On Wed, Jul 29, 2009 at 02:21:38AM +0200, Carl-Daniel Hailfinger wrote: > On 29.07.2009 00:36, Robert Millan wrote: > > The Multiboot spec is a bit too permissive about this, as it doesn't > > specify the state of direction flag when payload is called. Some payloads > > (we found this in ReactOS FreeLDR) assume it is cleared, and fail otherwise. > > > > We adjusted GRUB to be sure it's always cleared. I think coreboot should do > > the same. Here's a patch for v3. > > > > AFAIK this patch is unneeded. The GCC ABI on x86 and x86_64 states that > the direction flag must always be cleared before running any gcc > compiled code, so if you need to execute cld in the middle of C code, it > means that all C code before that cld had undefined behaviour. > > The correct place for cld is early asm startup code before any C code > gets executed.
Isn't C code allowed to set it back? -- Robert Millan The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and how) you may access your data; but nobody's threatening your freedom: we still allow you to remove your data and not access it at all." -- coreboot mailing list: [email protected] http://www.coreboot.org/mailman/listinfo/coreboot
