry, at ../../gold/object.h:1814

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D66704

llvm-svn: 369878
2019-08-26 06:23:53 +00:00
Fangrui Song af47d0021c [ELF] Align the first section of a PT_LOAD even if its type is SHT_NOBITS
Reported at https://reviews.llvm.org/D64930#1642223

If the only section of a PT_LOAD is a SHT_NOBITS section (e.g. .bss), we
may not align its sh_offset. p_offset of the PT_LOAD will be set to
sh_offset, and we will get p_offset!=p_vaddr (mod p_align).  If such
executable is mapped by the Linux kernel, it will segfault.

After D64906, this may happen the non-linker script case.

The linker script case has had this issue for a long time.
This was fixed by rL321657 (but the test linkerscript/nobits-offset.s
failed to test a SHT_NOBITS section), but broken by rL345154.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D66658

llvm-svn: 369828
2019-08-24 00:41:15 +00:00
Fangrui Song 2d37bf843c [ELF][ARM] Simplify some llvm-objdump tests with both ARM/Thumb states
llvm-objdump can switch between ARM/Thumb states after D60927.

In a few lld tests, we run both

* llvm-objdump -d -triple=thumbv7a-none-linux-gnueabi %t
* llvm-objdump -d -triple=armv7a-none-linux-gnueabi %t

to test ARM/Thumb parts of the same file. In many cases we can just
run one command. There is a problem that prevents us from cleaning
more tests (e.g. test/ELF/arm-thumb-interwork-thunk.s):

In llvm-objdump, while we have ARM/Thumb (primary and secondary)
MCDisassembler and MCSubtargetInfo, we have just one MCInstrAnalysis
which is used to resolve the targets of calls in both ARM/Thumb parts.

    // ThumbMCInstrAnalysis evaluating ARM parts or ARMMCInstrAnalysis evaluating Thumb parts
    // will have incorrect offsets.
    // An example of llvm-objdump -d -triple=thumbv7a on ARM part:
    1304: 3d ff ff fa  blx     #-780                 # no <...>
    1308: 06 00 00 ea  b       #24 <arm_caller+0x24> # wrong target due to wrong offset

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D66539

llvm-svn: 369535
2019-08-21 15:30:55 +00:00
George Rimar a50f115d36 [LLD][ELF] - Simplify the bad-archive.s test case.
This removes the precompiled binary and improves the
check of the error reported.

Differential revision: https://reviews.llvm.org/D66523

llvm-svn: 369516
2019-08-21 11:19:50 +00:00
Fangrui Song 2d337fdc95 Reland D65242 "[ELF] More dynamic relocation packing""
This fixed a bug in r369488. When config->isRela is false, i->r_addend
is not initialized (see encodeDynamicReloc). So we should check
config->isRela before accessing r_addend:

- if (j - i < 3 || i->r_addend)
+ if (j - i < 3 || (config->isRela && i->r_addend != 0))

Original description:

Currently, with Android dynamic relocation packing, only relative
relocations are grouped together. This patch implements similar
packing for non-relative relocations.

The implementation groups non-relative relocations with the same
r_info and r_addend, if using RELA. By requiring a minimum group
size of 3, this achieves smaller relocation sections. Building Android
for an ARM32 device, I see the total size of /system/lib decrease by
392 KB.

Grouping by r_info also allows the runtime dynamic linker to implement
an 1-entry cache to reduce the number of symbol lookup required. With
such 1-entry cache implemented on Android, I'm seeing 10% to 20%
reduction in total time spent in runtime linker for several executables
that I tested.

As a simple correctness check, I've also built x86_64 Android and booted
successfully.

Differential Revision: https://reviews.llvm.org/D65242
Patch by Vic Yang

llvm-svn: 369507
2019-08-21 09:21:37 +00:00
Fangrui Song b2895a8cdc Revert D65242 "[ELF] More dynamic relocation packing"
This reverts r369488 and r369489. The change broke build bots:

http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap-ubsan/builds/14511
http://lab.llvm.org:8011/builders/lld-x86_64-freebsd/builds/34407

llvm-svn: 369497
2019-08-21 06:50:08 +00:00
Fangrui Song d840a9cbed [ELF][test] Add CHECK lines omitted in r369488
Add append .o to some object file names

llvm-svn: 369489
2019-08-21 03:15:57 +00:00
Fangrui Song 35f9a84a15 [ELF] More dynamic relocation packing
Currently, with Android dynamic relocation packing, only relative
relocations are grouped together. This patch implements similar
packing for non-relative relocations.

The implementation groups non-relative relocations with the same
r_info and r_addend, if using RELA. By requiring a minimum group
size of 3, this achieves smaller relocation sections. Building Android
for an ARM32 device, I see the total size of /system/lib decrease by
392 KB.

Grouping by r_info also allows the runtime dynamic linker to implement
an 1-entry cache to reduce the number of symbol lookup required. With
such 1-entry cache implemented on Android, I'm seeing 10% to 20%
reduction in total time spent in runtime linker for several executables
that I tested.

As a simple correctness check, I've also built x86_64 Android and booted
successfully.

Differential Revision: https://reviews.llvm.org/D66491
Patch by Vic Yang!

llvm-svn: 369488
2019-08-21 03:02:08 +00:00
Fangrui Song 12d83b4270 [ELF][PPC] Allow PT_LOAD to have overlapping p_offset ranges on EM_PPC
Ported the D64906 technique to EM_PPC.

Delete ppc-rela.s that is covered by ppc32-abs-pic.s

llvm-svn: 369351
2019-08-20 09:20:05 +00:00
Fangrui Song 9c371309f3 [ELF][X86] Allow PT_LOAD to have overlapping p_offset ranges on EM_386
Ported the D64906 technique to EM_386.

If `sh_addralign(.tdata) < sh_addralign(.tbss)`,
we can potentially make `p_vaddr(PT_TLS)%p_align(PT_TLS) != 0`.

ld.so that are known to have problems if p_vaddr%p_align!=0:

* FreeBSD 13.0-CURRENT rtld-elf
* glibc https://sourceware.org/bugzilla/show_bug.cgi?id=24606

New test i386-tls-vaddr-align.s checks our workaround makes p_vaddr%p_align = 0.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D65865

llvm-svn: 369347
2019-08-20 08:43:47 +00:00
Fangrui Song f66b767abe [ELF][AArch64] Allow PT_LOAD to have overlapping p_offset ranges
Ported the D64906 technique to AArch64. It deletes 3 alignments at
PT_LOAD boundaries for the default case: the size of an aarch64 binary
decreases by at most 192kb.

If `sh_addralign(.tdata) < sh_addralign(.tbss)`,
we can potentially make `p_vaddr(PT_TLS)%p_align(PT_TLS) != 0`.

ld.so that are known to have problems if p_vaddr%p_align!=0:

* musl<=1.1.22
* FreeBSD 13.0-CURRENT (and before) rtld-elf arm64

New test aarch64-tls-vaddr-align.s checks that our workaround makes p_vaddr%p_align = 0.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D64930

llvm-svn: 369344
2019-08-20 08:34:56 +00:00
Fangrui Song 01c7f4b606 [ELF][PPC] Allow PT_LOAD to have overlapping p_offset ranges
This change affects the non-linker script case (precisely, when the
`SECTIONS` command is not used). It deletes 3 alignments at PT_LOAD
boundaries for the default case: the size of a powerpc64 binary can be
decreased by at most 192kb. The technique can be ported to other
targets.

Let me demonstrate the idea with a maxPageSize=65536 example:

When assigning the address to the first output section of a new PT_LOAD,
if the end p_vaddr of the previous PT_LOAD is 0x10020, we advance to
the next multiple of maxPageSize: 0x20000. The new PT_LOAD will thus
have p_vaddr=0x20000. Because p_offset and p_vaddr are congruent modulo
maxPageSize, p_offset will be 0x20000, leaving a p_offset gap [0x10020,
0x20000) in the output.

