Mon Aug 10 09:38:48 2020 UTC ()

Forbid to set odd address to PC in process_write_regs() and process_set_pc().

Otherwise, address error occurs in kernel at rte instruction when returning
to the user level.

Found by tests/lib/libc/t_ptrace_*:access_regs_set_unaligned_pc_0x[137].


(rin)

diff -r1.30 -r1.31 src/sys/arch/m68k/m68k/process_machdep.c

--- src/sys/arch/m68k/m68k/process_machdep.c 2014/01/04 00:10:02	1.30
+++ src/sys/arch/m68k/m68k/process_machdep.c 2020/08/10 09:38:48	1.31

 @@ -1,14 +1,14 @@
-/*	$NetBSD: process_machdep.c,v 1.30 2014/01/04 00:10:02 dsl Exp $	*/
+/*	$NetBSD: process_machdep.c,v 1.31 2020/08/10 09:38:48 rin Exp $	*/
 /*
  * Copyright (c) 1993 Christopher G. Demetriou
  * All rights reserved.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
 @@ -43,27 +43,27 @@
  *	Update the current register set from the passed in regs
  *	structure.  Take care to avoid clobbering special CPU
  *	registers or privileged bits in the PSL.
  *	The process is stopped at the time write_regs is called.
+ *
  * process_sstep(proc)
  *	Arrange for the process to trap after executing a single instruction.
+ *
  * process_set_pc(proc)
  *	Set the process's program counter.
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: process_machdep.c,v 1.30 2014/01/04 00:10:02 dsl Exp $");
+__KERNEL_RCSID(0, "$NetBSD: process_machdep.c,v 1.31 2020/08/10 09:38:48 rin Exp $");
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/kernel.h>
 #include <sys/proc.h>
 #include <sys/vnode.h>
 #include <sys/ptrace.h>
 #include <machine/frame.h>
 #include <machine/pcb.h>
 #include <machine/psl.h>
 static inline struct frame *
 @@ -104,33 +104,30 @@ process_read_fpregs(struct lwp *l, struc
 	regs->r_fpcr = frame->fpf_fpcr;
 	regs->r_fpsr = frame->fpf_fpsr;
 	regs->r_fpiar = frame->fpf_fpiar;
 	return 0;
+}
 int
 process_write_regs(struct lwp *l, const struct reg *regs)
+{
 	struct frame *frame = process_frame(l);
 	/*
-	 * in the hp300 machdep.c _write_regs, PC alignment wasn't
+	 * Avoid kernel address error at rte instruction.
 	 * checked.  If an odd address is placed in the PC and the
 	 * program is allowed to run, it will cause an Address Error
 	 * which will be transmitted to the process by a SIGBUS.
 	 * No reasonable debugger would let this happen, but
 	 * it's not our problem.
 	 */
 	if (regs->r_pc & 1)
 		return EINVAL;
 	/*
 	 * XXX
 	 * in hp300 machdep.c, it just cleared/set these bits
 	 * automatically.  here, we barf.  well-written programs
 	 * shouldn't munge them.
 	 */
 	if ((regs->r_sr & PSL_USERCLR) != 0 ||
 	    (regs->r_sr & PSL_USERSET) != PSL_USERSET)
 		return EPERM;
 	memcpy(frame->f_regs, regs->r_regs, sizeof(frame->f_regs));
 	frame->f_sr = regs->r_sr;
 @@ -161,25 +158,21 @@ process_sstep(struct lwp *l, int sstep)
 		frame->f_sr |= PSL_T;
 	else
 		frame->f_sr &= ~PSL_T;
 	return 0;
+}
 int
 process_set_pc(struct lwp *l, void *addr)
+{
 	struct frame *frame = process_frame(l);
 	/*
-	 * in the hp300 machdep.c _set_pc, PC alignment is guaranteed
+	 * Avoid kernel address error at rte instruction.
 	 * by chopping off the low order bit of the new pc.
 	 * If an odd address was placed in the PC and the program
 	 * is allowed to run, it will cause an Address Error
 	 * which will be transmitted to the process by a SIGBUS.
 	 * No reasonable debugger would let this happen, but
 	 * it's not our problem.
 	 */
 	if ((u_int)addr & 1)
 		return EINVAL;
 	frame->f_pc = (u_int)addr;
 	return 0;
+}