linux-kernel - Re: [PATCH 1/3] kernel.h: drop STACK

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Message-ID: <3e7ddbea-978f-44f7-abdd-7319908fd83c@kernel.org>
Date: Mon, 1 Dec 2025 10:38:01 +0100
From: "Christophe Leroy (CS GROUP)" <chleroy@...nel.org>
To: "Yury Norov (NVIDIA)" <yury.norov@...il.com>,
 Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 Randy Dunlap <rdunlap@...radead.org>, Ingo Molnar <mingo@...nel.org>,
 Jani Nikula <jani.nikula@...ux.intel.com>,
 Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
 Rodrigo Vivi <rodrigo.vivi@...el.com>, Tvrtko Ursulin
 <tursulin@...ulin.net>, Petr Pavlu <petr.pavlu@...e.com>,
 Daniel Gomez <da.gomez@...nel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org,
 intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-modules@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] kernel.h: drop STACK_MAGIC macro

Le 29/11/2025 à 20:53, Yury Norov (NVIDIA) a écrit :
> The macro is only used by i915. Move it to a local header and drop from
> the kernel.h.

At the begining of the git history we have:

$ git grep STACK_MAGIC 1da177e4c3f41
1da177e4c3f41:arch/h8300/kernel/traps.c:        if (STACK_MAGIC != 
*(unsigned long *)((unsigned long)current+PAGE_SIZE))
1da177e4c3f41:arch/m68k/mac/macints.c:          if (STACK_MAGIC != 
*(unsigned long *)current->kernel_stack_page)
1da177e4c3f41:include/linux/kernel.h:#define STACK_MAGIC        0xdeadbeef

Would be good to know the history of its usage over time.

I see:
- Removed from m68k by 3cd53b14e7c4 ("m68k/mac: Improve NMI handler")
- Removed from h8300 by 1c4b5ecb7ea1 ("remove the h8300 architecture")
- Started being used in i915 selftest by 250f8c8140ac ("drm/i915/gtt: 
Read-only pages for insert_entries on bdw+")

Christophe

> 
> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@...il.com>
> ---
>   drivers/gpu/drm/i915/i915_utils.h | 2 ++
>   include/linux/kernel.h            | 2 --
>   2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h
> index a0c892e4c40d..6c197e968305 100644
> --- a/drivers/gpu/drm/i915/i915_utils.h
> +++ b/drivers/gpu/drm/i915/i915_utils.h
> @@ -32,6 +32,8 @@
>   #include <linux/workqueue.h>
>   #include <linux/sched/clock.h>
>   
> +#define STACK_MAGIC	0xdeadbeef
> +
>   #ifdef CONFIG_X86
>   #include <asm/hypervisor.h>
>   #endif
> diff --git a/include/linux/kernel.h b/include/linux/kernel.h
> index 5b46924fdff5..61d63c57bc2d 100644
> --- a/include/linux/kernel.h
> +++ b/include/linux/kernel.h
> @@ -40,8 +40,6 @@
>   
>   #include <uapi/linux/kernel.h>
>   
> -#define STACK_MAGIC	0xdeadbeef
> -
>   struct completion;
>   struct user;
>