[Devel] Re: [PATCH] Save and restore the [compat_]robust_list member of the task struct.

[Nathan Lynch]

Matt Helsley <matthltc at us.ibm.com> writes:
> diff --git a/include/linux/futex.h b/include/linux/futex.h
> index 4326f81..934cf98 100644
> --- a/include/linux/futex.h
> +++ b/include/linux/futex.h
> @@ -185,9 +185,46 @@ union futex_key {
>  #define FUTEX_KEY_INIT (union futex_key) { .both = { .ptr = NULL } }
>  
>  #ifdef CONFIG_FUTEX
> +extern long do_set_robust_list(struct robust_list_head __user *head, size_t len);
>  extern void exit_robust_list(struct task_struct *curr);
>  extern void exit_pi_state_list(struct task_struct *curr);
>  extern int futex_cmpxchg_enabled;
> +
> +#ifdef CONFIG_CHECKPOINT
> +#include <linux/checkpoint_hdr.h>
> +
> +static inline void save_task_robust_futex_list(struct ckpt_hdr_task *h,
> +					       struct task_struct *t)
> +{
> +	/*
> +	 * These are __user pointers and thus can be saved without
> +	 * the objhash.
> +	 */
> +	h->robust_futex_list = (unsigned long)t->robust_list;
> +	h->robust_futex_head_len = sizeof(*t->robust_list);
> +#ifdef CONFIG_COMPAT
> +	h->compat_robust_futex_list = ptr_to_compat(t->compat_robust_list);
> +	h->compat_robust_futex_head_len = sizeof(*t->compat_robust_list);
> +#endif
> +}
> +
> +static inline void restore_task_robust_futex_list(struct ckpt_hdr_task *h)
> +{
> +	/* Since we restore the memory map the address remains the same and
> +	 * this is safe. This is the same as [compat_]sys_set_robust_list() */
> +	if (h->robust_futex_list) {
> +		struct robust_list_head __user *rfl = (void __user *)(unsigned long)h->robust_futex_list;
> +		do_set_robust_list(rfl, h->robust_futex_head_len);
> +	}
> +#ifdef CONFIG_COMPAT
> +	if (h->compat_robust_futex_list) {
> +		struct compat_robust_list_head __user *crfl = compat_ptr(h->compat_robust_futex_list);
> +		do_compat_set_robust_list(crfl, h->compat_robust_futex_head_len);
> +	}
> +#endif
> +}
> +#endif /* CONFIG_CHECKPOINT */
> +
>  #else
>  static inline void exit_robust_list(struct task_struct *curr)
>  {
> @@ -195,6 +232,15 @@ static inline void exit_robust_list(struct task_struct *curr)
>  static inline void exit_pi_state_list(struct task_struct *curr)
>  {
>  }
> +#ifdef CONFIG_CHECKPOINT
> +static inline void save_task_robust_futex_list(struct ckpt_hdr_task *h,
> +					      struct task_struct *t)
> +{
> +}
> +static inline void restore_task_robust_futex_list(struct ckpt_hdr_task *h)
> +{
> +}
> +#endif /* CONFIG_CHECKPOINT */
>  #endif
>  #endif /* __KERNEL__ */
>  

powerpc build with CONFIG_CHECKPOINT=y fails.  I suspect any
CONFIG_COMPAT=y build fails?

In file included from kernel/fork.c:42:
include/linux/futex.h: In function ‘save_task_robust_futex_list’:
include/linux/futex.h:206: error: implicit declaration of function ‘ptr_to_compat’
include/linux/futex.h:207: error: dereferencing pointer to incomplete type
include/linux/futex.h: In function ‘restore_task_robust_futex_list’:
include/linux/futex.h:221: error: implicit declaration of function ‘compat_ptr’
include/linux/futex.h:221: warning: initialization makes pointer from integer without a cast
include/linux/futex.h:222: error: implicit declaration of function ‘do_compat_set_robust_list’

fix:

diff --git a/include/linux/futex.h b/include/linux/futex.h
index 934cf98..f40a9bf 100644
--- a/include/linux/futex.h
+++ b/include/linux/futex.h
@@ -3,6 +3,7 @@
 
 #include <linux/compiler.h>
 #include <linux/types.h>
+#include <linux/compat.h>
 
 struct inode;
 struct mm_struct;

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