/*    NetWinder Floating Point Emulator    (c) Corel Computer Corporation, 1998    (c) Philip Blundell 1998-1999    Direct questions, comments to Scott Bambrough <scottb@netwinder.org>    This program is free software; you can redistribute it and/or modify    it under the terms of the GNU General Public License as published by    the Free Software Foundation; either version 2 of the License, or    (at your option) any later version.    This program is distributed in the hope that it will be useful,    but WITHOUT ANY WARRANTY; without even the implied warranty of    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the    GNU General Public License for more details.    You should have received a copy of the GNU General Public License    along with this program; if not, write to the Free Software    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.*/#include <asm/constants.h>/* This is the kernel's entry point into the floating point emulator.It is called from the kernel with code similar to this:	mov	fp, #0	teqp	pc, #I_BIT | MODE_SVC	ldr	r4, .LC2	ldr	pc, [r4]		@ Call FP module USR entry pointThe kernel expects the emulator to return via one of two possiblepoints of return it passes to the emulator.  The emulator, ifsuccessful in its emulation, jumps to ret_from_exception and thekernel takes care of returning control from the trap to the user code.If the emulator is unable to emulate the instruction, it returns tofpundefinstr and the kernel halts the user program with a core dump.This routine does four things:1) It saves SP into a variable called userRegisters.  The kernel hascreated a struct pt_regs on the stack and saved the user registersinto it.  See /usr/include/asm/proc/ptrace.h for details.  Theemulator code uses userRegisters as the base of an array of words fromwhich the contents of the registers can be extracted.2) It locates the FP emulator work area within the TSS structure andpoints `fpa11' to it.3) It calls EmulateAll to emulate a floating point instruction.EmulateAll returns 1 if the emulation was successful, or 0 if not.4) If an instruction has been emulated successfully, it looks ahead atthe next instruction.  If it is a floating point instruction, itexecutes the instruction, without returning to user space.  In thisway it repeatedly looks ahead and executes floating point instructionsuntil it encounters a non floating point instruction, at which time itreturns via _fpreturn.This is done to reduce the effect of the trap overhead on eachfloating point instructions.  GCC attempts to group floating pointinstructions to allow the emulator to spread the cost of the trap overseveral floating point instructions.  */	.globl	nwfpe_enternwfpe_enter:	ldr	r4, =userRegisters	str	sp, [r4]		@ save pointer to user regs	mov	r10, sp, lsr #13	@ find workspace	mov	r10, r10, lsl #13	add	r10, r10, #TSS_FPESAVE	ldr	r4, =fpa11	str	r10, [r4]		@ store pointer to our state	mov	r4, sp			@ use r4 for local pointer	ldr	r5, [r4, #60]		@ get contents of PC	bic	r5, r5, #0xfc000003	ldr	r0, [r5, #-4]		@ get actual instruction into r0	bl	EmulateAll		@ emulate the instruction1:	cmp	r0, #0			@ was emulation successful	beq	fpundefinstr		@ no, return failurenext:	ldrt	r6, [r5], #4		@ get the next instruction and					@ increment PC	and	r2, r6, #0x0F000000	@ test for FP insns	teq	r2, #0x0C000000	teqne	r2, #0x0D000000	teqne	r2, #0x0E000000	bne	ret_from_exception	@ return ok if not a fp insn	ldr	r9, [r4, #60]		@ get new condition codes	and	r9, r9, #0xfc000003	orr	r7, r5, r9	str	r7, [r4, #60]		@ update PC copy in regs	mov	r0, r6			@ save a copy	mov	r1, r9			@ fetch the condition codes	bl	checkCondition		@ check the condition	cmp	r0, #0			@ r0 = 0 ==> condition failed	@ if condition code failed to match, next insn	beq	next			@ get the next instruction;	    	mov	r0, r6			@ prepare for EmulateAll()	adr	lr, 1b	orr	lr, lr, #3	b	EmulateAll		@ if r0 != 0, goto EmulateAll