[PATCH v12 09/17] riscv: Add ptrace vector support

[Vineet Gupta]

Trimmed CC list

On 9/21/22 14:43, Chris Stillson wrote:
> From: Greentime Hu <greentime.hu at sifive.com>
> 
> This patch adds ptrace support for riscv vector. The vector registers will
> be saved in datap pointer of __riscv_v_state. This pointer will be set
> right after the __riscv_v_state data structure then it will be put in ubuf
> for ptrace system call to get or set. It will check if the datap got from
> ubuf is set to the correct address or not when the ptrace system call is
> trying to set the vector registers.
> 
> Co-developed-by: Vincent Chen <vincent.chen at sifive.com>
> Signed-off-by: Vincent Chen <vincent.chen at sifive.com>
> Signed-off-by: Greentime Hu <greentime.hu at sifive.com>
> ---
>   arch/riscv/include/uapi/asm/ptrace.h |  6 +++
>   arch/riscv/kernel/ptrace.c           | 71 ++++++++++++++++++++++++++++
>   include/uapi/linux/elf.h             |  1 +
>   3 files changed, 78 insertions(+)
> 
> diff --git a/arch/riscv/include/uapi/asm/ptrace.h b/arch/riscv/include/uapi/asm/ptrace.h
> index 6ee1ca2edfa7..2491875be80d 100644
> --- a/arch/riscv/include/uapi/asm/ptrace.h
> +++ b/arch/riscv/include/uapi/asm/ptrace.h
> @@ -94,6 +94,12 @@ struct __riscv_v_state {
>   	 */
>   };
>   
> +/*
> + * According to spec: The number of bits in a single vector register,
> + * VLEN >= ELEN, which must be a power of 2, and must be no greater than
> + * 2^16 = 65536bits = 8192bytes
> + */
> +#define RISCV_MAX_VLENB (8192)

Need a line here.

>   #endif /* __ASSEMBLY__ */
>   
>   #endif /* _UAPI_ASM_RISCV_PTRACE_H */
> diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
> index 2ae8280ae475..cce459ff551d 100644
> --- a/arch/riscv/kernel/ptrace.c
> +++ b/arch/riscv/kernel/ptrace.c
> @@ -27,6 +27,9 @@ enum riscv_regset {
>   #ifdef CONFIG_FPU
>   	REGSET_F,
>   #endif
> +#ifdef CONFIG_VECTOR
> +	REGSET_V,
> +#endif
>   };
>   
>   static int riscv_gpr_get(struct task_struct *target,
> @@ -83,6 +86,64 @@ static int riscv_fpr_set(struct task_struct *target,
>   }
>   #endif
>   
> +#ifdef CONFIG_VECTOR
> +static int riscv_vr_get(struct task_struct *target,
> +			const struct user_regset *regset,
> +			struct membuf to)
> +{
> +	struct __riscv_v_state *vstate = &target->thread.vstate;
> +
> +	/*
> +	 * Ensure the vector registers have been saved to the memory before
> +	 * copying them to membuf.
> +	 */
> +	if (target == current)
> +		vstate_save(current, task_pt_regs(current));
> +
> +	/* Copy vector header from vstate. */
> +	membuf_write(&to, vstate, RISCV_V_STATE_DATAP);
> +	membuf_zero(&to, sizeof(void *));
> +#if __riscv_xlen == 32
> +	membuf_zero(&to, sizeof(__u32));
> +#endif
> +
> +	/* Copy all the vector registers from vstate. */
> +	return membuf_write(&to, vstate->datap, riscv_vsize);
> +}
> +
> +static int riscv_vr_set(struct task_struct *target,
> +			 const struct user_regset *regset,
> +			 unsigned int pos, unsigned int count,
> +			 const void *kbuf, const void __user *ubuf)
> +{
> +	int ret, size;
> +	struct __riscv_v_state *vstate = &target->thread.vstate;
> +
> +	/* Copy rest of the vstate except datap and __padding. */
> +	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, vstate, 0,
> +				 RISCV_V_STATE_DATAP);
> +	if (unlikely(ret))
> +		return ret;
> +
> +	/* Skip copy datap. */
> +	size = sizeof(vstate->datap);
> +	count -= size;
> +	ubuf += size;
> +#if __riscv_xlen == 32
> +	/* Skip copy _padding. */
> +	size = sizeof(vstate->__padding);
> +	count -= size;
> +	ubuf += size;
> +#endif
> +
> +	/* Copy all the vector registers. */
> +	pos = 0;
> +	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, vstate->datap,
> +				 0, riscv_vsize);
> +	return ret;
> +}
> +#endif
> +
>   static const struct user_regset riscv_user_regset[] = {
>   	[REGSET_X] = {
>   		.core_note_type = NT_PRSTATUS,
> @@ -102,6 +163,16 @@ static const struct user_regset riscv_user_regset[] = {
>   		.set = riscv_fpr_set,
>   	},
>   #endif
> +#ifdef CONFIG_VECTOR
> +	[REGSET_V] = {
> +		.core_note_type = NT_RISCV_VECTOR,
> +		.align = 16,
> +		.n = (32 * RISCV_MAX_VLENB)/sizeof(__u32),
> +		.size = sizeof(__u32),
> +		.regset_get = riscv_vr_get,
> +		.set = riscv_vr_set,
> +	},
> +#endif
>   };
>   
>   static const struct user_regset_view riscv_user_native_view = {
> diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
> index c7b056af9ef0..5a5056c6a2a1 100644
> --- a/include/uapi/linux/elf.h
> +++ b/include/uapi/linux/elf.h
> @@ -439,6 +439,7 @@ typedef struct elf64_shdr {
>   #define NT_MIPS_DSP	0x800		/* MIPS DSP ASE registers */
>   #define NT_MIPS_FP_MODE	0x801		/* MIPS floating-point mode */
>   #define NT_MIPS_MSA	0x802		/* MIPS SIMD registers */
> +#define NT_RISCV_VECTOR	0x900		/* RISC-V vector registers */
>   #define NT_LOONGARCH_CPUCFG	0xa00	/* LoongArch CPU config registers */
>   #define NT_LOONGARCH_CSR	0xa01	/* LoongArch control and status registers */
>   #define NT_LOONGARCH_LSX	0xa02	/* LoongArch Loongson SIMD Extension registers */

I think we should break this one out as a seperate patch to be applied 
independently, avoid merge conflicts (but this file doesn't change much 
anyways. @Arnd or is it ok to carry with riscv change ?