Define the central place the default FCSR value is set from, initialised
in `cpu_probe'. Determine the FCSR mask applied to values written to
the register with CTC1 in the full emulation mode and via ptrace(2),
according to the ISA level of processor hardware or the writability of
bits 31:18 if actual FPU hardware is used.
Software may rely on FCSR bits whose functions our emulator does not
implement, so it should not allow them to be set or software may get
confused. For ptrace(2) it's just sanity.
Signed-off-by: Maciej W. Rozycki <macro@xxxxxxxxxxxxxx>
---
linux-mips-emu-fcsr-isa.diff
Index: linux/arch/mips/include/asm/cpu-info.h
===================================================================
--- linux.orig/arch/mips/include/asm/cpu-info.h 2015-04-02 20:18:47.496475000 +0100
+++ linux/arch/mips/include/asm/cpu-info.h 2015-04-02 20:27:59.740240000 +0100
@@ -49,6 +49,8 @@ struct cpuinfo_mips {
unsigned int udelay_val;
unsigned int processor_id;
unsigned int fpu_id;
+ unsigned int fpu_csr31;
+ unsigned int fpu_msk31;
unsigned int msa_id;
unsigned int cputype;
int isa_level;
Index: linux/arch/mips/include/asm/elf.h
===================================================================
--- linux.orig/arch/mips/include/asm/elf.h 2015-04-02 20:18:47.497482000 +0100
+++ linux/arch/mips/include/asm/elf.h 2015-04-02 20:27:59.742251000 +0100
@@ -11,6 +11,9 @@
#include <linux/fs.h>
#include <uapi/linux/elf.h>
+#include <asm/cpu-info.h>
+#include <asm/current.h>
+
/* ELF header e_flags defines. */
/* MIPS architecture level. */
#define EF_MIPS_ARCH_1 0x00000000 /* -mips1 code. */
@@ -297,6 +300,8 @@ do { \
mips_set_personality_fp(state); \
\
current->thread.abi = &mips_abi; \
+ \
+ current->thread.fpu.fcr31 = current_cpu_data.fpu_csr31; \
} while (0)
#endif /* CONFIG_32BIT */
@@ -356,6 +361,8 @@ do { \
else \
current->thread.abi = &mips_abi; \
\
+ current->thread.fpu.fcr31 = current_cpu_data.fpu_csr31; \
+ \
p = personality(current->personality); \
if (p != PER_LINUX32 && p != PER_LINUX) \
set_personality(PER_LINUX); \
Index: linux/arch/mips/include/asm/fpu.h
===================================================================
--- linux.orig/arch/mips/include/asm/fpu.h 2015-04-02 20:18:47.499480000 +0100
+++ linux/arch/mips/include/asm/fpu.h 2015-04-02 20:27:59.745241000 +0100
@@ -14,6 +14,7 @@
#include <linux/thread_info.h>
#include <linux/bitops.h>
+#include <asm/current.h>
#include <asm/mipsregs.h>
#include <asm/cpu.h>
#include <asm/cpu-features.h>
@@ -30,7 +31,7 @@
struct sigcontext;
struct sigcontext32;
-extern void _init_fpu(void);
+extern void _init_fpu(unsigned int);
extern void _save_fp(struct task_struct *);
extern void _restore_fp(struct task_struct *);
