On Wed, Jun 03, 2020 at 08:33:15PM -0700, Nathan Chancellor wrote:
On Wed, Jun 03, 2020 at 04:32:02PM -0700, Kees Cook wrote:
quoted
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-glider@google.com/ (local)
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/ (local)
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/ (local)
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/ (local)
Signed-off-by: Kees Cook <redacted>
<snip>
quoted
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.
Ah, thanks! I wonder why I don't have CONFIG_ALTIVEC in any of my ppc
builds. Hmmm.
-Kees
--
Kees Cook