From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from nyc.source.kernel.org (nyc.source.kernel.org [147.75.193.91]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A1E3D1DFD83 for ; Mon, 2 Dec 2024 23:01:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=147.75.193.91 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733180484; cv=none; b=DuKMVRUIOo28L50l4nqyssApOIY3bV4ZB0hf/0PpFrbs4Xic6x+NqsHnwTOnqf/sgMWTWNtMXDi23v4ahE7Ezdt98n/7w9KaZ1I8ckpLq+t1iuYlU8Vsdndje0Z+cmjmUK2e8TTdy+Hm1sC6Mfl3EBTFOkkCkY2U+Xadh3B9//Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733180484; c=relaxed/simple; bh=O40mKIuVkUdaPGlRuJu+ExjHuIkuF5fFK8LoYE40cs4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=bk8GNmvH4bNi4SiVhtOq4HrWZFyGKxYT5BNDN/lYSA19IXQoj5aaUkM5/TjTsNyt/SfCwfcNBTVliJ4MHGAsXak7RYSJ4PPHHejBgjs5PeRHVQ+Av2pIilX+qxmQvJco0gExlxbVFxaw3CVaS3fRsjiYBSLu+TF2CrEGNFNJAs0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org; spf=pass smtp.mailfrom=kernel.org; arc=none smtp.client-ip=147.75.193.91 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id 5132EA412E3; Mon, 2 Dec 2024 22:59:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 93FC0C4CED1; Mon, 2 Dec 2024 23:01:18 +0000 (UTC) Message-ID: <34055476-e711-4e7e-9bc1-ba3e29ddbff1@linux-m68k.org> Date: Tue, 3 Dec 2024 09:01:16 +1000 Precedence: bulk X-Mailing-List: linux-m68k@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 2/2] arch: m68k: Add STACKTRACE support To: Jean-Michel Hautbois , linux-m68k@lists.linux-m68k.org Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, rostedt@goodmis.org, Michael Schmitz , Geert Uytterhoeven References: <20241021-add-m68k-tracing-support-v1-0-0883d704525b@yoseli.org> <20241021-add-m68k-tracing-support-v1-2-0883d704525b@yoseli.org> <501c04d7-1a7d-4000-a948-e9effb281a05@yoseli.org> <7fef0321-5a24-4d8d-9717-8fe02f80b8c2@yoseli.org> Content-Language: en-US From: Greg Ungerer In-Reply-To: <7fef0321-5a24-4d8d-9717-8fe02f80b8c2@yoseli.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi JM, On 3/12/24 00:52, Jean-Michel Hautbois wrote: > On 02/12/2024 15:41, Greg Ungerer wrote: >> On 27/11/24 21:26, Jean-Michel Hautbois wrote: >>> On 21/10/2024 11:44, Jean-Michel Hautbois wrote: >>>> In order to use tracing, implement a basic arch_stack_walk() based on >>>> the one in PowerPC. >>>> Tested on a M54418 coldfire. >>> >>> Well, I said it was tested, but it was only compile tested basically. >>> AFAICT now, I think it is not working as when I use wakeup_rt as a tracer, I don't have the stack trace: >>> >>> # wakeup_rt latency trace v1.1.5 on 6.12.0-10380-gb66f06337b66-dirty >>> # -------------------------------------------------------------------- >>> # latency: 2000 us, #18/18, CPU#0 | (M:preempt VP:0, KP:0, SP:0 HP:0) >>> #    ----------------- >>> #    | task: irq/100-enet-fe-118 (uid:0 nice:0 policy:1 rt_prio:50) >>> #    ----------------- >>> # >>> #                    _------=> CPU# >>> #                   / _-----=> irqs-off/BH-disabled >>> #                  | / _----=> need-resched >>> #                  || / _---=> hardirq/softirq >>> #                  ||| / _--=> preempt-depth >>> #                  |||| / _-=> migrate-disable >>> #                  ||||| /     delay >>> #  cmd     pid     |||||| time  |   caller >>> #     \   /        ||||||  \    |    / >>> kworker/-11        0dnh5.    