Index: lib/libc/sys/ptrace.2
===================================================================
--- lib/libc/sys/ptrace.2
+++ lib/libc/sys/ptrace.2
@@ -2,7 +2,7 @@
 .\"	$NetBSD: ptrace.2,v 1.2 1995/02/27 12:35:37 cgd Exp $
 .\"
 .\" This file is in the public domain.
-.Dd July 15, 2019
+.Dd April 10, 2021
 .Dt PTRACE 2
 .Os
 .Sh NAME
@@ -807,6 +807,20 @@
 The
 .Fa data
 argument is ignored.
+.It Dv PT_COREDUMP
+This request creates a coredump for the stopped program.
+.Fa addr
+argument specifies a pointer to a
+.Vt "struct ptrace_coredump" ,
+which is defined as follows:
+.Bd -literal
+struct ptrace_coredump {
+	TODO;
+};
+.Ed
+.Pp
+The size of the structmust be passed in
+.Fa data .
 .El
 .Sh ARM MACHINE-SPECIFIC REQUESTS
 .Bl -tag -width "Dv PT_SETVFPREGS"
Index: sys/kern/sys_process.c
===================================================================
--- sys/kern/sys_process.c
+++ sys/kern/sys_process.c
@@ -51,6 +51,8 @@
 #include <sys/sx.h>
 #include <sys/malloc.h>
 #include <sys/signalvar.h>
+#include <sys/caprights.h>
+#include <sys/filedesc.h>
 
 #include <machine/reg.h>
 
@@ -446,6 +448,33 @@
 	return (error);
 }
 
+static int
+ptrace_coredump(struct thread *tracer, struct thread *tracee,
+    struct ptrace_coredump *pc)
+{
+	int error;
+	struct file *fp;
+	struct vnode *vp;
+	struct proc *p = tracee->td_proc;
+
+	if (p->p_sysent->sv_coredump == NULL)
+		return (ENOSYS);
+
+	error = getvnode(tracer, pc->pc_fd, &cap_write_rights, &fp);
+	if (error != 0)
+		return (error);
+
+	vp = fp->f_vnode;
+	/* do not try writing to non-regular files */
+	if (vp->v_type != VREG)
+		return (EFAULT);
+
+	error = p->p_sysent->sv_coredump(tracee, vp, OFF_MAX, 0);
+
+	fdrop(fp, tracer);
+	return (error);
+}
+
 /*
  * Process debugging system call.
  */
@@ -469,6 +498,7 @@
 		struct ptrace_io_desc piod;
 		struct ptrace_lwpinfo pl;
 		struct ptrace_vm_entry pve;
+		struct ptrace_coredump pc;
 		struct dbreg dbreg;
 		struct fpreg fpreg;
 		struct reg reg;
@@ -519,6 +549,12 @@
 	case PT_VM_ENTRY:
 		error = copyin(uap->addr, &r.pve, sizeof(r.pve));
 		break;
+	case PT_COREDUMP:
+		if (uap->data != sizeof(r.pc))
+			error = EINVAL;
+		else
+			error = copyin(uap->addr, &r.pc, uap->data);
+		break;
 	default:
 		addr = uap->addr;
 		break;
@@ -1299,6 +1335,12 @@
 		PROC_LOCK(p);
 		break;
 
+	case PT_COREDUMP:
+		PROC_UNLOCK(p);
+		error = ptrace_coredump(td, td2, addr);
+		PROC_LOCK(p);
+		break;
+
 	default:
 #ifdef __HAVE_PTRACE_MACHDEP
 		if (req >= PT_FIRSTMACH) {
Index: sys/sys/ptrace.h
===================================================================
--- sys/sys/ptrace.h
+++ sys/sys/ptrace.h
@@ -74,6 +74,8 @@
 #define	PT_GET_SC_ARGS	27	/* fetch syscall args */
 #define	PT_GET_SC_RET	28	/* fetch syscall results */
 
+#define PT_COREDUMP	29	/* create a coredump */
+
 #define PT_GETREGS      33	/* get general-purpose registers */
 #define PT_SETREGS      34	/* set general-purpose registers */
 #define PT_GETFPREGS    35	/* get floating-point registers */
@@ -176,6 +178,11 @@
 	char		*pve_path;	/* Path name of object. */
 };
 
+/* Argument structure for PT_COREDUMP. */
+struct ptrace_coredump {
+	int		pc_fd;		/* File descriptor to write dump to. */
+};
+
 #ifdef _KERNEL
 
 int	ptrace_set_pc(struct thread *_td, unsigned long _addr);