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nds32: Avoid IEX status being incorrectly modified

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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: Vincent Chen <vincentc@andestech.com>
Acked-by: Greentime Hu <greentime@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>
This commit is contained in:
Vincent Chen 2019-05-20 09:21:12 +08:00 • committed by Greentime Hu
parent 8183db10db
commit ed32949e0a
9 changed files with 58 additions and 46 deletions
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2
arch/nds32/include/asm/bitfield.h
View file

@ -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)

2
arch/nds32/include/asm/fpu.h
View file

@ -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

2
arch/nds32/include/asm/syscalls.h
View file

@ -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>

16
arch/nds32/include/uapi/asm/fp_udfiex_crtl.h Normal file
View file

@ -0,0 +1,16 @@
/* 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 */

24
arch/nds32/include/uapi/asm/sigcontext.h
View file

@ -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 {

13
arch/nds32/include/uapi/asm/udftrap.h
View file

@ -1,13 +0,0 @@
/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright (C) 2005-2018 Andes Technology Corporation */
#ifndef _ASM_SETFPUTRAP
#define _ASM_SETFPUTRAP
/*
* Options for setfputrap system call
*/
#define DISABLE_UDFTRAP 0 /* disable underflow exception trap */
#define ENABLE_UDFTRAP 1 /* enable undeflos exception trap */
#define GET_UDFTRAP 2 /* only get undeflos exception trap status */
#endif /* _ASM_CACHECTL */

4
arch/nds32/include/uapi/asm/unistd.h
View file

@ -11,6 +11,6 @@
/* Additional NDS32 specific syscalls. */
#define __NR_cacheflush (__NR_arch_specific_syscall)
#define __NR_udftrap (__NR_arch_specific_syscall + 1)
#define __NR_fp_udfiex_crtl (__NR_arch_specific_syscall + 1)
__SYSCALL(__NR_cacheflush, sys_cacheflush)
__SYSCALL(__NR_udftrap, sys_udftrap)
__SYSCALL(__NR_fp_udfiex_crtl, sys_fp_udfiex_crtl)

15
arch/nds32/kernel/fpu.c
View file

@ -14,7 +14,7 @@ const struct fpu_struct init_fpuregs = {
.fd_regs = {[0 ... 31] = sNAN64},
.fpcsr = FPCSR_INIT,
#if IS_ENABLED(CONFIG_SUPPORT_DENORMAL_ARITHMETIC)
.UDF_trap = 0
.UDF_IEX_trap = 0
#endif
};
@ -178,7 +178,7 @@ inline void do_fpu_context_switch(struct pt_regs *regs)
/* First time FPU user. */
load_fpu(&init_fpuregs);
#if IS_ENABLED(CONFIG_SUPPORT_DENORMAL_ARITHMETIC)
current->thread.fpu.UDF_trap = init_fpuregs.UDF_trap;
current->thread.fpu.UDF_IEX_trap = init_fpuregs.UDF_IEX_trap;
#endif
set_used_math();
}
@ -206,7 +206,7 @@ inline void handle_fpu_exception(struct pt_regs *regs)
unsigned int fpcsr;
int si_code = 0, si_signo = SIGFPE;
#if IS_ENABLED(CONFIG_SUPPORT_DENORMAL_ARITHMETIC)
unsigned long redo_except = FPCSR_mskDNIT|FPCSR_mskUDFT;
unsigned long redo_except = FPCSR_mskDNIT|FPCSR_mskUDFT|FPCSR_mskIEXT;
#else
unsigned long redo_except = FPCSR_mskDNIT;
#endif
@ -215,21 +215,18 @@ inline void handle_fpu_exception(struct pt_regs *regs)
fpcsr = current->thread.fpu.fpcsr;
if (fpcsr & redo_except) {
#if IS_ENABLED(CONFIG_SUPPORT_DENORMAL_ARITHMETIC)
if (fpcsr & FPCSR_mskUDFT)
current->thread.fpu.fpcsr &= ~FPCSR_mskIEX;
#endif
si_signo = do_fpuemu(regs, &current->thread.fpu);
fpcsr = current->thread.fpu.fpcsr;
if (!si_signo)
if (!si_signo) {
current->thread.fpu.fpcsr &= ~(redo_except);
goto done;
}
} else if (fpcsr & FPCSR_mskRIT) {
if (!user_mode(regs))
do_exit(SIGILL);
si_signo = SIGILL;
}
switch (si_signo) {
case SIGFPE:
fill_sigfpe_signo(fpcsr, &si_code);

26
arch/nds32/kernel/sys_nds32.c
View file

@ -6,8 +6,8 @@
#include <asm/cachectl.h>
#include <asm/proc-fns.h>
#include <asm/udftrap.h>
#include <asm/fpu.h>
#include <asm/fp_udfiex_crtl.h>
SYSCALL_DEFINE6(mmap2, unsigned long, addr, unsigned long, len,
unsigned long, prot, unsigned long, flags,
@ -51,31 +51,33 @@ SYSCALL_DEFINE3(cacheflush, unsigned int, start, unsigned int, end, int, cache)
return 0;
}
SYSCALL_DEFINE1(udftrap, int, option)
SYSCALL_DEFINE2(fp_udfiex_crtl, unsigned int, cmd, unsigned int, act)
{
#if IS_ENABLED(CONFIG_SUPPORT_DENORMAL_ARITHMETIC)
int old_udftrap;
int old_udf_iex;
if (!used_math()) {
load_fpu(&init_fpuregs);
current->thread.fpu.UDF_trap = init_fpuregs.UDF_trap;
current->thread.fpu.UDF_IEX_trap = init_fpuregs.UDF_IEX_trap;
set_used_math();
}
old_udftrap = current->thread.fpu.UDF_trap;
switch (option) {
case DISABLE_UDFTRAP:
current->thread.fpu.UDF_trap = 0;
old_udf_iex = current->thread.fpu.UDF_IEX_trap;
act &= (FPCSR_mskUDFE | FPCSR_mskIEXE);
switch (cmd) {
case DISABLE_UDF_IEX_TRAP:
current->thread.fpu.UDF_IEX_trap &= ~act;
break;
case ENABLE_UDFTRAP:
current->thread.fpu.UDF_trap = FPCSR_mskUDFE;
case ENABLE_UDF_IEX_TRAP:
current->thread.fpu.UDF_IEX_trap |= act;
break;
case GET_UDFTRAP:
case GET_UDF_IEX_TRAP:
break;
default:
return -EINVAL;
}
return old_udftrap;
return old_udf_iex;
#else
return -ENOTSUPP;
#endif