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#include "ultra64/asm.h"
#include "ultra64/regdef.h"
#include "ultra64/R4300.h"
.text
/**
* u32 __osProbeTLB(void* vaddr);
*
* Searches the TLB for the physical address associated with
* the virtual address `vaddr`.
*
* Returns the physical address if found, or -1 if not found.
*/
LEAF(__osProbeTLB)
.set noreorder
/* Set C0_ENTRYHI based on supplied vaddr */
mfc0 t0, C0_ENTRYHI
and t1, t0, TLBHI_PIDMASK
and t2, a0, TLBHI_VPN2MASK
or t1, t1, t2
mtc0 t1, C0_ENTRYHI
nop
nop
nop
/* TLB probe, sets C0_INX to a value matching C0_ENTRYHI. */
/* If no match is found the TLBINX_PROBE bit is set to indicate this. */
tlbp
nop
nop
/* Read result */
mfc0 t3, C0_INX
and t3, t3, TLBINX_PROBE
/* Branch if no match was found */
bnez t3, 3f
nop
/* Read TLB, sets C0_ENTRYHI, C0_ENTRYLO0, C0_ENTRYLO1 and C0_PAGEMASK for the TLB */
/* entry indicated by C0_INX */
tlbr
nop
nop
nop
/* Calculate page size = (page mask + 0x2000) >> 1 */
mfc0 t3, C0_PAGEMASK
add t3, t3, 0x2000
srl t3, t3, 1
/* & with vaddr */
and t4, t3, a0
/* Select C0_ENTRYLO0 or C0_ENTRYLO1 */
bnez t4, 1f
add t3, t3, -1 /* make bitmask out of page size */
mfc0 v0, C0_ENTRYLO0
b 2f
nop
1:
mfc0 v0, C0_ENTRYLO1
2:
/* Check valid bit and branch if not valid */
and t5, v0, TLBLO_V
beqz t5, 3f
nop
/* Extract the Page Frame Number from the entry */
and v0, v0, TLBLO_PFNMASK
sll v0, v0, TLBLO_PFNSHIFT
/* Mask vaddr with page size mask */
and t5, a0, t3
/* Add masked vaddr to pfn to obtain the physical address */
add v0, v0, t5
b 4f
nop
3:
/* No physical address for the supplied virtual address was found, */
/* return -1 */
li v0, -1
4:
/* Restore original C0_ENTRYHI value before returning */
mtc0 t0, C0_ENTRYHI
jr ra
nop
.set reorder
END(__osProbeTLB)
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