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. 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? I see two other drivers accessing the nvram here arch/m68k/mvme16x/config.c:static MK48T08ptr_t volatile rtc = (MK48T08ptr_t)MVME_RTC_BASE; arch/m68k/mvme16x/rtc.c: volatile MK48T08ptr_t rtc = (MK48T08ptr_t)MVME_RTC_BASE; The same trick should work here, just create a local variable with a volatile pointer and read from that. Arnd
