Hi Arnd, On Wed, Sep 8, 2021 at 11:50 AM Arnd Bergmann <arnd@xxxxxxxxxx> wrote: > On Wed, Sep 8, 2021 at 9:49 AM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > > On Wed, Sep 8, 2021 at 7:16 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote: > > > On 9/7/21 9:48 PM, Al Viro wrote: > > > > On Tue, Sep 07, 2021 at 09:28:38PM -0700, Guenter Roeck wrote: > > > >> memcpy(eth_addr, sanitize_address((void *) 0xfffc1f2c), ETH_ALEN); > > > >> > > > >> but that just seems weird. Is there a better solution ? > > > > > > > > (char (*)[ETH_ALEN])? Said that, shouldn't that be doing something like > > > > ioremap(), rather than casting explicit constants? > > > > > > Typecasts or even assigning the address to a variable does not help. > > > The sanitizer function can not be static either. > > > > So it can only be fixed by obfuscating the constant address in a > > chain of out-of-line functions... > > How is this compiler to be used for bare-metal programming? > > I reported this as a gcc bug when I first saw it back in March: > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578 > > Martin Sebor suggested marking the pointer as 'volatile' as a workaround, > which is probably fine for bare-metal programming, but I would consider > that bad style for the kernel boot arguments. The RELOC_HIDE trick is probably > fine here, as there are only a couple of instances, and for the network > driver, using volatile is probably appropriate as well. Yeah, volatile should be fine for drivers. In fact this is one of the few places where I/O registers are accessed without involving volatile. > I still hope this can be fixed in a future gcc-11.x release. Maybe we should > add further instances of the problem on the gcc bug to boost the priority? > > > > I don't know the hardware, so I can not answer the ioremap() question. > > > > Yes it should. But this driver dates back to 2.1.110, when only > > half of the architectures already had ioremap(). > > How does mvme16x even create the mapping? Is this a virtual address > that is hardwired to the bus or do you have a static mapping somewhere? It's part of the transparent mapping of the top address space for I/O devices in arch/m68k/kernel/head.S. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
