On 2024/6/20 09:05, Charlie Jenkins wrote:
On Wed, Jun 19, 2024 at 10:01:27AM +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. Since user_regs_struct is a subset of pt_regs, we also need to adjust the position of the orig_a0 field in pt_regs to achieve the correct copy.
Signed-off-by: Quan Zhou zhouquan@iscas.ac.cn
arch/riscv/include/asm/ptrace.h | 4 ++-- arch/riscv/include/uapi/asm/ptrace.h | 2 ++ 2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/riscv/include/asm/ptrace.h b/arch/riscv/include/asm/ptrace.h index b5b0adcc85c1..37f48d40ae46 100644 --- a/arch/riscv/include/asm/ptrace.h +++ b/arch/riscv/include/asm/ptrace.h @@ -45,12 +45,12 @@ 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 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
This is a good addition!
Since orig_a0 is no longer at the bottom of pt_regs, MAX_REG_OFFSET is now incorrect.
Can you adjust the value of:
#define MAX_REG_OFFSET offsetof(struct pt_regs, orig_a0)
in arch/riscv/include/asm/ptrace.h to be:
#define MAX_REG_OFFSET offsetof(struct pt_regs, cause)
This is something that is very easy to miss. I think it would be valuable to leave a comment at the top of struct pt_regs pointing out that MAX_REG_OFFSET needs to be adjusted if struct pt_regs changes.
- Charlie
Oh, good idea! I'm sorry for missing such an important point earlier.
Once enough information is gathered from this RFC, I will include what you mentioned in the V1 series.
Thanks, Quan
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