Messages in this thread | | | Date | Wed, 12 Nov 2014 19:46:01 +0900 | From | AKASHI Takahiro <> | Subject | Re: [RFC] ptrace: add generic SET_SYSCALL request |
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Will,
On 11/07/2014 11:04 PM, Oleg Nesterov wrote: > On 11/07, AKASHI Takahiro wrote: >> >> --- a/arch/arm/kernel/ptrace.c >> +++ b/arch/arm/kernel/ptrace.c >> @@ -853,11 +853,6 @@ long arch_ptrace(struct task_struct *child, long request, >> datap); >> break; >> >> - case PTRACE_SET_SYSCALL: >> - task_thread_info(child)->syscall = data; >> - ret = 0; >> - break; >> - >> #ifdef CONFIG_CRUNCH >> case PTRACE_GETCRUNCHREGS: >> ret = ptrace_getcrunchregs(child, datap); >> diff --git a/kernel/ptrace.c b/kernel/ptrace.c >> index 54e7522..d7048fa 100644 >> --- a/kernel/ptrace.c >> +++ b/kernel/ptrace.c >> @@ -1001,6 +1001,12 @@ int ptrace_request(struct task_struct *child, long request, >> break; >> } >> #endif >> + >> +#ifdef PTRACE_SET_SYSCALL >> + case PTRACE_SET_SYSCALL: >> + ret = syscall_set_nr(child, task_pt_regs(child), data); >> + break; >> +#endif > > I too do not understand why it makes sense to move PTRACE_SET_SYSCALL into > the common kernel/ptrace.c.
I think I explained why we need a new (atomic) interface of changing a system call number while tracing with ptrace. But I don't have a strong preference, either ptrace(SET_SYSCALL) or ptrace(SETREGSET, NT_SYSTEM_CALL).
> To me the fact that PTRACE_SET_SYSCALL can be undefined and syscall_set_nr() > is very much arch-dependant (but most probably trivial) means that this code > should live in arch_ptrace().
Thinking of Oleg's comment above, it doesn't make sense neither to define generic NT_SYSTEM_CALL (user_regset) in uapi/linux/elf.h and implement it in ptrace_regset() in kernel/ptrace.c with arch-defined syscall_(g)set_nr().
Since we should have the same interface on arm and arm64, we'd better implement ptrace(PTRACE_SET_SYSCALL) locally on arm64 for now (as I originally submitted).
-Takahiro AKASHI
> In any case, I think it doesn't make sense to pass task_pt_regs(child), this > helper can do this itself if it needs struct pt_regs. > > Oleg. >
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