Messages in this thread | | | From | Arnd Bergmann <> | Date | Wed, 1 Jan 2020 21:51:02 +0100 | Subject | Re: [PATCH] MIPS: Don't declare __current_thread_info globally |
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On Wed, Jan 1, 2020 at 6:57 PM Paul Burton <paulburton@kernel.org> wrote: > diff --git a/arch/mips/include/asm/thread_info.h b/arch/mips/include/asm/thread_info.h > index 4993db40482c..aceefc3f9a1a 100644 > --- a/arch/mips/include/asm/thread_info.h > +++ b/arch/mips/include/asm/thread_info.h > @@ -50,10 +50,10 @@ struct thread_info { > } > > /* How to get the thread information struct from C. */ > -register struct thread_info *__current_thread_info __asm__("$28"); > - > static inline struct thread_info *current_thread_info(void) > { > + register struct thread_info *__current_thread_info __asm__("$28"); > + > return __current_thread_info; > }
This looks like a nice fix, but are you sure it doesn't allow the compiler to reuse $28 for another purpose in the kernel under register pressure, which would break current_thread_info()?
I see in the MIPS ABI document that $28 is preserved across function calls, but I don't see any indication that a function is not allowed to modify it and later restore the original content.
Arnd
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