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Arm64:[PAC-RET] Use hint-space instruction for stripping return address #129130

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Merged
jkotas merged 2 commits into from
Jun 8, 2026
+18 −8
Merged

Arm64:[PAC-RET] Use hint-space instruction for stripping return address #129130

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9e84621
Arm64:[PAC-RET] Use hint-space instruction for stripping return address
SwapnilGaikwad Jun 8, 2026
19f10f2
Fix build errors on Windows
SwapnilGaikwad Jun 8, 2026
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13 changes: 9 additions & 4 deletions src/coreclr/vm/arm64/asmhelpers.S
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Original file line number Diff line number Diff line change
Expand Up @@ -160,11 +160,16 @@ NESTED_END OnHijackTripThread, _TEXT
// void* PacStripPtr(void *);
// This function strips the pointer of PAC info that is passed as an argument.
// We prefer to strip a pointer where it's not going to be used to branch execution to.
// It is a no-op on non-PAC enabled machines.
.arch_extension pauth
LEAF_ENTRY PacStripPtr, _TEXT
xpaci x0
ret
LEAF_END PacStripPtr, _TEXT
NESTED_ENTRY PacStripPtr, _TEXT, NoHandler
PROLOG_SAVE_REG_PAIR_INDEXED fp, lr, -16
mov lr, x0
xpaclri
mov x0, lr
EPILOG_RESTORE_REG_PAIR_INDEXED fp, lr, 16
EPILOG_RETURN
NESTED_END PacStripPtr, _TEXT

// void* PacSignPtr(void *, void *);
// This function signs the input pointer using x1 as salt. It is a no-op on non-PAC enabled machines.
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13 changes: 9 additions & 4 deletions src/coreclr/vm/arm64/asmhelpers.asm
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Original file line number Diff line number Diff line change
Expand Up @@ -323,10 +323,15 @@ OnHijackTripThreadReturn
; void* PacStripPtr(void *);
; This function strips the pointer of PAC info that is passed as an argument.
; We prefer to strip a pointer where it's not going to be used to branch execution to.
LEAF_ENTRY PacStripPtr
DCD 0xDAC143E0 ; xpaci x0 instruction in binary to avoid requiring PAC-enabled assemblers
ret
LEAF_END PacStripPtr
; It is a no-op on non-PAC enabled machines.
NESTED_ENTRY PacStripPtr
PROLOG_SAVE_REG_PAIR fp, lr, #-16!
mov lr, x0
DCD 0xD50320FF ; xpaclri instruction in binary to avoid requiring PAC-enabled assemblers
mov x0, lr
EPILOG_RESTORE_REG_PAIR fp, lr, #16!
EPILOG_RETURN
NESTED_END

; void* PacSignPtr(void *, void *);
; This function signs the input pointer using x1 as salt. It is a no-op on non-PAC enabled machines.
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