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Message-ID: <3a5b6047-3382-49a1-9419-1d493d6bdcab@iscas.ac.cn>
Date: Mon, 22 Jul 2024 11:26:11 +0800
From: Zhu Hengbo <zhuhengbo@...as.ac.cn>
To: Jisheng Zhang <jszhang@...nel.org>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>,
Andrew Morton <akpm@...ux-foundation.org>,
Suren Baghdasaryan <surenb@...gle.com>,
Alexandre Ghiti <alexghiti@...osinc.com>,
Kefeng Wang <wangkefeng.wang@...wei.com>,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] riscv: add tracepoints for page fault
On 2024/7/22 11:21, Zhu Hengbo wrote:
> On 2024/7/20 18:18, Jisheng Zhang wrote:
>> On Wed, Jul 17, 2024 at 08:27:19AM +0000, Zhu Hengbo wrote:
>>> Introduce page_fault_user and page_fault_kernel for riscv page fault.
>>> Help to get more detail information when page fault happen.
>> Just curious what's the expected usage? The mm subsystem has supported
>> page faults perf software event, is it enough?
>
> I think there will still be situations where we need to use debugfs for debugging in cases where perf is not available.
>
> In fact, I am working to achieve parity in functionality for RISC-V with x86 and ARM.
> In x86, there are both perf software events and tracepoints.
>
If this is not needed, that's fine too. Please let me know.
Thanks for your attention.
>>> Signed-off-by: Zhu Hengbo <zhuhengbo@...as.ac.cn>
>>> ---
>>> Changes in v2:
>>> - Add print instruction point info
>>>
>>> Simple test go below:
>>>
>>> root@...cv-ubuntu2204 ~ # bin/perf list | grep exceptions
>>> exceptions:page_fault_kernel [Tracepoint event]
>>> exceptions:page_fault_user [Tracepoint event]
>>>
>>> root@...cv-ubuntu2204 ~ # bin/perf record -e exceptions:page_fault_kernel -e exceptions:page_fault_user
>>> [ perf record: Woken up 1 times to write data ]
>>> [ perf record: Captured and wrote 0.091 MB perf.data (19 samples) ]
>>>
>>> perf report tracepoint:
>>> perf 563 [007] 115.824363: exceptions:page_fault_user: user page fault, address=0x7fff94cf6400 epc=0x55558632808e cause=0xd
>>> perf 563 [007] 115.824441: exceptions:page_fault_user: user page fault, address=0x7fff94c75400 epc=0x55558632808e cause=0xd
>>> perf 563 [007] 115.824518: exceptions:page_fault_user: user page fault, address=0x7fff94bf4400 epc=0x55558632808e cause=0xd
>>> perf 563 [007] 115.824907: exceptions:page_fault_kernel: kernel page fault, address=0x7fff94bf5000 epc=fault_in_readable cause=0xd
>>> perf 563 [007] 115.825238: exceptions:page_fault_user: user page fault, address=0x7fff94bf4408 epc=0x5555863281bc cause=0xf
>>> perf 564 [000] 116.247999: exceptions:page_fault_user: user page fault, address=0x7fff94b73400 epc=0x55558632808e cause=0xd
>>> perf 564 [000] 116.248558: exceptions:page_fault_user: user page fault, address=0x7fff94af2400 epc=0x55558632808e cause=0xd
>>> ---
>>> arch/riscv/include/asm/trace/exceptions.h | 66 +++++++++++++++++++++++
>>> arch/riscv/mm/fault.c | 15 ++++++
>>> 2 files changed, 81 insertions(+)
>>> create mode 100644 arch/riscv/include/asm/trace/exceptions.h
>>>
>>> diff --git a/arch/riscv/include/asm/trace/exceptions.h b/arch/riscv/include/asm/trace/exceptions.h
>>> new file mode 100644
>>> index 000000000000..ff258da2f45f
>>> --- /dev/null
