tree 7644a49475354c617440d116c6c9815180a6b84f
parent 866f1cd6a9146b3ee6ed012c0d90e02bc96d4e16
author Ming-Yi Lai <ming-yi.lai@mediatek.com> 1747194539 +0800
committer GitHub <noreply@github.com> 1747194539 +0800
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[RISCV] Emit .note.gnu.property section when Zicfiss-based shadow stack is enabled (#127036)

RISC-V Zicfiss-based shadow stack needs to let the linker/loader know if
the binary is built with the mechanism enabled to support proper
link-time/load-time management of this feature. The information is
encoded as a bit in the `.note.gnu.property` section. This patch
implements emitting the section for RISC-V targets when Zicfiss-based
shadow stack is enabled.

When Clang receives the `-fcf-protection=return` flag, it adds the
`hw-shadow-stack` attribute to LLVM functions, and adds a non-zero
valued attribute named `cf-protection-return` to the LLVM module it
generates. The backend depends on the `hw-shadow-stack` attributes to
generate Zicfiss-based shadow stack instructions for each function, but
at the module scope, the `cf-protection-return` attribute is a better
indication of whether the translation unit is built with Zicfiss-based
shadow stack enabled, so this patch emits the `.note.gnu.property`
section with the "Zicfiss-based shadow stack" bit toggled on when it
sees the `cf-protection-return` attribute.