115 lines
4.0 KiB
ArmAsm
115 lines
4.0 KiB
ArmAsm
/*
|
|
NetWinder Floating Point Emulator
|
|
(c) Rebel.COM, 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/asm-offsets.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, #PSR_I_BIT | MODE_SVC
|
|
ldr r4, .LC2
|
|
ldr pc, [r4] @ Call FP module USR entry point
|
|
|
|
The kernel expects the emulator to return via one of two possible
|
|
points of return it passes to the emulator. The emulator, if
|
|
successful in its emulation, jumps to ret_from_exception and the
|
|
kernel takes care of returning control from the trap to the user code.
|
|
If the emulator is unable to emulate the instruction, it returns to
|
|
fpundefinstr 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 has
|
|
created a struct pt_regs on the stack and saved the user registers
|
|
into it. See /usr/include/asm/proc/ptrace.h for details. The
|
|
emulator code uses userRegisters as the base of an array of words from
|
|
which the contents of the registers can be extracted.
|
|
|
|
2) It locates the FP emulator work area within the TSS structure and
|
|
points `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 at
|
|
the next instruction. If it is a floating point instruction, it
|
|
executes the instruction, without returning to user space. In this
|
|
way it repeatedly looks ahead and executes floating point instructions
|
|
until it encounters a non floating point instruction, at which time it
|
|
returns via _fpreturn.
|
|
|
|
This is done to reduce the effect of the trap overhead on each
|
|
floating point instructions. GCC attempts to group floating point
|
|
instructions to allow the emulator to spread the cost of the trap over
|
|
several floating point instructions. */
|
|
|
|
.globl nwfpe_enter
|
|
nwfpe_enter:
|
|
mov sl, sp
|
|
bl FPA11_CheckInit @ check to see if we are initialised
|
|
|
|
ldr r5, [sp, #60] @ get contents of PC
|
|
bic r5, r5, #0xfc000003
|
|
ldr r0, [r5, #-4] @ get actual instruction into r0
|
|
bl EmulateAll @ emulate the instruction
|
|
1: cmp r0, #0 @ was emulation successful
|
|
beq fpundefinstr @ no, return failure
|
|
|
|
next:
|
|
.Lx1: 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, [sp, #60] @ get new condition codes
|
|
and r9, r9, #0xfc000003
|
|
orr r7, r5, r9
|
|
str r7, [sp, #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
|
|
|
|
.Lret: b ret_from_exception @ let the user eat segfaults
|
|
|
|
@ We need to be prepared for the instruction at .Lx1 to fault.
|
|
@ Emit the appropriate exception gunk to fix things up.
|
|
.section __ex_table,"a"
|
|
.align 3
|
|
.long .Lx1
|
|
ldr lr, [lr, $(.Lret - .Lx1)/4]
|
|
.previous
|