[pauthabi64] Add Auth variants of TLSDESC generating GOT relocations #295
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Add static Auth equivalents of the existing relocations: * R_AARCH64_TLSDESC_ADR_PAGE21 * R_AARCH64_TLSDESC_LD64_LO12 * R_AARCH64_TLSDESC_ADD_LO12 These are sufficient to implement the small code-model for TLSDESC using the PAuthABI. Support for the tiny and large code-model is not implemented for the PAuthABI, or for the normal ABI in both clang and GCC so we defer from specifiying Auth variants of all possible relocations. I've followed the convention that non-zero addends are not permitted for GOT generating relocations. As each unique S+A combination needs its own pair of GOT slots indexed by S+A and no static linker supports that. Fixes ARM-software#293
kovdan01
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Nov 18, 2024
…ons (#113716) See specification ARM-software/abi-aa#295
smithp35
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In the initial draft relocations for signing GOT entries were defined in the private space reserved for experiments. It was not known if these relocations would be useful as if RELRO is supported the GOT does not need to be signed. There is now at least one user of the GOT signing relocations so we should move the relocations out of the private space and into the space reserved for the PAuthABI. This PR includes relocations added in ARM-software#295 Fixes: ARM-software#298
stuij
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Jan 9, 2025
pauthabielf64/pauthabielf64.rst
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| +-------------+----------------------------------------+----------------------------------------+--------------------------+ | ||
| | 0x811E | R\_AARCH64\_AUTH\_TLSDESC\_ADR\_PAGE21 | Page(G(ENCD(GTLSDESC(S)))) - Page(P) | Set an ADRP immediate | | ||
| | | | | field to bits [32:12] of | | ||
| | | | | X; check –2\ :sup:`20` | |
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The range for ADRP is ±4GB [1], so I think that the check should be between -2^32 and 2^32, instead of 20.
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ACK. It looks like I used the text from R_<CLS>_TLSDESC_ ADR_PREL21 in the table rather than the similarly named R_<CLS>_TLSDESC_ ADR_PAGE21
Will fix.
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I've updated the PR to use -2^32 and 2^32
The R_AARCH64_AUTH_TLSDESC_ADR_PAGE21 now has the correct range check of +- 2^32.
smithp35
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In the initial draft relocations for signing GOT entries were defined in the private space reserved for experiments. It was not known if these relocations would be useful as if RELRO is supported the GOT does not need to be signed. There is now at least one user of the GOT signing relocations so we should move the relocations out of the private space and into the space reserved for the PAuthABI. This PR includes relocations added in ARM-software#295 Fixes: ARM-software#298
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Add static Auth equivalents of the existing relocations:
These are sufficient to implement the small code-model for TLSDESC using the PAuthABI. Support for the tiny and large code-model is not implemented for the PAuthABI, or for the normal ABI in both clang and GCC so we defer from specifiying Auth variants of all possible relocations.
I've followed the convention that non-zero addends are not permitted for GOT generating relocations. As each unique S+A combination needs its own pair of GOT slots indexed by S+A and no static linker supports that.
Fixes #293