Commit ed32949e authored by Vincent Chen's avatar Vincent Chen Committed by Greentime Hu
Browse files

nds32: Avoid IEX status being incorrectly modified 



In order for kernel to capture each denormalized output, the UDF
trapping enable bit is always raised in $fpcsr. Because underflow case will
issue not an underflow exception but also an inexact exception, it causes
that the IEX, IEX cumulative exception, flag in $fpcsr to be raised in each
denormalized output handling. To make the emulation transparent to the
user, the emulator needs to clear the IEX flag in $fpcsr if the result is a
denormalized number. However, if the IEX flag has been raised before this
floating point emulation, this cleanup may be incorrect. To avoid the IEX
flags in $fpcsr be raised in each denormalized output handling, the IEX
trap shall be always enabled.

Signed-off-by: default avatarVincent Chen <vincentc@andestech.com>
Acked-by: default avatarGreentime Hu <greentime@andestech.com>
Signed-off-by: default avatarGreentime Hu <greentime@andestech.com>
parent 8183db10

arch/nds32/include/asm/bitfield.h

+1 −1
Original line number Diff line number Diff line
@@ -937,7 +937,7 @@ 
#define FPCSR_mskDNIT           ( 0x1  << FPCSR_offDNIT )

#define FPCSR_mskRIT		( 0x1  << FPCSR_offRIT )

#define FPCSR_mskALL		(FPCSR_mskIVO | FPCSR_mskDBZ | FPCSR_mskOVF | FPCSR_mskUDF | FPCSR_mskIEX)

#define FPCSR_mskALLE_NO_UDFE	(FPCSR_mskIVOE | FPCSR_mskDBZE | FPCSR_mskOVFE | FPCSR_mskIEXE)

#define FPCSR_mskALLE_NO_UDF_IEXE (FPCSR_mskIVOE | FPCSR_mskDBZE | FPCSR_mskOVFE)

#define FPCSR_mskALLE		(FPCSR_mskIVOE | FPCSR_mskDBZE | FPCSR_mskOVFE | FPCSR_mskUDFE | FPCSR_mskIEXE)

#define FPCSR_mskALLT           (FPCSR_mskIVOT | FPCSR_mskDBZT | FPCSR_mskOVFT | FPCSR_mskUDFT | FPCSR_mskIEXT |FPCSR_mskDNIT | FPCSR_mskRIT)

arch/nds32/include/asm/fpu.h

+1 −1
Original line number Diff line number Diff line
@@ -36,7 +36,7 @@ extern int do_fpuemu(struct pt_regs *regs, struct fpu_struct *fpu); 
 * enabled by default and kerenl will re-execute it by fpu emulator

 * when getting underflow exception.

 */

#define FPCSR_INIT  FPCSR_mskUDFE

#define FPCSR_INIT  (FPCSR_mskUDFE | FPCSR_mskIEXE)

#else

#define FPCSR_INIT  0x0UL

#endif

arch/nds32/include/asm/syscalls.h

+1 −1
Original line number Diff line number Diff line
@@ -7,7 +7,7 @@ 
asmlinkage long sys_cacheflush(unsigned long addr, unsigned long len, unsigned int op);

asmlinkage long sys_fadvise64_64_wrapper(int fd, int advice, loff_t offset, loff_t len);

asmlinkage long sys_rt_sigreturn_wrapper(void);

asmlinkage long sys_udftrap(int option);

asmlinkage long sys_fp_udfiex_crtl(int cmd, int act);



#include <asm-generic/syscalls.h>

arch/nds32/include/uapi/asm/fp_udfiex_crtl.h

0 → 100644
+16 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

/* Copyright (C) 2005-2019 Andes Technology Corporation */

#ifndef	_FP_UDF_IEX_CRTL_H

#define	_FP_UDF_IEX_CRTL_H



/*

 * The cmd list of sys_fp_udfiex_crtl()

 */

/* Disable UDF or IEX trap based on the content of parameter act */

#define DISABLE_UDF_IEX_TRAP	0

/* Enable UDF or IEX trap based on the content of parameter act */

#define ENABLE_UDF_IEX_TRAP	1

/* Get current status of UDF and IEX trap */

#define GET_UDF_IEX_TRAP	2



#endif /* _FP_UDF_IEX_CRTL_H */

arch/nds32/include/uapi/asm/sigcontext.h

+17 −7
Original line number Diff line number Diff line
@@ -13,14 +13,24 @@ struct fpu_struct { 
	unsigned long long fd_regs[32];

	unsigned long fpcsr;

	/*

	 * UDF_trap is used to recognize whether underflow trap is enabled

	 * or not. When UDF_trap == 1, this process will be traped and then

	 * get a SIGFPE signal when encountering an underflow exception.

	 * UDF_trap is only modified through setfputrap syscall. Therefore,

	 * UDF_trap needn't be saved or loaded to context in each context

	 * switch.

	 * When CONFIG_SUPPORT_DENORMAL_ARITHMETIC is defined, kernel prevents

	 * hardware from treating the denormalized output as an underflow case

	 * and rounding it to a normal number. Hence kernel enables the UDF and

	 * IEX trap in the fpcsr register to step in the calculation.

	 * However, the UDF and IEX trap enable bit in $fpcsr also lose

	 * their use.

	 *

	 * UDF_IEX_trap replaces the feature of UDF and IEX trap enable bit in

	 * $fpcsr to control the trap of underflow and inexact. The bit filed

	 * of UDF_IEX_trap is the same as $fpcsr, 10th bit is used to enable UDF

	 * exception trapping and 11th bit is used to enable IEX exception

	 * trapping.

	 *

	 * UDF_IEX_trap is only modified through fp_udfiex_crtl syscall.

	 * Therefore, UDF_IEX_trap needn't be saved and restored in each

	 * context switch.

	 */

	unsigned long UDF_trap;

	unsigned long UDF_IEX_trap;

};



struct zol_struct {

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