Re: [PATCH v4 2/2] arch: m68k: Add STACKTRACE support

[Greg Ungerer]

Hi JM,

On 4/12/24 17:14, 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.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautb...@yoseli.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 
793ab1e2762609725bbf793f6dffecfa3ecfff0f..3ad8596aab71190807f8c11dd5876aa1198760f3
 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -106,6 +106,11 @@ 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

+       def_bool MMU_COLDFIRE

Modulo testing is there any reason this is enabled only for MMU ColdFire 
targets?
There doesn't look to be anything that is ColdFire specific in these changes,
looks like it should work on any m68k machine.

Regards
Greg

+       select ARCH_STACKWALK
+       select ARCH_WANT_FRAME_POINTERS
+
  menu "Platform setup"

source "arch/m68k/Kconfig.cpu"

diff --git a/arch/m68k/kernel/Makefile b/arch/m68k/kernel/Makefile
index 
6c732ed3998b714a4842ee29c977550a61979779..cb02bcfe04c6b265fa97db9237395a262e649989
 100644
--- a/arch/m68k/kernel/Makefile
+++ b/arch/m68k/kernel/Makefile
@@ -23,3 +23,4 @@ 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..4c2fb6b0cf675ee5a3a21393a50603fea98a1b03
--- /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 %%fp, %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;
+       }
+}