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bh=4tAW3SlP431F7bjWdI4ygJqmG7YuYjWhSnR8WVAPb5Q=; b=wgwhPxy8Tk1YMJ1hy/Ypbhb4r1 xWswkSfytQMmBcdva/7O7JMfMNnKn4BMxHBGxKnDVBVaN6inyuo4O8W9t7K/emQ3H4FVgQvx47BeK 45m1cOLuYsZgllZRJogqRAsj1o8/kgw4f3p/kD/EkenWTlvSFbsEszvw8116pQrZbPpQUSto3TKzW 3DI53KR9Qznor5mfThIGGEwofi/PY1e5r2cuf9fb3mnv+mB3a4cXwisUnbN6DzLGbdGJZ2wsEFKiR 22UxwFKn/640pqKtmcR4GNZBvePNE78jqGV67ciq2cm/YHQY+80D2ZarNCPc1Inv+GEayJEt1La9H FMfMCs2g==; Received: from [50.53.43.113] (helo=[192.168.254.34]) by bombadil.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBI6U-00000001aN3-2nto; Mon, 28 Sep 2026 20:37:38 +0000 Message-ID: <5c6edcfe-8332-4db6-b0fa-ca5d137a2075@infradead.org> Date: Mon, 28 Sep 2026 13:37:37 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 12/15] sched/task_stack: Introduce ARCH_HAS_VARIABLE_STACK_SIZE To: Mostafa Saleh , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-hardening@vger.kernel.org, linux-rt-devel@lists.linux.dev Cc: corbet@lwn.net, skhan@linuxfoundation.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, akpm@linux-foundation.org, urezki@gmail.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, kees@kernel.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, gustavoars@kernel.org, bigeasy@linutronix.de, clrkwllms@kernel.org References: <20260928174122.3380703-1-smostafa@google.com> <20260928174122.3380703-13-smostafa@google.com> Content-Language: en-US From: Randy Dunlap In-Reply-To: <20260928174122.3380703-13-smostafa@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Stat-Signature: cer5ya9pqfx5hd3qzryqy1beuxqfsjai X-Rspam-User: X-Rspamd-Queue-Id: 4A7D1140007 X-HE-Tag: 1790627861-902030 X-HE-Meta: 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 xzs4oGAo xAgos6e7jKgS90GTTb8czthut/vVRov/S3ziqRh23HQFUyo5EnR6jSTTi4YD84/bVXlui4X92dUHT99WUoK4Qk22LGAHkWuyomFT34kJMXj9tQa/fWHGg7AuaTvbEmfyRLhFdGwd3VqeqqmjvI3R/Mwp1udHGbaYHjUUeSElya7R6iVkQ/ydSjdWG9SntXTOMFBmp6ehUw9k4eaaGoN6bLK/nVhLRDXpwlzt5qS5lWd0sNXVgIWFv7QP8c4K4PEU63PJ1b/OcQXsNKsww207aQPgnmmpx6P++F20cNMaoQfWzbiotrSgtZPoVdnYOOnnzD6kPtHE87iUJJrkXjpGhmOQiMunBHj3rDntB/cYBcUYhLpK9ws2uJdQXDoBTZ4eWajlQkXvzZ5jTTXA= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/28/26 10:41 AM, Mostafa Saleh wrote: > When CONFIG_ARCH_HAS_VARIABLE_STACK_SIZE is enabled, the kernel stack > may not be fully populated with the THREAD_SIZE virtual area. > > Teach task_stack_size() to return the size of the vm area and not a > fixed size. > > This propagates to end_of_stack() which makes functions like > stack_not_used() and set_task_stack_end_magic() to use the lowest > valid stack address instead of THREAD_SIZE which would cause data > aborts. > > Signed-off-by: Mostafa Saleh > --- > arch/Kconfig | 10 ++++++++++ > include/linux/sched/task_stack.h | 5 +++++ > 2 files changed, 15 insertions(+) > > diff --git a/arch/Kconfig b/arch/Kconfig > index 45c657772362..d6fa2ccb0599 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -431,6 +431,16 @@ config HAVE_ASM_MODVERSIONS > to support the module versioning for symbols > exported from assembly code. > > +config ARCH_HAS_VARIABLE_STACK_SIZE > + bool > + depends on VMAP_STACK > + depends on !STACK_GROWSUP > + depends on THREAD_INFO_IN_TASK > + help > + An arch should select this if it supports dynamically configuring the > + kernel stack size. > + For example the kernel stack size can be from the command line. can be set from the command line. ? > + > config HAVE_REGS_AND_STACK_ACCESS_API > bool > help > diff --git a/include/linux/sched/task_stack.h b/include/linux/sched/task_stack.h > index 4a808f9c4631..07d73adaecd1 100644 > --- a/include/linux/sched/task_stack.h > +++ b/include/linux/sched/task_stack.h > @@ -10,6 +10,7 @@ > #include > #include > #include > +#include > > #ifdef CONFIG_THREAD_INFO_IN_TASK > > @@ -96,6 +97,10 @@ static inline unsigned long *end_of_stack(const struct task_struct *p) > */ > static __always_inline unsigned long task_stack_size(const struct task_struct *task) > { > +#ifdef CONFIG_ARCH_HAS_VARIABLE_STACK_SIZE > + if (task->stack_vm_area) > + return task->stack_vm_area->nr_pages * PAGE_SIZE; > +#endif > return THREAD_SIZE; > } > -- ~Randy