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From:   Heiko Carstens <hca@linux.ibm.com>
To:     Kees Cook <keescook@chromium.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Popov <alex.popov@linux.com>
Cc:     Vasily Gorbik <gor@linux.ibm.com>, linux-kernel@vger.kernel.org
Subject: [PATCH 1/2] stackleak: allow to specify arch specific stackleak poison function
Date:   Wed,  5 Apr 2023 15:08:40 +0200
Message-Id: <20230405130841.1350565-2-hca@linux.ibm.com>
In-Reply-To: <20230405130841.1350565-1-hca@linux.ibm.com>
References: <20230405130841.1350565-1-hca@linux.ibm.com>
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Factor out the code that fills the stack with the stackleak poison value
in order to allow architectures to provide a faster implementation.

Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
---
 kernel/stackleak.c | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/kernel/stackleak.c b/kernel/stackleak.c
index c2c33d2202e9..34c9d81eea94 100644
--- a/kernel/stackleak.c
+++ b/kernel/stackleak.c
@@ -70,6 +70,18 @@ late_initcall(stackleak_sysctls_init);
 #define skip_erasing()	false
 #endif /* CONFIG_STACKLEAK_RUNTIME_DISABLE */
 
+#ifndef __stackleak_poison
+static __always_inline void __stackleak_poison(unsigned long erase_low,
+					       unsigned long erase_high,
+					       unsigned long poison)
+{
+	while (erase_low < erase_high) {
+		*(unsigned long *)erase_low = poison;
+		erase_low += sizeof(unsigned long);
+	}
+}
+#endif
+
 static __always_inline void __stackleak_erase(bool on_task_stack)
 {
 	const unsigned long task_stack_low = stackleak_task_low_bound(current);
@@ -101,10 +113,7 @@ static __always_inline void __stackleak_erase(bool on_task_stack)
 	else
 		erase_high = task_stack_high;
 
-	while (erase_low < erase_high) {
-		*(unsigned long *)erase_low = STACKLEAK_POISON;
-		erase_low += sizeof(unsigned long);
-	}
+	__stackleak_poison(erase_low, erase_high, STACKLEAK_POISON);
 
 	/* Reset the 'lowest_stack' value for the next syscall */
 	current->lowest_stack = task_stack_high;
-- 
2.37.2