MIPS: Support for 64-bit FP with O32 binaries

CPUs implementing MIPS32 R2 may include a 64-bit FPU, just as MIPS64 CPUs
do. In order to preserve backwards compatibility a 64-bit FPU will act
like a 32-bit FPU (by accessing doubles from the least significant 32
bits of an even-odd pair of FP registers) when the Status.FR bit is
zero, again just like a mips64 CPU. The standard O32 ABI is defined
expecting a 32-bit FPU, however recent toolchains support use of a
64-bit FPU from an O32 MIPS32 executable. When an ELF executable is
built to use a 64-bit FPU a new flag (EF_MIPS_FP64) is set in the ELF
header.

With this patch the kernel will check the EF_MIPS_FP64 flag when
executing an O32 binary, and set Status.FR accordingly. The addition
of O32 64-bit FP support lessens the opportunity for optimisation in
the FPU emulator, so a CONFIG_MIPS_O32_FP64_SUPPORT Kconfig option is
introduced to allow this support to be disabled for those that don't
require it.

Inspired by an earlier patch by Leonid Yegoshin, but implemented more
cleanly & correctly.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Paul Burton <paul.burton@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/6154/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

6 files changed, 214 insertions, 157 deletions

diff --git a/arch/mips/include/asm/asmmacro-32.h b/arch/mips/include/asm/asmmacro-32.h
index 2413afe..70e1f17 100644
--- a/arch/mips/include/asm/asmmacro-32.h
+++ b/arch/mips/include/asm/asmmacro-32.h
@@ -12,27 +12,6 @@
 #include <asm/fpregdef.h>
 #include <asm/mipsregs.h>
 
-	.macro	fpu_save_double thread status tmp1=t0
-	cfc1	\tmp1,  fcr31
-	sdc1	$f0,  THREAD_FPR0(\thread)
-	sdc1	$f2,  THREAD_FPR2(\thread)
-	sdc1	$f4,  THREAD_FPR4(\thread)
-	sdc1	$f6,  THREAD_FPR6(\thread)
-	sdc1	$f8,  THREAD_FPR8(\thread)
-	sdc1	$f10, THREAD_FPR10(\thread)
-	sdc1	$f12, THREAD_FPR12(\thread)
-	sdc1	$f14, THREAD_FPR14(\thread)
-	sdc1	$f16, THREAD_FPR16(\thread)
-	sdc1	$f18, THREAD_FPR18(\thread)
-	sdc1	$f20, THREAD_FPR20(\thread)
-	sdc1	$f22, THREAD_FPR22(\thread)
-	sdc1	$f24, THREAD_FPR24(\thread)
-	sdc1	$f26, THREAD_FPR26(\thread)
-	sdc1	$f28, THREAD_FPR28(\thread)
-	sdc1	$f30, THREAD_FPR30(\thread)
-	sw	\tmp1, THREAD_FCR31(\thread)
-	.endm
-
 	.macro	fpu_save_single thread tmp=t0
 	cfc1	\tmp,  fcr31
 	swc1	$f0,  THREAD_FPR0(\thread)
@@ -70,27 +49,6 @@
 	sw	\tmp, THREAD_FCR31(\thread)
 	.endm
 
-	.macro	fpu_restore_double thread status tmp=t0
-	lw	\tmp, THREAD_FCR31(\thread)
-	ldc1	$f0,  THREAD_FPR0(\thread)
-	ldc1	$f2,  THREAD_FPR2(\thread)
-	ldc1	$f4,  THREAD_FPR4(\thread)
-	ldc1	$f6,  THREAD_FPR6(\thread)
-	ldc1	$f8,  THREAD_FPR8(\thread)
-	ldc1	$f10, THREAD_FPR10(\thread)
-	ldc1	$f12, THREAD_FPR12(\thread)
-	ldc1	$f14, THREAD_FPR14(\thread)
-	ldc1	$f16, THREAD_FPR16(\thread)
-	ldc1	$f18, THREAD_FPR18(\thread)
-	ldc1	$f20, THREAD_FPR20(\thread)
-	ldc1	$f22, THREAD_FPR22(\thread)
-	ldc1	$f24, THREAD_FPR24(\thread)
-	ldc1	$f26, THREAD_FPR26(\thread)
-	ldc1	$f28, THREAD_FPR28(\thread)
-	ldc1	$f30, THREAD_FPR30(\thread)
-	ctc1	\tmp, fcr31
-	.endm
-
 	.macro	fpu_restore_single thread tmp=t0
 	lw	\tmp, THREAD_FCR31(\thread)
 	lwc1	$f0,  THREAD_FPR0(\thread)
diff --git a/arch/mips/include/asm/asmmacro-64.h b/arch/mips/include/asm/asmmacro-64.h
index 08a527d..38ea609 100644
--- a/arch/mips/include/asm/asmmacro-64.h
+++ b/arch/mips/include/asm/asmmacro-64.h
@@ -13,102 +13,6 @@
 #include <asm/fpregdef.h>
 #include <asm/mipsregs.h>
 