@@ -182,6 +183,7 @@ static inline void lose_fpu(int save)
static inline int init_fpu(void)
{
+ unsigned int fcr31 = current->thread.fpu.fcr31;
int ret = 0;
if (cpu_has_fpu) {
@@ -192,7 +194,7 @@ static inline int init_fpu(void)
return ret;
if (!cpu_has_fre) {
- _init_fpu();
+ _init_fpu(fcr31);
return 0;
}
@@ -206,7 +208,7 @@ static inline int init_fpu(void)
config5 = clear_c0_config5(MIPS_CONF5_FRE);
enable_fpu_hazard();
- _init_fpu();
+ _init_fpu(fcr31);
/* Restore FRE */
write_c0_config5(config5);
Index: linux/arch/mips/include/asm/fpu_emulator.h
===================================================================
--- linux.orig/arch/mips/include/asm/fpu_emulator.h 2015-04-02 20:27:58.453234000 +0100
+++ linux/arch/mips/include/asm/fpu_emulator.h 2015-04-02 20:27:59.747241000 +0100
@@ -87,8 +87,6 @@ static inline void fpu_emulator_init_fpu
struct task_struct *t = current;
int i;
- t->thread.fpu.fcr31 = 0;
-
for (i = 0; i < 32; i++)
set_fpr64(&t->thread.fpu.fpr[i], 0, SIGNALLING_NAN);
}
Index: linux/arch/mips/kernel/cpu-probe.c
===================================================================
--- linux.orig/arch/mips/kernel/cpu-probe.c 2015-04-02 20:27:58.890231000 +0100
+++ linux/arch/mips/kernel/cpu-probe.c 2015-04-02 20:27:59.750245000 +0100
@@ -33,6 +33,35 @@
#include <asm/uaccess.h>
/*
+ * Determine the FCSR mask for FPU hardware.
+ */
+static inline void cpu_set_fpu_fcsr_mask(struct cpuinfo_mips *c)
+{
+ unsigned long sr, mask, fcsr, fcsr0, fcsr1;
+
+ mask = FPU_CSR_ALL_X | FPU_CSR_ALL_E | FPU_CSR_ALL_S | FPU_CSR_RM;
+
+ sr = read_c0_status();
+ __enable_fpu(FPU_AS_IS);
+
+ fcsr = read_32bit_cp1_register(CP1_STATUS);
+
+ fcsr0 = fcsr & mask;
+ write_32bit_cp1_register(CP1_STATUS, fcsr0);
+ fcsr0 = read_32bit_cp1_register(CP1_STATUS);
+
+ fcsr1 = fcsr | ~mask;
+ write_32bit_cp1_register(CP1_STATUS, fcsr1);
+ fcsr1 = read_32bit_cp1_register(CP1_STATUS);
+
+ write_32bit_cp1_register(CP1_STATUS, fcsr);
+
+ write_c0_status(sr);
+
+ c->fpu_msk31 = ~(fcsr0 ^ fcsr1) & ~mask;
+}
+
+/*
* Set the FIR feature flags for the FPU emulator.
*/
static void cpu_set_nofpu_id(struct cpuinfo_mips *c)
@@ -50,11 +79,15 @@ static void cpu_set_nofpu_id(struct cpui
c->fpu_id = value;
}
+/* Determined FPU emulator mask to use for the boot CPU with "nofpu". */
+static unsigned int mips_nofpu_msk31;
+
static int mips_fpu_disabled;
static int __init fpu_disable(char *s)
{
boot_cpu_data.options &= ~MIPS_CPU_FPU;
+ boot_cpu_data.fpu_msk31 = mips_nofpu_msk31;
cpu_set_nofpu_id(&boot_cpu_data);
mips_fpu_disabled = 1;
@@ -595,6 +628,7 @@ static inline void cpu_probe_legacy(stru
case PRID_IMP_R2000:
c->cputype = CPU_R2000;
__cpu_name[cpu] = "R2000";
+ c->fpu_msk31 |= FPU_CSR_CONDX | FPU_CSR_FS;
