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Message-ID: <501c04d7-1a7d-4000-a948-e9effb281a05@yoseli.org>
Date: Wed, 27 Nov 2024 12:26:43 +0100
From: Jean-Michel Hautbois <jeanmichel.hautbois@...eli.org>
To: linux-m68k@...ts.linux-m68k.org
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
rostedt@...dmis.org, Greg Ungerer <gerg@...ux-m68k.org>,
Michael Schmitz <schmitzmic@...il.com>,
Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH RFC 2/2] arch: m68k: Add STACKTRACE support
Hi there,
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 : <stack trace>
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 : <stack trace>
telnetd-229 0Dnh4. 0us : 229:120:R + [000] 118:
49:R irq/100-enet-fe
telnetd-229 0Dnh4. 0us : <stack trace>
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 : <stack trace>
telnetd-229 0dn.5. 0us : 229:120:R + [000] 118:
49:R irq/100-enet-fe
telnetd-229 0dn.5. 0us : <stack trace>
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 : <stack trace>
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 <jeanmichel.hautbois@...eli.org>
> ---
> 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 <asm/current.h>
> +#include <asm/ptrace.h>
> +#include <linux/sched.h>
> +#include <linux/sched/task_stack.h>
> +#include <linux/stacktrace.h>
> +
> +static inline unsigned long current_stack_frame(void)
> +{
> + unsigned long sp;
> +
> + asm volatile("movl %%sp, %0" : "=r"(sp));
> + return sp;
> +}
> +
> +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;
> + }
> +}
>
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