[src/trunk]: src/sys/arch/amd64/amd64 No, do not just copy code from i386 and...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/dde81632a419
branches:  trunk
changeset: 351306:dde81632a419
user:      maxv <maxv%NetBSD.org@localhost>
date:      Thu Feb 09 08:38:25 2017 +0000

description:
No, do not just copy code from i386 and expect it to work on amd64. There
are several structural differences. At least two issues here: segment
registers that could fault in kernel mode with userland TLS, and a non-
canonical %eip on iret.

Not even tested, but just obvious. By the way, I believe this function is
still buggy since we don't call cpu_fsgs_reload while %fs/%gs could have
been reloaded.

diffstat:

 sys/arch/amd64/amd64/netbsd32_machdep.c |  30 ++++++++++++++++++++++++------
 1 files changed, 24 insertions(+), 6 deletions(-)

diffs (54 lines):

diff -r c29b9c14def0 -r dde81632a419 sys/arch/amd64/amd64/netbsd32_machdep.c
--- a/sys/arch/amd64/amd64/netbsd32_machdep.c   Thu Feb 09 08:23:46 2017 +0000
+++ b/sys/arch/amd64/amd64/netbsd32_machdep.c   Thu Feb 09 08:38:25 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: netbsd32_machdep.c,v 1.101 2017/02/06 16:34:37 maxv Exp $      */
+/*     $NetBSD: netbsd32_machdep.c,v 1.102 2017/02/09 08:38:25 maxv Exp $      */
 
 /*
  * Copyright (c) 2001 Wasabi Systems, Inc.
@@ -36,7 +36,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: netbsd32_machdep.c,v 1.101 2017/02/06 16:34:37 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: netbsd32_machdep.c,v 1.102 2017/02/09 08:38:25 maxv Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_compat_netbsd.h"
@@ -531,13 +531,31 @@
 int
 netbsd32_process_write_regs(struct lwp *l, const struct reg32 *regs)
 {
-       struct trapframe *tf = l->l_md.md_regs;
+       struct trapframe *tf;
+       struct pcb *pcb;
+
+       tf = l->l_md.md_regs;
+       pcb = lwp_getpcb(l);
 
        /*
-        * Check for security violations. Taken from i386/process_machdep.c.
+        * Check for security violations.
         */
-       if (((regs->r_eflags ^ tf->tf_rflags) & PSL_USERSTATIC) != 0 ||
-           !VALID_USER_CSEL32(regs->r_cs))
+       if (((regs->r_eflags ^ tf->tf_rflags) & PSL_USERSTATIC) != 0)
+               return EINVAL;
+       if (!VALID_USER_CSEL32(regs->r_cs))
+               return EINVAL;
+       if (regs->r_fs != 0 && !VALID_USER_DSEL32(regs->r_fs) &&
+           !(VALID_USER_FSEL32(regs->r_fs) && pcb->pcb_fs != 0))
+               return EINVAL;
+       if (regs->r_gs != 0 && !VALID_USER_DSEL32(regs->r_gs) &&
+           !(VALID_USER_GSEL32(regs->r_gs) && pcb->pcb_gs != 0))
+               return EINVAL;
+       if (regs->r_es != 0 && !VALID_USER_DSEL32(regs->r_es))
+               return EINVAL;
+       if (!VALID_USER_DSEL32(regs->r_ds) ||
+           !VALID_USER_DSEL32(regs->r_ss))
+               return EINVAL;
+       if (regs->r_eip >= VM_MAXUSER_ADDRESS32)
                return EINVAL;
 
        tf->tf_rax = regs->r_eax;