c->options = MIPS_CPU_TLB | MIPS_CPU_3K_CACHE |
MIPS_CPU_NOFPUEX;
if (__cpu_has_fpu())
@@ -614,6 +648,7 @@ static inline void cpu_probe_legacy(stru
c->cputype = CPU_R3000;
__cpu_name[cpu] = "R3000";
}
+ c->fpu_msk31 |= FPU_CSR_CONDX | FPU_CSR_FS;
c->options = MIPS_CPU_TLB | MIPS_CPU_3K_CACHE |
MIPS_CPU_NOFPUEX;
if (__cpu_has_fpu())
@@ -662,6 +697,7 @@ static inline void cpu_probe_legacy(stru
}
set_isa(c, MIPS_CPU_ISA_III);
+ c->fpu_msk31 |= FPU_CSR_CONDX;
c->options = R4K_OPTS | MIPS_CPU_FPU | MIPS_CPU_32FPR |
MIPS_CPU_WATCH | MIPS_CPU_VCE |
MIPS_CPU_LLSC;
@@ -669,6 +705,7 @@ static inline void cpu_probe_legacy(stru
break;
case PRID_IMP_VR41XX:
set_isa(c, MIPS_CPU_ISA_III);
+ c->fpu_msk31 |= FPU_CSR_CONDX;
c->options = R4K_OPTS;
c->tlbsize = 32;
switch (c->processor_id & 0xf0) {
@@ -710,6 +747,7 @@ static inline void cpu_probe_legacy(stru
c->cputype = CPU_R4300;
__cpu_name[cpu] = "R4300";
set_isa(c, MIPS_CPU_ISA_III);
+ c->fpu_msk31 |= FPU_CSR_CONDX;
c->options = R4K_OPTS | MIPS_CPU_FPU | MIPS_CPU_32FPR |
MIPS_CPU_LLSC;
c->tlbsize = 32;
@@ -718,6 +756,7 @@ static inline void cpu_probe_legacy(stru
c->cputype = CPU_R4600;
__cpu_name[cpu] = "R4600";
set_isa(c, MIPS_CPU_ISA_III);
+ c->fpu_msk31 |= FPU_CSR_CONDX;
c->options = R4K_OPTS | MIPS_CPU_FPU | MIPS_CPU_32FPR |
MIPS_CPU_LLSC;
c->tlbsize = 48;
@@ -733,11 +772,13 @@ static inline void cpu_probe_legacy(stru
c->cputype = CPU_R4650;
__cpu_name[cpu] = "R4650";
set_isa(c, MIPS_CPU_ISA_III);
+ c->fpu_msk31 |= FPU_CSR_CONDX;
c->options = R4K_OPTS | MIPS_CPU_FPU | MIPS_CPU_LLSC;
c->tlbsize = 48;
break;
#endif
case PRID_IMP_TX39:
+ c->fpu_msk31 |= FPU_CSR_CONDX | FPU_CSR_FS;
c->options = MIPS_CPU_TLB | MIPS_CPU_TX39_CACHE;
if ((c->processor_id & 0xf0) == (PRID_REV_TX3927 & 0xf0)) {
@@ -763,6 +804,7 @@ static inline void cpu_probe_legacy(stru
c->cputype = CPU_R4700;
__cpu_name[cpu] = "R4700";
set_isa(c, MIPS_CPU_ISA_III);
+ c->fpu_msk31 |= FPU_CSR_CONDX;
c->options = R4K_OPTS | MIPS_CPU_FPU | MIPS_CPU_32FPR |
MIPS_CPU_LLSC;
c->tlbsize = 48;
@@ -771,6 +813,7 @@ static inline void cpu_probe_legacy(stru
c->cputype = CPU_TX49XX;
__cpu_name[cpu] = "R49XX";
set_isa(c, MIPS_CPU_ISA_III);
+ c->fpu_msk31 |= FPU_CSR_CONDX;
c->options = R4K_OPTS | MIPS_CPU_LLSC;
if (!(c->processor_id & 0x08))
c->options |= MIPS_CPU_FPU | MIPS_CPU_32FPR;
@@ -812,6 +855,7 @@ static inline void cpu_probe_legacy(stru
c->cputype = CPU_R6000;
__cpu_name[cpu] = "R6000";
set_isa(c, MIPS_CPU_ISA_II);
+ c->fpu_msk31 |= FPU_CSR_CONDX | FPU_CSR_FS;
c->options = MIPS_CPU_TLB | MIPS_CPU_FPU |
MIPS_CPU_LLSC;
c->tlbsize = 32;
@@ -820,6 +864,7 @@ static inline void cpu_probe_legacy(stru
c->cputype = CPU_R6000A;
__cpu_name[cpu] = "R6000A";
set_isa(c, MIPS_CPU_ISA_II);
