Re: [PATCH v2] riscv: fix oops caused by irq on/off tracer

From: ChangbinCONFIG_IRQSOFF_TRACER Du
Date: Mon Feb 07 2022 - 08:10:37 EST

On Mon, Feb 07, 2022 at 01:25:03AM +0800, Jisheng Zhang wrote:
> On Sat, Jan 29, 2022 at 08:42:26AM +0800, Changbin Du wrote:
> > The trace_hardirqs_on/off requires at least two parent call frames.
> > If not, the code generated by CALLER_ADDR1 (aka. ftrace_return_address(1))
> > could trigger memory access fault.
> >
> > [ 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
> >
>
> Hi Changbin,
>
> Could you please provide the reproduce steps? It looks a bit
> interesting.
>
Just enable CONFIG_IRQSOFF_TRACER and rebuild kernel with llvm. Then boot the
new kernel.

> > To fix above issue, here we add one extra level wrapper so they can be
> > safely called by low level entry code.
> >
> > Signed-off-by: Changbin Du <changbin.du@xxxxxxxxx>
> >
> > ---
> > v2: fix compile warning.
> > ---
> > arch/riscv/kernel/Makefile | 2 ++
> > arch/riscv/kernel/entry.S | 10 +++++-----
> > arch/riscv/kernel/trace_irq.c | 26 ++++++++++++++++++++++++++
> > arch/riscv/kernel/trace_irq.h | 11 +++++++++++
> > 4 files changed, 44 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..fc194c56a35d
> > --- /dev/null
> > +++ b/arch/riscv/kernel/trace_irq.c
> > @@ -0,0 +1,26 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (C) 2022 Changbin Du <changbin.du@xxxxxxxxx>
> > + */
> > +
> > +#include <linux/irqflags.h>
> > +#include <linux/kprobes.h>
> > +#include "trace_irq.h"
> > +
> > +/**
> > + * trace_hardirqs_on/off requires at least two parent call frames.
> > + * Here we add one extra level so they can be safely called by low
> > + * level entry code.
> > + */
>
> Hmm, I believe there's elegant solution without this grue, maybe
> fix in stacktrace implementation or something else?
>
This is not about stacktrace. As describe in commit msg, the problem is
introduced by ftrace_return_address(1). The complier doesn't have knowledge
about how many frames available at rumtime and wether each frame is valid.

>
> > +
> > +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@xxxxxxxxx>
> > + */
> > +#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
> >
> >
> > _______________________________________________
> > linux-riscv mailing list
> > linux-riscv@xxxxxxxxxxxxxxxxxxx
> > http://lists.infradead.org/mailman/listinfo/linux-riscv

--
Cheers,
Changbin Du