powerpc/kcsan: Exclude udelay to prevent recursive instrumentation

[ Upstream 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
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 934d8ae66cc63b12e599a49cb1c2d04920b7a4ad..4406d7a89558bb5330378856924820b2bff9b3f7 100644 (file)
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -450,7 +450,7 @@ 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;
 
@@ -471,7 +471,7 @@ 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);
 }