+ c->fpu_msk31 |= FPU_CSR_CONDX | FPU_CSR_FS;
c->options = MIPS_CPU_TLB | MIPS_CPU_FPU |
MIPS_CPU_LLSC;
c->tlbsize = 32;
@@ -886,12 +931,14 @@ static inline void cpu_probe_legacy(stru
__cpu_name[cpu] = "ICT Loongson-2";
set_elf_platform(cpu, "loongson2e");
set_isa(c, MIPS_CPU_ISA_III);
+ c->fpu_msk31 |= FPU_CSR_CONDX;
break;
case PRID_REV_LOONGSON2F:
c->cputype = CPU_LOONGSON2;
__cpu_name[cpu] = "ICT Loongson-2";
set_elf_platform(cpu, "loongson2f");
set_isa(c, MIPS_CPU_ISA_III);
+ c->fpu_msk31 |= FPU_CSR_CONDX;
break;
case PRID_REV_LOONGSON3A:
c->cputype = CPU_LOONGSON3;
@@ -1328,6 +1375,9 @@ void cpu_probe(void)
c->cputype = CPU_UNKNOWN;
c->writecombine = _CACHE_UNCACHED;
+ c->fpu_csr31 = FPU_CSR_RN;
+ c->fpu_msk31 = FPU_CSR_RSVD | FPU_CSR_ABS2008 | FPU_CSR_NAN2008;
+
c->processor_id = read_c0_prid();
switch (c->processor_id & PRID_COMP_MASK) {
case PRID_COMP_LEGACY:
@@ -1386,6 +1436,7 @@ void cpu_probe(void)
if (c->options & MIPS_CPU_FPU) {
c->fpu_id = cpu_get_fpu_id();
+ mips_nofpu_msk31 = c->fpu_msk31;
if (c->isa_level & (MIPS_CPU_ISA_M32R1 | MIPS_CPU_ISA_M64R1 |
MIPS_CPU_ISA_M32R2 | MIPS_CPU_ISA_M64R2 |
@@ -1395,6 +1446,8 @@ void cpu_probe(void)
if (c->fpu_id & MIPS_FPIR_FREP)
c->options |= MIPS_CPU_FRE;
}
+
+ cpu_set_fpu_fcsr_mask(c);
} else
cpu_set_nofpu_id(c);
Index: linux/arch/mips/kernel/ptrace.c
===================================================================
--- linux.orig/arch/mips/kernel/ptrace.c 2015-04-02 20:18:47.505476000 +0100
+++ linux/arch/mips/kernel/ptrace.c 2015-04-02 20:27:59.753242000 +0100
@@ -32,6 +32,7 @@
#include <asm/byteorder.h>
#include <asm/cpu.h>
+#include <asm/cpu-info.h>
#include <asm/dsp.h>
#include <asm/fpu.h>
#include <asm/mipsregs.h>
@@ -137,6 +138,9 @@ int ptrace_setfpregs(struct task_struct
{
union fpureg *fregs;
u64 fpr_val;
+ u32 fcr31;
+ u32 value;
+ u32 mask;
int i;
if (!access_ok(VERIFY_READ, data, 33 * 8))
@@ -149,8 +153,10 @@ int ptrace_setfpregs(struct task_struct
set_fpr64(&fregs[i], 0, fpr_val);
}
- __get_user(child->thread.fpu.fcr31, data + 64);
- child->thread.fpu.fcr31 &= ~FPU_CSR_ALL_X;
+ __get_user(value, data + 64);
+ fcr31 = child->thread.fpu.fcr31;
+ mask = current_cpu_data.fpu_msk31;
+ child->thread.fpu.fcr31 = (value & ~mask) | (fcr31 & mask);
/* FIR may not be written. */
Index: linux/arch/mips/kernel/r2300_switch.S
===================================================================
--- linux.orig/arch/mips/kernel/r2300_switch.S 2015-04-02 20:18:47.506481000 +0100
+++ linux/arch/mips/kernel/r2300_switch.S 2015-04-02 20:27:59.755248000 +0100
@@ -115,11 +115,9 @@ LEAF(_restore_fp)
* the property that no matter whether considered as single or as double
* precision represents signaling NANS.
