On 12/07/19 11:12, Arnd Bergmann wrote: > clang finds a contruct suspicious that converts an unsigned > character to a signed integer and back, causing an overflow:
I like how the commit message conveys the braindead-ness of the warning. Queued, thanks. Paolo > arch/x86/kvm/mmu.c:4605:39: error: implicit conversion from 'int' to 'u8' > (aka 'unsigned char') changes value from -205 to 51 > [-Werror,-Wconstant-conversion] > u8 wf = (pfec & PFERR_WRITE_MASK) ? ~w : 0; > ~~ ^~ > arch/x86/kvm/mmu.c:4607:38: error: implicit conversion from 'int' to 'u8' > (aka 'unsigned char') changes value from -241 to 15 > [-Werror,-Wconstant-conversion] > u8 uf = (pfec & PFERR_USER_MASK) ? ~u : 0; > ~~ ^~ > arch/x86/kvm/mmu.c:4609:39: error: implicit conversion from 'int' to 'u8' > (aka 'unsigned char') changes value from -171 to 85 > [-Werror,-Wconstant-conversion] > u8 ff = (pfec & PFERR_FETCH_MASK) ? ~x : 0; > ~~ ^~ > > Add an explicit cast to tell clang that everything works as > intended here. > > Signed-off-by: Arnd Bergmann <a...@arndb.de> > --- > arch/x86/kvm/mmu.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 17ece7b994b1..aea7f969ecb8 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -4602,11 +4602,11 @@ static void update_permission_bitmask(struct kvm_vcpu > *vcpu, > */ > > /* Faults from writes to non-writable pages */ > - u8 wf = (pfec & PFERR_WRITE_MASK) ? ~w : 0; > + u8 wf = (pfec & PFERR_WRITE_MASK) ? (u8)~w : 0; > /* Faults from user mode accesses to supervisor pages */ > - u8 uf = (pfec & PFERR_USER_MASK) ? ~u : 0; > + u8 uf = (pfec & PFERR_USER_MASK) ? (u8)~u : 0; > /* Faults from fetches of non-executable pages*/ > - u8 ff = (pfec & PFERR_FETCH_MASK) ? ~x : 0; > + u8 ff = (pfec & PFERR_FETCH_MASK) ? (u8)~x : 0; > /* Faults from kernel mode fetches of user pages */ > u8 smepf = 0; > /* Faults from kernel mode accesses of user pages */ >
