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Add options for enable code gen with CFI `-fcf-protection=[full|branc… #54

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Add options for enable code gen with CFI `-fcf-protection=[full|branc… #54

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23 changes: 23 additions & 0 deletions src/toolchain-conventions.adoc
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Expand Up @@ -406,6 +406,29 @@ NOTE: This option does not affect inline assembly.
The precedence among `-m[no]-scalar-strict-align`, `-m[no-]vector-strict-align`,
and `-m[no-]strict-align` is determined by the last one specified.

=== `-fcf-protection=[full|branch|return|none]`/`-fcf-protection`


Enable control flow protection. The compiler will insert control flow integrity
instructions to protect the program against control flow hijacking attacks.

`-fcf-protection` is alias to `-fcf-protection=full`.

- `none`: Disable control flow protection.
- `full`: Protect all control flow instructions, will enable branch protection
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This sentence reads like branch protection requires Zimop, but I think only return protection requires Zimop?

and return protection if the `Zimop` extension is available.
- `branch`: Protect branch instructions only by insert landing pad.
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insert -> inserting

- `return`: Protect return instructions only, this require `Zimop` extension.

=== `-mcf-branch-label-scheme=[unlabeled|func-sig]`

Specify the label scheme for the `-fcf-protection=branch`. The default is value
is platform defined.

- `unlabeled`: Use simple label scheme, the label is always `0`.
- `func-sig`: Use function signature as the label, the label is generated by the
compiler, the rule is defined in psABI spec.

== TODO

- `-mdiv`, `-mno-div`, `-mfdiv`, `-mno-fdiv`, `-msave-restore`,
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