From: Claudio Jeker <cjeker@diehard.n-r-g.com>
Subject: Re: extend ptrace(2) PT_GET_THREAD_* to include thread names
To: kurt@intricatesoftware.com
Cc: jca@wxcvbn.org, mark.kettenis@xs4all.nl, pascal@stumpf.co, ports@openbsd.org, tech@openbsd.org
Date: Wed, 10 Dec 2025 20:03:24 +0100

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@

> 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