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: Vincent Chen <vincentc@andestech.com>
Acked-by: Greentime Hu <greentime@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>

2 files changed, 20 insertions, 21 deletions

diff --git a/arch/nds32/kernel/fpu.c b/arch/nds32/kernel/fpu.c
index fddd40c7a16f..cf0b8760f261 100644
--- a/arch/nds32/kernel/fpu.c
+++ b/arch/nds32/kernel/fpu.c
@@ -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);
diff --git a/arch/nds32/kernel/sys_nds32.c b/arch/nds32/kernel/sys_nds32.c
index 0835277636ce..cb2d1e219bb3 100644
--- a/arch/nds32/kernel/sys_nds32.c
+++ b/arch/nds32/kernel/sys_nds32.c
@@ -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