On 2024/6/20 09:05, Charlie Jenkins wrote:
On Wed, Jun 19, 2024 at 10:01:27AM +0800, zhouquan@xxxxxxxxxxx wrote:
From: Quan Zhou <zhouquan@xxxxxxxxxxx>
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@xxxxxxxxxxx>
---
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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