From 47565b742e7af3a7965ea58d06375098439da77b Mon Sep 17 00:00:00 2001
From: deraadt <deraadt@openbsd.org>
Date: Thu, 16 Feb 2023 04:42:06 +0000
Subject: [PATCH] Add pinsyscall(2).  With this you can tell the kernel the
 location (start,len) of the syscall stub in libc.so for a specified syscall
 (using SYS_* notation).  Only SYS_execve is supported at this time. ok gnezdo
 mortimer kettenis

---
 sys/kern/syscalls.master |  4 ++--
 sys/uvm/uvm_extern.h     |  4 +++-
 sys/uvm/uvm_mmap.c       | 35 ++++++++++++++++++++++++++++++++++-
 3 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/sys/kern/syscalls.master b/sys/kern/syscalls.master
index d799adcc9b2..67a5424af2f 100644
--- a/sys/kern/syscalls.master
+++ b/sys/kern/syscalls.master
@@ -1,4 +1,4 @@
-;	$OpenBSD: syscalls.master,v 1.243 2023/02/14 08:34:49 mvs Exp $
+;	$OpenBSD: syscalls.master,v 1.244 2023/02/16 04:42:06 deraadt Exp $
 ;	$NetBSD: syscalls.master,v 1.32 1996/04/23 10:24:21 mycroft Exp $
 
 ;	@(#)syscalls.master	8.2 (Berkeley) 1/13/94
@@ -284,7 +284,7 @@
 143	STD		{ int sys_setthrname(pid_t tid, const char *name); }
 144	OBSOL		ogetrlimit
 145	OBSOL		osetrlimit
-146	OBSOL		okillpg
+146	STD NOLOCK	{ int sys_pinsyscall(int syscall, void *addr, size_t len); }
 147	STD		{ int sys_setsid(void); }
 148	STD		{ int sys_quotactl(const char *path, int cmd, \
 			    int uid, char *arg); }
diff --git a/sys/uvm/uvm_extern.h b/sys/uvm/uvm_extern.h
index 6f4ddc5327a..994957f7c9e 100644
--- a/sys/uvm/uvm_extern.h
+++ b/sys/uvm/uvm_extern.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_extern.h,v 1.166 2022/11/17 18:53:05 deraadt Exp $	*/
+/*	$OpenBSD: uvm_extern.h,v 1.167 2023/02/16 04:42:07 deraadt Exp $	*/
 /*	$NetBSD: uvm_extern.h,v 1.57 2001/03/09 01:02:12 chs Exp $	*/
 
 /*
@@ -214,6 +214,8 @@ struct vmspace {
 	caddr_t	vm_daddr;	/* [I] user virtual address of data */
 	caddr_t vm_maxsaddr;	/* [I] user VA at max stack growth */
 	caddr_t vm_minsaddr;	/* [I] user VA at top of stack */
+	vaddr_t	vm_execve;	/* [v] execve systemcall stub region */
+	vaddr_t vm_execve_end;	/* [v] execve systemcall stub region */
 };
 
 /*
diff --git a/sys/uvm/uvm_mmap.c b/sys/uvm/uvm_mmap.c
index e3dcd41089e..db0adcfdcc4 100644
--- a/sys/uvm/uvm_mmap.c
+++ b/sys/uvm/uvm_mmap.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_mmap.c,v 1.178 2023/02/11 23:22:19 deraadt Exp $	*/
+/*	$OpenBSD: uvm_mmap.c,v 1.179 2023/02/16 04:42:08 deraadt Exp $	*/
 /*	$NetBSD: uvm_mmap.c,v 1.49 2001/02/18 21:19:08 chs Exp $	*/
 
 /*
@@ -68,6 +68,7 @@
 
 #include <machine/exec.h>	/* for __LDPGSZ */
 
+#include <sys/syscall.h>
 #include <sys/syscallargs.h>
 
 #include <uvm/uvm.h>
@@ -615,6 +616,38 @@ sys_msyscall(struct proc *p, void *v, register_t *retval)
 	return uvm_map_syscall(&p->p_vmspace->vm_map, addr, addr+size);
 }
 
+/*
+ * sys_pinsyscall
+ */
+int
+sys_pinsyscall(struct proc *p, void *v, register_t *retval)
+{
+	struct sys_pinsyscall_args /* {
+		syscallarg(int) syscall;
+		syscallarg(void *) addr;
+		syscallarg(size_t) len;
+	} */ *uap = v;
+	struct vmspace *vm = p->p_vmspace;
+	vm_map_t map = &p->p_vmspace->vm_map;
+	vaddr_t start, end;
+
+	if (SCARG(uap, syscall) != SYS_execve)
+		return (EINVAL);
+	start = (vaddr_t)SCARG(uap, addr);
+	end = start + (vsize_t)SCARG(uap, len);
+	if (start >= end || start < map->min_offset || end > map->max_offset)
+		return (EFAULT);
+	vm_map_lock(map);
+	if (vm->vm_execve) {
+		vm_map_unlock(map);
+		return (EPERM);
+	}
+	vm->vm_execve = start;
+	vm->vm_execve_end = end;
+	vm_map_unlock(map);
+	return (0);
+}
+
 /*
  * sys_mimmutable: the mimmutable system call
  */
-- 
2.20.1