arm: remote GDB: rationalize structure of register offsets

Currently, the wire format of register values in g- and G-packets is
modelled using a union of uint8/16/32/64 arrays.  The offset positions
of each register are expressed as a "register count" scaled according
to the width of the register in question.  This results in counter-
intuitive and error-prone "register count arithmetic", and some
formats would even be altogether unrepresentable in such model, e.g.
a 64-bit register following a 32-bit one would have a fractional index
in the regs64 array.
Another difficulty is that the array is allocated before the actual
architecture of the workload is known (and therefore before the correct
size for the array can be calculated).

With this patch I propose a simpler mechanism for expressing the
register set structure.  In the new code, GdbRegCache is an abstract
class; its subclasses contain straightforward structs reflecting the
register representation.  The determination whether to use e.g. the
AArch32 vs. AArch64 register set (or SPARCv8 vs SPARCv9, etc.) is made
by polymorphically dispatching getregs() to the concrete subclass.
The subclass is not instantiated until it is needed for actual
g-/G-packet processing, when the mode is already known.

This patch is not meant to be merged in on its own, because it changes
the contract between src/base/remote_gdb.* and src/arch/*/remote_gdb.*,
so as it stands right now, it would break the other architectures.
In this patch only the base and the ARM code are provided for review;
once we agree on the structure, I will provide src/arch/*/remote_gdb.*
for the other architectures; those patches could then be merged in
together.

Review Request: http://reviews.gem5.org/r/3207/
Pushed by Joel Hestness <jthestness@gmail.com>

