WSL2-Linux-Kernel/arch/arm/mm/copypage-v4wt.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/arch/arm/mm/copypage-v4wt.S
 *
 *  Copyright (C) 1995-1999 Russell King
 *
 *  This is for CPUs with a writethrough cache and 'flush ID cache' is
 *  the only supported cache operation.
 */
#include <linux/init.h>
#include <linux/highmem.h>

/*
 * ARMv4 optimised copy_user_highpage
 *
 * Since we have writethrough caches, we don't have to worry about
 * dirty data in the cache.  However, we do have to ensure that
 * subsequent reads are up to date.
 */
static void v4wt_copy_user_page(void *kto, const void *kfrom)
{
	int tmp;

	asm volatile ("\
	.syntax unified\n\
	ldmia	%1!, {r3, r4, ip, lr}		@ 4\n\
1:	stmia	%0!, {r3, r4, ip, lr}		@ 4\n\
	ldmia	%1!, {r3, r4, ip, lr}		@ 4+1\n\
	stmia	%0!, {r3, r4, ip, lr}		@ 4\n\
	ldmia	%1!, {r3, r4, ip, lr}		@ 4\n\
	stmia	%0!, {r3, r4, ip, lr}		@ 4\n\
	ldmia	%1!, {r3, r4, ip, lr}		@ 4\n\
	subs	%2, %2, #1			@ 1\n\
	stmia	%0!, {r3, r4, ip, lr}		@ 4\n\
	ldmiane	%1!, {r3, r4, ip, lr}		@ 4\n\
	bne	1b				@ 1\n\
	mcr	p15, 0, %2, c7, c7, 0		@ flush ID cache"
	: "+&r" (kto), "+&r" (kfrom), "=&r" (tmp)
	: "2" (PAGE_SIZE / 64)
	: "r3", "r4", "ip", "lr");
}

void v4wt_copy_user_highpage(struct page *to, struct page *from,
	unsigned long vaddr, struct vm_area_struct *vma)
{
	void *kto, *kfrom;

	kto = kmap_atomic(to);
	kfrom = kmap_atomic(from);
	v4wt_copy_user_page(kto, kfrom);
	kunmap_atomic(kfrom);
	kunmap_atomic(kto);
}

/*
 * ARMv4 optimised clear_user_page
 *
 * Same story as above.
 */
void v4wt_clear_user_highpage(struct page *page, unsigned long vaddr)
{
	void *ptr, *kaddr = kmap_atomic(page);
	asm volatile("\
	mov	r1, %2				@ 1\n\
	mov	r2, #0				@ 1\n\
	mov	r3, #0				@ 1\n\
	mov	ip, #0				@ 1\n\
	mov	lr, #0				@ 1\n\
1:	stmia	%0!, {r2, r3, ip, lr}		@ 4\n\
	stmia	%0!, {r2, r3, ip, lr}		@ 4\n\
	stmia	%0!, {r2, r3, ip, lr}		@ 4\n\
	stmia	%0!, {r2, r3, ip, lr}		@ 4\n\
	subs	r1, r1, #1			@ 1\n\
	bne	1b				@ 1\n\
	mcr	p15, 0, r2, c7, c7, 0		@ flush ID cache"
	: "=r" (ptr)
	: "0" (kaddr), "I" (PAGE_SIZE / 64)
	: "r1", "r2", "r3", "ip", "lr");
	kunmap_atomic(kaddr);
}

struct cpu_user_fns v4wt_user_fns __initdata = {
	.cpu_clear_user_highpage = v4wt_clear_user_highpage,
	.cpu_copy_user_highpage	= v4wt_copy_user_highpage,
};