[PATCH v2 2/2] csky: add CONFIG_CPU_HAS_MATHEMU and use in traps

From: Wang Junqiang
Date: Tue May 11 2021 - 09:23:44 EST

This patch contains the use of fpu instruction emulation by trap_c.
It defined _fcr, _fesr for user space in processor.h which is used in fpu.c
and instruction emulation. During initialization, all fpe are enabled,
and the config that read/write fcr and fesr in glibc library is captured
when privilege exception is triggered by mfcr and mtcr < ,15>.

steps:
1.enable all fpe interrupts
2.mfcr/mtcr trigger privilege exception
3.synchronize fcr and fesr of user app through fpu_libc_helper function
4.fpe interrupt at runtime
5.fpu instruction simulation is based on user_fcr and user_fesr
6.clearing interrupts and synchronizing fcr fesr
7.state restore and continue running

Change in v2:
- fixup Kconfig bug by Randy and Guo Ren
- move CONFIG_CPU_HAS_MATHEMU to fpu.h by define macro
- del usr_fcr usr_fesr in struct user_fp and define in processor.h
- del mathemu use in do_trap_ and use in fpu_fpe

Signed-off-by: Wang Junqiang <wangjunqiang@xxxxxxxxxxx>
Signed-off-by: Li Weiwei <liweiwei@xxxxxxxxxxx>
---
arch/csky/Kconfig | 7 +++++++
arch/csky/Makefile | 1 +
arch/csky/abiv2/fpu.c | 21 +++++++++++++------
arch/csky/abiv2/inc/abi/fpu.h | 34 +++++++++++++++++++++++++++++--
arch/csky/include/asm/processor.h | 11 ++++++++++
arch/csky/kernel/traps.c | 5 ++---
6 files changed, 68 insertions(+), 11 deletions(-)

diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
index 8de5b987edb9..1f47ff2294c9 100644
--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@ -285,6 +285,13 @@ config CPU_HAS_FPU
bool "CPU has FPU coprocessor"
depends on CPU_CK807 || CPU_CK810 || CPU_CK860

+config CPU_HAS_MATHEMU
+ bool "CPU has FPU Mathemu Instructions"
+ depends on (CPU_CK810 || CPU_CK860) && CPU_HAS_FPU
+ default y
+ help
+ Say Y/N here to allow turning FPU Instructions simulation on/off.
+
config CPU_HAS_ICACHE_INS
bool "CPU has Icache invalidate instructions"
depends on CPU_HAS_CACHEV2
diff --git a/arch/csky/Makefile b/arch/csky/Makefile
index 37f593a4bf53..495f3a2fad6a 100644
--- a/arch/csky/Makefile
+++ b/arch/csky/Makefile
@@ -64,6 +64,7 @@ head-y := arch/csky/kernel/head.o
core-y += arch/csky/kernel/
core-y += arch/csky/mm/
core-y += arch/csky/$(CSKYABI)/
+core-$(CONFIG_CPU_HAS_MATHEMU) += arch/csky/math-emu/

libs-y += arch/csky/lib/ \
$(shell $(CC) $(KBUILD_CFLAGS) $(KCFLAGS) -print-libgcc-file-name)
diff --git a/arch/csky/abiv2/fpu.c b/arch/csky/abiv2/fpu.c
index 5acc5c2e544e..a7f6f0bb8537 100644
--- a/arch/csky/abiv2/fpu.c
+++ b/arch/csky/abiv2/fpu.c
@@ -38,8 +38,7 @@ int fpu_libc_helper(struct pt_regs *regs)
return 0;

tinstr = instr_hi | ((unsigned long)instr_low << 16);
-
- if (((tinstr >> 21) & 0x1F) != 2)
+ if (((tinstr >> 21) & 0x1F) != CR_NUM)
return 0;

if ((tinstr & MTCR_MASK) == MTCR_DIST) {
@@ -54,9 +53,9 @@ int fpu_libc_helper(struct pt_regs *regs)
regx = *(&regs->a0 + index);

if (tmp == 1)
- mtcr("cr<1, 2>", regx);
+ MTCR_FCR(regx)
else if (tmp == 2)
- mtcr("cr<2, 2>", regx);
+ MTCR_FESR(regx)
else
return 0;

@@ -74,9 +73,9 @@ int fpu_libc_helper(struct pt_regs *regs)
return 0;

if (tmp == 1)
- regx = mfcr("cr<1, 2>");
+ regx = MFCR_FCR;
else if (tmp == 2)
- regx = mfcr("cr<2, 2>");
+ regx = MFCR_FESR;
else
return 0;

@@ -94,6 +93,16 @@ void fpu_fpe(struct pt_regs *regs)
int sig, code;
unsigned int fesr;