>>> +++ b/arch/riscv/include/asm/trace/exceptions.h
>>> @@ -0,0 +1,66 @@
>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>> +/*
>>> + * Tracepoints for RISC-V exceptions
>>> + *
>>> + * Copyright (C) 2024 ISCAS. All rights reserved
>>> + *
>>> + */
>>> +
>>> +#if !defined(_TRACE_PAGE_FAULT_H) || defined(TRACE_HEADER_MULTI_READ)
>>> +#define _TRACE_PAGE_FAULT_H
>>> +
>>> +#include <linux/tracepoint.h>
>>> +
>>> +#undef TRACE_SYSTEM
>>> +#define TRACE_SYSTEM exceptions
>>> +
>>> +TRACE_EVENT(page_fault_user,
>>> + TP_PROTO(struct pt_regs *regs),
>>> + TP_ARGS(regs),
>>> +
>>> + TP_STRUCT__entry(
>>> + __field(unsigned long, address)
>>> + __field(unsigned long, epc)
>>> + __field(unsigned long, cause)
>>> + ),
>>> +
>>> + TP_fast_assign(
>>> + __entry->address = regs->badaddr;
>>> + __entry->epc = regs->epc;
>>> + __entry->cause = regs->cause;
>>> + ),
>>> +
>>> + TP_printk("user page fault, address=%ps epc=%ps cause=0x%lx",
>>> + (void *)__entry->address, (void *)__entry->epc,
>>> + __entry->cause)
>>> +);
>>> +
>>> +TRACE_EVENT(page_fault_kernel,
>>> + TP_PROTO(struct pt_regs *regs),
>>> + TP_ARGS(regs),
>>> +
>>> + TP_STRUCT__entry(
>>> + __field(unsigned long, address)
>>> + __field(unsigned long, epc)
>>> + __field(unsigned long, cause)
>>> + ),
>>> +
>>> + TP_fast_assign(
>>> + __entry->address = regs->badaddr;
>>> + __entry->epc = regs->epc;
>>> + __entry->cause = regs->cause;
>>> + ),
>>> +
>>> + TP_printk("kernel page fault, address=%ps epc=%ps cause=0x%lx",
>>> + (void *)__entry->address, (void *)__entry->epc,
>>> + __entry->cause)
>>> +);
>>> +
>>> +#undef TRACE_INCLUDE_PATH
>>> +#undef TRACE_INCLUDE_FILE
>>> +#define TRACE_INCLUDE_PATH asm/trace/
>>> +#define TRACE_INCLUDE_FILE exceptions
>>> +#endif /* _TRACE_PAGE_FAULT_H */
>>> +
>>> +/* This part must be outside protection */
>>> +#include <trace/define_trace.h>
>>> diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
>>> index 5224f3733802..22874074c5bc 100644
>>> --- a/arch/riscv/mm/fault.c
>>> +++ b/arch/riscv/mm/fault.c
>>> @@ -22,6 +22,10 @@
>>>
>>> #include "../kernel/head.h"
>>>
>>> +
>>> +#define CREATE_TRACE_POINTS
>>> +#include <asm/trace/exceptions.h>
>>> +
>>> static void die_kernel_fault(const char *msg, unsigned long addr,
>>> struct pt_regs *regs)
>>> {
>>> @@ -215,6 +219,15 @@ static inline bool access_error(unsigned long cause, struct vm_area_struct *vma)
>>> return false;
>>> }
>>>
>>> +
>>> +static inline void trace_page_fault(struct pt_regs *regs)
>>> +{
>>> + if (user_mode(regs))
>>> + trace_page_fault_user(regs);
>>> + else
>>> + trace_page_fault_kernel(regs);
>>> +}
>>> +
>>> /*
>>> * This routine handles page faults. It determines the address and the
>>> * problem, and then passes it off to one of the appropriate routines.
>>> @@ -235,6 +248,8 @@ void handle_page_fault(struct pt_regs *regs)
>>> tsk = current;
>>> mm = tsk->mm;
>>>
>>> + trace_page_fault(regs);
>>> +
>>> if (kprobe_page_fault(regs, cause))
>>> return;
>>>
>>> --
>>> 2.34.1
>>>
>>>
>>> _______________________________________________
>>> linux-riscv mailing list
>>> linux-riscv@...ts.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/linux-riscv
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
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