[src/trunk]: src/sys/arch Add accessors for available x86 Debug Registers

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

details:   https://anonhg.NetBSD.org/src/rev/5503e578bb51
branches:  trunk
changeset: 349179:5503e578bb51
user:      kamil <kamil%NetBSD.org@localhost>
date:      Sun Nov 27 14:49:21 2016 +0000

description:
Add accessors for available x86 Debug Registers

There are 8 Debug Registers on i386 (available at least since 80386) and 16
on AMD64. Currently DR4 and DR5 are reserved on both cpu-families and
DR9-DR15 are still reserved on AMD64. Therefore add accessors for DR0-DR3,
DR6-DR7 for all ports.

Debug Registers x86:
 * DR0-DR3  Debug Address Registers
 * DR4-DR5  Reserved
 * DR6      Debug Status Register
 * DR7      Debug Control Register
 * DR8-DR15 Reserved

Access the registers is available only from a kernel (ring 0) as there is
needed top protected access. For this reason there is need to use special
XEN functions to get and set the registers in the XEN3 kernels.

XEN specific functions as defined in NetBSD:
 - HYPERVISOR_get_debugreg()
 - HYPERVISOR_set_debugreg()

This code extends the existing rdr6() and ldr6() accessor for additional:
 - rdr0() & ldr0()
 - rdr1() & ldr1()
 - rdr2() & ldr2()
 - rdr3() & ldr3()
 - rdr7() & ldr7()

Traditionally accessors for DR6 were passing vaddr_t argument, while it's
appropriate type for DR0-DR3, DR6-DR7 should be using u_long, however it's
not a big deal. The resulting functionality should be equivalent so stick
to this convention and use the vaddr_t type for all DR accessors.

There was already a function defined for rdr6() in XEN, but it had a nit on
AMD64 as it was casting HYPERVISOR_get_debugreg() to u_int (32-bit on
AMD64), truncating result. It still works for DR6, but for the sake of
simplicity always return full 64-bit value.

New accessors duplicate functionality of the dr0() function available on
i386 within the KSTACK_CHECK_DR0 option. dr0() is a specialized layer with
logic to set appropriate types of interrupts, now accessors are designed to
pass verbatim values from user-land (with simple sanity checks in the
kernel). At the moment there are no plans to make possible to coexist
KSTACK_CHECK_DR0 with debug registers for user applications (debuggers).

     options KSTACK_CHECK_DR0
     Detect kernel stack overflow using DR0 register.  This option uses DR0
     register exclusively so you can't use DR0 register for other purpose
     (e.g., hardware breakpoint) if you turn this on.

The KSTACK_CHECK_DR0 functionality was designed for i386 and never ported
to amd64.

Code tested on i386 and amd64 with kernels: GENERIC, XEN3_DOMU, XEN3_DOM0.

Sponsored by <The NetBSD Foundation>

diffstat:

 sys/arch/amd64/amd64/cpufunc.S |  42 ++++++++++++++++++++++-
 sys/arch/i386/i386/i386func.S  |  59 +++++++++++++++++++++++++++++++-
 sys/arch/x86/include/cpufunc.h |  12 ++++++-
 sys/arch/x86/include/dbregs.h  |  45 ++++++++++++++++++++++++
 sys/arch/xen/x86/xenfunc.c     |  77 +++++++++++++++++++++++++++++++++++++++--
 5 files changed, 226 insertions(+), 9 deletions(-)

diffs (truncated from 335 to 300 lines):

diff -r ebb963439497 -r 5503e578bb51 sys/arch/amd64/amd64/cpufunc.S
--- a/sys/arch/amd64/amd64/cpufunc.S    Sun Nov 27 02:32:56 2016 +0000
+++ b/sys/arch/amd64/amd64/cpufunc.S    Sun Nov 27 14:49:21 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: cpufunc.S,v 1.26 2016/11/27 02:32:56 kamil Exp $       */
+/*     $NetBSD: cpufunc.S,v 1.27 2016/11/27 14:49:21 kamil Exp $       */
 
