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

From: Guo Ren
Date: Tue May 11 2021 - 22:13:51 EST

Hi Wang,

On Tue, May 11, 2021 at 9:23 PM Wang Junqiang <wangjunqiang@xxxxxxxxxxx> wrote:
>
> 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
Just: depends on CPU_HAS_FPU
For fpu, CK807 = CK810 and CK610 hasn't 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)
static inline void init_fpu(void)
{
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)
static inline void init_fpu(void)
{
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;
> +}
Remove it and move it to above.

>
> 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);
> -
No need.

> #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
>


--
Best Regards
Guo Ren

ML: https://lore.kernel.org/linux-csky/