git: 8b9f8a7e763d - stable/14 - arm64: Clear td_frame when returning to userspace

The branch stable/14 has been updated by andrew:

URL: https://cgit.FreeBSD.org/src/commit/?id=8b9f8a7e763dfc533ce2abd5b48d1ba9f54165e2

commit 8b9f8a7e763dfc533ce2abd5b48d1ba9f54165e2
Author:     Andrew Turner <andrew@FreeBSD.org>
AuthorDate: 2024-06-12 13:08:13 +0000
Commit:     Andrew Turner <andrew@FreeBSD.org>
CommitDate: 2024-09-02 08:48:17 +0000

    arm64: Clear td_frame when returning to userspace
    
    When returning from an exception to userspace clear the saved td_frame.
    On the next exception this should point to the frame, however this is
    not guaranteed.
    
    To ensure the trap frame pointer is either valid or NULL clear it
    before returning to userspace in the EL0 synchronous exception handler.
    
    Reviewed by:    kib, markj
    Sponsored by:   Arm Ltd
    Differential Revision:  https://reviews.freebsd.org/D44807
    
    (cherry picked from commit 4eec584d79c1e8375d863c7eec7229ac7ec3f13b)
---
 sys/arm64/arm64/exception.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/sys/arm64/arm64/exception.S b/sys/arm64/arm64/exception.S
index b1990fc71281..0df440863632 100644
--- a/sys/arm64/arm64/exception.S
+++ b/sys/arm64/arm64/exception.S
@@ -214,9 +214,11 @@ ENTRY(handle_el0_sync)
 	save_registers 0
 	ldr	x0, [x18, #PC_CURTHREAD]
 	mov	x1, sp
+	mov	x22, x0
 	str	x1, [x0, #TD_FRAME]
 	bl	do_el0_sync
 	do_ast
+	str	xzr, [x22, #TD_FRAME]
 	restore_registers 0
 	ERET
 END(handle_el0_sync)