0us :       11:120:R   + [000]      22: 98:R irq_work/0 >>> kworker/-11        0dnh5.    0us : >>> kworker/-11        0dnh5.    0us : 0 >>> kworker/-11        0d..3.    0us : __schedule >>> kworker/-11        0d..3.    0us :       11:120:R ==> [000]      22: 98:R irq_work/0 >>> kworker/-11        0d..3.    0us : >>>   telnetd-229       0Dnh4.    0us :      229:120:R   + [000]     118: 49:R irq/100-enet-fe >>>   telnetd-229       0Dnh4.    0us : >>>   telnetd-229       0Dnh4.    0us : 0 >>>   telnetd-229       0D..3.    0us : __schedule >>>   telnetd-229       0D..3.    0us :      229:120:R ==> [000]     118: 49:R irq/100-enet-fe >>>   telnetd-229       0D..3.    0us : >>>   telnetd-229       0dn.5.    0us :      229:120:R   + [000]     118: 49:R irq/100-enet-fe >>>   telnetd-229       0dn.5.    0us : >>>   telnetd-229       0dn.5.    0us#: 0 >>>   telnetd-229       0d..3. 2000us : __schedule >>>   telnetd-229       0d..3. 2000us :      229:120:R ==> [000]     118: 49:R irq/100-enet-fe >>>   telnetd-229       0d..3. 2000us : >>> >>> Geert, Greg, and maybe other highly skilled m68k people, could you please help me with this particular function :-) ? >>> >>> Thanks ! >>> JM >>> >>>> >>>> Signed-off-by: Jean-Michel Hautbois >>>> --- >>>>   arch/m68k/Kconfig             |  5 ++++ >>>>   arch/m68k/kernel/Makefile     |  1 + >>>>   arch/m68k/kernel/stacktrace.c | 70 ++++++++++++++++++++++++++++++++ +++++++++++ >>>>   3 files changed, 76 insertions(+) >>>> >>>> diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig >>>> index ab3375475721fa63418c40d4ba6ac76679ebc77d..7142f9759181a90269ae1ba9e682d331ee2ddbf6 100644 >>>> --- a/arch/m68k/Kconfig >>>> +++ b/arch/m68k/Kconfig >>>> @@ -40,6 +40,7 @@ config M68K >>>>       select UACCESS_MEMCPY if !MMU >>>>       select ZONE_DMA >>>>       select TRACE_IRQFLAGS_SUPPORT >>>> +    select ARCH_STACKWALK >>>>   config CPU_BIG_ENDIAN >>>>       def_bool y >>>> @@ -107,6 +108,10 @@ config BOOTINFO_PROC >>>>         Say Y to export the bootinfo used to boot the kernel in a >>>>         "bootinfo" file in procfs.  This is useful with kexec. >>>> +config STACKTRACE_SUPPORT >>>> +    bool >>>> +    default y >>>> + >>>>   menu "Platform setup" >>>>   source "arch/m68k/Kconfig.cpu" >>>> diff --git a/arch/m68k/kernel/Makefile b/arch/m68k/kernel/Makefile >>>> index f335bf3268a108a45bab079fbf0a1c8ead9beb71..4efe92af0b711b19cb1d5129f74e67a739e289b1 100644 >>>> --- a/arch/m68k/kernel/Makefile >>>> +++ b/arch/m68k/kernel/Makefile >>>> @@ -31,3 +31,4 @@ obj-$(CONFIG_UBOOT)        += uboot.o >>>>   obj-$(CONFIG_EARLY_PRINTK)    += early_printk.o >>>> +obj-y    += stacktrace.o >>>> diff --git a/arch/m68k/kernel/stacktrace.c b/arch/m68k/kernel/ stacktrace.c >>>> new file mode 100644 >>>> index 0000000000000000000000000000000000000000..06c7459373bd25b3bb3540cfe2a909259c1db3ce >>>> --- /dev/null >>>> +++ b/arch/m68k/kernel/stacktrace.c >>>> @@ -0,0 +1,70 @@ >>>> +// SPDX-License-Identifier: GPL-2.0 >>>> + >>>> +/* >>>> + * Stack trace utility functions etc. >>>> + * >>>> + * Copyright 2024 Jean-Michel Hautbois, Yoseli SAS. >>>> + */ >>>> + >>>> +#include >>>> +#include >>>> +#include >>>> +#include >>>> +#include >>>> + >>>> +static inline unsigned long current_stack_frame(void) >>>> +{ >>>> +    unsigned long sp; >>>> + >>>> +    asm volatile("movl %%sp, %0" : "=r"(sp)); >>>> +    return sp; >>>> +} >> >> If I am understanding what this is intended to do then this is probably not right. >> This will be returning the current stack pointer, which will almost certainly not >> be the current stack frame pointer. This will be the top of stack at the call site, >> which will be after the pushed locals and saved registers at the very least for m68k. >> >> Does your kernel config have CONFIG_FRAME_POINTER enabled? >> The default for m68k is usually disabled. Without this there won't be a >> chain of frame pointers to follow like the code is trying to do below in >> arch_stack_walk(). > > Sorry for my preceding mail, it *is* better: > # tail -10 trace > #                  |||| / _-=> migrate-disable > #                  ||||| /     delay > #  cmd     pid     |||||| time  |   caller > #     \   /        ||||||  \    |    / >   -0         0dnh5.   11us+:        0:120:R   + [000]     119: 49:R irq/104-enet-fe >   -0         0dnh5.   42us+: >   -0         0dnh5.   57us!: wake_up_process <-__handle_irq_event_percpu >   -0         0d..3.  282us+: __schedule <-schedule_idle >   -0         0d..3.  302us+:        0:120:R ==> [000]     119: 49:R irq/104-enet-fe >   -0         0d..3.  325us : Oh, yeah, there is more required. The current_stack_frame() function needs to change to actually return with the start of the frame pointer chain. You need it to look like this: static inline unsigned long current_stack_frame(void) { unsigned long sp; asm volatile("movl %%fp, %0" : "=r"(sp)); return sp; } Note that it is returning the "%fp" register - the current frame pointer. Regards Greg > JM > >> Regards >> Greg >> >> >>>> +static inline int validate_sp(unsigned long sp, struct task_struct *task) >>>> +{ >>>> +    unsigned long stack_start, stack_end; >>>> + >>>> +    if (task == current) >>>> +        stack_start = (unsigned long)task_stack_page(task); >>>> +    else >>>> +        stack_start = (unsigned long)task->thread.esp0; >>>> + >>>> +    stack_end = stack_start + THREAD_SIZE; >>>> + >>>> +    if (sp < stack_start || sp >= stack_end) >>>> +        return 0; >>>> + >>>> +    return 1; >>>> +} >>>> + >>>> +void __no_sanitize_address arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie, >>>> +                       struct task_struct *task, struct pt_regs *regs) >>>> +{ >>>> +    unsigned long sp; >>>> + >>>> +    if (regs && !consume_entry(cookie, regs->pc)) >>>> +        return; >>>> + >>>> +    if (regs) >>>> +        sp = (unsigned long) regs; >>>> +    else if (task == current) >>>> +        sp = current_stack_frame(); >>>> +    else >>>> +        sp = task->thread.ksp; >>>> + >>>> +    for (;;) { >>>> +        unsigned long *stack = (unsigned long *) sp; >>>> +        unsigned long newsp, ip; >>>> + >>>> +        if (!validate_sp(sp, task)) >>>> +            return; >>>> + >>>> +        newsp = stack[0]; >>>> +        ip = stack[1]; >>>> + >>>> +        if (!consume_entry(cookie, ip)) >>>> +            return; >>>> + >>>> +        sp = newsp; >>>> +    } >>>> +} >>>> >>> > >