Re: [PATCH v1 1/2] riscv: Expose orig_a0 in the user_regs_struct structure

Charlie Jenkins
2024-07-02T04:34:20Z

On Thu, Jun 27, 2024 at 11:02:46AM +0800, zhouquan@iscas.ac.cn wrote:
> From: Quan Zhou <zhouquan@iscas.ac.cn>
>
> Expose orig_a0 to userspace to ensure that users can modify
> the actual value of `a0` in the traced process through the
> ptrace(PTRACE_SETREGSET, ...) path.
>
> The addition of orig_a0 also requires the following adjustments:
> 1) Adjust the position of orig_a0 in pt_regs to ensure correct copying.
> 2) MAX_REG_OFFSET should match the new bottom of pt_regs.
>
> Suggested-by: Charlie Jenkins <charlie@rivosinc.com>
> Signed-off-by: Quan Zhou <zhouquan@iscas.ac.cn>
> ---
> arch/riscv/include/asm/ptrace.h | 7 ++++---
> arch/riscv/include/uapi/asm/ptrace.h | 2 ++
> 2 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/include/asm/ptrace.h b/arch/riscv/include/asm/ptrace.h
> index b5b0adcc85c1..380cf54c1f3d 100644
> --- a/arch/riscv/include/asm/ptrace.h
> +++ b/arch/riscv/include/asm/ptrace.h
> @@ -12,6 +12,7 @@
>
> #ifndef __ASSEMBLY__
>
> +/* MAX_REG_OFFSET should match the bottom of pt_regs */
> struct pt_regs {
> unsigned long epc;
> unsigned long ra;
> @@ -45,12 +46,12 @@ struct pt_regs {
> unsigned long t4;
> unsigned long t5;
> unsigned long t6;
> + /* a0 value before the syscall */
> + unsigned long orig_a0;
> /* Supervisor/Machine CSRs */
> unsigned long status;
> unsigned long badaddr;
> unsigned long cause;
> - /* a0 value before the syscall */
> - unsigned long orig_a0;
> };
>
> #define PTRACE_SYSEMU 0x1f
> @@ -64,7 +65,7 @@ struct pt_regs {
>
> #define user_mode(regs) (((regs)->status & SR_PP) == 0)
>
> -#define MAX_REG_OFFSET offsetof(struct pt_regs, orig_a0)
> +#define MAX_REG_OFFSET offsetof(struct pt_regs, cause)
>
> /* Helpers for working with the instruction pointer */
> static inline unsigned long instruction_pointer(struct pt_regs *regs)
> diff --git a/arch/riscv/include/uapi/asm/ptrace.h b/arch/riscv/include/uapi/asm/ptrace.h
> index a38268b19c3d..3e37f80cb3e8 100644
> --- a/arch/riscv/include/uapi/asm/ptrace.h
> +++ b/arch/riscv/include/uapi/asm/ptrace.h
> @@ -54,6 +54,8 @@ struct user_regs_struct {
> unsigned long t4;
> unsigned long t5;
> unsigned long t6;
> + /* a0 value before the syscall */
> + unsigned long orig_a0;
> };
>
> struct __riscv_f_ext_state {
> --
> 2.34.1
>

Thank you!

Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>