-	.macro	fpu_save_16even thread tmp=t0
-	cfc1	\tmp, fcr31
-	sdc1	$f0,  THREAD_FPR0(\thread)
-	sdc1	$f2,  THREAD_FPR2(\thread)
-	sdc1	$f4,  THREAD_FPR4(\thread)
-	sdc1	$f6,  THREAD_FPR6(\thread)
-	sdc1	$f8,  THREAD_FPR8(\thread)
-	sdc1	$f10, THREAD_FPR10(\thread)
-	sdc1	$f12, THREAD_FPR12(\thread)
-	sdc1	$f14, THREAD_FPR14(\thread)
-	sdc1	$f16, THREAD_FPR16(\thread)
-	sdc1	$f18, THREAD_FPR18(\thread)
-	sdc1	$f20, THREAD_FPR20(\thread)
-	sdc1	$f22, THREAD_FPR22(\thread)
-	sdc1	$f24, THREAD_FPR24(\thread)
-	sdc1	$f26, THREAD_FPR26(\thread)
-	sdc1	$f28, THREAD_FPR28(\thread)
-	sdc1	$f30, THREAD_FPR30(\thread)
-	sw	\tmp, THREAD_FCR31(\thread)
-	.endm
-
-	.macro	fpu_save_16odd thread
-	sdc1	$f1,  THREAD_FPR1(\thread)
-	sdc1	$f3,  THREAD_FPR3(\thread)
-	sdc1	$f5,  THREAD_FPR5(\thread)
-	sdc1	$f7,  THREAD_FPR7(\thread)
-	sdc1	$f9,  THREAD_FPR9(\thread)
-	sdc1	$f11, THREAD_FPR11(\thread)
-	sdc1	$f13, THREAD_FPR13(\thread)
-	sdc1	$f15, THREAD_FPR15(\thread)
-	sdc1	$f17, THREAD_FPR17(\thread)
-	sdc1	$f19, THREAD_FPR19(\thread)
-	sdc1	$f21, THREAD_FPR21(\thread)
-	sdc1	$f23, THREAD_FPR23(\thread)
-	sdc1	$f25, THREAD_FPR25(\thread)
-	sdc1	$f27, THREAD_FPR27(\thread)
-	sdc1	$f29, THREAD_FPR29(\thread)
-	sdc1	$f31, THREAD_FPR31(\thread)
-	.endm
-
-	.macro	fpu_save_double thread status tmp
-	sll	\tmp, \status, 5
-	bgez	\tmp, 2f
-	fpu_save_16odd \thread
-2:
-	fpu_save_16even \thread \tmp
-	.endm
-
-	.macro	fpu_restore_16even thread tmp=t0
-	lw	\tmp, THREAD_FCR31(\thread)
-	ldc1	$f0,  THREAD_FPR0(\thread)
-	ldc1	$f2,  THREAD_FPR2(\thread)
-	ldc1	$f4,  THREAD_FPR4(\thread)
-	ldc1	$f6,  THREAD_FPR6(\thread)
-	ldc1	$f8,  THREAD_FPR8(\thread)
-	ldc1	$f10, THREAD_FPR10(\thread)
-	ldc1	$f12, THREAD_FPR12(\thread)
-	ldc1	$f14, THREAD_FPR14(\thread)
-	ldc1	$f16, THREAD_FPR16(\thread)
-	ldc1	$f18, THREAD_FPR18(\thread)
-	ldc1	$f20, THREAD_FPR20(\thread)
-	ldc1	$f22, THREAD_FPR22(\thread)
-	ldc1	$f24, THREAD_FPR24(\thread)
-	ldc1	$f26, THREAD_FPR26(\thread)
-	ldc1	$f28, THREAD_FPR28(\thread)
-	ldc1	$f30, THREAD_FPR30(\thread)
-	ctc1	\tmp, fcr31
-	.endm
-
-	.macro	fpu_restore_16odd thread
-	ldc1	$f1,  THREAD_FPR1(\thread)
-	ldc1	$f3,  THREAD_FPR3(\thread)
-	ldc1	$f5,  THREAD_FPR5(\thread)
-	ldc1	$f7,  THREAD_FPR7(\thread)
-	ldc1	$f9,  THREAD_FPR9(\thread)
-	ldc1	$f11, THREAD_FPR11(\thread)
-	ldc1	$f13, THREAD_FPR13(\thread)
-	ldc1	$f15, THREAD_FPR15(\thread)
-	ldc1	$f17, THREAD_FPR17(\thread)
-	ldc1	$f19, THREAD_FPR19(\thread)
-	ldc1	$f21, THREAD_FPR21(\thread)
-	ldc1	$f23, THREAD_FPR23(\thread)
-	ldc1	$f25, THREAD_FPR25(\thread)
-	ldc1	$f27, THREAD_FPR27(\thread)
-	ldc1	$f29, THREAD_FPR29(\thread)
-	ldc1	$f31, THREAD_FPR31(\thread)
-	.endm
-
-	.macro	fpu_restore_double thread status tmp
-	sll	\tmp, \status, 5
-	bgez	\tmp, 1f				# 16 register mode?
-
-	fpu_restore_16odd \thread
-1:	fpu_restore_16even \thread \tmp
-	.endm
-
 	.macro	cpu_save_nonscratch thread
 	LONG_S	s0, THREAD_REG16(\thread)
 	LONG_S	s1, THREAD_REG17(\thread)
diff --git a/arch/mips/include/asm/asmmacro.h b/arch/mips/include/asm/asmmacro.h
index 6c8342a..3220c93 100644
--- a/arch/mips/include/asm/asmmacro.h
+++ b/arch/mips/include/asm/asmmacro.h
@@ -62,6 +62,113 @@
 	.endm
 #endif /* CONFIG_MIPS_MT_SMTC */
 
