[PATCH] riscv/ptrace: add new regset to get original a0 register

[Björn Töpel]

Thanks for working on this!

Celeste Liu <uwu at coelacanthus.name> writes:

> The orig_a0 is missing in struct user_regs_struct of riscv, and there is
> no way to add it without breaking UAPI. (See Link tag below)
>
> Like NT_ARM_SYSTEM_CALL do, we add a new regset name NT_RISCV_ORIG_A0 to
> access original a0 register from userspace via ptrace API.
>
> Link: https://lore.kernel.org/all/59505464-c84a-403d-972f-d4b2055eeaac@gmail.com/
> Signed-off-by: Celeste Liu <uwu at coelacanthus.name>
> ---
>  arch/riscv/kernel/ptrace.c | 33 +++++++++++++++++++++++++++++++++
>  include/uapi/linux/elf.h   |  1 +
>  2 files changed, 34 insertions(+)
>
> diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
> index ea67e9fb7a583683b922fe2c017ea61f3bc848db..faa46de9000376eb445a32d43a40210d7b846844 100644
> --- a/arch/riscv/kernel/ptrace.c
> +++ b/arch/riscv/kernel/ptrace.c
> @@ -31,6 +31,7 @@ enum riscv_regset {
>  #ifdef CONFIG_RISCV_ISA_SUPM
>  	REGSET_TAGGED_ADDR_CTRL,
>  #endif
> +	REGSET_ORIG_A0,
>  };
>  
>  static int riscv_gpr_get(struct task_struct *target,
> @@ -184,6 +185,30 @@ static int tagged_addr_ctrl_set(struct task_struct *target,
>  }
>  #endif
>  
> +static int riscv_orig_a0_get(struct task_struct *target,
> +			     const struct user_regset *regset,
> +			     struct membuf to)

Use full 100 chars!

> +{
> +	return membuf_store(&to, task_pt_regs(target)->orig_a0);
> +}
> +
> +static int riscv_orig_a0_set(struct task_struct *target,
> +			     const struct user_regset *regset,
> +			     unsigned int pos, unsigned int count,
> +			     const void *kbuf, const void __user *ubuf)

Dito!

> +{
> +	int orig_a0 = task_pt_regs(target)->orig_a0;

64b regs on RV64.

> +	int ret;
> +
> +	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &orig_a0, 0, -1);
> +	if (ret)
> +		return ret;
> +
> +	task_pt_regs(target)->orig_a0 = orig_a0;
> +	return ret;
> +}
> +
> +

Multiple blanks.

>  static const struct user_regset riscv_user_regset[] = {
>  	[REGSET_X] = {
>  		.core_note_type = NT_PRSTATUS,
> @@ -224,6 +249,14 @@ static const struct user_regset riscv_user_regset[] = {
>  		.set = tagged_addr_ctrl_set,
>  	},
>  #endif
> +	[REGSET_ORIG_A0] = {
> +		.core_note_type = NT_RISCV_ORIG_A0,
> +		.n = 1,
> +		.size = sizeof(elf_greg_t),
> +		.align = sizeof(elf_greg_t),

...and sizeof(elf_greg_t) is 64b in RV64 -- mismatch above.


Björn