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 <[email protected]>
> ---
> 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
> <asm/asm-prototypes.h> 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 <linux/magic.h>
> #include <linux/refcount.h>
> #include <linux/kasan.h>
> +#include <linux/vmalloc.h>
>
> #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