 /*-
  * Copyright (c) 1998, 2007, 2008 The NetBSD Foundation, Inc.
@@ -158,6 +158,38 @@
        movq    %rax, %cr3
        ret
 
+ENTRY(ldr0)
+       movq    %rdi, %dr0
+       ret
+
+ENTRY(rdr0)
+       movq    %dr0, %rax
+       ret
+
+ENTRY(ldr1)
+       movq    %rdi, %dr1
+       ret
+
+ENTRY(rdr1)
+       movq    %dr1, %rax
+       ret
+
+ENTRY(ldr2)
+       movq    %rdi, %dr2
+       ret
+
+ENTRY(rdr2)
+       movq    %dr2, %rax
+       ret
+
+ENTRY(ldr3)
+       movq    %rdi, %dr3
+       ret
+
+ENTRY(rdr3)
+       movq    %dr3, %rax
+       ret
+
 ENTRY(ldr6)
        movq    %rdi, %dr6
        ret
@@ -166,6 +198,14 @@
        movq    %dr6, %rax
        ret
 
+ENTRY(ldr7)
+       movq    %rdi, %dr7
+       ret
+
+ENTRY(rdr7)
+       movq    %dr7, %rax
+       ret
+
 ENTRY(x86_disable_intr)
        cli
        ret
diff -r ebb963439497 -r 5503e578bb51 sys/arch/i386/i386/i386func.S
--- a/sys/arch/i386/i386/i386func.S     Sun Nov 27 02:32:56 2016 +0000
+++ b/sys/arch/i386/i386/i386func.S     Sun Nov 27 14:49:21 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: i386func.S,v 1.17 2012/08/29 22:43:35 rmind Exp $      */
+/*     $NetBSD: i386func.S,v 1.18 2016/11/27 14:49:21 kamil Exp $      */
 
 /*-
  * Copyright (c) 1998, 2007, 2008 The NetBSD Foundation, Inc.
@@ -36,7 +36,7 @@
  */
 
 #include <machine/asm.h>
-__KERNEL_RCSID(0, "$NetBSD: i386func.S,v 1.17 2012/08/29 22:43:35 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: i386func.S,v 1.18 2016/11/27 14:49:21 kamil Exp $");
 
 #include <machine/specialreg.h>
 #include <machine/segments.h>
@@ -123,6 +123,50 @@
        ret
 END(tlbflush)
 
+ENTRY(ldr0)
+       movl    4(%esp), %eax
+       movl    %eax, %dr0
+       ret
+END(ldr0)
+
+ENTRY(rdr0)
+       movl    %dr0, %eax
+       ret
+END(rdr0)
+
+ENTRY(ldr1)
+       movl    4(%esp), %eax
+       movl    %eax, %dr1
+       ret
+END(ldr1)
+
+ENTRY(rdr1)
+       movl    %dr1, %eax
+       ret
+END(rdr1)
+
+ENTRY(ldr2)
+       movl    4(%esp), %eax
+       movl    %eax, %dr2
+       ret
+END(ldr2)
+
+ENTRY(rdr2)
+       movl    %dr2, %eax
+       ret
+END(rdr2)
+
+ENTRY(ldr3)
+       movl    4(%esp), %eax
+       movl    %eax, %dr3
+       ret
+END(ldr3)
+
+ENTRY(rdr3)
+       movl    %dr3, %eax
+       ret
+END(rdr3)
+
 ENTRY(ldr6)
        movl    4(%esp), %eax
        movl    %eax, %dr6
@@ -134,6 +178,17 @@
        ret
 END(rdr6)
 
+ENTRY(ldr7)
+       movl    4(%esp), %eax
+       movl    %eax, %dr7
+       ret
+END(ldr7)
+
+ENTRY(rdr7)
+       movl    %dr7, %eax
+       ret
+END(rdr7)
+
 ENTRY(rcr2)
        movl    %cr2, %eax
        ret
diff -r ebb963439497 -r 5503e578bb51 sys/arch/x86/include/cpufunc.h
--- a/sys/arch/x86/include/cpufunc.h    Sun Nov 27 02:32:56 2016 +0000
+++ b/sys/arch/x86/include/cpufunc.h    Sun Nov 27 14:49:21 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: cpufunc.h,v 1.19 2016/01/05 10:20:22 hannken Exp $     */
+/*     $NetBSD: cpufunc.h,v 1.20 2016/11/27 14:49:21 kamil Exp $       */
 
