[PATCH v2] powerpc: Fix irq_soft_mask_set() and irq_soft_mask_return() with sanitizer

From: Christophe Leroy
Date: Tue Aug 23 2022 - 14:23:18 EST


In ppc, compiler based sanitizer will generate instrument instructions
around statement WRITE_ONCE(local_paca->irq_soft_mask, mask):

0xc000000000295cb0 <+0>: addis r2,r12,774
0xc000000000295cb4 <+4>: addi r2,r2,16464
0xc000000000295cb8 <+8>: mflr r0
0xc000000000295cbc <+12>: bl 0xc00000000008bb4c <mcount>
0xc000000000295cc0 <+16>: mflr r0
0xc000000000295cc4 <+20>: std r31,-8(r1)
0xc000000000295cc8 <+24>: addi r3,r13,2354
0xc000000000295ccc <+28>: mr r31,r13
0xc000000000295cd0 <+32>: std r0,16(r1)
0xc000000000295cd4 <+36>: stdu r1,-48(r1)
0xc000000000295cd8 <+40>: bl 0xc000000000609b98 <__asan_store1+8>
0xc000000000295cdc <+44>: nop
0xc000000000295ce0 <+48>: li r9,1
0xc000000000295ce4 <+52>: stb r9,2354(r31)
0xc000000000295ce8 <+56>: addi r1,r1,48
0xc000000000295cec <+60>: ld r0,16(r1)
0xc000000000295cf0 <+64>: ld r31,-8(r1)
0xc000000000295cf4 <+68>: mtlr r0

If there is a context switch before "stb r9,2354(r31)", r31 may
not equal to r13, in such case, irq soft mask will not work.

The same problem occurs in irq_soft_mask_return() with
READ_ONCE(local_paca->irq_soft_mask).

This patch partially reverts commit ef5b570d3700 ("powerpc/irq: Don't
open code irq_soft_mask helpers") with a more modern inline assembly.

Reported-by: Zhouyi Zhou <zhouzhouyi@xxxxxxxxx>
Fixes: ef5b570d3700 ("powerpc/irq: Don't open code irq_soft_mask helpers")
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
---
v2: Use =m constraint for stb instead of m constraint
---
arch/powerpc/include/asm/hw_irq.h | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
index 26ede09c521d..815420988ef3 100644
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -113,7 +113,11 @@ static inline void __hard_RI_enable(void)

static inline notrace unsigned long irq_soft_mask_return(void)
{
- return READ_ONCE(local_paca->irq_soft_mask);
+ unsigned long flags;
+
+ asm volatile("lbz%X1 %0,%1" : "=r" (flags) : "m" (local_paca->irq_soft_mask));
+
+ return flags;
}

/*
@@ -140,8 +144,7 @@ static inline notrace void irq_soft_mask_set(unsigned long mask)
if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
WARN_ON(mask && !(mask & IRQS_DISABLED));

- WRITE_ONCE(local_paca->irq_soft_mask, mask);
- barrier();
+ asm volatile("stb%X0 %1,%0" : "=m" (local_paca->irq_soft_mask) : "r" (mask) : "memory");
}

static inline notrace unsigned long irq_soft_mask_set_return(unsigned long mask)
--
2.37.1