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Commit e6a9522a authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Thomas Gleixner
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drm/i915: Remove redundant user_access_end() from __copy_from_user() error path 



Objtool reports:

  drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: .altinstr_replacement+0x36: redundant UACCESS disable

__copy_from_user() already does both STAC and CLAC, so the
user_access_end() in its error path adds an extra unnecessary CLAC.

Fixes: 0b2c8f8b ("i915: fix missing user_access_end() in page fault exception case")
Reported-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reported-by: default avatarSedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Tested-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Tested-by: default avatarSedat Dilek <sedat.dilek@gmail.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Link: https://github.com/ClangBuiltLinux/linux/issues/617
Link: https://lkml.kernel.org/r/51a4155c5bc2ca847a9cbe85c1c11918bb193141.1564086017.git.jpoimboe@redhat.com
parent 33920f1e

drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c

+9 −11
Original line number Diff line number Diff line
@@ -1628,6 +1628,7 @@ static int check_relocations(const struct drm_i915_gem_exec_object2 *entry) 


static int eb_copy_relocations(const struct i915_execbuffer *eb)

{

	struct drm_i915_gem_relocation_entry *relocs;

	const unsigned int count = eb->buffer_count;

	unsigned int i;

	int err;
@@ -1635,7 +1636,6 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb) 
	for (i = 0; i < count; i++) {

		const unsigned int nreloc = eb->exec[i].relocation_count;

		struct drm_i915_gem_relocation_entry __user *urelocs;

		struct drm_i915_gem_relocation_entry *relocs;

		unsigned long size;

		unsigned long copied;
@@ -1663,14 +1663,8 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb) 


			if (__copy_from_user((char *)relocs + copied,

					     (char __user *)urelocs + copied,

					     len)) {

end_user:

				user_access_end();

end:

				kvfree(relocs);

				err = -EFAULT;

				goto err;

			}

					     len))

				goto end;



			copied += len;

		} while (copied < size);
@@ -1699,10 +1693,14 @@ static int eb_copy_relocations(const struct i915_execbuffer *eb) 


	return 0;



end_user:

	user_access_end();

end:

	kvfree(relocs);

	err = -EFAULT;

err:

	while (i--) {

		struct drm_i915_gem_relocation_entry *relocs =

			u64_to_ptr(typeof(*relocs), eb->exec[i].relocs_ptr);

		relocs = u64_to_ptr(typeof(*relocs), eb->exec[i].relocs_ptr);

		if (eb->exec[i].relocation_count)

			kvfree(relocs);

	}