> diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
> index f94f3fdf15fc..6e850c9d3f0c 100644
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -12,6 +12,7 @@
> #include <linux/resume_user_mode.h>
> #include <linux/tick.h>
> #include <linux/kmsan.h>
> +#include <linux/unwind_deferred.h>
>
> #include <asm/entry-common.h>
> #include <asm/syscall.h>
> @@ -362,6 +363,7 @@ static __always_inline void exit_to_user_mode(void)
> lockdep_hardirqs_on_prepare();
> instrumentation_end();
>
> + unwind_exit_to_user_mode();
So I was expecting this to do the actual unwind, and was about to go
yell this is the wrong place for that.
But this is not that. Perhaps find a better name like:
unwind_clear_cache() or so?
> user_enter_irqoff();
> arch_exit_to_user_mode();
> lockdep_hardirqs_on(CALLER_ADDR0);
> diff --git a/include/linux/unwind_deferred_types.h
> b/include/linux/unwind_deferred_types.h
> index aa32db574e43..db5b54b18828 100644
> --- a/include/linux/unwind_deferred_types.h
> +++ b/include/linux/unwind_deferred_types.h
> @@ -2,8 +2,13 @@
> #ifndef _LINUX_UNWIND_USER_DEFERRED_TYPES_H
> #define _LINUX_UNWIND_USER_DEFERRED_TYPES_H
>
> +struct unwind_cache {
> + unsigned int nr_entries;
> + unsigned long entries[];
> +};
> +
> struct unwind_task_info {
> - unsigned long *entries;
> + struct unwind_cache *cache;
> };
>
> #endif /* _LINUX_UNWIND_USER_DEFERRED_TYPES_H */
> diff --git a/kernel/unwind/deferred.c b/kernel/unwind/deferred.c
> index 0bafb95e6336..e3913781c8c6 100644
> --- a/kernel/unwind/deferred.c
> +++ b/kernel/unwind/deferred.c
> @@ -24,6 +24,7 @@
> int unwind_deferred_trace(struct unwind_stacktrace *trace)
> {
> struct unwind_task_info *info = ¤t->unwind_info;
> + struct unwind_cache *cache;
>
> /* Should always be called from faultable context */
> might_fault();
> @@ -31,17 +32,30 @@ int unwind_deferred_trace(struct unwind_stacktrace *trace)
> if (current->flags & PF_EXITING)
> return -EINVAL;
>
> - if (!info->entries) {
> - info->entries = kmalloc_array(UNWIND_MAX_ENTRIES, sizeof(long),
> - GFP_KERNEL);
> - if (!info->entries)
> + if (!info->cache) {
> + info->cache = kzalloc(struct_size(cache, entries,
> UNWIND_MAX_ENTRIES),
> + GFP_KERNEL);
And now you're one 'long' larger than a page. Surely that's a crap size
for an allocator?
