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libdwarf: make catch type field singly referenced #192

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sb10q merged 1 commits from occheung/artiq-zynq:target2-rel into master 2022-05-31 18:26:30 +08:00
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occheung commented 2022-05-30 18:03:30 +08:00
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Description

This PR changes the parsing of the exception type of an exception entry in the .ARM.extab section, from doubly referenced to singly referenced.

Related PR

ARTIQ PR 1898

Background

Compiler generates a R_ARM_TARGET2 relocation that points to the exception type for the linker. By default, ld.lld resolves R_ARM_TARGET2 using "got-prel", which

  • inserts an entry into the GOT that references the exception type; and
  • relocate the relative offset of the GOT entry to PC.
    It results in exception type being doubly referenced. By specifying the option --target2=rel to ld.lld, the R_ARM_TARGET2 relocation is instead resolved as a relative address offset to the exception type. It bypasses the generation of a GOT entry.

This PR consist of the changes such that the exception type field is read as a singly referenced value. The change of ld.lld options is in the corresponding patch to mainline ARTIQ.

## Description This PR changes the parsing of the exception type of an exception entry in the `.ARM.extab` section, from doubly referenced to singly referenced. ### Related PR [ARTIQ PR 1898](https://github.com/m-labs/artiq/pull/1898) ### Background Compiler generates a `R_ARM_TARGET2` relocation that points to the exception type for the linker. By default, ld.lld resolves `R_ARM_TARGET2` using "got-prel", which - inserts an entry into the GOT that references the exception type; and - relocate the relative offset of the GOT entry to PC. It results in exception type being doubly referenced. By specifying the option `--target2=rel` to ld.lld, the `R_ARM_TARGET2` relocation is instead resolved as a relative address offset to the exception type. It bypasses the generation of a GOT entry. This PR consist of the changes such that the exception type field is read as a singly referenced value. The change of ld.lld options is in the corresponding patch to mainline ARTIQ.
occheung added 1 commit 2022-05-30 18:03:31 +08:00
sb10q merged commit f0febe0ee4 into master 2022-05-31 18:26:30 +08:00
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Reference: M-Labs/artiq-zynq#192
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