From 684c68d92e2e1b97fa2f31c35c1b0f7671a8618a Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Wed, 31 Aug 2022 23:10:52 +1000 Subject: [PATCH] Revert "powerpc/irq: Don't open code irq_soft_mask helpers" This reverts commit ef5b570d3700fbb8628a58da0487486ceeb713cd. Zhouyi reported that commit is causing crashes when running rcutorture with KASAN enabled: BUG: using smp_processor_id() in preemptible [00000000] code: rcu_torture_rea/100 caller is rcu_preempt_deferred_qs_irqrestore+0x74/0xed0 CPU: 4 PID: 100 Comm: rcu_torture_rea Tainted: G W 5.19.0-rc5-next-20220708-dirty #253 Call Trace: dump_stack_lvl+0xbc/0x108 (unreliable) check_preemption_disabled+0x154/0x160 rcu_preempt_deferred_qs_irqrestore+0x74/0xed0 __rcu_read_unlock+0x290/0x3b0 rcu_torture_read_unlock+0x30/0xb0 rcutorture_one_extend+0x198/0x810 rcu_torture_one_read+0x58c/0xc90 rcu_torture_reader+0x12c/0x360 kthread+0x1e8/0x220 ret_from_kernel_thread+0x5c/0x64 KASAN will generate instrumentation instructions around the 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 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 usual solution of marking the code ineligible for instrumentation forces the code out-of-line, which we would prefer to avoid. Christophe proposed a partial revert, but Nick raised some concerns with that. So for now do a full revert. Reported-by: Zhouyi Zhou [mpe: Construct change log based on Zhouyi's original report] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220831131052.42250-1-mpe@ellerman.id.au --- arch/powerpc/include/asm/hw_irq.h | 43 ++++++++++++++++++++++++++----- 1 file changed, 36 insertions(+), 7 deletions(-) diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h index 3c8cb48f88ae..983551859891 100644 --- a/arch/powerpc/include/asm/hw_irq.h +++ b/arch/powerpc/include/asm/hw_irq.h @@ -113,7 +113,14 @@ 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 %0,%1(13)" + : "=r" (flags) + : "i" (offsetof(struct paca_struct, irq_soft_mask))); + + return flags; } /* @@ -140,24 +147,46 @@ 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 %0,%1(13)" + : + : "r" (mask), + "i" (offsetof(struct paca_struct, irq_soft_mask)) + : "memory"); } static inline notrace unsigned long irq_soft_mask_set_return(unsigned long mask) { - unsigned long flags = irq_soft_mask_return(); + unsigned long flags; - irq_soft_mask_set(mask); +#ifdef CONFIG_PPC_IRQ_SOFT_MASK_DEBUG + WARN_ON(mask && !(mask & IRQS_DISABLED)); +#endif + + asm volatile( + "lbz %0,%1(13); stb %2,%1(13)" + : "=&r" (flags) + : "i" (offsetof(struct paca_struct, irq_soft_mask)), + "r" (mask) + : "memory"); return flags; } static inline notrace unsigned long irq_soft_mask_or_return(unsigned long mask) { - unsigned long flags = irq_soft_mask_return(); + unsigned long flags, tmp; - irq_soft_mask_set(flags | mask); + asm volatile( + "lbz %0,%2(13); or %1,%0,%3; stb %1,%2(13)" + : "=&r" (flags), "=r" (tmp) + : "i" (offsetof(struct paca_struct, irq_soft_mask)), + "r" (mask) + : "memory"); + +#ifdef CONFIG_PPC_IRQ_SOFT_MASK_DEBUG + WARN_ON((mask | flags) && !((mask | flags) & IRQS_DISABLED)); +#endif return flags; }