linux-kernel - [PATCH v2 10/16] KVM: PPC: Book3S PR: Remove uninitialized

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Date:   Fri, 19 Jun 2020 20:30:01 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Joe Perches <joe@...ches.com>,
        Andy Whitcroft <apw@...onical.com>, x86@...nel.org,
        drbd-dev@...ts.linbit.com, linux-block@...r.kernel.org,
        b43-dev@...ts.infradead.org, netdev@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-wireless@...r.kernel.org,
        linux-ide@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-mm@...ck.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH v2 10/16] KVM: PPC: Book3S PR: Remove uninitialized_var() usage

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. As a precursor
to removing[2] this[3] macro[4], just remove this variable since it was
actually unused:

arch/powerpc/kvm/book3s_pr.c:1832:16: warning: unused variable 'vrsave' [-Wunused-variable]
        unsigned long vrsave;
                      ^

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Suggested-by: Nathan Chancellor <natechancellor@...il.com>
Fixes: f05ed4d56e9c ("KVM: PPC: Split out code from book3s.c into book3s_pr.c")
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/powerpc/kvm/book3s_pr.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index ef54f917bdaf..ed12dfbf9bb5 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -1828,9 +1828,6 @@ static int kvmppc_vcpu_run_pr(struct kvm_vcpu *vcpu)
 {
 	struct kvm_run *run = vcpu->run;
 	int ret;
-#ifdef CONFIG_ALTIVEC
-	unsigned long uninitialized_var(vrsave);
-#endif
 
 	/* Check if we can run the vcpu at all */
 	if (!vcpu->arch.sane) {
-- 
2.25.1