Commit Graph

12 Commits

Author SHA1 Message Date
Fangrui Song cf783be8d7 Reland D114783/D115603 [ELF] Split scanRelocations into scanRelocations/postScanRelocations
(Fixed an issue about GOT on a copy relocated alias.)
(Fixed an issue about not creating r_addend=0 IRELATIVE for unreferenced non-preemptible ifunc.)

The idea is to make scanRelocations mark some actions are needed (GOT/PLT/etc)
and postpone the real work to postScanRelocations. It gives some flexibility:

* Make it feasible to support .plt.got (PR32938): we need to know whether GLOB_DAT and JUMP_SLOT are both needed.
* Make non-preemptible IFUNC handling slightly cleaner: avoid setting/clearing sym.gotInIgot
* -z nocopyrel: report all copy relocation places for one symbol
* Make GOT deduplication feasible
* Make parallel relocation scanning feasible (if we can avoid all stateful operations and make Symbol attributes atomic), but parallelism may not be the appealing choice

Since this patch moves a large chunk of code out of ELFT templates. My x86-64
executable is actually a few hundred bytes smaller.

For ppc32-ifunc-nonpreemptible-pic.s: I remove absolute relocation references to non-preemptible ifunc
because absolute relocation references are incorrect in -fpie mode.

Reviewed By: peter.smith, ikudrin

Differential Revision: https://reviews.llvm.org/D114783
2021-12-14 16:28:41 -08:00
Fangrui Song ea15b862d7 Revert D114783 [ELF] Split scanRelocations into scanRelocations/postScanRelocations
May cause a failure for non-preemptible `bcmp` in a glibc -static link.
2021-12-14 14:33:50 -08:00
Fangrui Song e7a95b0674 Reland [ELF] Split scanRelocations into scanRelocations/postScanRelocations
(Fixed an issue about GOT on a copy relocated alias.)

The idea is to make scanRelocations mark some actions are needed (GOT/PLT/etc)
and postpone the real work to postScanRelocations. It gives some flexibility:

* Make it feasible to support .plt.got (PR32938): we need to know whether GLOB_DAT and JUMP_SLOT are both needed.
* Make non-preemptible IFUNC handling slightly cleaner: avoid setting/clearing sym.gotInIgot
* -z nocopyrel: report all copy relocation places for one symbol
* Make GOT deduplication feasible
* Make parallel relocation scanning feasible (if we can avoid all stateful operations and make Symbol attributes atomic), but parallelism may not be the appealing choice

Since this patch moves a large chunk of code out of ELFT templates. My x86-64
executable is actually a few hundred bytes smaller.

For ppc32-ifunc-nonpreemptible-pic.s: I remove absolute relocation references to non-preemptible ifunc
because absolute relocation references are incorrect in -fpie mode.

Reviewed By: peter.smith, ikudrin

Differential Revision: https://reviews.llvm.org/D114783
2021-12-13 20:11:24 -08:00
Fangrui Song 0b8b86e30f Revert "[ELF] Split scanRelocations into scanRelocations/postScanRelocations"
This reverts commit fc33861d48.

`replaceWithDefined` should copy needsGot, otherwise an alias for a copy
relocated symbol may not have GOT entry if its needsGot was originally true.
2021-12-13 19:29:53 -08:00
Fangrui Song fc33861d48 [ELF] Split scanRelocations into scanRelocations/postScanRelocations
The idea is to make scanRelocations mark some actions are needed (GOT/PLT/etc)
and postpone the real work to postScanRelocations. It gives some flexibility:

* Make it feasible to support .plt.got (PR32938): we need to know whether GLOB_DAT and JUMP_SLOT are both needed.
* Make non-preemptible IFUNC handling slightly cleaner: avoid setting/clearing sym.gotInIgot
* -z nocopyrel: report all copy relocation places for one symbol
* Make parallel relocation scanning possible (if we can avoid all stateful operations and make Symbol attributes atomic), but parallelism may not be the appealing choice
* Make GOT deduplication feasible

Since this patch moves a large chunk of code out of ELFT templates. My x86-64
executable is actually a few hundred bytes smaller.

For ppc32-ifunc-nonpreemptible-pic.s: I remove absolute relocation references to non-preemptible ifunc
because absolute relocation references are incorrect in -fpie mode.

