From: Mark Kettenis <mark.kettenis@xs4all.nl>
Subject: Re: extend ptrace(2) PT_GET_THREAD_* to include thread names
To: Claudio Jeker <cjeker@diehard.n-r-g.com>
Cc: kurt@intricatesoftware.com, jca@wxcvbn.org, pascal@stumpf.co, ports@openbsd.org, tech@openbsd.org
Date: Thu, 11 Dec 2025 14:15:37 +0100

> Date: Wed, 10 Dec 2025 20:03:24 +0100
> From: Claudio Jeker <cjeker@diehard.n-r-g.com>
> 
> On Wed, Dec 10, 2025 at 04:41:27PM +0000, kurt@intricatesoftware.com wrote:
> > Instead of gdb using sysctl(2) to get thread names let's extend
> > ptrace(2) PT_GET_THREAD_* to include thread names. This allows
> > gdb to use ptrace for both thread names and thread is alive 
> > detection.
> > 
> > I'm using a new define larger then _MAXCOMLEN to avoid that
> > define and header from propagating in to ptrace.h as well.
> > 
> > The diff for gdb to use this and remove sysctl use follows
> > below as well. This would be committed a few days after the
> > pthread change is committed.
> > 
> > okay for both?
> 
> One comment for the kernel bits. Instead of the comment in ptrace.h I
> would add a CTASSERT() to sys_process.c, either
> 	CTASSERT(PT_PTS_NAMELEN >= _MAXCOMLEN);
> or
> 	CTASSERT(PT_PTS_NAMELEN >= sizeof(p->p_name);
> 
> With that the kernel bits are OK claudio@

Yeah, that makes sense.  The comment could be ignored or could get out
of date.

> > Index: sys/sys/ptrace.h
> > ===================================================================
> > RCS file: /cvs/src/sys/sys/ptrace.h,v
> > diff -u -p -u -r1.16 ptrace.h
> > --- sys/sys/ptrace.h	16 Mar 2020 11:58:46 -0000	1.16
> > +++ sys/sys/ptrace.h	10 Dec 2025 15:56:13 -0000
> > @@ -82,8 +82,11 @@ typedef struct ptrace_state {
> >  #define PT_GET_THREAD_FIRST	15
> >  #define PT_GET_THREAD_NEXT	16
> >  
> > +#define PT_PTS_NAMELEN	32	/* must be >= sizeof(p_name) in struct proc */
> > +
> >  struct ptrace_thread_state {
> >  	pid_t	pts_tid;
> > +	char	pts_name[PT_PTS_NAMELEN];
> >  };
> >  
> >  #define	PT_FIRSTMACH	32	/* for machine-specific requests */
> > Index: sys/kern/sys_process.c
> > ===================================================================
> > RCS file: /cvs/src/sys/kern/sys_process.c,v
> > diff -u -p -u -r1.106 sys_process.c
> > --- sys/kern/sys_process.c	17 Feb 2025 15:45:55 -0000	1.106
> > +++ sys/kern/sys_process.c	10 Dec 2025 15:56:13 -0000
> > @@ -605,8 +605,10 @@ ptrace_kstate(struct proc *p, int req, p
> >  
> >  		if (t == NULL)
> >  			pts->pts_tid = -1;
> > -		else
> > +		else {
> >  			pts->pts_tid = t->p_tid + THREAD_PID_OFFSET;
> > +			strlcpy(pts->pts_name, t->p_name, sizeof(pts->pts_name));
> > +		}
> >  		return 0;
> >  	      }
> >  	}
> 
> -- 
> :wq Claudio
>