linux-kernel - Re: [PATCH v10 0/4] Add kprobe and kretprobe support for LoongArch

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Date:   Mon, 12 Dec 2022 17:35:13 +0800
From:   Qing Zhang <zhangqing@...ngson.cn>
To:     Hengqi Chen <chenhengqi@...look.com>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>,
        WANG Xuerui <kernel@...0n.name>,
        Masami Hiramatsu <mhiramat@...nel.org>
Cc:     loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 0/4] Add kprobe and kretprobe support for LoongArch

Hi, Hengqi

On 2022/12/12 下午4:41, Hengqi Chen wrote:
> Hi, Tiezhu:
> 
> I tested this patchset from BPF side, failed with EINVAL:
> 
>      $ cat /sys/kernel/tracing/error_log
>      [  262.299093] trace_kprobe: error: Failed to register probe event
>        Command: p:kprobes/libbpf_4609_inet_bind_0x0_0 inet_bind+0x0
> 
This is because KPROBE_ON_FTRACE is not yet supported. Trace Event 
cannot be used now.
We will support it soon, if you want to test it by install 
kprobe_example.ko as jeff did.

Thanks
-Qing                                                ^
> --
> Hengqi
> 
> On 2022/12/9 16:52, Tiezhu Yang wrote:
>> v10:
>>    -- Remove sign_extend() based on the latest code
>>    -- Rename insns_are_not_supported() to insns_not_supported()
>>    -- Rename insns_are_not_simulated() to insns_not_simulated()
>>    -- Set KPROBE_HIT_SSDONE if cur->post_handler is not NULL
>>    -- Enable preemption for KPROBE_REENTER in kprobe_fault_handler()
>>
>> v9:
>>    -- Rename sign_extended() to sign_extend()
>>    -- Modify kprobe_fault_handler() to handle all of kprobe_status
>>
>> v8:
>>    -- Put "regs->csr_prmd &= ~CSR_PRMD_PIE;" ahead to save one line
>>    -- Add code comment of preempt_disable()
>>    -- Put kprobe_page_fault() in __do_page_fault()
>>    -- Modify the check condition of break insn in kprobe_breakpoint_handler()
>>
>> v7:
>>    -- Remove stop_machine_cpuslocked() related code
>>
>> v6:
>>    -- Add a new patch to redefine larch_insn_patch_text() with
>>       stop_machine_cpuslocked()
>>    -- Modify kprobe_breakpoint_handler() to consider the original
>>       insn is break and return the correct value
>>    -- Modify do_bp() to refresh bcode when original insn is break
>>
>> v5:
>>    -- Rebase on the latest code
>>    -- Use stop_machine_cpuslocked() to modify insn to avoid CPU race
>>
>> v4:
>>    -- Remove kprobe_exceptions_notify() in kprobes.c
>>    -- Call kprobe_breakpoint_handler() and kprobe_singlestep_handler()
>>       in do_bp()
>>
>> v3:
>>    -- Rebase on the latest code
>>    -- Check the alignment of PC in simu_branch() and simu_pc()
>>    -- Add ibar in flush_insn_slot()
>>    -- Rename kprobe_{pre,post}_handler() to {post_}kprobe_handler
>>    -- Add preempt_disable() and preempt_enable_no_resched()
>>    -- Remove r0 save/restore and do some minor changes
>>       in kprobes_trampoline.S
>>    -- Do not enable CONFIG_KPROBES by default
>>
>> v2:
>>    -- Split simu_branch() and simu_pc() into a single patch
>>    -- Call kprobe_page_fault() in do_page_fault()
>>    -- Add kprobes_trampoline.S for kretprobe
>>
>> Tiezhu Yang (4):
>>    LoongArch: Simulate branch and PC instructions
>>    LoongArch: Add kprobe support
>>    LoongArch: Add kretprobe support
>>    samples/kprobes: Add LoongArch support
>>
>>   arch/loongarch/Kconfig                     |   2 +
>>   arch/loongarch/include/asm/inst.h          |  20 ++
>>   arch/loongarch/include/asm/kprobes.h       |  59 +++++
>>   arch/loongarch/include/asm/ptrace.h        |   1 +
>>   arch/loongarch/kernel/Makefile             |   2 +
>>   arch/loongarch/kernel/inst.c               | 123 ++++++++++
>>   arch/loongarch/kernel/kprobes.c            | 364 +++++++++++++++++++++++++++++
>>   arch/loongarch/kernel/kprobes_trampoline.S |  96 ++++++++
>>   arch/loongarch/kernel/traps.c              |  13 +-
>>   arch/loongarch/mm/fault.c                  |   3 +
>>   samples/kprobes/kprobe_example.c           |   8 +
>>   11 files changed, 687 insertions(+), 4 deletions(-)
>>   create mode 100644 arch/loongarch/include/asm/kprobes.h
>>   create mode 100644 arch/loongarch/kernel/kprobes.c
>>   create mode 100644 arch/loongarch/kernel/kprobes_trampoline.S
>>