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

From: Guo Ren
Date: Tue Apr 27 2021 - 11:02:39 EST

Hi Wang & Li,

On Wed, Apr 21, 2021 at 10:56 AM 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 ptrace.h which is used in fpu.c
> and instruction emulation. During initialization, all fpe are enabled,
> and the configuration that read/write fcr and fesr in glibc library is captured
> when privilege exception is triggerd 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
>
> Signed-off-by: Wang Junqiang <wangjunqiang@xxxxxxxxxxx>
> Signed-off-by: Li Weiwei <liweiwei@xxxxxxxxxxx>
> ---
> arch/csky/Kconfig | 8 ++++++++
> arch/csky/Makefile | 1 +
> arch/csky/abiv2/fpu.c | 31 ++++++++++++++++++++++++-----
> arch/csky/abiv2/inc/abi/fpu.h | 9 ++++++++-
> arch/csky/include/uapi/asm/ptrace.h | 6 ++++++
> arch/csky/kernel/traps.c | 30 +++++++++++++++++++++++++---
> 6 files changed, 76 insertions(+), 9 deletions(-)
>
> diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
> index 34e91224adc3..a414225570c1 100644
> --- a/arch/csky/Kconfig
> +++ b/arch/csky/Kconfig
> @@ -97,6 +97,9 @@ config CPU_HAS_CACHEV2
> config CPU_HAS_FPUV2
> bool
>
> +config CPU_HAS_MATHEMU
> + bool
> +
Duplicated

> config CPU_HAS_HILO
> bool
>
> @@ -281,6 +284,11 @@ config CPU_HAS_VDSP
> bool "CPU has VDSP coprocessor"
> depends on CPU_HAS_FPU && CPU_HAS_FPUV2
>
> +config CPU_HAS_MATHEMU
> + bool "CPU has FPU Mathemu Instructions"
> + depends on CPU_CK810 || CPU_CK860
> + default n
No need "default n", only "default y" need.

> +
> config CPU_HAS_FPU
> bool "CPU has FPU coprocessor"
> depends on CPU_CK807 || CPU_CK810 || CPU_CK860
> 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..3cd17cf9319e 100644
> --- a/arch/csky/abiv2/fpu.c
> +++ b/arch/csky/abiv2/fpu.c
> @@ -38,8 +38,11 @@ int fpu_libc_helper(struct pt_regs *regs)
> return 0;
>
> tinstr = instr_hi | ((unsigned long)instr_low << 16);
> -
> +#ifdef CONFIG_CPU_HAS_MATHEMU
> + if (((tinstr >> 21) & 0x1F) != 15)
> +#else
> if (((tinstr >> 21) & 0x1F) != 2)
> +#endif
> return 0;
>
> if ((tinstr & MTCR_MASK) == MTCR_DIST) {
> @@ -53,10 +56,19 @@ int fpu_libc_helper(struct pt_regs *regs)
>
> regx = *(&regs->a0 + index);
>
> - if (tmp == 1)
> + if (tmp == 1) {
> +#ifdef CONFIG_CPU_HAS_MATHEMU
> + mtcr("cr<1, 2>", regx | 0x3f);
> + current->thread.user_fp.user_fcr = regx;
> +#else
> mtcr("cr<1, 2>", regx);
> - else if (tmp == 2)
> +#endif
> + } else if (tmp == 2) {
> mtcr("cr<2, 2>", regx);
> +#ifdef CONFIG_CPU_HAS_MATHEMU
> + current->thread.user_fp.user_fesr = regx;
> +#endif
> + }
> else
> return 0;
>
> @@ -73,10 +85,19 @@ int fpu_libc_helper(struct pt_regs *regs)
> if (tmp > 2)
> return 0;
>
> - if (tmp == 1)
> + if (tmp == 1) {
> +#ifndef CONFIG_CPU_HAS_MATHEMU
> regx = mfcr("cr<1, 2>");
> - else if (tmp == 2)
> +#else
> + regx = current->thread.user_fp.user_fcr;
> +#endif
> + } else if (tmp == 2) {
> +#ifndef CONFIG_CPU_HAS_MATHEMU
> regx = mfcr("cr<2, 2>");
> +#else
> + regx = current->thread.user_fp.user_fesr;
> +#endif
> + }
> else
> return 0;
>
> diff --git a/arch/csky/abiv2/inc/abi/fpu.h b/arch/csky/abiv2/inc/abi/fpu.h
> index aabb79355013..c3509ace542c 100644
> --- a/arch/csky/abiv2/inc/abi/fpu.h
> +++ b/arch/csky/abiv2/inc/abi/fpu.h
> @@ -9,7 +9,14 @@
> 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)
> +{
> +#ifdef CONFIG_CPU_HAS_MATHEMU
> + mtcr("cr<1, 2>", 0x3f);
> +#else
> + mtcr("cr<1, 2>", 0);
> +#endif
> +}
Could we put all CONFIG_CPU_HAS_MATHEMU differences in fpu.h?