3 files changed, 49 insertions, 197 deletions

diff --git a/src/arch/alpha/kgdb.h b/src/arch/alpha/kgdb.h
deleted file mode 100644
index 0883dc02f..000000000
--- a/src/arch/alpha/kgdb.h
+++ /dev/null
@@ -1,163 +0,0 @@
-/*
- * Copyright (c) 1992, 1993 The Regents of the University of California
- * All rights reserved.
- *
- * This software was developed by the Computer Systems Engineering group
- * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
- * contributed to Berkeley.
- *
- * All advertising materials mentioning features or use of this software
- * must display the following acknowledgement:
- *	This product includes software developed by the University of
- *	California, Lawrence Berkeley Laboratories.
- *
- * 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.
- * 3. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *	This product includes software developed by the University of
- *	California, Berkeley and its contributors.
- * 4. Neither the name of the University nor the names of its contributors
- *    may be used to endorse or promote products derived from this software
- *    without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
- *
- *	@(#)remote-sl.h	8.1 (Berkeley) 6/11/93
- */
-
-/*	$NetBSD: kgdb.h,v 1.4 1998/08/13 02:10:59 eeh Exp $	*/
-
-#ifndef __KGDB_H__
-#define __KGDB_H__
-
-/*
- * Message types.
- */
-#define KGDB_SIGNAL		'?'	// last sigal
-#define KGDB_SET_BAUD		'b'	// set baud (deprecated)
-#define KGDB_SET_BREAK		'B'	// set breakpoint (deprecated)
-#define KGDB_CONT		'c'	// resume
-#define KGDB_ASYNC_CONT		'C'	// continue with signal
-#define KGDB_DEBUG		'd'	// toggle debug flags (deprecated)
-#define KGDB_DETACH		'D'	// detach remote gdb
-#define KGDB_REG_R		'g'	// read general registers
-#define KGDB_REG_W		'G'	// write general registers
-#define KGDB_SET_THREAD		'H'	// set thread
-#define KGDB_CYCLE_STEP		'i'	// step a single cycle
-#define KGDB_SIG_CYCLE_STEP	'I'	// signal then single cycle step
-#define KGDB_KILL		'k'	// kill program
-#define KGDB_MEM_R		'm'	// read memory
-#define KGDB_MEM_W		'M'	// write memory
-#define KGDB_READ_REG		'p'	// read register
-#define KGDB_SET_REG		'P'	// write register
-#define KGDB_QUERY_VAR		'q'	// query variable
-#define KGDB_SET_VAR		'Q'	// set variable
-#define KGDB_RESET		'r'	// reset system.  (Deprecated)
-#define KGDB_STEP		's'	// step
-#define KGDB_ASYNC_STEP		'S'	// signal and step
-#define KGDB_THREAD_ALIVE	'T'	// find out if the thread is alive.
-#define KGDB_TARGET_EXIT	'W'	// target exited
-#define KGDB_BINARY_DLOAD	'X'	// write memory
-#define KGDB_CLR_HW_BKPT	'z'	// remove breakpoint or watchpoint
-#define KGDB_SET_HW_BKPT	'Z'	// insert breakpoint or watchpoint
-
-/*
- * start of frame/end of frame
- */
-#define KGDB_START	'$'
-#define KGDB_END	'#'
-#define KGDB_GOODP	'+'
-#define KGDB_BADP	'-'
-
-/*
- * Stuff for KGDB.
- */
-#define	KGDB_NUMREGS	66	/* from tm-alpha.h, NUM_REGS */
-#define	KGDB_REG_V0	0
-#define	KGDB_REG_T0	1
-#define	KGDB_REG_T1	2
-#define	KGDB_REG_T2	3
-#define	KGDB_REG_T3	4
-#define	KGDB_REG_T4	5
-#define	KGDB_REG_T5	6
-#define	KGDB_REG_T6	7
-#define	KGDB_REG_T7	8
-#define	KGDB_REG_S0	9
-#define	KGDB_REG_S1	10
-#define	KGDB_REG_S2	11
-#define	KGDB_REG_S3	12
-#define	KGDB_REG_S4	13
-#define	KGDB_REG_S5	14
-#define	KGDB_REG_S6	15	/* FP */
-#define	KGDB_REG_A0	16
-#define	KGDB_REG_A1	17
-#define	KGDB_REG_A2	18
-#define	KGDB_REG_A3	19
-#define	KGDB_REG_A4	20
-#define	KGDB_REG_A5	21
-#define	KGDB_REG_T8	22
-#define	KGDB_REG_T9	23
-#define	KGDB_REG_T10	24
-#define	KGDB_REG_T11	25
-#define	KGDB_REG_RA	26
-#define	KGDB_REG_T12	27
-#define	KGDB_REG_AT	28
-#define	KGDB_REG_GP	29
-#define	KGDB_REG_SP	30
-#define	KGDB_REG_ZERO	31
-#define	KGDB_REG_F0	32
-#define	KGDB_REG_F1	33
-#define	KGDB_REG_F2	34
-#define	KGDB_REG_F3	35
-#define	KGDB_REG_F4	36
-#define	KGDB_REG_F5	37
-#define	KGDB_REG_F6	38
-#define	KGDB_REG_F7	39
-#define	KGDB_REG_F8	40
-#define	KGDB_REG_F9	41
-#define	KGDB_REG_F10	42
-#define	KGDB_REG_F11	43
-#define	KGDB_REG_F12	44
-#define	KGDB_REG_F13	45
-#define	KGDB_REG_F14	46
-#define	KGDB_REG_F15	47
-#define	KGDB_REG_F16	48
-#define	KGDB_REG_F17	49
-#define	KGDB_REG_F18	50
-#define	KGDB_REG_F19	51
-#define	KGDB_REG_F20	52
-#define	KGDB_REG_F21	53
-#define	KGDB_REG_F22	54
-#define	KGDB_REG_F23	55
-#define	KGDB_REG_F24	56
-#define	KGDB_REG_F25	57
-#define	KGDB_REG_F26	58
-#define	KGDB_REG_F27	59
-#define	KGDB_REG_F28	60
-#define	KGDB_REG_F29	61
-#define	KGDB_REG_F30	62
-#define	KGDB_REG_F31	63
-#define	KGDB_REG_PC	64
-#define	KGDB_REG_VFP	65
-
-/* Too much?  Must be large enough for register transfer. */
-#define	KGDB_BUFLEN	1024
-
-#endif /* __KGDB_H__ */
diff --git a/src/arch/alpha/remote_gdb.cc b/src/arch/alpha/remote_gdb.cc
index a3fcf6136..f32d49e97 100644
--- a/src/arch/alpha/remote_gdb.cc
+++ b/src/arch/alpha/remote_gdb.cc
@@ -124,7 +124,6 @@
 
 
 #include "arch/alpha/decoder.hh"
-#include "arch/alpha/kgdb.h"
 #include "arch/alpha/regredir.hh"
 #include "arch/alpha/remote_gdb.hh"
 #include "arch/alpha/utility.hh"
@@ -146,9 +145,8 @@ using namespace std;
 using namespace AlphaISA;
 
 RemoteGDB::RemoteGDB(System *_system, ThreadContext *tc)
-    : BaseRemoteGDB(_system, tc, KGDB_NUMREGS * sizeof(uint64_t))
+    : BaseRemoteGDB(_system, tc)
 {
-    memset(gdbregs.regs, 0, gdbregs.bytes());
 }
 
 /*
@@ -203,47 +201,41 @@ RemoteGDB::acc(Addr va, size_t len)
     return true;
 }
 
-/*
- * Translate the kernel debugger register format into the GDB register
- * format.
- */
 void
-RemoteGDB::getregs()
+RemoteGDB::AlphaGdbRegCache::getRegs(ThreadContext *context)
 {
-    memset(gdbregs.regs, 0, gdbregs.bytes());
+    DPRINTF(GDBAcc, "getRegs in remotegdb \n");
 
-    gdbregs.regs64[KGDB_REG_PC] = context->pcState().pc();
+    r.pc = context->pcState().pc();
 
