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Subject[PATCH 5.1 062/121] nds32: Avoid IEX status being incorrectly modified
Date
[ Upstream commit ed32949e0acb73e7bc054bb02e0453d4d561ceda ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/nds32/include/asm/bitfield.h | 2 +-
arch/nds32/include/asm/fpu.h | 2 +-
arch/nds32/include/asm/syscalls.h | 2 +-
arch/nds32/include/uapi/asm/fp_udfiex_crtl.h | 16 ++++++++++++
arch/nds32/include/uapi/asm/sigcontext.h | 24 ++++++++++++------
arch/nds32/include/uapi/asm/udftrap.h | 13 ----------
arch/nds32/include/uapi/asm/unistd.h | 4 +--
arch/nds32/kernel/fpu.c | 15 +++++------
arch/nds32/kernel/sys_nds32.c | 26 +++++++++++---------
9 files changed, 58 insertions(+), 46 deletions(-)
create mode 100644 arch/nds32/include/uapi/asm/fp_udfiex_crtl.h
delete mode 100644 arch/nds32/include/uapi/asm/udftrap.h

diff --git a/arch/nds32/include/asm/bitfield.h b/arch/nds32/include/asm/bitfield.h
index 7414fcbbab4e..03bbb6d27828 100644
--- 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 019f1bcfc5ee..8294ed4aaa2c 100644
--- 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 da32101b455d..b9c9becce5d6 100644
--- 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
index 000000000000..d54a5d6c6538
--- /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 58afc416473e..b53634033e32 100644
--- 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
index 433f79d679c0..000000000000
--- 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 4ec8f543103f..6b9ff90e3ae5 100644
--- 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 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
--
2.20.1


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