2016年2月20日 星期六

Build Bochs with Debugger, smp, x86_x64 enable

Bochs is a pure software emulator for X86 CPU. It is slower than others like QEMU or VirtualBox which use hardware virtualization.

However Bochs is good for fully debug in OS kernel development without expansive hardware tracer.

Bochs come with prebuilt execution file. But the exe that support long mode didn't support debugger. The debugger enable one didn't support long mode. If you want to play with long mode and SMP and debugger. You need to build a Bochs yourself.

refer Bochs building instruction
http://bochs.sourceforge.net/doc/docbook/user/compiling.html

0. download latest Bochs source code
1. download MingGW and setup it.
2. select msys-base, mingw32-gcc-g++, mingw32-base, mingw-developer-toolkit
3. modify /etc/fstab to mount your bochs source code
4. run msys
5. decompress Bochs source code tgz
6. run ./configure with these Options
 --with-win32 \
 --enable-smp \
 --enable-vmx \
 --enable-avx \
 --enable-x86-debugger \
 --enable-debugger \
 --enable-debugger-gui \
 --enable-x86-64 \
 --enable-configurable-msrs \
--enable-all-optimizations \
--enable-long-phy-address \
 --enable-pci \
  --enable-clgd54xx \
  --enable-voodoo \ 
  --enable-sb16
 --enable-es1370 \
  --enable-usb \
  --enable-usb-ohci \
  --enable-usb-xhci \
 
below copy from http://wiki.osdev.org/Bochs

I/O debugger macros

Some useful macros when Bochs is compiled with the I/O debug ports enabled (port_e9_hack: enabled=1 if Bochs 2.4 or newer, configure --port-e9-hack if not):

Magic Breakpoint

When you're using Bochs with the internal debugger, you can trigger the debugger via a facility called magic breakpoints. To trigger a breakpoint, you can insert xchg bx, bx (in GAS syntax, xchgw %bx, %bx) anywhere in the code and Bochs will trap into the debugger as soon as it executes it. On real hardware this has no effect as it merely replaces the BX register with itself.
You should put the following line in your Bochs configuration file to have it listen to magic breakpoints:
magic_break: enabled=1

Debugging SMP

When using the internal debugger, you may use the following command to switch CPUs:
 set $cpu = n
 

Internal debugger commands

You can pass a file containing debug commands to automatically run whenever you start bochs with the internal debugger. (bochs -rc )
Bochs places an automatic breakpoint just before the BIOS loads, this can be automatically skipped by putting continue as the first command in the said file.

Debugging Triple Faults

When using the internal debugger, you may change this line in your Bochs configuration file:
reset_on_triple_fault 0
 
This line disables the emulator reset on a Triple fault, enabling you to debug the code after a Triple fault occured (Very useful while implementing paging). 

 
 refer
 
http://bochs.sourceforge.net/doc/docbook/user/bochsrc.html

Below copy from Bochs developer manual

3.1. I/O Interface to Bochs Debugger

This device was added by Dave Poirier (eks@void-core.2y.net).
Compiling Bochs with iodebug support
./configure --enable-iodebug
make
Other optional fields may be added to the ./configure line, see Bochs documentation for all the information. To enable the iodebug plugin at runtime, it must be loaded with the 'plugin_ctrl' bochsrc option.
Using the I/O Interface to the debugger

port range:  0x8A00 - 0x8A01

Port 0x8A00 servers as command register. You can use it to enable the i/o interface,
change which data register is active, etc.

Port 0x8A01 is used as data register for the memory monitoring.

3.1.1. Commands supported by port 0x8A00

0x8A00

 Used to enable the device. Any I/O to the debug module before this command is sent
 is sent will simply be ignored.


0x8A01

 Selects register 0: Memory monitoring range start address (inclusive)


0x8A02

 Selects register 1: Memory monitoring range end address (exclusive)


0x8A80

 Enable address range memory monitoring as indicated by register 0 and 1 and
 clears both registers


0x8AE0 - Return to Debugger Prompt

 If the debugger is enabled (via --enable-debugger), sending 0x8AE0 to port 0x8A00
 after the device has been enabled will return the Bochs to the debugger prompt.
 Basically the same as doing CTRL+C.