Alternatively, if we advance to 0x20020, the new PT_LOAD will have
p_vaddr=0x20020. We can pick either 0x10020 or 0x20020 for p_offset!
Obviously 0x10020 is the choice because it leaves no gap. At runtime,
p_vaddr will be rounded down by pagesize (65536 if
pagesize=maxPageSize). This PT_LOAD will load additional initial
contents from p_offset ranges [0x10000,0x10020), which will also be
loaded by the previous PT_LOAD. This is fine if -z noseparate-code is in
effect or if we are not transiting between executable and non-executable
segments.

ld.bfd -z noseparate-code leverages this technique to keep output small.
This patch implements the technique in lld, which is mostly effective on
targets with large defaultMaxPageSize (AArch64/MIPS/PPC: 65536). The 3
removed alignments can save almost 3*65536 bytes.

Two places that rely on p_vaddr%pagesize = 0 have to be updated.

1) We used to round p_memsz(PT_GNU_RELRO) up to commonPageSize (defaults
  to 4096 on all targets). Now p_vaddr%commonPageSize may be non-zero.
  The updated formula takes account of that factor.
2) Our TP offsets formulae are only correct if p_vaddr%p_align = 0.
  Fix them. See the updated comments in InputSection.cpp for details.

  On targets that we enable the technique (only PPC64 now),
  we can potentially make `p_vaddr(PT_TLS)%p_align(PT_TLS) != 0`
  if `sh_addralign(.tdata) < sh_addralign(.tbss)`

  This exposes many problems in ld.so implementations, especially the
  offsets of dynamic TLS blocks. Known issues:

  FreeBSD 13.0-CURRENT rtld-elf (i386/amd64/powerpc/arm64)
  glibc (HEAD) i386 and x86_64 https://sourceware.org/bugzilla/show_bug.cgi?id=24606
  musl<=1.1.22 on TLS Variant I architectures (aarch64/powerpc64/...)

  So, force p_vaddr%p_align = 0 by rounding dot up to p_align(PT_TLS).

The technique will be enabled (with updated tests) for other targets in
subsequent patches.

Reviewed By: ruiu

Differential Revision: https://reviews.llvm.org/D64906

llvm-svn: 369343
2019-08-20 08:34:25 +00:00
Fangrui Song ec4540d8a6 [ELF] Simplify processRelocAux and allow a corner-case error
After D66007/r369262, if the control flow reaches `if (sym.isUndefined())`, we know:

* The relocation is not a link-time constant => symbol is preemptable => Undefined or SharedSymbol
* Not an undef weak.
* -no-pie.
* The symbol type is neither STT_OBJECT nor STT_FUNC.

ld.lld --export-dynamic --unresolved-symbols=ignore-all %t.o can satisfy
these conditions. Delete the isUndefined() test so that we error
`symbol '...' has no type`, because we don't know the type to make the
decision to create copy relocation/canonical PLT.

llvm-svn: 369271
2019-08-19 15:52:29 +00:00
Fangrui Song ac0e6c6502 [ELF] Move (copy relocation/canonical PLT) before error checking
In processRelocAux(), we handle errors before copy relocation/canonical PLT.
This makes error checking a bit complex because we have to check for
conditions that will be allowed by copy relocation/canonical PLT.

Instead, move copy relocation/canonical PLT before error checking. This
simplifies the previous clumsy error checking code

`config->shared || (config->pie && expr == R_ABS && type != target->symbolicRel)`

to the simple `config->isPic`. Some diagnostics can be reported in
different ways. The code motion changes diagnostics for some contrived
test cases:

* copy-rel-pie-error.s -> copy-rel-pie2.s:
  It was rejected before but accepted now. ld.bfd also accepts the case.
* copy-errors.s: "cannot preempt symbol" changes to "symbol 'bar' has no type"
* got32{,x}-i386.s: the suggestion changes from "-fPIC or -Wl,-z,notext" to "-fPIE"
* x86-64-dyn-rel-error5.s: one diagnostic changes for -pie case