+#ifdef CONFIG_CPU_HAS_MATHEMU
+ unsigned int inst;
+
+ inst = get_fpu_insn(regs);
+ if (inst && !do_fpu_insn(inst, regs)) {
+ regs->pc += 4;
+ return;
+ }
+#endif
+
fesr = mfcr("cr<2, 2>");

sig = SIGFPE;
diff --git a/arch/csky/abiv2/inc/abi/fpu.h b/arch/csky/abiv2/inc/abi/fpu.h
index aabb79355013..6521f8814fd1 100644
--- a/arch/csky/abiv2/inc/abi/fpu.h
+++ b/arch/csky/abiv2/inc/abi/fpu.h
@@ -6,14 +6,44 @@
#include <asm/sigcontext.h>
#include <asm/ptrace.h>

+
+#ifdef CONFIG_CPU_HAS_MATHEMU
+#define FPU_INIT mtcr("cr<1, 2>", 0x3f)
+#define MFCR_FCR current->thread.emul_fp.user_fcr
+#define MFCR_FESR current->thread.emul_fp.user_fesr
+#define MTCR_FCR(regx) \
+ { \
+ mtcr("cr<1, 2>", regx | 0x3f); \
+ current->thread.emul_fp.user_fcr = regx; \
+ }
+#define MTCR_FESR(regx) \
+ { \
+ mtcr("cr<2, 2>", regx); \
+ current->thread.emul_fp.user_fesr = regx; \
+ }
+#define CR_NUM 15
+
+inline unsigned int get_fpu_insn(struct pt_regs *regs);
+inline int do_fpu_insn(unsigned int inst, struct pt_regs *regs);
+#else
+#define FPU_INIT mtcr("cr<1, 2>", 0)
+#define MFCR_FCR mfcr("cr<1, 2>")
+#define MFCR_FESR mfcr("cr<2, 2>")
+#define MTCR_FCR(regx) { mtcr("cr<1, 2>", regx); }
+#define MTCR_FESR(regx) { mtcr("cr<2, 2>", regx); }
+#define CR_NUM 2
+#endif
+
int fpu_libc_helper(struct pt_regs *regs);
void fpu_fpe(struct pt_regs *regs);

-static inline void init_fpu(void) { mtcr("cr<1, 2>", 0); }
+static inline void init_fpu(void)
+{
+ FPU_INIT;
+}

void save_to_user_fp(struct user_fp *user_fp);
void restore_from_user_fp(struct user_fp *user_fp);
-
/*
* Define the fesr bit for fpe handle.
*/
diff --git a/arch/csky/include/asm/processor.h b/arch/csky/include/asm/processor.h
index 9e933021fe8e..645b6b27841d 100644
--- a/arch/csky/include/asm/processor.h
+++ b/arch/csky/include/asm/processor.h
@@ -21,6 +21,14 @@ struct cpuinfo_csky {

extern struct cpuinfo_csky cpu_data[];

+#ifdef CONFIG_CPU_HAS_MATHEMU
+struct emul_fp {
+ unsigned long user_fcr;
+ unsigned long user_fesr;
+ unsigned long reserved1;
+ unsigned long reserved2;
+};
+#endif
/*
* User space process size: 2GB. This is hardcoded into a few places,
* so don't change it unless you know what you are doing. TASK_SIZE
@@ -45,6 +53,9 @@ struct thread_struct {

/* FPU regs */
struct user_fp __aligned(16) user_fp;
+#ifdef CONFIG_CPU_HAS_MATHEMU
+ struct emul_fp __aligned(16) emul_fp;
+#endif
};

#define INIT_THREAD { \
diff --git a/arch/csky/kernel/traps.c b/arch/csky/kernel/traps.c
index e5fbf8653a21..a63a56eca0a2 100644
--- a/arch/csky/kernel/traps.c
+++ b/arch/csky/kernel/traps.c
@@ -187,7 +187,6 @@ asmlinkage void do_trap_bkpt(struct pt_regs *regs)
asmlinkage void do_trap_illinsn(struct pt_regs *regs)
{
current->thread.trap_no = trap_no(regs);
-
#ifdef CONFIG_KPROBES
if (kprobe_breakpoint_handler(regs))
return;
@@ -209,7 +208,7 @@ asmlinkage void do_trap_illinsn(struct pt_regs *regs)

asmlinkage void do_trap_fpe(struct pt_regs *regs)
{
-#ifdef CONFIG_CPU_HAS_FP
+#ifdef CONFIG_CPU_HAS_FPU
return fpu_fpe(regs);
#else
do_trap_error(regs, SIGILL, ILL_ILLOPC, regs->pc,
@@ -219,7 +218,7 @@ asmlinkage void do_trap_fpe(struct pt_regs *regs)

asmlinkage void do_trap_priv(struct pt_regs *regs)
{
-#ifdef CONFIG_CPU_HAS_FP
+#ifdef CONFIG_CPU_HAS_FPU
if (user_mode(regs) && fpu_libc_helper(regs))
return;
#endif
--
2.17.1