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. A related one, I guess, is: arch/m68k/include/asm/string.h:72:25: error: argument 2 null where non-null expected [-Werror=nonnull] 72 | #define memcpy(d, s, n) __builtin_memcpy(d, s, n) | ^~~~~~~~~~~~~~~~~~~~~~~~~ drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c:387:4: note: in expansion of macro ‘memcpy’ 387 | memcpy((char *)kmap(pages[0]) + | ^~~~~~ Seen with my sun3-allmodconfig build. As NO_DMA=y, dmam_alloc_coherent() returns NULL, and the compiler discovers that g_fragments_base is never assigned to and thus must be NULL. 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