+	.macro	fpu_save_16even thread tmp=t0
+	cfc1	\tmp, fcr31
+	sdc1	$f0,  THREAD_FPR0(\thread)
+	sdc1	$f2,  THREAD_FPR2(\thread)
+	sdc1	$f4,  THREAD_FPR4(\thread)
+	sdc1	$f6,  THREAD_FPR6(\thread)
+	sdc1	$f8,  THREAD_FPR8(\thread)
+	sdc1	$f10, THREAD_FPR10(\thread)
+	sdc1	$f12, THREAD_FPR12(\thread)
+	sdc1	$f14, THREAD_FPR14(\thread)
+	sdc1	$f16, THREAD_FPR16(\thread)
+	sdc1	$f18, THREAD_FPR18(\thread)
+	sdc1	$f20, THREAD_FPR20(\thread)
+	sdc1	$f22, THREAD_FPR22(\thread)
+	sdc1	$f24, THREAD_FPR24(\thread)
+	sdc1	$f26, THREAD_FPR26(\thread)
+	sdc1	$f28, THREAD_FPR28(\thread)
+	sdc1	$f30, THREAD_FPR30(\thread)
+	sw	\tmp, THREAD_FCR31(\thread)
+	.endm
+
+	.macro	fpu_save_16odd thread
+	.set	push
+	.set	mips64r2
+	sdc1	$f1,  THREAD_FPR1(\thread)
+	sdc1	$f3,  THREAD_FPR3(\thread)
+	sdc1	$f5,  THREAD_FPR5(\thread)
+	sdc1	$f7,  THREAD_FPR7(\thread)
+	sdc1	$f9,  THREAD_FPR9(\thread)
+	sdc1	$f11, THREAD_FPR11(\thread)
+	sdc1	$f13, THREAD_FPR13(\thread)
+	sdc1	$f15, THREAD_FPR15(\thread)
+	sdc1	$f17, THREAD_FPR17(\thread)
+	sdc1	$f19, THREAD_FPR19(\thread)
+	sdc1	$f21, THREAD_FPR21(\thread)
+	sdc1	$f23, THREAD_FPR23(\thread)
+	sdc1	$f25, THREAD_FPR25(\thread)
+	sdc1	$f27, THREAD_FPR27(\thread)
+	sdc1	$f29, THREAD_FPR29(\thread)
+	sdc1	$f31, THREAD_FPR31(\thread)
+	.set	pop
+	.endm
+
+	.macro	fpu_save_double thread status tmp
+#if defined(CONFIG_MIPS64) || defined(CONFIG_CPU_MIPS32_R2)
+	sll	\tmp, \status, 5
+	bgez	\tmp, 10f
+	fpu_save_16odd \thread
+10:
+#endif
+	fpu_save_16even \thread \tmp
+	.endm
+
+	.macro	fpu_restore_16even thread tmp=t0
+	lw	\tmp, THREAD_FCR31(\thread)
+	ldc1	$f0,  THREAD_FPR0(\thread)
+	ldc1	$f2,  THREAD_FPR2(\thread)
+	ldc1	$f4,  THREAD_FPR4(\thread)
+	ldc1	$f6,  THREAD_FPR6(\thread)
+	ldc1	$f8,  THREAD_FPR8(\thread)
+	ldc1	$f10, THREAD_FPR10(\thread)
+	ldc1	$f12, THREAD_FPR12(\thread)
+	ldc1	$f14, THREAD_FPR14(\thread)
+	ldc1	$f16, THREAD_FPR16(\thread)
+	ldc1	$f18, THREAD_FPR18(\thread)
+	ldc1	$f20, THREAD_FPR20(\thread)
+	ldc1	$f22, THREAD_FPR22(\thread)
+	ldc1	$f24, THREAD_FPR24(\thread)
+	ldc1	$f26, THREAD_FPR26(\thread)
+	ldc1	$f28, THREAD_FPR28(\thread)
+	ldc1	$f30, THREAD_FPR30(\thread)
+	ctc1	\tmp, fcr31
+	.endm
+
+	.macro	fpu_restore_16odd thread
+	.set	push
+	.set	mips64r2
+	ldc1	$f1,  THREAD_FPR1(\thread)
+	ldc1	$f3,  THREAD_FPR3(\thread)
+	ldc1	$f5,  THREAD_FPR5(\thread)
+	ldc1	$f7,  THREAD_FPR7(\thread)
+	ldc1	$f9,  THREAD_FPR9(\thread)
+	ldc1	$f11, THREAD_FPR11(\thread)
+	ldc1	$f13, THREAD_FPR13(\thread)
+	ldc1	$f15, THREAD_FPR15(\thread)
+	ldc1	$f17, THREAD_FPR17(\thread)
+	ldc1	$f19, THREAD_FPR19(\thread)
+	ldc1	$f21, THREAD_FPR21(\thread)
+	ldc1	$f23, THREAD_FPR23(\thread)
+	ldc1	$f25, THREAD_FPR25(\thread)
+	ldc1	$f27, THREAD_FPR27(\thread)
+	ldc1	$f29, THREAD_FPR29(\thread)
+	ldc1	$f31, THREAD_FPR31(\thread)
+	.set	pop
+	.endm
+
+	.macro	fpu_restore_double thread status tmp
+#if defined(CONFIG_MIPS64) || defined(CONFIG_CPU_MIPS32_R2)
+	sll	\tmp, \status, 5
+	bgez	\tmp, 10f				# 16 register mode?
+
+	fpu_restore_16odd \thread
+10:
+#endif
+	fpu_restore_16even \thread \tmp
+	.endm
+
 /*
  * Temporary until all gas have MT ASE support
  */
diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
index a66359e..d414405 100644
--- a/arch/mips/include/asm/elf.h
+++ b/arch/mips/include/asm/elf.h
@@ -36,6 +36,7 @@
 #define EF_MIPS_ABI2		0x00000020
 #define EF_MIPS_OPTIONS_FIRST	0x00000080
 #define EF_MIPS_32BITMODE	0x00000100
+#define EF_MIPS_FP64		0x00000200
 #define EF_MIPS_ABI		0x0000f000
 #define EF_MIPS_ARCH		0xf0000000
 
