On 8/5/20 11:37 AM, Linus Torvalds wrote: > On Wed, Aug 5, 2020 at 11:24 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote: >> >> Same with older versions of gcc. I don't see the problem with the >> mainline kernel. > > https://www.youtube.com/watch?v=-b5aW08ivHU > >> I think this is caused by more recursive includes. >> arch/arm64/include/asm/archrandom.h includes include/linux/random.h >> which includes arch/arm64/include/asm/archrandom.h to get the definition >> of arch_get_random_seed_long_early (which it won't get because of >> the recursion). >> >> What I don't really understand is how this works with new versions >> of gcc. > > Is that the only place it triggers? > > Because the trivial fix would be something like the appended, which is > the right thing to do anyway. > Correct. gcc-7.x and older don't support CONFIG_ARM64_PTR_AUTH. Result is that ./arch/arm64/include/asm/pointer_auth.h doesn't include <linux/random.h> for those compiler versions, which results in the problem. In the mainline kernel, ./arch/arm64/include/asm/pointer_auth.h always includes <linux/random.h>, so the problem isn't seen (or, rather, it is hidden) there. The problem is caused (exposed) by Marc's commit ("arm64: Workaround circular dependency in pointer_auth.h"), which makes the include of linux/random.h conditional. Guenter > Linus > > diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c > index 07c4c8cc4a67..9ded4237e1c1 100644 > --- a/arch/arm64/kernel/kaslr.c > +++ b/arch/arm64/kernel/kaslr.c > @@ -11,8 +11,8 @@ > #include <linux/sched.h> > #include <linux/types.h> > #include <linux/pgtable.h> > +#include <linux/random.h> > > -#include <asm/archrandom.h> > #include <asm/cacheflush.h> > #include <asm/fixmap.h> > #include <asm/kernel-pgtable.h> >
