Make dynamic string table simpler to use #95
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
partaror
force-pushed
the
DynStrTab
branch
3 times, most recently
from
May 16, 2025 18:52
e497dc8 to
dbb21f1
Compare
quic-seaswara
approved these changes
May 16, 2025
| return DynamicStringTableContents.size(); | ||
| } | ||
|
|
||
| std::optional<std::size_t> getOffsetInDynStrTab(const std::string &S) const { |
There was a problem hiding this comment.
This API is used during image writing step. It expects the string has already been inserted in the dynamic string table. If this is not true, then this API returns an empty optional object (and the user of this API can choose to error/assert as appropriate). It does not add the string in the dynamic string table as the counterpart function addStringToDynStrTab.
Currently, dynamic string table is used as follows:
1) Before layout: Compute the size of the dynamic string table by
traversing over dynamic symbols, sonames, DT_NEEDED entries and so
on.
2) During output image writing: Again traverse over dynamic symbols,
sonames, DT_NEEDED entries, ..., This time copy the string into the
dynamic string table and set the string offset in the dynamic-related
section that was referring the string.
This separation of computing size, offsets and actually writing makes
the dynamic string table use cumbersome and error-prone. Especially for
sections such as `.gnu.version_r` and `.gnu.version_d`.
With this commit, the dynamic string table can be used as:
```
std::size_t SONameOffset = FileFormat->addStringToDynStrTab(
llvm::cast<ELFDynObjectFile>(lib)->getSOName());
auto DTEntry = dynamic()->reserveNeedEntry();
DTEntry->setValue(llvm::ELF::DT_NEEDED, SONameOffset);
```
There is no need to separate size and offset computation anymore.
Another added benefit is that now we reuse the `.dynstr` table entries
wherever possible instead of repeating the same string multiple times in
the dynamic string table.
Closes qualcomm#94
Signed-off-by: Parth Arora <partaror@qti.qualcomm.com>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Currently, dynamic string table is used as follows:
traversing over dynamic symbols, sonames, DT_NEEDED entries and so
on.
sonames, DT_NEEDED entries, ..., This time copy the string into the
dynamic string table and set the string offset in the dynamic-related
section that was referring the string.
This separation of computing size, offsets and actually writing makes the dynamic string table use cumbersome and error-prone. Especially for sections such as
.gnu.version_rand.gnu.version_d.With this commit, the dynamic string table can be used as:
There is no need to separate size and offset computation anymore.
Another added benefit is that now we reuse the
.dynstrtable entrieswherever possible instead of repeating the same string multiple times in
the dynamic string table.
Closes #94