#ifdef CONFIG_CPU_HAS_MATHEMU
#define MFCR_FESR current->thread.user_fp.user_fesr
#define MFCR_FCR current->thread.user_fp.user_fcr
#define MTCR_FESR(regx) {current->thread.user_fp.user_fesr = regx; ...}
#define MTCR_FCR(regx) {current->thread.user_fp.user_fcr = regx; ...}
#define CR_NUM 15
#else
#define MFCR_FESR(regx) mtcr("cr<1, 2>", regx)
#define MFCR_FESR(regx) mtcr("cr<1, 2>", regx)
...
#define CR_NUM 2
#endif

>
> void save_to_user_fp(struct user_fp *user_fp);
> void restore_from_user_fp(struct user_fp *user_fp);
> diff --git a/arch/csky/include/uapi/asm/ptrace.h b/arch/csky/include/uapi/asm/ptrace.h
> index 3be9c14334a6..1ffb6190686a 100644
> --- a/arch/csky/include/uapi/asm/ptrace.h
> +++ b/arch/csky/include/uapi/asm/ptrace.h
> @@ -45,6 +45,12 @@ struct user_fp {
> unsigned long fesr;
> unsigned long fid;
> unsigned long reserved;
> +#ifdef CONFIG_CPU_HAS_MATHEMU
> + unsigned long user_fcr;
> + unsigned long user_fesr;
> + unsigned long reserved1;
> + unsigned long reserved2;
> +#endif
> };
No, we couldn't modify user_fp, it'll break the old version toolchain.
(signal context)

A new struct of saving them in thread struct is enough.

>
> #endif /* __ASSEMBLY__ */
> diff --git a/arch/csky/kernel/traps.c b/arch/csky/kernel/traps.c
> index e5fbf8653a21..053a4f7dff9e 100644
> --- a/arch/csky/kernel/traps.c
> +++ b/arch/csky/kernel/traps.c
> @@ -27,6 +27,10 @@
>
> #ifdef CONFIG_CPU_HAS_FPU
> #include <abi/fpu.h>
> +#ifdef CONFIG_CPU_HAS_MATHEMU
> +extern inline unsigned int get_fpu_insn(struct pt_regs *regs);
> +extern inline int do_fpu_insn(unsigned int inst, struct pt_regs *regs);
> +#endif
> #endif
>
> int show_unhandled_signals = 1;
> @@ -186,8 +190,19 @@ 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_CPU_HAS_FPU
> +#ifdef CONFIG_CPU_HAS_MATHEMU
CONFIG_CPU_HAS_FPU && CONFIG_CPU_HAS_MATHEMU ?

> + unsigned int inst;
> +
> + inst = get_fpu_insn(regs);
> + if (inst && !do_fpu_insn(inst, regs)) {
> + regs->pc += 4;
> + return;
> + }
> +#endif
> +#endif
Don't double.

>
> + current->thread.trap_no = trap_no(regs);
> #ifdef CONFIG_KPROBES
> if (kprobe_breakpoint_handler(regs))
> return;
> @@ -209,7 +224,16 @@ asmlinkage void do_trap_illinsn(struct pt_regs *regs)
>
> asmlinkage void do_trap_fpe(struct pt_regs *regs)
> {
> -#ifdef CONFIG_CPU_HAS_FP
Thx for fixup.

> +#ifdef CONFIG_CPU_HAS_FPU
> +#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
Move above into fpu_fpe.

> return fpu_fpe(regs);
> #else
> do_trap_error(regs, SIGILL, ILL_ILLOPC, regs->pc,
> @@ -219,7 +243,7 @@ asmlinkage void do_trap_fpe(struct pt_regs *regs)
>
> asmlinkage void do_trap_priv(struct pt_regs *regs)
> {
> -#ifdef CONFIG_CPU_HAS_FP
Thx for fixup.

> +#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/