Messages in this thread | | | Date | Tue, 11 Dec 2018 16:29:54 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH v5 24/25] ptrace: add PTRACE_GET_SYSCALL_INFO request |
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On 12/10, Dmitry V. Levin wrote: > > On Mon, Dec 10, 2018 at 03:11:07PM +0100, Oleg Nesterov wrote: > > On 12/10, Dmitry V. Levin wrote: > > > > > > +struct ptrace_syscall_info { > > > + __u8 op; /* PTRACE_SYSCALL_INFO_* */ > > > + __u8 __pad0[3]; > > > + __u32 arch; > > > + __u64 instruction_pointer; > > > + __u64 stack_pointer; > > > + __u64 frame_pointer; > > > + union { > > > + struct { > > > + __u64 nr; > > > + __u64 args[6]; > > > + } entry; > > > + struct { > > > + __s64 rval; > > > + __u8 is_error; > > > + __u8 __pad1[7]; > > > + } exit; > > > + struct { > > > + __u64 nr; > > > + __u64 args[6]; > > > + __u32 ret_data; > > > + __u8 __pad2[4]; > > > + } seccomp; > > > + }; > > > +}; > > > > Could you explain why ptrace_syscall_info needs __pad{0,1,2} ? I simply can't > > understand why... > > I suppose the idea behind the use of these pads was to make the structure > arch-independent.
Still can't understand... are you saying that without (say) __pad2[4] sizeof(ptrace_syscall_info) or offsetofend(ptrace_syscall_info, seccomp) will depend on arch? Or what? I am just curious.
> I don't think we really need to keep it exactly the same on all > architectures - the only practical requirement is to avoid any compat > issues, but I don't mind keeping the structure arch-independent.
OK, but may be you can add a short comment to explain these pads.
Oleg.
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