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D66007

llvm-svn: 369262
2019-08-19 14:30:12 +00:00
Sid Manning a0a4c6b722 [lld][Hexagon] Add GOTREL relocations.
Add GOTREL relocation support. (S + A - GOT)

Differential Revision: https://reviews.llvm.org/D66260

llvm-svn: 369258
2019-08-19 13:32:32 +00:00
Peter Smith 2cafd872fb [ELF][ARM] Add a test that maxes out the thunk convergence limit
Add a test that takes the maximum amount of passes permitted to converge.
This will make sure that any symbol defined in a linker script gets the
correct value and that any other convergence limit involving symbol address
doesn't restrict Thunk convergence.

Differential Revision: https://reviews.llvm.org/D66346

llvm-svn: 369246
2019-08-19 09:46:52 +00:00
Fangrui Song d5d79dfd56 [ELF][PPC] Fix getRelExpr for R_PPC64_REL16_HI
Fixes https://github.com/ClangBuiltLinux/linux/issues/640

R_PPC64_REL16_HI was incorrectly computed as an R_ABS relocation.
rLLD368964 made it a linker failure. Change it to use R_PC to fix the
failures.

Add ppc64-reloc-rel.s for these R_PPC64_REL* tests.

llvm-svn: 369184
2019-08-17 06:28:03 +00:00
Sid Manning 2d3ebeb813 [lld][Hexagon]Support HEX_32 when building shared objects
Differential Revision: https://reviews.llvm.org/D66105

llvm-svn: 369121
2019-08-16 15:35:02 +00:00
Fangrui Song e54ed4789f [ELF][AArch64] Improve error message for unknown relocations
Like rLLD354040.

Previously, for unrecognized relocation types, in -no-pie/-pie mode, we got something like:

  foo.o: unrecognized relocation ...

In -shared mode:

  error: can't create dynamic relocation ... against symbol: yyy in readonly segment

Delete the default case from AArch64::getRelExpr and add the error there.

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D66277

llvm-svn: 368983
2019-08-15 10:02:54 +00:00
Fangrui Song b9138bc52b [ELF][test] Update silent-ignore.test
Some options are implemented now:

--no-warn-common : r263413
--allow-shlib-undefined : r352826

Some are ignored but were not reflected in this test.

llvm-svn: 368837
2019-08-14 12:20:21 +00:00
Jordan Rupprecht 7859641626 [lld][test] Update test to print ELF note description data
llvm-svn: 368710
2019-08-13 16:11:09 +00:00
Fangrui Song dc06b0bc9a [ELF] Don't special case symbolic relocations with 0 addend to ifunc in writable locations
Currently the following 3 relocation types do not trigger the creation
of a canonical PLT (which changes STT_GNU_IFUNC to STT_FUNC and
redirects all references):

1) GOT-generating (`needsGot`)
2) PLT-generating (`needsPlt`)
3) R_ABS with 0 addend in a writable location. This is used for
  for ifunc function pointers in writable sections such as .data and .toc.

This patch deletes case 3) to simplify the R_*_IRELATIVE generating
logic added in D57371. Other advantages:

* It is guaranteed no more than 1 R_*_IRELATIVE is created for an ifunc.
* PPC64: no need to special case ifunc in toc-indirect to toc-relative relaxation. See D65755

The deleted elf::addIRelativeRelocs demonstrates that one-pass scan
through relocations makes several optimizations difficult. This is
something we can think about in the future.

Reviewed By: peter.smith

Differential Revision: https://reviews.llvm.org/D65995

llvm-svn: 368661
2019-08-13 09:43:40 +00:00
Fangrui Song 892cdc73be [ELF][test] Add dynamic-list-preempt2.s
When producing a DSO, the isPreemptible property of a Defined with
default or protected visibility is affected by the --dynamic-list file,
but not by interposable symbols in other DSOs.

llvm-svn: 368649
2019-08-13 05:08:46 +00:00