From 2a7ce82dc46c591c9244057d89a6591c9639b9b9 Mon Sep 17 00:00:00 2001
From: Rohan McLure <rmclure@linux.ibm.com>
Date: Mon, 6 Feb 2023 13:17:58 +1100
Subject: [PATCH] powerpc/kcsan: Exclude udelay to prevent recursive
 instrumentation

References: bsc#1194869
Patch-mainline: v6.3-rc1
Git-commit: 2a7ce82dc46c591c9244057d89a6591c9639b9b9

In order for KCSAN to increase its likelihood of observing a data race,
it sets a watchpoint on memory accesses and stalls, allowing for
detection of conflicting accesses by other kernel threads or interrupts.

Stalls are implemented by injecting a call to udelay in instrumented code.
To prevent recursive instrumentation, exclude udelay from being instrumented.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230206021801.105268-3-rmclure@linux.ibm.com
Acked-by: Michal Suchanek <msuchanek@suse.de>
---
 arch/powerpc/kernel/time.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -356,7 +356,7 @@ void vtime_flush(struct task_struct *tsk)
 #define calc_cputime_factors()
 #endif
 
-void __delay(unsigned long loops)
+void __no_kcsan __delay(unsigned long loops)
 {
 	unsigned long start;
 
@@ -377,7 +377,7 @@ void __delay(unsigned long loops)
 }
 EXPORT_SYMBOL(__delay);
 
-void udelay(unsigned long usecs)
+void __no_kcsan udelay(unsigned long usecs)
 {
 	__delay(tb_ticks_per_usec * usecs);
 }
-- 
2.40.0