From 5941edfcdc17ed51b65125c25d3fac632bf4cd81 Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Tue, 1 Dec 2020 17:04:46 +0000
Subject: Add a kstack_contains() helper function.

This is useful for stack unwinders which need to avoid out-of-bounds
reads of a kernel stack which can trigger kernel faults.

Reviewed by:	kib, markj
Obtained from:	CheriBSD
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D27356
---
 sys/sys/proc.h | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'sys/sys/proc.h')

diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 23bac23b5188..0d92dfb7578d 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -1198,6 +1198,13 @@ curthread_pflags2_restore(int save)
 	curthread->td_pflags2 &= save;
 }
 
+static __inline bool
+kstack_contains(struct thread *td, vm_offset_t va, size_t len)
+{
+	return (va >= td->td_kstack && va + len >= va &&
+	    va + len <= td->td_kstack + td->td_kstack_pages * PAGE_SIZE);
+}
+
 static __inline __pure2 struct td_sched *
 td_get_sched(struct thread *td)
 {
-- 
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