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SubjectRe: linux-next: Tree for Apr 17 (objtool)
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.

---
commit 8f4faed01e3015955801c8ef066ec7fd7a8b3902
Author: Peter Zijlstra <peterz@infradead.org>
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@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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;
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