Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Zhouyi Zhou <zhouzhouyi@gmail.com>
To:     mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu,
        atrajeev@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, lance@osuosl.org, paulmck@kernel.org,
        rcu@vger.kernel.org
Cc:     Zhouyi Zhou <zhouzhouyi@gmail.com>
Subject: [PATCH linux-next] powerpc: disable sanitizer in irq_soft_mask_set
Date:   Sun, 21 Aug 2022 09:00:30 +0800
Message-Id: <20220821010030.97539-1-zhouzhouyi@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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.

This patch disable sanitizer in irq_soft_mask_set.

Signed-off-by: Zhouyi Zhou <zhouzhouyi@gmail.com>
---
Dear PPC developers

I found this bug when trying to do rcutorture tests in ppc VM of
Open Source Lab of Oregon State University following Paul E. McKenny's guidance.

console.log report following bug:

[  346.527467][  T100] BUG: using smp_processor_id() in preemptible [00000000] code: rcu_torture_rea/100^M
[  346.529416][  T100] caller is rcu_preempt_deferred_qs_irqrestore+0x74/0xed0^M
[  346.531157][  T100] CPU: 4 PID: 100 Comm: rcu_torture_rea Tainted: G        W          5.19.0-rc5-next-20220708-dirty #253^M
[  346.533620][  T100] Call Trace:^M
[  346.534449][  T100] [c0000000094876c0] [c000000000ce2b68] dump_stack_lvl+0xbc/0x108 (unreliable)^M
[  346.536632][  T100] [c000000009487710] [c000000001712954] check_preemption_disabled+0x154/0x160^M
[  346.538665][  T100] [c0000000094877a0] [c0000000002ce2d4] rcu_preempt_deferred_qs_irqrestore+0x74/0xed0^M
[  346.540830][  T100] [c0000000094878b0] [c0000000002cf3c0] __rcu_read_unlock+0x290/0x3b0^M
[  346.542746][  T100] [c000000009487910] [c0000000002bb330] rcu_torture_read_unlock+0x30/0xb0^M
[  346.544779][  T100] [c000000009487930] [c0000000002b7ff8] rcutorture_one_extend+0x198/0x810^M
[  346.546851][  T100] [c000000009487a10] [c0000000002b8bfc] rcu_torture_one_read+0x58c/0xc90^M
[  346.548844][  T100] [c000000009487ca0] [c0000000002b942c] rcu_torture_reader+0x12c/0x360^M
[  346.550784][  T100] [c000000009487db0] [c0000000001de978] kthread+0x1e8/0x220^M
[  346.552555][  T100] [c000000009487e10] [c00000000000cd54] ret_from_kernel_thread+0x5c/0x64^M

After 12 days debugging, I finally narrow the problem to irq_soft_mask_set.

I am a beginner, hope I can be of some beneficial to the community ;-)

Thanks
Zhouyi
--
 arch/powerpc/include/asm/hw_irq.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h
index 26ede09c521d..a5ae8d82cc9d 100644
--- a/arch/powerpc/include/asm/hw_irq.h
+++ b/arch/powerpc/include/asm/hw_irq.h
@@ -121,7 +121,7 @@ static inline notrace unsigned long irq_soft_mask_return(void)
  * for the critical section and as a clobber because
  * we changed paca->irq_soft_mask
  */
-static inline notrace void irq_soft_mask_set(unsigned long mask)
+static inline notrace __no_kcsan __no_sanitize_address void irq_soft_mask_set(unsigned long mask)
 {
 	/*
 	 * The irq mask must always include the STD bit if any are set.
-- 
2.34.1