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riscv: fix oops caused by irqsoff latency tracer 

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@gmail.com>
Fixes: 3c46979829 ("riscv: Enable LOCKDEP_SUPPORT & fixup TRACE_IRQFLAGS_SUPPORT")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Changbin Du 2022-02-13 16:18:45 +08:00 committed by Palmer Dabbelt
parent 762e52f79c
commit 22e2100b1b
No known key found for this signature in database
GPG Key ID: 2E1319F35FBB1889
4 changed files with 45 additions and 5 deletions
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2
arch/riscv/kernel/Makefile
View File

@ -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

10
arch/riscv/kernel/entry.S
View File

@ -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)

27
arch/riscv/kernel/trace_irq.c Normal file
View File

@ -0,0 +1,27 @@
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2022 Changbin Du <changbin.du@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);

11
arch/riscv/kernel/trace_irq.h Normal file
View File

@ -0,0 +1,11 @@
/* SPDX-License-Identifier: GPL-2.0 */
/*
* Copyright (C) 2022 Changbin Du <changbin.du@gmail.com>
*/
#ifndef __TRACE_IRQ_H
#define __TRACE_IRQ_H
void __trace_hardirqs_on(void);
void __trace_hardirqs_off(void);
#endif /* __TRACE_IRQ_H */