Commit Graph

13 Commits

Author SHA1 Message Date
Georgii Rymar bb7d2b1780 [LLD][ELF] - Disambiguate "=fillexp" with a primary expression to allow =0x90 /DISCARD/
Fixes https://bugs.llvm.org/show_bug.cgi?id=44903

It is about the following case:

```
SECTIONS {
  .foo : { *(.foo) } =0x90909090
  /DISCARD/ : { *(.bar) }
}
```

Here while parsing the fill expression we treated the
"/" of "/DISCARD/" as operator.

With this change, suggested by Fangrui Song, we do
not allow expressions with operators (e.g. "0x1100 + 0x22")
that are not wrapped into round brackets. It should not
be an issue for users, but helps to resolve parsing ambiguity.

Differential revision: https://reviews.llvm.org/D74687
2020-03-19 12:49:25 +03:00
Fangrui Song f0374e7db2 [test] lld/test/: change llvm-objdump single-dash long options to double-dash options 2020-03-15 17:48:36 -07:00
Fangrui Song 81cebfd008 [ELF][test] Change -o %t to -o /dev/null if the output is not needed 2020-02-12 21:54:50 -08:00
George Rimar c44a23f8f4 [LLD][ELF] - Linkerscript: fix FILL() expressions handling.
D64130 introduced a bug described in the following message:
https://reviews.llvm.org/D64130#1571560

The problem can happen with the following script:

SECTIONS {
  .out : {
...
   FILL(0x10101010)
   *(.aaa)
...
}

The current code tries to read (0x10101010) as an expression and
does not break when meets *, what results in a script parsing error.

In this patch, I verify that FILL command's expression always wrapped in ().
And at the same time =<fillexp> expression can be both wrapped or unwrapped.
I checked it matches to bfd/gold.

Differential revision: https://reviews.llvm.org/D64476

llvm-svn: 365635
2019-07-10 14:36:48 +00:00
George Rimar 0810f16fb9 [LLD][ELF] - Linkerscript: add a support for expressions for section's filling
Imagine the script:

.section: {
...
} = FILL_EXPR
LLD assumes that FILL_EXPR is a number, and does not allow
it to be an expression. Though that is allowed by specification:
https://sourceware.org/binutils/docs-2.32/ld/Output-Section-Fill.html

This patch adds a support for cases when FILL_EXPR is simple math expression.

Fixes https://bugs.llvm.org/show_bug.cgi?id=42482.

Differential revision: https://reviews.llvm.org/D64130

llvm-svn: 365143
2019-07-04 14:17:31 +00:00
James Henderson 9d9a663731 [ELF] Recommit r299635 to pad x86 executable sections with 0xcc
This follows r299748 which fixed a latent bug the original commit exposed.

llvm-svn: 299755
2017-04-07 10:36:42 +00:00
James Henderson d983180778 Revert r299635 because it exposed a latent bug.
llvm-svn: 299655
2017-04-06 15:22:58 +00:00
James Henderson 8dd4c06a77 [ELF] Pad x86 executable sections with 0xcc int3 instructions
Executable sections should not be padded with zero by default. On some
architectures, 0x00 is the start of a valid instruction sequence, so can confuse
disassembly between InputSections (and indeed the start of the next InputSection
in some situations). Further, in the case of misjumps into padding, padding may
start to be executed silently.

On x86, the "0xcc" byte represents the int3 trap instruction. It is a single
byte long so can serve well as padding. This change switches x86 (and x86_64) to
use this value for padding in executable sections, if no linker script directive
overrides it. It also puts the behaviour into place making it easy to change the
behaviour of other targets when desired. I do not know the relevant instruction
sequences for trap instructions on other targets however, so somebody should add
this separately.

Because the old behaviour simply wrote padding in the whole section before
overwriting most of it, this change also modifies the padding algorithm to write
padding only where needed. This in turn has caused a small behaviour change with
regards to what values are written via Fill commands in linker scripts, bringing
it into line with ld.bfd. The fill value is now written starting from the end of
the previous block, which means that it always starts from the first byte of the
fill, whereas the old behaviour meant that the padding sometimes started mid-way
through the fill value. See the test changes for more details.

Reviewed by: ruiu

Differential Revision: https://reviews.llvm.org/D30886

Bugzilla: http://bugs.llvm.org/show_bug.cgi?id=32227
llvm-svn: 299635
2017-04-06 09:29:08 +00:00
George Rimar 7185a1acec [ELF] - Support optional comma after output section command.
I found this when tried to link linux kernel with LLD:

https://github.com/torvalds/linux/blob/master/arch/x86/entry/vdso/vdso-layout.lds.S#L86

Output section command can have optional comma at the end:

.text		: { *(.text*) }			:text	=0x90909090,

It was documented about 3 years ago for binutils:
https://sourceware.org/ml/binutils/2014-04/msg00045.html

Differential revision: https://reviews.llvm.org/D28803

llvm-svn: 292225
2017-01-17 15:32:12 +00:00
George Rimar 4ebc562052 [ELF] - Linkerscript: accept space between '=' and expression in section filler.
Previously we failed to parse next scripts because disallowed
a space between filler value and '=':

  .text : {
...
  } :text = 0x9090

Differential revision: https://reviews.llvm.org/D24831

llvm-svn: 282248
2016-09-23 13:29:20 +00:00
Rafael Espindola 1b87995f31 Make tests less dependent on the exact layout.
In most cases that means just not checking the address when we don't
need it.

For some tests it is easier to just set . to a known value.

llvm-svn: 281976
2016-09-20 15:08:24 +00:00
George Rimar ff1f29e0f6 [ELF] - Linkerscript: implemented FILL command as alias for =fillexpr
Patch implements FILL just as alias for =fillexpr. 
This allows to make implementation much shorted and simpler than D24186.

Differential revision: https://reviews.llvm.org/D24227

llvm-svn: 280708
2016-09-06 13:51:57 +00:00
Rui Ueyama 66ba9f08b9 Remove useless file prefix.
Differential Revision: https://reviews.llvm.org/D24207

llvm-svn: 280540
2016-09-02 20:40:53 +00:00