On Wed, Jan 15, 2025 at 07:13:27PM +0800, Celeste Liu wrote:
> 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.
>
> Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API")
> Link:
> https://lore.kernel.org/all/59505464-c84a-403d-972f-d4b2055ee...@gmail.com/
> Cc: sta...@vger.kernel.org
> Reviewed-by: Björn Töpel <bj...@rivosinc.com>
> Signed-off-by: Celeste Liu <u...@coelacanthus.name>
Thank you!
Reviewed-by: Charlie Jenkins <char...@rivosinc.com>
Tested-by: Charlie Jenkins <char...@rivosinc.com>
> ---
> arch/riscv/kernel/ptrace.c | 32 ++++++++++++++++++++++++++++++++
> include/uapi/linux/elf.h | 1 +
> 2 files changed, 33 insertions(+)
>
> diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
> index
> ea67e9fb7a583683b922fe2c017ea61f3bc848db..ef9ab74c8575a5c440155973b1c625c06a867c97
> 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 +185,29 @@ 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)
> +{
> + 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)
> +{
> + unsigned long orig_a0 = task_pt_regs(target)->orig_a0;
> + 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 0;
> +}
> +
> static const struct user_regset riscv_user_regset[] = {
> [REGSET_X] = {
> .core_note_type = NT_PRSTATUS,
> @@ -224,6 +248,14 @@ 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),
> + .regset_get = riscv_orig_a0_get,
> + .set = riscv_orig_a0_set,
> + },
> };
>
> 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
> b44069d29cecc0f9de90ee66bfffd2137f4275a8..390060229601631da2fb27030d9fa2142e676c14
> 100644
> --- a/include/uapi/linux/elf.h
> +++ b/include/uapi/linux/elf.h
> @@ -452,6 +452,7 @@ typedef struct elf64_shdr {
> #define NT_RISCV_CSR 0x900 /* RISC-V Control and Status Registers
> */
> #define NT_RISCV_VECTOR 0x901 /* RISC-V vector registers */
> #define NT_RISCV_TAGGED_ADDR_CTRL 0x902 /* RISC-V tagged address
> control (prctl()) */
> +#define NT_RISCV_ORIG_A0 0x903 /* RISC-V original a0 register */
> #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 */
>
> --
> 2.48.0
>
