Commit Graph

3 Commits

Author SHA1 Message Date
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 7cd429f27d [ELF] Add -z force-ibt and -z shstk for Intel Control-flow Enforcement Technology
This patch is a joint work by Rui Ueyama and me based on D58102 by Xiang Zhang.

It adds Intel CET (Control-flow Enforcement Technology) support to lld.
The implementation follows the draft version of psABI which you can
download from https://github.com/hjl-tools/x86-psABI/wiki/X86-psABI.

CET introduces a new restriction on indirect jump instructions so that
you can limit the places to which you can jump to using indirect jumps.

In order to use the feature, you need to compile source files with
-fcf-protection=full.

* IBT is enabled if all input files are compiled with the flag. To force enabling ibt, pass -z force-ibt.
* SHSTK is enabled if all input files are compiled with the flag, or if -z shstk is specified.

IBT-enabled executables/shared objects have two PLT sections, ".plt" and
".plt.sec".  For the details as to why we have two sections, please read
the comments.

Reviewed By: xiangzhangllvm

Differential Revision: https://reviews.llvm.org/D59780
2020-01-13 23:39:28 -08:00