Document a limitation of the DW_CFA_AARCH64_negate_ra_state. #129
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nsz-arm
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Feb 10, 2022
aadwarf64/aadwarf64.rst
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| @@ -582,6 +582,9 @@ This ABI defines one vendor call frame instruction | |||
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| The ``DW_CFA_AARCH64_negate_ra_state`` operation negates bit[0] of the | |||
| RA_SIGN_STATE pseudo-register. It does not take any operands. | |||
| The ``DW_CFA_AARCH64_negate_ra_state`` shall not be mixed with other DWARF operations on the | |||
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i think we should use the "Register Rule Instruction" terminology from 6.4.2.3 of https://www.dwarfstd.org/doc/DWARF5.pdf
because we want to allow "Row State Instructions" from 6.4.2.4. to be mixed with negate_ra_state.
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either that or we should call out DW_CFA_remember_state/restore_state explicitly.
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Thanks @nsz-arm, change is updated.
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walkerkd
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Feb 24, 2022
DW_CFA_AARCH64_negate_ra_state depends on the previous state of the RA_SIGN_STATE register which makes complex to handle in cases when the register is set by DWARF expressions because expression are lasily evaulated in runtime.
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@walkerkd Thanks, done. |
walkerkd
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Mar 7, 2022
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Looks good to me |
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Program may set the RA_SIGN_STATE pseudo register by expressions. Libunwind expected only the DW_CFA_AARCH64_negate_ra_state could change the value of the register which leads to runtime errors on PAC enabled systems. In the recent version of the aadwarf64[1] a limitation is added[2] to forbid the mixing the DW_CFA_AARCH64_negate_ra_state with other DWARF Register Rule Instructions. [1] https://github.com/ARM-software/abi-aa/releases/tag/2022Q1 [2] ARM-software/abi-aa#129 Reviewed By: #libunwind, MaskRay Differential Revision: https://reviews.llvm.org/D123692
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Program may set the RA_SIGN_STATE pseudo register by expressions. Libunwind expected only the DW_CFA_AARCH64_negate_ra_state could change the value of the register which leads to runtime errors on PAC enabled systems. In the recent version of the aadwarf64[1] a limitation is added[2] to forbid the mixing the DW_CFA_AARCH64_negate_ra_state with other DWARF Register Rule Instructions. [1] https://github.com/ARM-software/abi-aa/releases/tag/2022Q1 [2] ARM-software/abi-aa#129 Reviewed By: #libunwind, MaskRay Differential Revision: https://reviews.llvm.org/D123692 Reland: test moved because it depends on exceptions.
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Program may set the RA_SIGN_STATE pseudo register by expressions. Libunwind expected only the DW_CFA_AARCH64_negate_ra_state could change the value of the register which leads to runtime errors on PAC enabled systems. In the recent version of the aadwarf64[1] a limitation is added[2] to forbid the mixing the DW_CFA_AARCH64_negate_ra_state with other DWARF Register Rule Instructions. [1] https://github.com/ARM-software/abi-aa/releases/tag/2022Q1 [2] ARM-software/abi-aa#129 Reviewed By: #libunwind, MaskRay Differential Revision: https://reviews.llvm.org/D123692
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Program may set the RA_SIGN_STATE pseudo register by expressions. Libunwind expected only the DW_CFA_AARCH64_negate_ra_state could change the value of the register which leads to runtime errors on PAC enabled systems. In the recent version of the aadwarf64[1] a limitation is added[2] to forbid the mixing the DW_CFA_AARCH64_negate_ra_state with other DWARF Register Rule Instructions. [1] https://github.com/ARM-software/abi-aa/releases/tag/2022Q1 [2] ARM-software/abi-aa#129 Reviewed By: #libunwind, MaskRay Differential Revision: https://reviews.llvm.org/D123692 Reland: test moved because it depends on exceptions.
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Program may set the RA_SIGN_STATE pseudo register by expressions. Libunwind expected only the DW_CFA_AARCH64_negate_ra_state could change the value of the register which leads to runtime errors on PAC enabled systems. In the recent version of the aadwarf64[1] a limitation is added[2] to forbid the mixing the DW_CFA_AARCH64_negate_ra_state with other DWARF Register Rule Instructions. [1] https://github.com/ARM-software/abi-aa/releases/tag/2022Q1 [2] ARM-software/abi-aa#129 Reviewed By: #libunwind, MaskRay Differential Revision: https://reviews.llvm.org/D123692
arichardson
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Program may set the RA_SIGN_STATE pseudo register by expressions. Libunwind expected only the DW_CFA_AARCH64_negate_ra_state could change the value of the register which leads to runtime errors on PAC enabled systems. In the recent version of the aadwarf64[1] a limitation is added[2] to forbid the mixing the DW_CFA_AARCH64_negate_ra_state with other DWARF Register Rule Instructions. [1] https://github.com/ARM-software/abi-aa/releases/tag/2022Q1 [2] ARM-software/abi-aa#129 Reviewed By: #libunwind, MaskRay Differential Revision: https://reviews.llvm.org/D123692 Reland: test moved because it depends on exceptions.
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DW_CFA_AARCH64_negate_ra_state depends on the previous state of the RA_SIGN_STATE
register which makes complex to handle in cases when the register is set by
DWARF expressions because expression are lasily evaulated in runtime.