Re: ptrace single-stepping change breaks Wine

Linus Torvalds
2004-11-19T21:22:35Z

On Fri, 19 Nov 2004, Eric Pouech wrote:
>
> wine mixes both approches, we have (to control what's generated inside the
> various exception) to ptrace from our NT-kernel-like process (the ptracer) to
> get the context of the exception. Restart from the ptracer is done with
> PTRACE_SINGLESTEP.

Here's a new patch to try. Totally untested.

It is more careful about clearing PT_DTRACED (which by now should probably
be renamed PT_PRACE_SINGLESTEP or something on x86, since we should never
be lazy about this thing any more), and it may or may not help.

Pls test _together_ with the previous patch (which is already applied in
the current top-of-tree for anybody with really recent kernels).

Linus

-----
===== arch/i386/kernel/ptrace.c 1.27 vs edited =====
--- 1.27/arch/i386/kernel/ptrace.c 2004-11-07 18:10:34 -08:00
+++ edited/arch/i386/kernel/ptrace.c 2004-11-19 13:18:56 -08:00
@@ -138,6 +138,26 @@
return retval;
}

+static void set_singlestep(struct task_struct *child)
+{
+ long eflags;
+
+ set_tsk_thread_flag(child, TIF_SINGLESTEP);
+ eflags = get_stack_long(child, EFL_OFFSET);
+ put_stack_long(child, EFL_OFFSET, eflags | TRAP_FLAG);
+ child->ptrace |= PT_DTRACE;
+}
+
+static void clear_singlestep(struct task_struct *child)
+{
+ long eflags;
+
+ clear_tsk_thread_flag(child, TIF_SINGLESTEP);
+ eflags = get_stack_long(child, EFL_OFFSET);
+ put_stack_long(child, EFL_OFFSET, eflags & ~TRAP_FLAG);
+ child->ptrace &= ~PT_DTRACE;
+}
+
/*
* Called by kernel/ptrace.c when detaching..
*
@@ -145,11 +165,7 @@
*/
void ptrace_disable(struct task_struct *child)
{
- long tmp;
-
- clear_tsk_thread_flag(child, TIF_SINGLESTEP);
- tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
- put_stack_long(child, EFL_OFFSET, tmp);
+ clear_singlestep(child);
}

/*
@@ -388,10 +404,8 @@
}
break;

- case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
- case PTRACE_CONT: { /* restart after signal. */
- long tmp;
-
+ case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
+ case PTRACE_CONT: /* restart after signal. */
ret = -EIO;
if ((unsigned long) data > _NSIG)
break;
@@ -401,56 +415,39 @@
else {
clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
}
- clear_tsk_thread_flag(child, TIF_SINGLESTEP);
child->exit_code = data;
- /* make sure the single step bit is not set. */
- tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
- put_stack_long(child, EFL_OFFSET,tmp);
+ /* make sure the single step bit is not set. */
+ clear_singlestep(child);
wake_up_process(child);
ret = 0;
break;
- }

/*
* make the child exit. Best I can do is send it a sigkill.
* perhaps it should be put in the status that it wants to
* exit.
*/
- case PTRACE_KILL: {
- long tmp;
-
+ case PTRACE_KILL:
ret = 0;
if (child->exit_state == EXIT_ZOMBIE) /* already dead */
break;
child->exit_code = SIGKILL;
- clear_tsk_thread_flag(child, TIF_SINGLESTEP);
/* make sure the single step bit is not set. */
- tmp = get_stack_long(child, EFL_OFFSET) & ~TRAP_FLAG;
- put_stack_long(child, EFL_OFFSET, tmp);
+ clear_singlestep(child);
wake_up_process(child);
break;
- }
-
- case PTRACE_SINGLESTEP: { /* set the trap flag. */
- long tmp;

+ case PTRACE_SINGLESTEP: /* set the trap flag. */
ret = -EIO;
if ((unsigned long) data > _NSIG)
break;
clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
- if ((child->ptrace & PT_DTRACE) == 0) {
- /* Spurious delayed TF traps may occur */
- child->ptrace |= PT_DTRACE;
- }
- tmp = get_stack_long(child, EFL_OFFSET) | TRAP_FLAG;
- put_stack_long(child, EFL_OFFSET, tmp);
- set_tsk_thread_flag(child, TIF_SINGLESTEP);
+ set_singlestep(child);
child->exit_code = data;
/* give it a chance to run. */
wake_up_process(child);
ret = 0;
break;
- }

case PTRACE_DETACH:
/* detach a process that was attached. */