Commit Graph

4 Commits

Author SHA1 Message Date
Fangrui Song 16c30c3c23 [ELF] Change --shuffle-sections=<seed> to --shuffle-sections=<section-glob>=<seed>
`--shuffle-sections=<seed>` applies to all sections.  The new
`--shuffle-sections=<section-glob>=<seed>` makes shuffling selective.  To the
best of my knowledge, the option is only used as debugging, so just drop the
original form.

`--shuffle-sections '.init_array*=-1'` `--shuffle-sections '.fini_array*=-1'`.
reverses static constructors/destructors of the same priority.
Useful to detect some static initialization order fiasco.

`--shuffle-sections '.data*=-1'`
reverses `.data*` sections. Useful to detect unfunded pointer comparison results
of two unrelated objects.

If certain sections have an intrinsic order, the old form cannot be used.

Differential Revision: https://reviews.llvm.org/D98679
2021-03-18 10:18:19 -07:00
Fangrui Song 9e33c09647 [ELF] Keep orphan section names (.rodata.foo .text.foo) unchanged if !hasSectionsCommand
This behavior matches GNU ld and seems reasonable.

```
// If a SECTIONS command is not specified
.text.* -> .text
.rodata.* -> .rodata
.init_array.* -> .init_array
```

A proposed Linux feature CONFIG_FG_KASLR may depend on the GNU ld behavior.

Reword a comment about -z keep-text-section-prefix and a comment about
CommonSection (deleted by rL286234).

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D75225
2020-03-23 10:30:06 -07:00
Rafael Ávila de Espíndola 7b44f0428a Add a llvm::shuffle and use it in lld
With this --shuffle-sections=seed produces the same result in every
host.

Reviewed By: grimar, MaskRay

Differential Revision: https://reviews.llvm.org/D74971
2020-02-22 10:05:29 -08:00
Fangrui Song dbd7281aa7 [ELF] Shuffle .init_array/.fini_array with --shuffle-sections=
Useful for detecting static initialization order fiasco.

Reviewed By: grimar

Differential Revision: https://reviews.llvm.org/D74887
2020-02-21 08:16:07 -08:00