On Wed, Jun 03, 2020 at 04:32:02PM -0700, Kees Cook wrote:
> Using uninitialized_var() is dangerous as it papers over real bugs[1]
> (or can in the future), and suppresses unrelated compiler warnings
> (e.g. "unused variable"). If the compiler thinks it is uninitialized,
> either simply initialize the variable or make compiler changes.
>
> I preparation for removing[2] the[3] macro[4], remove all remaining
> needless uses with the following script:
>
> git grep '\buninitialized_var\b' | cut -d: -f1 | sort -u | \
> xargs perl -pi -e \
> 's/\buninitialized_var\(([^\)]+)\)/\1/g;
> s:\s*/\* (GCC be quiet|to make compiler happy) \*/$::g;'
>
> drivers/video/fbdev/riva/riva_hw.c was manually tweaked to avoid
> pathological white-space.
>
> No outstanding warnings were found building allmodconfig with GCC 9.3.0
> for x86_64, i386, arm64, arm, powerpc, powerpc64le, s390x, mips, sparc64,
> alpha, and m68k.
>
> [1] https://lore.kernel.org/lkml/20200603174714.192027-1-gli...@google.com/
> [2]
> https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1tgqcr5vqkczwj0qxk6cernou6eedsuda...@mail.gmail.com/
> [3]
> https://lore.kernel.org/lkml/ca+55afwgbgqhbp1fkxvrkepzyr5j8n1vkt1vzdz9knmpuxh...@mail.gmail.com/
> [4]
> https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yvju65tplgn_ybynv0ve...@mail.gmail.com/
>
> Signed-off-by: Kees Cook <keesc...@chromium.org>
<snip>
> diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
> index a0f6813f4560..a71fa7204882 100644
> --- a/arch/powerpc/kvm/book3s_pr.c
> +++ b/arch/powerpc/kvm/book3s_pr.c
> @@ -1829,7 +1829,7 @@ static int kvmppc_vcpu_run_pr(struct kvm_run *kvm_run,
> struct kvm_vcpu *vcpu)
> {
> int ret;
> #ifdef CONFIG_ALTIVEC
> - unsigned long uninitialized_var(vrsave);
> + unsigned long vrsave;
> #endif
This variable is actually unused:
../arch/powerpc/kvm/book3s_pr.c:1832:16: warning: unused variable 'vrsave'
[-Wunused-variable]
unsigned long vrsave;
^
1 warning generated.
It has been unused since commit 99dae3bad28d ("KVM: PPC: Load/save
FP/VMX/VSX state directly to/from vcpu struct").
$ git grep vrsave 99dae3bad28d8fdd32b7bfdd5e2ec7bb2d4d019d
arch/powerpc/kvm/book3s_pr.c
99dae3bad28d8fdd32b7bfdd5e2ec7bb2d4d019d:arch/powerpc/kvm/book3s_pr.c:
unsigned long uninitialized_var(vrsave);
I would nuke the whole '#ifdef' block.
Cheers,
Nathan