*
- * We initialize fcr31 to rounding to nearest, no exceptions.
+ * The value to initialize fcr31 to comes in $a0.
*/
-#define FPU_DEFAULT 0x00000000
-
.set push
SET_HARDFLOAT
@@ -129,8 +127,7 @@ LEAF(_init_fpu)
or t0, t1
mtc0 t0, CP0_STATUS
- li t1, FPU_DEFAULT
- ctc1 t1, fcr31
+ ctc1 a0, fcr31
li t0, -1
Index: linux/arch/mips/kernel/r4k_switch.S
===================================================================
--- linux.orig/arch/mips/kernel/r4k_switch.S 2015-04-02 20:18:47.508482000 +0100
+++ linux/arch/mips/kernel/r4k_switch.S 2015-04-02 20:27:59.758240000 +0100
@@ -165,11 +165,9 @@ LEAF(_init_msa_upper)
* the property that no matter whether considered as single or as double
* precision represents signaling NANS.
*
- * We initialize fcr31 to rounding to nearest, no exceptions.
+ * The value to initialize fcr31 to comes in $a0.
*/
-#define FPU_DEFAULT 0x00000000
-
.set push
SET_HARDFLOAT
@@ -180,8 +178,7 @@ LEAF(_init_fpu)
mtc0 t0, CP0_STATUS
enable_fpu_hazard
- li t1, FPU_DEFAULT
- ctc1 t1, fcr31
+ ctc1 a0, fcr31
li t1, -1 # SNaN
Index: linux/arch/mips/loongson/loongson-3/cop2-ex.c
===================================================================
--- linux.orig/arch/mips/loongson/loongson-3/cop2-ex.c 2015-04-02 20:18:47.515499000 +0100
+++ linux/arch/mips/loongson/loongson-3/cop2-ex.c 2015-04-02 20:27:59.767246000 +0100
@@ -43,7 +43,7 @@ static int loongson_cu2_call(struct noti
if (!fpu_owned) {
set_thread_flag(TIF_USEDFPU);
if (!used_math()) {
- _init_fpu();
+ _init_fpu(current->thread.fpu.fcr31);
set_used_math();
} else
_restore_fp(current);
Index: linux/arch/mips/math-emu/cp1emu.c
===================================================================
--- linux.orig/arch/mips/math-emu/cp1emu.c 2015-04-02 20:27:59.304242000 +0100
+++ linux/arch/mips/math-emu/cp1emu.c 2015-04-02 20:27:59.771244000 +0100
@@ -908,6 +908,7 @@ static inline void cop1_ctc(struct pt_re
{
u32 fcr31 = ctx->fcr31;
u32 value;
+ u32 mask;
if (MIPSInst_RT(ir) == 0)
value = 0;
@@ -919,9 +920,9 @@ static inline void cop1_ctc(struct pt_re
pr_debug("%p gpr[%d]->csr=%08x\n",
(void *)xcp->cp0_epc, MIPSInst_RT(ir), value);
- /* Don't write unsupported bits. */
- fcr31 = value &
- ~(FPU_CSR_RSVD | FPU_CSR_ABS2008 | FPU_CSR_NAN2008);
+ /* Preserve read-only bits. */
+ mask = current_cpu_data.fpu_msk31;
+ fcr31 = (value & ~mask) | (fcr31 & mask);
break;
case FPCREG_FENR:
