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>

diff --git a/arch/nds32/include/asm/bitfield.h b/arch/nds32/include/asm/bitfield.h
index e75212c76b2044aa17badc5d77f5f5ad61cf8f30..b02a58e71f8097ec56dd7ee089c5ed76ed0e2ee7 100644 (file)
--- a/arch/nds32/include/asm/bitfield.h
+++ b/arch/nds32/include/asm/bitfield.h
@@ -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)
 

diff --git a/arch/nds32/include/asm/fpu.h b/arch/nds32/include/asm/fpu.h
index 019f1bcfc5ee17e4f5390ebaa7806ec90395e9f2..8294ed4aaa2cc950aec294aa69d50c16ee7f443d 100644 (file)
--- a/arch/nds32/include/asm/fpu.h
+++ b/arch/nds32/include/asm/fpu.h
@@ -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

diff --git a/arch/nds32/include/asm/syscalls.h b/arch/nds32/include/asm/syscalls.h
index f3b16f602cb5389c924a18c57e4d105407faaee4..4e7216082a6725e79030c8a06c19a4996d2e4319 100644 (file)
--- a/arch/nds32/include/asm/syscalls.h
+++ b/arch/nds32/include/asm/syscalls.h
@@ -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>
 

diff --git a/arch/nds32/include/uapi/asm/fp_udfiex_crtl.h b/arch/nds32/include/uapi/asm/fp_udfiex_crtl.h
new file mode 100644 (file)
index 0000000..d54a5d6
--- /dev/null
+++ b/arch/nds32/include/uapi/asm/fp_udfiex_crtl.h
@@ -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 */

diff --git a/arch/nds32/include/uapi/asm/sigcontext.h b/arch/nds32/include/uapi/asm/sigcontext.h
index 628ff6b75825a18c77562c1285268c3c189846e7..dc89af7ddcc3d0ce497c13a04787c78f12df12ba 100644 (file)
--- a/arch/nds32/include/uapi/asm/sigcontext.h
+++ b/arch/nds32/include/uapi/asm/sigcontext.h
@@ -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 {

diff --git a/arch/nds32/include/uapi/asm/udftrap.h b/arch/nds32/include/uapi/asm/udftrap.h
deleted file mode 100644 (file)
index 433f79d..0000000
--- a/arch/nds32/include/uapi/asm/udftrap.h
+++ /dev/null
@@ -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 */

diff --git a/arch/nds32/include/uapi/asm/unistd.h b/arch/nds32/include/uapi/asm/unistd.h
index c691735017ed59724f760b859a2c739780835b10..a0b2f7b9c0f29a8b1b2c5a42f6c7032033590d22 100644 (file)
--- a/arch/nds32/include/uapi/asm/unistd.h
+++ b/arch/nds32/include/uapi/asm/unistd.h
@@ -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)

diff --git a/arch/nds32/kernel/fpu.c b/arch/nds32/kernel/fpu.c
index fddd40c7a16f9880d2082cb71aa3431ac4192ac5..cf0b8760f2616d287fe238854dbe0b53e55a40ea 100644 (file)
--- 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 0835277636ce31f1a3ba75dbbcd33a7d0f0d31eb..cb2d1e219bb3b77387ff7607231edf8a2475b55c 100644 (file)
--- 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