On Wed, Jun 19, 2024 at 10:01:27AM +0800, [email protected] wrote: > From: Quan Zhou <[email protected]> > > 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 <[email protected]> > --- > 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
