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