arch/mips/lib/uncached.c

Source file repositories/reference/linux-study-clean/arch/mips/lib/uncached.c

File Facts

System
Linux kernel
Corpus path
arch/mips/lib/uncached.c
Extension
.c
Size
2112 bytes
Lines
83
Domain
Architecture Layer
Bucket
arch/mips
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

#include <asm/addrspace.h>
#include <asm/bug.h>
#include <asm/cacheflush.h>

#ifndef CKSEG2
#define CKSEG2 CKSSEG
#endif
#ifndef TO_PHYS_MASK
#define TO_PHYS_MASK -1
#endif

/*
 * FUNC is executed in one of the uncached segments, depending on its
 * original address as follows:
 *
 * 1. If the original address is in CKSEG0 or CKSEG1, then the uncached
 *    segment used is CKSEG1.
 * 2. If the original address is in XKPHYS, then the uncached segment
 *    used is XKPHYS(2).
 * 3. Otherwise it's a bug.
 *
 * The same remapping is done with the stack pointer.  Stack handling
 * works because we don't handle stack arguments or more complex return
 * values, so we can avoid sharing the same stack area between a cached
 * and the uncached mode.
 */
unsigned long run_uncached(void *func)
{
	register long ret __asm__("$2");
	long lfunc = (long)func, ufunc;
	long usp;
	long sp;

	__asm__("move %0, $sp" : "=r" (sp));

	if (sp >= (long)CKSEG0 && sp < (long)CKSEG2)
		usp = CKSEG1ADDR(sp);
#ifdef CONFIG_64BIT
	else if ((long long)sp >= (long long)PHYS_TO_XKPHYS(0, 0) &&
		 (long long)sp < (long long)PHYS_TO_XKPHYS(8, 0))
		usp = PHYS_TO_XKPHYS(K_CALG_UNCACHED,
				     XKPHYS_TO_PHYS((long long)sp));
#endif
	else {
		BUG();
		usp = sp;
	}
	if (lfunc >= (long)CKSEG0 && lfunc < (long)CKSEG2)
		ufunc = CKSEG1ADDR(lfunc);
#ifdef CONFIG_64BIT
	else if ((long long)lfunc >= (long long)PHYS_TO_XKPHYS(0, 0) &&
		 (long long)lfunc < (long long)PHYS_TO_XKPHYS(8, 0))
		ufunc = PHYS_TO_XKPHYS(K_CALG_UNCACHED,
				       XKPHYS_TO_PHYS((long long)lfunc));
#endif
	else {
		BUG();
		ufunc = lfunc;
	}

	__asm__ __volatile__ (
		"	move	$16, $sp\n"
		"	move	$sp, %1\n"
		"	jalr	%2\n"
		"	move	$sp, $16"
		: "=r" (ret)
		: "r" (usp), "r" (ufunc)
		: "$16", "$31");

	return ret;
}

Annotation

Implementation Notes