| commit | a4d3c0c69d5ef3bb37407f421ae16883ee4c1d63 | [log] [tgz] |
|---|---|---|
| author | Anatoly Trosinenko <atrosinenko@accesssoftek.com> | Wed Sep 24 13:56:58 2025 |
| committer | Anatoly Trosinenko <atrosinenko@accesssoftek.com> | Fri Sep 26 12:52:59 2025 |
| tree | 8e023049bfd00ef092205b3289c36b1c794e3c10 | |
| parent | c10befb9d3b2b50e37048f2aba5dda0f77031ba3 [diff] |
[AArch64][PAC] Simplify emission of authenticated pointer check (NFC)
The AArch64AsmPrinter::emitPtrauthCheckAuthenticatedValue method accepts
two arguments, `bool ShouldTrap` and `const MCSymbol *OnFailure`, that
control the behavior of the emitted instruction sequence when the check
fails:
* `ShouldTrap` requests an error to be generated
* `OnFailure` requests branching to the given label after clearing the
PAC field
An assertion in `emitPtrauthCheckAuthenticatedValue` ensures that
`OnFailure` must be null when `ShouldTrap` is set. But the opposite is
also true: when `ShouldTrap` is false, `OnFailure` is always non-null,
as otherwise the entire sequence following `AUT[ID][AB]` instruction
would turn into a very expensive equivalent of XPAC (unless the CPU
implements FEAT_FPAC):
authenticate Xn
inspect PAC field of Xn
if PAC field was not cleared:
clear PAC field
The only caller that makes use of checking-but-not-trapping mode of
emitPtrauthCheckAuthenticatedValue is emitPtrauthAuthResign, and it
passes a non-null pointer as OnFailure when ShouldTrap is false.
This commit makes the invariant explicit by omitting the ShouldTrap
argument and inferring its value from the OnFailure argument instead.
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