@@ -176,6 +177,18 @@ typedef elf_fpreg_t elf_fpregset_t[ELF_NFPREG];
 #ifdef CONFIG_32BIT
 
 /*
+ * In order to be sure that we don't attempt to execute an O32 binary which
+ * requires 64 bit FP (FR=1) on a system which does not support it we refuse
+ * to execute any binary which has bits specified by the following macro set
+ * in its ELF header flags.
+ */
+#ifdef CONFIG_MIPS_O32_FP64_SUPPORT
+# define __MIPS_O32_FP64_MUST_BE_ZERO	0
+#else
+# define __MIPS_O32_FP64_MUST_BE_ZERO	EF_MIPS_FP64
+#endif
+
+/*
  * This is used to ensure we don't load something for the wrong architecture.
  */
 #define elf_check_arch(hdr)						\
@@ -192,6 +205,8 @@ typedef elf_fpreg_t elf_fpregset_t[ELF_NFPREG];
 	if (((__h->e_flags & EF_MIPS_ABI) != 0) &&			\
 	    ((__h->e_flags & EF_MIPS_ABI) != EF_MIPS_ABI_O32))		\
 		__res = 0;						\
+	if (__h->e_flags & __MIPS_O32_FP64_MUST_BE_ZERO)		\
+		__res = 0;						\
 									\
 	__res;								\
 })
@@ -249,6 +264,11 @@ extern struct mips_abi mips_abi_n32;
 