 /*-
  * Copyright (c) 1998, 2007 The NetBSD Foundation, Inc.
@@ -69,8 +69,18 @@
 void   tlbflush(void);
 void   tlbflushg(void);
 void   dr0(void *, uint32_t, uint32_t, uint32_t);
+vaddr_t        rdr0(void);
+void   ldr0(vaddr_t);
+vaddr_t        rdr1(void);
+void   ldr1(vaddr_t);
+vaddr_t        rdr2(void);
+void   ldr2(vaddr_t);
+vaddr_t        rdr3(void);
+void   ldr3(vaddr_t);
 vaddr_t        rdr6(void);
 void   ldr6(vaddr_t);
+vaddr_t        rdr7(void);
+void   ldr7(vaddr_t);
 void   wbinvd(void);
 void   breakpoint(void);
 void   x86_hlt(void);
diff -r ebb963439497 -r 5503e578bb51 sys/arch/x86/include/dbregs.h
--- /dev/null   Thu Jan 01 00:00:00 1970 +0000
+++ b/sys/arch/x86/include/dbregs.h     Sun Nov 27 14:49:21 2016 +0000
@@ -0,0 +1,45 @@
+/*     $NetBSD: dbregs.h,v 1.1 2016/11/27 14:49:21 kamil Exp $ */
+
+/*-
+ * Copyright (c) 2016 The NetBSD Foundation, Inc.
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+
+#ifndef        _X86_DBREGS_H_
+#define        _X86_DBREGS_H_
+
+#ifdef _KERNEL
+
+struct lwp;
+struct dbreg;
+
+void reset_dbregs(void);
+
+int process_write_dbregs(struct lwp *lwp, const struct dbreg *regs);
+int process_read_dbregs(struct lwp *lwp, struct dbreg *regs);
+
+#endif
+
+#endif /* _X86_FPU_H_ */
diff -r ebb963439497 -r 5503e578bb51 sys/arch/xen/x86/xenfunc.c
--- a/sys/arch/xen/x86/xenfunc.c        Sun Nov 27 02:32:56 2016 +0000
+++ b/sys/arch/xen/x86/xenfunc.c        Sun Nov 27 14:49:21 2016 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: xenfunc.c,v 1.13 2011/11/06 11:40:47 cherry Exp $      */
+/*     $NetBSD: xenfunc.c,v 1.14 2016/11/27 14:49:21 kamil Exp $       */
 
 /*
  *
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xenfunc.c,v 1.13 2011/11/06 11:40:47 cherry Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xenfunc.c,v 1.14 2016/11/27 14:49:21 kamil Exp $");
 
 #include <sys/param.h>
 
@@ -122,12 +122,65 @@
 }
 
 vaddr_t
+rdr0(void)
+{
+
+       return HYPERVISOR_get_debugreg(0);
+}
+
+void
+ldr0(vaddr_t val)
+{
+
+       HYPERVISOR_set_debugreg(0, val);
+}
+
+vaddr_t
+rdr1(void)
+{
+
+       return HYPERVISOR_get_debugreg(1);
+}
+
+void
+ldr1(vaddr_t val)
+{
+
+       HYPERVISOR_set_debugreg(1, val);
+}
+
+vaddr_t
+rdr2(void)
+{
+
+       return HYPERVISOR_get_debugreg(2);
+}
+
+void
+ldr2(vaddr_t val)
+{
+
+       HYPERVISOR_set_debugreg(2, val);
+}
+
+vaddr_t
+rdr3(void)
+{
+
+       return HYPERVISOR_get_debugreg(3);
+}
+
+void
+ldr3(vaddr_t val)
+{