From: Linus Torvalds
> Sent: 22 November 2024 19:35
>
> On Fri, 22 Nov 2024 at 11:13, Linus Torvalds
> <torva...@linux-foundation.org> wrote:
> >
> > I've only compiled it so far, about to actually boot into it.
>
> Looks fine. Sent out a proper patch with commit message etc at
>
>
> https://lore.kernel.org/all/20241122193305.7316-1-torva...@linux-foundation.org/
>
> because it looks good to me. Comments?
+static __always_inline int futex_read_inatomic(u32 *dest, u32 __user *from)
+{
+ u32 val;
+
+ if (can_do_masked_user_access())
+ from = masked_user_access_begin(from);
+ else if (!user_read_access_begin(from, sizeof(*from)))
+ return -EFAULT;
+ unsafe_get_user(val, from, Efault);
+ user_access_end();
+ *dest = val;
+ return 0;
+Efault:
+ user_access_end();
+ return -EFAULT;
+}
+
+static inline int futex_get_value_locked(u32 *dest, u32 __user *from)
+{
+ int ret;
+
+ pagefault_disable();
+ ret = futex_read_inatomic(dest, from);
+ pagefault_enable();
+
+ return ret;
+}
Is there an 'unsafe_get_user_nofault()' that uses a trap handler
that won't fault in a page?
That would save the inc/dec done by pagefault_en/disable().
I'd also have thought that the trap handler for unsafe_get_user()
would jump to the Efault label having already done user_access_end().
But maybe it doesn't work out that way?
David
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