Zhang, Yanmin wrote:
On Thu, 2006-11-16 at 17:42, bibo,mao wrote:Tony, please discard this patch. It can not fix completely. If ptrace caller wants to access vforked child process's user rbs, there will be problem.The patch is correct. If ptracer wants to access vforked child process's user rbs, find_thread_for_addr's first parameter, child, will points to the vforked task_struct instead of vforker's.
oh, I get messed with it. If ptracer wants to trace vforked child process, then pid should be vforked process's pid but not vforker parent process's pid. Then this parch is corrent. thanks bibo,mao
thanks bibo,mao bibo,mao wrote:hi, I encountered one problem when running ptrace test case, the situation is this: traced process's syscall parameter needs to be accessed, but for sys_clone system call with clone_flag (CLONE_VFORK | CLONE_VM | SIGCHLD) parameter. this syscall's parameter accessing result is wrong. The reason is that with clone_flag(CLONE_VFORK | CLONE_VM | SIGCHLD), cloned thread's mm point is the same, but tgid is different. without this patch find_thread_for_addr will return cloned thread, but not the thread which call sys_clone syscall. thanks bibo,mao --- 2.6.19-rc5.org/arch/ia64/kernel/ptrace.c 2006-11-16 16:23:31.000000000 +0800 +++ 2.6.19-rc5/arch/ia64/kernel/ptrace.c 2006-11-16 16:25:07.000000000 +0800 @@ -607,7 +607,7 @@ find_thread_for_addr (struct task_struct */ list_for_each_safe(this, next, ¤t->children) { p = list_entry(this, struct task_struct, sibling); - if (p->mm != mm) + if (p->tgid != child->tgid) continue; if (thread_matches(p, addr)) { child = p; -
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