Hi On Fri, Sep 6, 2013 at 12:59 PM, Geert Uytterhoeven <[email protected]> wrote: > On Fri, Sep 6, 2013 at 11:55 AM, David Herrmann <[email protected]> wrote: >> On Fri, Sep 6, 2013 at 11:32 AM, Tom Gundersen <[email protected]> wrote: >>> lfb_size can easily be say 4M, which would make the bitshit overflow and >>> the test fail. >>> >>> Signed-off-by: Tom Gundersen <[email protected]> >>> Cc: David Herrmann <[email protected]> >>> Cc: H. Peter Anvin <[email protected]> >>> --- >>> arch/x86/kernel/sysfb_simplefb.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/arch/x86/kernel/sysfb_simplefb.c >>> b/arch/x86/kernel/sysfb_simplefb.c >>> index 22513e9..fff44a5 100644 >>> --- a/arch/x86/kernel/sysfb_simplefb.c >>> +++ b/arch/x86/kernel/sysfb_simplefb.c >>> @@ -72,7 +72,7 @@ __init int create_simplefb(const struct screen_info *si, >>> * the part that is occupied by the framebuffer */ >>> len = mode->height * mode->stride; >>> len = PAGE_ALIGN(len); >>> - if (len > si->lfb_size << 16) { >>> + if (len > ((unsigned long) si->lfb_size) << 16) { > > On 32-bit, "unsigned long" is the same size as __u32, so this doesn't > make any difference.
lfb_size cannot be 4M on 32bit machines. Well, if it is, the firmware passed bogus information as you cannot have a 262G-region on 32bit. But on 64bit it can pass 4M just fine. So we don't care for the 32bit case here, only 64bit. The (__u64) cast would be more obvious. Don't know.. It's just a sanity check, anyways, so I'm fine with it. >> Nice catch. vesafb uses "lfb_size * 65535" which causes an implicit >> cast. I thought <<16 looks nicer but that doesn't do any implicit >> cast.. > > "lfb_size * 65535" is the same. "lfb_size" is __u32, "65535" is int. > So there's no implicit cast. Or am I missing something? Yepp, indeed. My bad, so vesafb doesn't do any better here. I wonder, though, which firmware passes such values. It means the lfb_size area is reserved >4G. We do have huge VMEM these days.. Tom, on what hardware did you hit that? Thanks David -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
