alpha: regularize the situation with asm/param.h

The only reason why alpha can't do what sparc et.al. are doing is that include/asm-generic/param.h relies upon the value of HZ set for userland header in uapi/asm/param.h being 100. We need that value to define USER_HZ and we need that definition to outlive the redefinition of HZ kernel-side. And alpha needs it to be 1024, not 100 like everybody else. So let's add __USER_HZ to uapi/asm-generic/param.h, defaulting to 100 and used to define HZ. That way include/asm-generic/param.h can use that thing instead of open-coding it - it won't be affected by undefining and redefining HZ. That done, alpha asm/param.h can be removed and uapi/asm/param.h switched to defining __USER_HZ and EXEC_PAGESIZE and then including <asm-generic/param.h> - asm/param.h will resolve to uapi/asm/param.h, which pulls <asm-generic/param.h>, which will do the right thing both in the kernel and userland contexts.

AVAl Viro committed 1 year ago