 #define SET_PERSONALITY(ex)						\
 do {									\
+	if ((ex).e_flags & EF_MIPS_FP64)				\
+		clear_thread_flag(TIF_32BIT_FPREGS);			\
+	else								\
+		set_thread_flag(TIF_32BIT_FPREGS);			\
+									\
 	if (personality(current->personality) != PER_LINUX)		\
 		set_personality(PER_LINUX);				\
 									\
@@ -271,14 +291,18 @@ do {									\
 #endif
 
 #ifdef CONFIG_MIPS32_O32
-#define __SET_PERSONALITY32_O32()					\
+#define __SET_PERSONALITY32_O32(ex)					\
 	do {								\
 		set_thread_flag(TIF_32BIT_REGS);			\
 		set_thread_flag(TIF_32BIT_ADDR);			\
+									\
+		if (!((ex).e_flags & EF_MIPS_FP64))			\
+			set_thread_flag(TIF_32BIT_FPREGS);		\
+									\
 		current->thread.abi = &mips_abi_32;			\
 	} while (0)
 #else
-#define __SET_PERSONALITY32_O32()					\
+#define __SET_PERSONALITY32_O32(ex)					\
 	do { } while (0)
 #endif
 
@@ -289,7 +313,7 @@ do {									\
 	     ((ex).e_flags & EF_MIPS_ABI) == 0)				\
 		__SET_PERSONALITY32_N32();				\
 	else								\
-		__SET_PERSONALITY32_O32();				\
+		__SET_PERSONALITY32_O32(ex);                            \
 } while (0)
 #else
 #define __SET_PERSONALITY32(ex) do { } while (0)
@@ -300,6 +324,7 @@ do {									\
 	unsigned int p;							\
 									\
 	clear_thread_flag(TIF_32BIT_REGS);				\
+	clear_thread_flag(TIF_32BIT_FPREGS);				\
 	clear_thread_flag(TIF_32BIT_ADDR);				\
 									\
 	if ((ex).e_ident[EI_CLASS] == ELFCLASS32)			\
diff --git a/arch/mips/include/asm/fpu.h b/arch/mips/include/asm/fpu.h
index 3bf023f..cfe092f 100644
--- a/arch/mips/include/asm/fpu.h
+++ b/arch/mips/include/asm/fpu.h
@@ -33,11 +33,48 @@ extern void _init_fpu(void);
 extern void _save_fp(struct task_struct *);
 extern void _restore_fp(struct task_struct *);
 
-#define __enable_fpu()							\
-do {									\
-	set_c0_status(ST0_CU1);						\
-	enable_fpu_hazard();						\
-} while (0)
+/*
+ * This enum specifies a mode in which we want the FPU to operate, for cores
+ * which implement the Status.FR bit. Note that FPU_32BIT & FPU_64BIT
+ * purposefully have the values 0 & 1 respectively, so that an integer value
+ * of Status.FR can be trivially casted to the corresponding enum fpu_mode.
+ */
+enum fpu_mode {
+	FPU_32BIT = 0,		/* FR = 0 */
+	FPU_64BIT,		/* FR = 1 */
+	FPU_AS_IS,
+};
+
+static inline int __enable_fpu(enum fpu_mode mode)
+{
+	int fr;
+
+	switch (mode) {
+	case FPU_AS_IS:
+		/* just enable the FPU in its current mode */
+		set_c0_status(ST0_CU1);
+		enable_fpu_hazard();
+		return 0;
+
+	case FPU_64BIT:
+#if !(defined(CONFIG_CPU_MIPS32_R2) || defined(CONFIG_MIPS64))
+		/* we only have a 32-bit FPU */
+		return SIGFPE;
+#endif
+		/* fall through */
+	case FPU_32BIT:
+		/* set CU1 & change FR appropriately */
+		fr = (int)mode;
+		change_c0_status(ST0_CU1 | ST0_FR, ST0_CU1 | (fr ? ST0_FR : 0));
+		enable_fpu_hazard();
+
+		/* check FR has the desired value */
+		return (!!(read_c0_status() & ST0_FR) == !!fr) ? 0 : SIGFPE;
+
+	default:
+		BUG();
+	}
+}
 
