| Message ID | 1418575877-21488-4-git-send-email-mst@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, Dec 14, 2014 at 04:52:09PM +0000, Michael S. Tsirkin wrote: > virtio wants to read bitwise types from userspace using get_user. At the > moment this triggers sparse errors, since the value is passed through an > integer. > > Fix that up using __force. > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > --- > arch/arm64/include/asm/uaccess.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h > index 3bf8f4e..8d66bcf 100644 > --- a/arch/arm64/include/asm/uaccess.h > +++ b/arch/arm64/include/asm/uaccess.h > @@ -147,7 +147,7 @@ do { \ > default: \ > BUILD_BUG(); \ > } \ > - (x) = (__typeof__(*(ptr)))__gu_val; \ > + (x) = (__force __typeof__(*(ptr)))__gu_val; \ > } while (0) > > #define __get_user(x, ptr) \ Acked-by: Will Deacon <will.deacon@arm.com> Will
On Mon, Dec 15, 2014 at 11:17:16AM +0000, Will Deacon wrote: > On Sun, Dec 14, 2014 at 04:52:09PM +0000, Michael S. Tsirkin wrote: > > virtio wants to read bitwise types from userspace using get_user. At the > > moment this triggers sparse errors, since the value is passed through an > > integer. > > > > Fix that up using __force. > > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > --- > > arch/arm64/include/asm/uaccess.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h > > index 3bf8f4e..8d66bcf 100644 > > --- a/arch/arm64/include/asm/uaccess.h > > +++ b/arch/arm64/include/asm/uaccess.h > > @@ -147,7 +147,7 @@ do { \ > > default: \ > > BUILD_BUG(); \ > > } \ > > - (x) = (__typeof__(*(ptr)))__gu_val; \ > > + (x) = (__force __typeof__(*(ptr)))__gu_val; \ > > } while (0) > > > > #define __get_user(x, ptr) \ > > Acked-by: Will Deacon <will.deacon@arm.com> This also means you can do stuff like: u32 *p; __le32 v; err = get_user(p, v); which is not right. Both the dereferenced pointer type and the destination type should be compatible, and if one is a bitwise type but the other isn't, that seems like a valid case to warn. I don't see any use of get_user() in drivers/virtio in mainline, so I can't check further.
On Mon, Dec 15, 2014 at 11:23:11AM +0000, Russell King - ARM Linux wrote: > On Mon, Dec 15, 2014 at 11:17:16AM +0000, Will Deacon wrote: > > On Sun, Dec 14, 2014 at 04:52:09PM +0000, Michael S. Tsirkin wrote: > > > virtio wants to read bitwise types from userspace using get_user. At the > > > moment this triggers sparse errors, since the value is passed through an > > > integer. > > > > > > Fix that up using __force. > > > > > > Signed-off-by: Michael S. Tsirkin <mst@redhat.com> > > > --- > > > arch/arm64/include/asm/uaccess.h | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h > > > index 3bf8f4e..8d66bcf 100644 > > > --- a/arch/arm64/include/asm/uaccess.h > > > +++ b/arch/arm64/include/asm/uaccess.h > > > @@ -147,7 +147,7 @@ do { \ > > > default: \ > > > BUILD_BUG(); \ > > > } \ > > > - (x) = (__typeof__(*(ptr)))__gu_val; \ > > > + (x) = (__force __typeof__(*(ptr)))__gu_val; \ > > > } while (0) > > > > > > #define __get_user(x, ptr) \ > > > > Acked-by: Will Deacon <will.deacon@arm.com> > > This also means you can do stuff like: > > u32 *p; > __le32 v; > > err = get_user(p, v); > > which is not right. Both the dereferenced pointer type and the destination > type should be compatible, and if one is a bitwise type but the other isn't, > that seems like a valid case to warn. I just verified this case: #define __force __attribute__((force)) #define __bitwise__ __attribute__((bitwise)) #define get_user(x, ptr) \ do {\ unsigned long __gu_val = 0; \ (x) = (__force __typeof__(*(ptr)))__gu_val; \ } while (0) typedef unsigned u32; typedef u32 __bitwise__ __le32; static u32 *p; static __le32 v; int main(int argc, char **argv) { get_user(v, p); return 0; } Produces a warning as expected. So I think the above comment is a result of a mistake. Can you confirm please? > I don't see any use of get_user() in drivers/virtio in mainline, so I can't > check further. this is an example of the case which I'm fixing: #define __force __attribute__((force)) #define __bitwise__ __attribute__((bitwise)) #define get_user(x, ptr) \ do {\ unsigned long __gu_val = 0; \ (x) = (__typeof__(*(ptr)))__gu_val; \ } while (0) typedef unsigned u32; typedef u32 __bitwise__ __le32; static __le32 *p; static __le32 v; int main(int argc, char **argv) { get_user(v, p); return 0; } the code is correct but produces a warning: a.c:18:9: warning: cast to restricted __le32 The cast near __typeof__ above needs __force, this is what my patch does. > -- > FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up > according to speedtest.net.
diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h index 3bf8f4e..8d66bcf 100644 --- a/arch/arm64/include/asm/uaccess.h +++ b/arch/arm64/include/asm/uaccess.h @@ -147,7 +147,7 @@ do { \ default: \ BUILD_BUG(); \ } \ - (x) = (__typeof__(*(ptr)))__gu_val; \ + (x) = (__force __typeof__(*(ptr)))__gu_val; \ } while (0) #define __get_user(x, ptr) \
virtio wants to read bitwise types from userspace using get_user. At the moment this triggers sparse errors, since the value is passed through an integer. Fix that up using __force. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> --- arch/arm64/include/asm/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)