On 4/24/19 9:22 AM, Peter Zijlstra wrote:
> On Wed, Apr 24, 2019 at 11:03:57AM -0500, Josh Poimboeuf wrote:
>> On Wed, Apr 17, 2019 at 08:41:34AM -0700, Randy Dunlap wrote:
>
>>> on x86_64:
>>>
>>> CC drivers/gpu/drm/i915/i915_gem_execbuffer.o
>>> drivers/gpu/drm/i915/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x18: redundant UACCESS disable
>
>> I haven't looked at this, do you know if this is the same issue as the
>> other note from Randy, or something else?
>
> That smells like the below commit went missing... But I cannot reproduce
> when building next/master myself.
>
This patch is already in linux-next of today & of the reported "problem."
> ---
> commit 8f4faed01e3015955801c8ef066ec7fd7a8b3902
> Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Date: Thu Feb 28 13:52:31 2019 +0100
>
> i915, uaccess: Fix redundant CLAC
>
> New tooling noticed this:
>
> drivers/gpu/drm/i915/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x3c: redundant UACCESS disable
> drivers/gpu/drm/i915/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x66: redundant UACCESS disable
>
> You don't need user_access_end() if user_access_begin() fails.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> index 02adcaf6ebea..16f80a448820 100644
> --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> @@ -1667,6 +1667,7 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb)
> len)) {
> end_user:
> user_access_end();
> +end:
> kvfree(relocs);
> err = -EFAULT;
> goto err;
> @@ -1686,7 +1687,7 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb)
> * relocations were valid.
> */
> if (!user_access_begin(urelocs, size))
> - goto end_user;
> + goto end;
>
> for (copied = 0; copied < nreloc; copied++)
> unsafe_put_user(-1,
> @@ -2695,7 +2696,7 @@ i915_gem_execbuffer2_ioctl(struct drm_device *dev, void *data,
> * when we did the "copy_from_user()" above.
> */
> if (!user_access_begin(user_exec_list, count * sizeof(*user_exec_list)))
> - goto end_user;
> + goto end;
>
> for (i = 0; i < args->buffer_count; i++) {
> if (!(exec2_list[i].offset & UPDATE))
> @@ -2709,6 +2710,7 @@ i915_gem_execbuffer2_ioctl(struct drm_device *dev, void *data,
> }
> end_user:
> user_access_end();
> +end:;
> }
>
> args->flags &= ~__I915_EXEC_UNKNOWN_FLAGS;
>
--
~Randy
