Shane McDonald 95e8f634d7 MIPS FPU emulator: allow Cause bits of FCSR to be writeable by ctc1 ... In the FPU emulator code of the MIPS, the Cause bits of the FCSR register are not currently writeable by the ctc1 instruction. In odd corner cases, this can cause problems. For example, a case existed where a divide-by-zero exception was generated by the FPU, and the signal handler attempted to restore the FPU registers to their state before the exception occurred. In this particular setup, writing the old value to the FCSR register would cause another divide-by-zero exception to occur immediately. The solution is to change the ctc1 instruction emulator code to allow the Cause bits of the FCSR register to be writeable. This is the behaviour of the hardware that the code is emulating. This problem was found by Shane McDonald, but the credit for the fix goes to Kevin Kissell. In Kevin's words: I submit that the bug is indeed in that ctc_op: case of the emulator. The Cause bits (17:12) are supposed to be writable by that instruction, but the CTC1 emulation won't let them be updated by the instruction. I think that actually if you just completely removed lines 387-388 [...] things would work a good deal better. At least, it would be a more accurate emulation of the architecturally defined FPU. If I wanted to be really, really pedantic (which I sometimes do), I'd also protect the reserved bits that aren't necessarily writable. Signed-off-by: Shane McDonald <mcdonald.shane@gmail.com> To: anemo@mba.ocn.ne.jp To: kevink@paralogos.com To: sshtylyov@mvista.com Patchwork: http://patchwork.linux-mips.org/patch/1205/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org> ---		2010-05-15 21:59:53 +01:00
..
cp1emu.c	MIPS FPU emulator: allow Cause bits of FCSR to be writeable by ctc1	2010-05-15 21:59:53 +01:00
dp_add.c
dp_cmp.c
dp_div.c
dp_fint.c
dp_flong.c
dp_frexp.c
dp_fsp.c
dp_logb.c
dp_modf.c
dp_mul.c
dp_scalb.c
dp_simple.c	MIPS: Fix abs.[sd] and neg.[sd] emulation for NaN operands	2009-11-02 12:00:05 +01:00
dp_sqrt.c
dp_sub.c	tree-wide: fix assorted typos all over the place	2009-12-04 15:39:55 +01:00
dp_tint.c
dp_tlong.c
dsemul.c	MIPS: Collect FPU emulator statistics per-CPU.	2009-12-17 01:57:08 +00:00
ieee754.c
ieee754.h
ieee754d.c	MIPS: Nuke trailing blank lines	2010-02-27 12:53:14 +01:00
ieee754dp.c	MIPS: Cleanup switches with cases that can be merged	2010-02-27 12:53:14 +01:00
ieee754dp.h
ieee754int.h
ieee754m.c
ieee754sp.c	MIPS: Cleanup switches with cases that can be merged	2010-02-27 12:53:14 +01:00
ieee754sp.h
ieee754xcpt.c	MIPS: Nuke trailing blank lines	2010-02-27 12:53:14 +01:00
kernel_linkage.c
Makefile
sp_add.c
sp_cmp.c
sp_div.c
sp_fdp.c
sp_fint.c
sp_flong.c
sp_frexp.c
sp_logb.c
sp_modf.c
sp_mul.c
sp_scalb.c
sp_simple.c	MIPS: Fix abs.[sd] and neg.[sd] emulation for NaN operands	2009-11-02 12:00:05 +01:00
sp_sqrt.c
sp_sub.c
sp_tint.c
sp_tlong.c