 #define __disable_fpu()							\
 do {									\
@@ -57,27 +94,46 @@ static inline int is_fpu_owner(void)
 	return cpu_has_fpu && __is_fpu_owner();
 }
 
-static inline void __own_fpu(void)
+static inline int __own_fpu(void)
 {
-	__enable_fpu();
+	enum fpu_mode mode;
+	int ret;
+
+	mode = !test_thread_flag(TIF_32BIT_FPREGS);
+	ret = __enable_fpu(mode);
+	if (ret)
+		return ret;
+
 	KSTK_STATUS(current) |= ST0_CU1;
+	if (mode == FPU_64BIT)
+		KSTK_STATUS(current) |= ST0_FR;
+	else /* mode == FPU_32BIT */
+		KSTK_STATUS(current) &= ~ST0_FR;
+
 	set_thread_flag(TIF_USEDFPU);
+	return 0;
 }
 
-static inline void own_fpu_inatomic(int restore)
+static inline int own_fpu_inatomic(int restore)
 {
+	int ret = 0;
+
 	if (cpu_has_fpu && !__is_fpu_owner()) {
-		__own_fpu();
-		if (restore)
+		ret = __own_fpu();
+		if (restore && !ret)
 			_restore_fp(current);
 	}
+	return ret;
 }
 
-static inline void own_fpu(int restore)
+static inline int own_fpu(int restore)
 {
+	int ret;
+
 	preempt_disable();
-	own_fpu_inatomic(restore);
+	ret = own_fpu_inatomic(restore);
 	preempt_enable();
+	return ret;
 }
 
 static inline void lose_fpu(int save)
@@ -93,16 +149,21 @@ static inline void lose_fpu(int save)
 	preempt_enable();
 }
 
-static inline void init_fpu(void)
+static inline int init_fpu(void)
 {
+	int ret = 0;
+
 	preempt_disable();
 	if (cpu_has_fpu) {
-		__own_fpu();
-		_init_fpu();
+		ret = __own_fpu();
+		if (!ret)
+			_init_fpu();
 	} else {
 		fpu_emulator_init_fpu();
 	}
+
 	preempt_enable();
+	return ret;
 }
 
 static inline void save_fp(struct task_struct *tsk)
diff --git a/arch/mips/include/asm/thread_info.h b/arch/mips/include/asm/thread_info.h
index 4f58ef6..24846f9 100644
--- a/arch/mips/include/asm/thread_info.h
+++ b/arch/mips/include/asm/thread_info.h
@@ -110,11 +110,12 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_NOHZ		19	/* in adaptive nohz mode */
 #define TIF_FIXADE		20	/* Fix address errors in software */
 #define TIF_LOGADE		21	/* Log address errors to syslog */
-#define TIF_32BIT_REGS		22	/* also implies 16/32 fprs */
+#define TIF_32BIT_REGS		22	/* 32-bit general purpose registers */
 #define TIF_32BIT_ADDR		23	/* 32-bit address space (o32/n32) */
 #define TIF_FPUBOUND		24	/* thread bound to FPU-full CPU set */
 #define TIF_LOAD_WATCH		25	/* If set, load watch registers */
 #define TIF_SYSCALL_TRACEPOINT	26	/* syscall tracepoint instrumentation */
+#define TIF_32BIT_FPREGS	27	/* 32-bit floating point registers */
 #define TIF_SYSCALL_TRACE	31	/* syscall trace active */
 
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
@@ -131,6 +132,7 @@ static inline struct thread_info *current_thread_info(void)
 #define _TIF_32BIT_ADDR		(1<<TIF_32BIT_ADDR)
 #define _TIF_FPUBOUND		(1<<TIF_FPUBOUND)
 #define _TIF_LOAD_WATCH		(1<<TIF_LOAD_WATCH)
+#define _TIF_32BIT_FPREGS	(1<<TIF_32BIT_FPREGS)
 #define _TIF_SYSCALL_TRACEPOINT	(1<<TIF_SYSCALL_TRACEPOINT)
 
 #define _TIF_WORK_SYSCALL_ENTRY	(_TIF_NOHZ | _TIF_SYSCALL_TRACE |	\