-    // @todo: Currently this is very Alpha specific.
-    if (PcPAL(gdbregs.regs64[KGDB_REG_PC])) {
-        for (int i = 0; i < NumIntArchRegs; ++i)
-            gdbregs.regs64[i] = context->readIntReg(reg_redir[i]);
+    if (PcPAL(r.pc)) {
+        for (int i = 0; i < 32; ++i)
+            r.gpr[i] = context->readIntReg(reg_redir[i]);
     } else {
-        for (int i = 0; i < NumIntArchRegs; ++i)
-            gdbregs.regs64[i] = context->readIntReg(i);
+        for (int i = 0; i < 32; ++i)
+            r.gpr[i] = context->readIntReg(i);
     }
 
+    for (int i = 0; i < 32; ++i)
 #ifdef KGDB_FP_REGS
-    for (int i = 0; i < NumFloatArchRegs; ++i)
-        gdbregs.regs64[i + KGDB_REG_F0] = context->readFloatRegBits(i);
+       r.fpr[i] = context->readFloatRegBits(i);
+#else
+       r.fpr[i] = 0;
 #endif
 }
 
-/*
- * Translate the GDB register format into the kernel debugger register
- * format.
- */
 void
-RemoteGDB::setregs()
+RemoteGDB::AlphaGdbRegCache::setRegs(ThreadContext *context) const
 {
-    // @todo: Currently this is very Alpha specific.
-    if (PcPAL(gdbregs.regs64[KGDB_REG_PC])) {
-        for (int i = 0; i < NumIntArchRegs; ++i) {
-            context->setIntReg(reg_redir[i], gdbregs.regs64[i]);
+    DPRINTF(GDBAcc, "setRegs in remotegdb \n");
+
+    if (PcPAL(r.pc)) {
+        for (int i = 0; i < 32; ++i) {
+            context->setIntReg(reg_redir[i], r.gpr[i]);
         }
     } else {
-        for (int i = 0; i < NumIntArchRegs; ++i) {
-            context->setIntReg(i, gdbregs.regs64[i]);
+        for (int i = 0; i < 32; ++i) {
+            context->setIntReg(i, r.gpr[i]);
         }
     }
 
@@ -252,7 +244,7 @@ RemoteGDB::setregs()
         context->setFloatRegBits(i, gdbregs.regs64[i + KGDB_REG_F0]);
     }
 #endif
-    context->pcState(gdbregs.regs64[KGDB_REG_PC]);
+    context->pcState(r.pc);
 }
 
 // Write bytes to kernel address space for debugger.
@@ -277,3 +269,9 @@ RemoteGDB::insertHardBreak(Addr addr, size_t len)
               "      See PCEventQueue::doService() in cpu/pc_event.cc.\n");
     return BaseRemoteGDB::insertHardBreak(addr, len);
 }
+
+RemoteGDB::BaseGdbRegCache*
+RemoteGDB::gdbRegs() {
+            return new AlphaGdbRegCache(this);
+}
+
diff --git a/src/arch/alpha/remote_gdb.hh b/src/arch/alpha/remote_gdb.hh
index 33994653d..4b71fd23a 100644
--- a/src/arch/alpha/remote_gdb.hh
+++ b/src/arch/alpha/remote_gdb.hh
@@ -1,4 +1,5 @@
 /*
+ * Copyright (c) 2015 LabWare
  * Copyright (c) 2002-2005 The Regents of The University of Michigan
  * All rights reserved.
  *
@@ -26,6 +27,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * Authors: Nathan Binkert
+ *          Boris Shingarov
  */
 
 #ifndef __ARCH_ALPHA_REMOTE_GDB_HH__
@@ -33,7 +35,6 @@
 
 #include <map>
 
-#include "arch/alpha/kgdb.h"
 #include "arch/alpha/types.hh"
 #include "base/pollevent.hh"
 #include "base/remote_gdb.hh"
@@ -48,17 +49,33 @@ namespace AlphaISA {
 class RemoteGDB : public BaseRemoteGDB
 {
   protected:
-    void getregs();
-    void setregs();
-
     // Machine memory
     bool acc(Addr addr, size_t len);
     bool write(Addr addr, size_t size, const char *data);
 
     bool insertHardBreak(Addr addr, size_t len);
 
+    class AlphaGdbRegCache : public BaseGdbRegCache
+    {
+      using BaseGdbRegCache::BaseGdbRegCache;
+      private:
+        struct {
+            uint64_t gpr[32];
+            uint64_t fpr[32];
+            uint64_t pc;
+            uint64_t vfp;
+        } r;
+      public:
+        char *data() const { return (char *)&r; }
+        size_t size() const { return sizeof(r); }
+        void getRegs(ThreadContext*);
+        void setRegs(ThreadContext*) const;
+        const std::string name() const { return gdb->name() + ".AlphaGdbRegCache"; }
+    };
+
   public:
     RemoteGDB(System *system, ThreadContext *context);
+    BaseGdbRegCache *gdbRegs();
 };
 
 } // namespace AlphaISA