Reviewed By: peter.smith, ikudrin

Differential Revision: https://reviews.llvm.org/D114783
2021-12-13 09:56:52 -08:00
Igor Kudrin e7fffa6f03 [llvm-objdump] Prefix memory operand addresses with '0x'
This helps to avoid ambiguity when the address contains only digits 0..9.

Differential Revision: https://reviews.llvm.org/D104909
2021-06-28 14:25:21 +07:00
Fangrui Song 5741dc87a5 [test] Improve x86-64-plt.s 2021-05-14 10:38:40 -07:00
Fangrui Song 87de9a0786 [X86InstPrinter] Change printPCRelImm to print the target address in hexadecimal form
```
// llvm-objdump -d output (before)
400000: e8 0b 00 00 00   callq 11
400005: e8 0b 00 00 00   callq 11

// llvm-objdump -d output (after)
400000: e8 0b 00 00 00  callq 0x400010
400005: e8 0b 00 00 00  callq 0x400015

// GNU objdump -d. The lack of 0x is not ideal because the result cannot be re-assembled
400000: e8 0b 00 00 00  callq 400010
400005: e8 0b 00 00 00  callq 400015
```

In llvm-objdump, we pass the address of the next MCInst. Ideally we
should just thread the address of the current address, unfortunately we
cannot call X86MCCodeEmitter::encodeInstruction (X86MCCodeEmitter
requires MCInstrInfo and MCContext) to get the length of the MCInst.

MCInstPrinter::printInst has other callers (e.g llvm-mc -filetype=asm, llvm-mca) which set Address to 0.
They leave MCInstPrinter::PrintBranchImmAsAddress as false and this change is a no-op for them.

Reviewed By: jhenderson

Differential Revision: https://reviews.llvm.org/D76580
2020-03-26 08:28:59 -07:00
Fangrui Song 71e2ca6e32 [llvm-objdump] -d: print `00000000 <foo>:` instead of `00000000 foo:`
The new behavior matches GNU objdump. A pair of angle brackets makes tests slightly easier.

`.foo:` is not unique and thus cannot be used in a `CHECK-LABEL:` directive.
Without `-LABEL`, the CHECK line can match the `Disassembly of section`
line and causes the next `CHECK-NEXT:` to fail.

```
Disassembly of section .foo:

0000000000001634 .foo:
```

Bdragon: <> has metalinguistic connotation. it just "feels right"

Reviewed By: rupprecht

Differential Revision: https://reviews.llvm.org/D75713
2020-03-05 18:05:28 -08:00
Fangrui Song d4306e90cb [ELF][X86] Allow PT_LOAD to have overlapping p_offset ranges on EM_X86_64
Port the D64906 technique to EM_X86_64.

Differential Revision: https://reviews.llvm.org/D67482

llvm-svn: 371958
2019-09-16 07:05:34 +00:00
Fangrui Song 2aace1ea22 [ELF][test] Make tests more tolerant to exact symbol addresses
llvm-svn: 371588
2019-09-11 06:20:14 +00:00
Fangrui Song 88796a7988 [ELF][test] Improve and reorganize another set of tests
Add file-level comments
Replace trivial Input/*.s with echo ... | llvm-mc
Delete insignificant addresses to make them more tolerant to layout changes
Simplify test output

Merge merge-section-types.s into compatible-section-types.s and add a missed case
Merge gnu-ifunc-gotpcrel.s (added in D19517) into gnu-ifunc-dso.s (added in D35119) and add missed cases
Delete typed-undef.s - covered by executable-undefined-ignoreall.s
Delete emit-relocs-shared.s - covered by emit-relocs-merge.s

Replace copy-rel-pie.s and copy-rel-pie2.s with canonical-plt-pcrel.s, canonical-plt-symbolic.s and copy-rel.s:
add -no-pie cases.
add a case that a canonical PLT can be created for STT_GNU_IFUNC. The logic in Symbols.h was untested:

  // ctor of SharedSymbol
  if (this->type == llvm::ELF::STT_GNU_IFUNC)
    this->type = llvm::ELF::STT_FUNC;

llvm-svn: 371361
2019-09-09 03:35:14 +00:00