ia64 find thread for user rbs address

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

arch/ia64/kernel/ptrace.c 2006-11-16 16:25:07.000000000 +0800 renamed from arch/ia64/kernel/ptrace.c 2006-11-16 16:23:31.000000000 +0800 +1 -2

@@ -607,7 +607,7 @@ find_thread_for_addr (struct task_struct
         */
        list_for_each_safe(this, next, &current->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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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.

thanks
bibo,mao

Quoted 26 lines · bibo,mao

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

arch/ia64/kernel/ptrace.c 2006-11-16 16:25:07.000000000 +0800 renamed from arch/ia64/kernel/ptrace.c 2006-11-16 16:23:31.000000000 +0800 +1 -2

@@ -607,7 +607,7 @@ find_thread_for_addr (struct task_struct
         */
        list_for_each_safe(this, next, &current->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;
-

Quoted 4 lines · bibo,mao

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.

Quoted 31 lines

thanks
bibo,mao

Quoted 26 lines · bibo,mao

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

arch/ia64/kernel/ptrace.c 2006-11-16 16:25:07.000000000 +0800 renamed from arch/ia64/kernel/ptrace.c 2006-11-16 16:23:31.000000000 +0800 +1 -2

@@ -607,7 +607,7 @@ find_thread_for_addr (struct task_struct
         */
        list_for_each_safe(this, next, &current->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;
-