[PATCH v4] riscv: fix oops caused by irqsoff latency tracer
Changbin Du
changbin.du at gmail.com
Sun Feb 13 00:18:45 PST 2022
The trace_hardirqs_{on,off}() require the caller to setup frame pointer
properly. This because these two functions use macro 'CALLER_ADDR1' (aka.
__builtin_return_address(1)) to acquire caller info. If the $fp is used
for other purpose, the code generated this macro (as below) could trigger
memory access fault.
0xffffffff8011510e <+80>: ld a1,-16(s0)
0xffffffff80115112 <+84>: ld s2,-8(a1) # <-- paging fault here
The oops message during booting if compiled with 'irqoff' tracer enabled:
[ 0.039615][ T0] Unable to handle kernel NULL pointer dereference at virtual address 00000000000000f8
[ 0.041925][ T0] Oops [#1]
[ 0.042063][ T0] Modules linked in:
[ 0.042864][ T0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.17.0-rc1-00233-g9a20c48d1ed2 #29
[ 0.043568][ T0] Hardware name: riscv-virtio,qemu (DT)
[ 0.044343][ T0] epc : trace_hardirqs_on+0x56/0xe2
[ 0.044601][ T0] ra : restore_all+0x12/0x6e
[ 0.044721][ T0] epc : ffffffff80126a5c ra : ffffffff80003b94 sp : ffffffff81403db0
[ 0.044801][ T0] gp : ffffffff8163acd8 tp : ffffffff81414880 t0 : 0000000000000020
[ 0.044882][ T0] t1 : 0098968000000000 t2 : 0000000000000000 s0 : ffffffff81403de0
[ 0.044967][ T0] s1 : 0000000000000000 a0 : 0000000000000001 a1 : 0000000000000100
[ 0.045046][ T0] a2 : 0000000000000000 a3 : 0000000000000000 a4 : 0000000000000000
[ 0.045124][ T0] a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000054494d45
[ 0.045210][ T0] s2 : ffffffff80003b94 s3 : ffffffff81a8f1b0 s4 : ffffffff80e27b50
[ 0.045289][ T0] s5 : ffffffff81414880 s6 : ffffffff8160fa00 s7 : 00000000800120e8
[ 0.045389][ T0] s8 : 0000000080013100 s9 : 000000000000007f s10: 0000000000000000
[ 0.045474][ T0] s11: 0000000000000000 t3 : 7fffffffffffffff t4 : 0000000000000000
[ 0.045548][ T0] t5 : 0000000000000000 t6 : ffffffff814aa368
[ 0.045620][ T0] status: 0000000200000100 badaddr: 00000000000000f8 cause: 000000000000000d
[ 0.046402][ T0] [<ffffffff80003b94>] restore_all+0x12/0x6e
This because the $fp(aka. $s0) register is not used as frame pointer in the
assembly entry code.
resume_kernel:
REG_L s0, TASK_TI_PREEMPT_COUNT(tp)
bnez s0, restore_all
REG_L s0, TASK_TI_FLAGS(tp)
andi s0, s0, _TIF_NEED_RESCHED
beqz s0, restore_all
call preempt_schedule_irq
j restore_all
To fix above issue, here we add one extra level wrapper for function
trace_hardirqs_{on,off}() so they can be safely called by low level entry
code.
Signed-off-by: Changbin Du <changbin.du at gmail.com>
---
v4: update explanation.
v3: fix warning reported by documentation system.
v2: fix compile warning.
---
arch/riscv/kernel/Makefile | 2 ++
arch/riscv/kernel/entry.S | 10 +++++-----
arch/riscv/kernel/trace_irq.c | 27 +++++++++++++++++++++++++++
arch/riscv/kernel/trace_irq.h | 11 +++++++++++
4 files changed, 45 insertions(+), 5 deletions(-)
create mode 100644 arch/riscv/kernel/trace_irq.c
create mode 100644 arch/riscv/kernel/trace_irq.h
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 612556faa527..ffc87e76b1dd 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -51,6 +51,8 @@ obj-$(CONFIG_MODULE_SECTIONS) += module-sections.o
obj-$(CONFIG_FUNCTION_TRACER) += mcount.o ftrace.o
obj-$(CONFIG_DYNAMIC_FTRACE) += mcount-dyn.o
+obj-$(CONFIG_TRACE_IRQFLAGS) += trace_irq.o
+
obj-$(CONFIG_RISCV_BASE_PMU) += perf_event.o
obj-$(CONFIG_PERF_EVENTS) += perf_callchain.o
obj-$(CONFIG_HAVE_PERF_REGS) += perf_regs.o
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index ed29e9c8f660..d6a46ed0bf05 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -108,7 +108,7 @@ _save_context:
.option pop
#ifdef CONFIG_TRACE_IRQFLAGS
- call trace_hardirqs_off
+ call __trace_hardirqs_off
#endif
#ifdef CONFIG_CONTEXT_TRACKING
@@ -143,7 +143,7 @@ skip_context_tracking:
li t0, EXC_BREAKPOINT
beq s4, t0, 1f
#ifdef CONFIG_TRACE_IRQFLAGS
- call trace_hardirqs_on
+ call __trace_hardirqs_on
#endif
csrs CSR_STATUS, SR_IE
@@ -234,7 +234,7 @@ ret_from_exception:
REG_L s0, PT_STATUS(sp)
csrc CSR_STATUS, SR_IE
#ifdef CONFIG_TRACE_IRQFLAGS
- call trace_hardirqs_off
+ call __trace_hardirqs_off
#endif
#ifdef CONFIG_RISCV_M_MODE
/* the MPP value is too large to be used as an immediate arg for addi */
@@ -270,10 +270,10 @@ restore_all:
REG_L s1, PT_STATUS(sp)
andi t0, s1, SR_PIE
beqz t0, 1f
- call trace_hardirqs_on
+ call __trace_hardirqs_on
j 2f
1:
- call trace_hardirqs_off
+ call __trace_hardirqs_off
2:
#endif
REG_L a0, PT_STATUS(sp)
diff --git a/arch/riscv/kernel/trace_irq.c b/arch/riscv/kernel/trace_irq.c
new file mode 100644
index 000000000000..095ac976d7da
--- /dev/null
+++ b/arch/riscv/kernel/trace_irq.c
@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2022 Changbin Du <changbin.du at gmail.com>
+ */
+
+#include <linux/irqflags.h>
+#include <linux/kprobes.h>
+#include "trace_irq.h"
+
+/*
+ * trace_hardirqs_on/off require the caller to setup frame pointer properly.
+ * Otherwise, CALLER_ADDR1 might trigger an pagging exception in kernel.
+ * Here we add one extra level so they can be safely called by low
+ * level entry code which $fp is used for other purpose.
+ */
+
+void __trace_hardirqs_on(void)
+{
+ trace_hardirqs_on();
+}
+NOKPROBE_SYMBOL(__trace_hardirqs_on);
+
+void __trace_hardirqs_off(void)
+{
+ trace_hardirqs_off();
+}
+NOKPROBE_SYMBOL(__trace_hardirqs_off);
diff --git a/arch/riscv/kernel/trace_irq.h b/arch/riscv/kernel/trace_irq.h
new file mode 100644
index 000000000000..99fe67377e5e
--- /dev/null
+++ b/arch/riscv/kernel/trace_irq.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2022 Changbin Du <changbin.du at gmail.com>
+ */
+#ifndef __TRACE_IRQ_H
+#define __TRACE_IRQ_H
+
+void __trace_hardirqs_on(void);
+void __trace_hardirqs_off(void);
+
+#endif /* __TRACE_IRQ_H */
--
2.32.0
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