On Sun, 1 Sep 2013 14:45:56 -0700 tip-bot for Al Viro <[email protected]> wrote: > > Commit-ID: bd1c149aa9915b9abb6d83d0f01dfd2ace0680b5 > Gitweb: http://git.kernel.org/tip/bd1c149aa9915b9abb6d83d0f01dfd2ace0680b5 > Author: Al Viro <[email protected]> > AuthorDate: Sun, 1 Sep 2013 20:35:01 +0100 > Committer: H. Peter Anvin <[email protected]> > CommitDate: Sun, 1 Sep 2013 14:16:33 -0700 > > Introduce [compat_]save_altstack_ex() to unbreak x86 SMAP > > For performance reasons, when SMAP is in use, SMAP is left open for an > entire put_user_try { ... } put_user_catch(); block, however, calling > __put_user() in the middle of that block will close SMAP as the > STAC..CLAC constructs intentionally do not nest. > > Furthermore, using __put_user() rather than put_user_ex() here is bad > for performance. > > Thus, introduce new [compat_]save_altstack_ex() helpers that replace > __[compat_]save_altstack() for x86, being currently the only > architecture which supports put_user_try { ... } put_user_catch(). > > Reported-by: H. Peter Anvin <[email protected]> > Signed-off-by: Al Viro <[email protected]> > Signed-off-by: H. Peter Anvin <[email protected]> > Cc: <[email protected]> # v3.8+ > Link: http://lkml.kernel.org/n/[email protected] > diff --git a/include/linux/compat.h b/include/linux/compat.h > index 7f0c1dd..ec1aee4 100644 > --- a/include/linux/compat.h > +++ b/include/linux/compat.h > @@ -669,6 +669,13 @@ asmlinkage long compat_sys_sigaltstack(const > compat_stack_t __user *uss_ptr, > > int compat_restore_altstack(const compat_stack_t __user *uss); > int __compat_save_altstack(compat_stack_t __user *, unsigned long); > +#define compat_save_altstack_ex(uss, sp) do { \ > + compat_stack_t __user *__uss = uss; \ > + struct task_struct *t = current; \ > + put_user_ex(ptr_to_compat((void __user *)t->sas_ss_sp), &__uss->ss_sp); > \ > + put_user_ex(sas_ss_flags(sp), &__uss->ss_flags); \ > + put_user_ex(t->sas_ss_size, &__uss->ss_size); \ > +} while (0);
I am just wondering if there is some reason that these macros are not
implemented as (static inline) C functions?
> +#define save_altstack_ex(uss, sp) do { \
> + stack_t __user *__uss = uss; \
> + struct task_struct *t = current; \
> + put_user_ex((void __user *)t->sas_ss_sp, &__uss->ss_sp); \
> + put_user_ex(sas_ss_flags(sp), &__uss->ss_flags); \
> + put_user_ex(t->sas_ss_size, &__uss->ss_size); \
> +} while (0);
> +
--
Cheers,
Stephen Rothwell [email protected]
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