Commit e3c92e81 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

runtime constants: add x86 architecture support 



This implements the runtime constant infrastructure for x86, allowing
the dcache d_hash() function to be generated using as a constant for
hash table address followed by shift by a constant of the hash index.

Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e7829855

arch/x86/include/asm/runtime-const.h

0 → 100644
+61 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

#ifndef _ASM_RUNTIME_CONST_H

#define _ASM_RUNTIME_CONST_H



#define runtime_const_ptr(sym) ({				\

	typeof(sym) __ret;					\

	asm_inline("mov %1,%0\n1:\n"				\

		".pushsection runtime_ptr_" #sym ",\"a\"\n\t"	\

		".long 1b - %c2 - .\n\t"			\

		".popsection"					\

		:"=r" (__ret)					\

		:"i" ((unsigned long)0x0123456789abcdefull),	\

		 "i" (sizeof(long)));				\

	__ret; })



// The 'typeof' will create at _least_ a 32-bit type, but

// will happily also take a bigger type and the 'shrl' will

// clear the upper bits

#define runtime_const_shift_right_32(val, sym) ({		\

	typeof(0u+(val)) __ret = (val);				\

	asm_inline("shrl $12,%k0\n1:\n"				\

		".pushsection runtime_shift_" #sym ",\"a\"\n\t"	\

		".long 1b - 1 - .\n\t"				\

		".popsection"					\

		:"+r" (__ret));					\

	__ret; })



#define runtime_const_init(type, sym) do {		\

	extern s32 __start_runtime_##type##_##sym[];	\

	extern s32 __stop_runtime_##type##_##sym[];	\

	runtime_const_fixup(__runtime_fixup_##type,	\

		(unsigned long)(sym), 			\

		__start_runtime_##type##_##sym,		\

		__stop_runtime_##type##_##sym);		\

} while (0)



/*

 * The text patching is trivial - you can only do this at init time,

 * when the text section hasn't been marked RO, and before the text

 * has ever been executed.

 */

static inline void __runtime_fixup_ptr(void *where, unsigned long val)

{

	*(unsigned long *)where = val;

}



static inline void __runtime_fixup_shift(void *where, unsigned long val)

{

	*(unsigned char *)where = val;

}



static inline void runtime_const_fixup(void (*fn)(void *, unsigned long),

	unsigned long val, s32 *start, s32 *end)

{

	while (start < end) {

		fn(*start + (void *)start, val);

		start++;

	}

}



#endif

arch/x86/kernel/vmlinux.lds.S

+3 −0
Original line number Diff line number Diff line
@@ -357,6 +357,9 @@ SECTIONS 
	PERCPU_SECTION(INTERNODE_CACHE_BYTES)

#endif



	RUNTIME_CONST(shift, d_hash_shift)

	RUNTIME_CONST(ptr, dentry_hashtable)



	. = ALIGN(PAGE_SIZE);



	/* freed after init ends here */