| Message ID | 1394478649-9453-4-git-send-email-peter.maydell@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
Am 10.03.2014 20:10, schrieb Peter Maydell: > Add U suffix to avoid undefined behaviour. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > hw/pci/pci_host.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/hw/pci/pci_host.c b/hw/pci/pci_host.c > index 77c7d1f..2c17916 100644 > --- a/hw/pci/pci_host.c > +++ b/hw/pci/pci_host.c > @@ -142,8 +142,9 @@ static uint64_t pci_host_data_read(void *opaque, > { > PCIHostState *s = opaque; > uint32_t val; > - if (!(s->config_reg & (1 << 31))) > + if (!(s->config_reg & (1u << 31))) { > return 0xffffffff; I suggest fixing that 0xffffffff, too. Do we expect here a 32 bit value (-1) which is expanded to a 64 bit value? Then 0xffffffffffffffffULL would be correct. Otherwise 0xffffffffU is clearer. Michael, are 8 byte reads possible here? If yes, the current code is wrong. > + } > val = pci_data_read(s->bus, s->config_reg | (addr & 3), len); > PCI_DPRINTF("read addr " TARGET_FMT_plx " len %d val %x\n", > addr, len, val); > What about using the BIT macro from qemu/bitops.h? I think that BIT(31) looks better than (1u << 31). Stefan
On Mon, Mar 10, 2014 at 09:03:08PM +0100, Stefan Weil wrote: > Am 10.03.2014 20:10, schrieb Peter Maydell: > > Add U suffix to avoid undefined behaviour. > > > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > > --- > > hw/pci/pci_host.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/hw/pci/pci_host.c b/hw/pci/pci_host.c > > index 77c7d1f..2c17916 100644 > > --- a/hw/pci/pci_host.c > > +++ b/hw/pci/pci_host.c > > @@ -142,8 +142,9 @@ static uint64_t pci_host_data_read(void *opaque, > > { > > PCIHostState *s = opaque; > > uint32_t val; > > - if (!(s->config_reg & (1 << 31))) > > + if (!(s->config_reg & (1u << 31))) { > > return 0xffffffff; > > I suggest fixing that 0xffffffff, too. Do we expect here a 32 bit value > (-1) which is expanded to a 64 bit value? Then 0xffffffffffffffffULL > would be correct. Otherwise 0xffffffffU is clearer. Hmm why is this clearer? The spec says: The type of an integer constant is the first of the corresponding list in which its value can be represented. Basically 0x<anything> is always a positive value and when cast to uint64_t is not sign extended. > Michael, are 8 byte reads possible here? If yes, the current code is wrong. AFAIK they aren't possible on any platform we support. So since we discard high bits 0 seems cleaner. > > + } > > val = pci_data_read(s->bus, s->config_reg | (addr & 3), len); > > PCI_DPRINTF("read addr " TARGET_FMT_plx " len %d val %x\n", > > addr, len, val); > > > > What about using the BIT macro from qemu/bitops.h? I think that BIT(31) > looks better than (1u << 31). > > Stefan I slightly prefer 1u << 31 personally, standard C as opposed to qemu macros.
On Mon, Mar 10, 2014 at 07:10:39PM +0000, Peter Maydell wrote: > Add U suffix to avoid undefined behaviour. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> > --- > hw/pci/pci_host.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/hw/pci/pci_host.c b/hw/pci/pci_host.c > index 77c7d1f..2c17916 100644 > --- a/hw/pci/pci_host.c > +++ b/hw/pci/pci_host.c > @@ -142,8 +142,9 @@ static uint64_t pci_host_data_read(void *opaque, > { > PCIHostState *s = opaque; > uint32_t val; > - if (!(s->config_reg & (1 << 31))) > + if (!(s->config_reg & (1u << 31))) { > return 0xffffffff; > + } > val = pci_data_read(s->bus, s->config_reg | (addr & 3), len); > PCI_DPRINTF("read addr " TARGET_FMT_plx " len %d val %x\n", > addr, len, val); > -- > 1.9.0 >
diff --git a/hw/pci/pci_host.c b/hw/pci/pci_host.c index 77c7d1f..2c17916 100644 --- a/hw/pci/pci_host.c +++ b/hw/pci/pci_host.c @@ -142,8 +142,9 @@ static uint64_t pci_host_data_read(void *opaque, { PCIHostState *s = opaque; uint32_t val; - if (!(s->config_reg & (1 << 31))) + if (!(s->config_reg & (1u << 31))) { return 0xffffffff; + } val = pci_data_read(s->bus, s->config_reg | (addr & 3), len); PCI_DPRINTF("read addr " TARGET_FMT_plx " len %d val %x\n", addr, len, val);
Add U suffix to avoid undefined behaviour. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- hw/pci/pci_host.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)