[v2] RISC-V: Add ptrace support for vectors

[Nick Desaulniers]

On Fri, Aug 25, 2023 at 05:02:46AM +0000, Andy Chiu wrote:
> This patch add back the ptrace support with the following fix:
>  - Define NT_RISCV_CSR and re-number NT_RISCV_VECTOR to prevent
>    conflicting with gdb's NT_RISCV_CSR.
>  - Use struct __riscv_v_regset_state to handle ptrace requests
> 
> Since gdb does not directly include the note description header in
> Linux and has already defined NT_RISCV_CSR as 0x900, we decide to
> sync with gdb and renumber NT_RISCV_VECTOR to solve and prevent future
> conflicts.
> 
> Fixes: 0c59922c769a ("riscv: Add ptrace vector support")
> Signed-off-by: Andy Chiu <andy.chiu at sifive.com>

Hi Andy, this is causing an instance of -Wunused-variable. PTAL.

Please use the following tags on the fix:

Reported-by: "kernelci.org bot" <bot at kernelci.org>
Closes: https://lore.kernel.org/linux-next/64f03ea1.170a0220.d3dbf.11fd@mx.google.com/

Let's see if I can get the regzbot tag correct; first time trying it.

#regzbot introduced dbe46b094026

> diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
> index 487303e3ef22..9a87e5d490b5 100644
> --- a/arch/riscv/kernel/ptrace.c
> +++ b/arch/riscv/kernel/ptrace.c
> @@ -81,6 +84,71 @@ static int riscv_fpr_set(struct task_struct *target,
>  }
>  #endif
>  
> +#ifdef CONFIG_RISCV_ISA_V
> +static int riscv_vr_get(struct task_struct *target,
> +			const struct user_regset *regset,
> +			struct membuf to)
> +{
> +	struct __riscv_v_ext_state *vstate = &target->thread.vstate;
> +	struct __riscv_v_regset_state ptrace_vstate;
> +
> +	if (!riscv_v_vstate_query(task_pt_regs(target)))
> +		return -EINVAL;
> +
> +	/*
> +	 * Ensure the vector registers have been saved to the memory before
> +	 * copying them to membuf.
> +	 */
> +	if (target == current)
> +		riscv_v_vstate_save(current, task_pt_regs(current));
> +
> +	ptrace_vstate.vstart = vstate->vstart;
> +	ptrace_vstate.vl = vstate->vl;
> +	ptrace_vstate.vtype = vstate->vtype;
> +	ptrace_vstate.vcsr = vstate->vcsr;
> +	ptrace_vstate.vlenb = vstate->vlenb;
> +
> +	/* Copy vector header from vstate. */
> +	membuf_write(&to, &ptrace_vstate, sizeof(struct __riscv_v_regset_state));
> +
> +	/* Copy all the vector registers from vstate. */
> +	return membuf_write(&to, vstate->datap, riscv_v_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;

^ arch/riscv/kernel/ptrace.c:123:11: warning: unused variable 'size' [-Wunused-variable]