0x8AE2 - Instruction Trace Disable

 If the debugger is enabled (via --enable-debugger), sending 0x8AE2 to port 0x8A00
 after the device has been enabled will disable instruction tracing


0x8AE3 - Instruction Trace Enable

 If the debugger is enabled (via --enable-debugger), sending 0x8AE3 to port 0x8A00
 after the device has been enabled will enable instruction tracing


0x8AE4 - Register Trace Disable

 If the debugger is enabled (via --enable-debugger), sending 0x8AE4 to port 0x8A00
 after the device has been enabled will disable register tracing.


0x8AE5 - Register Trace Enable

 If the debugger is enabled (via --enable-debugger), sending 0x8AE5 to port 0x8A00
 after the device has been enabled will enable register tracing. This currently
 output the value of all the registers for each instruction traced.
 Note: instruction tracing must be enabled to view the register tracing


0x8AFF

 Disable the I/O interface to the debugger and the memory monitoring functions.
Note: all accesses must be done using word
Note: reading this register will return 0x8A00 if currently activated, otherwise 0

3.1.2. Access to port 0x8A01 (write-only)

All accesses to this port must be done using words. Writing to this port will shift to the left by 16 the current value of the register and add the provided value to it.
Sample:

reg0 = 0x01234567

out port: 0x8A01 data: 0xABCD

reg0 = 0x4567ABCD

3.1.3. Sample

Enable memory monitoring on first page of text screen (0xb8000-0xb8fa0): add in bochrc file: optromimage1: file="asmio.rom", address=0xd0000
/*
 *      Make asmio ROM file:
 *      gcc -c asmio.S
 *      objcopy -O binary asmio.o asmio.rom
 */
        .text
        .global start
        .code16

/* ROM Header */
        .byte 0x55
        .byte 0xAA
        .byte 1                 /* 512 bytes long */

start:
/* Monitor memory access on first page of text screen */
        mov     $0x8A00,%dx     /* Enable iodebug (0x8A00->0x8A00) */
        mov     %dx,%ax
        out     %ax,%dx
        mov     $0x8A01,%ax     /* Select register 0 start addr (0x8A01->0x8A00) */
        out     %ax,%dx
        mov     $0x8A01,%dx     /* Write start addr 0xB8000 (high word first) */
        mov     $0xB,%ax
        out     %ax,%dx
        mov     $0x8000,%ax     /* Write start addr (low word) */
        out     %ax,%dx

        mov     $0x8A02,%ax     /* Select register 1 end addr (0x8A02->0x8A00) */
        mov     $0x8A00,%dx
        out     %ax,%dx
        mov     $0x8A01,%dx     /* Write end addr 0xB8FA0 (high word first) */
        mov     $0xB,%ax
        out     %ax,%dx
        mov     $0x8FA0,%ax     /* Write end addr (low word) */
        out     %ax,%dx

        mov     $0x8A00,%dx     /* Enable addr range memory monitoring (0x8A80->0x8A00) */
        mov     $0x8A80,%ax
        out     %ax,%dx

        mov     $0x8A00,%dx     /* Return to Bochs Debugger Prompt (0x8AE0->0x8A00) */
        mov     $0x8AE0,%ax
        out     %ax,%dx
        lret

        .byte 0x6b              /* Checksum (code dependent!, update it as needed) */
        .align 512              /* NOP follow */

8.13. Using Bochs internal debugger

You can now conditionally compile in a GDB like command line debugger, that allows you to set breakpoints, step through instructions, and other useful functions. If there isn't a command for something you believe is generally useful for the debugger, let me know and I'll implement it if possible.
Note: This section describes how to enable and use the Bochs command line debugger. For it's builtin graphical front-end please see the debugger gui section how to enable it.
To use the debugger, you must configure Bochs with the --enable-debugger and --enable-disasm flags. For example:
  ./configure --enable-debugger --enable-disasm
Note: You must use flex version 2.5.4 or greater. I have heard that version 2.5.2 will not work.
When you first start up Bochs, you will see the command line prompt
  bochs:1>
From here, you may use the following commands:

8.13.1. Execution Control

  c                           continue executing
  cont
  continue

  s     [count]               execute count instructions, default is 1
  step  [count]

  s     [cpu] [count]         for SMP simulation, execute count instructions on cpu, default is 1
  step  [cpu] [count]

  s     all [count]           for SMP simulation, execute count instructions on all cpus
  step  all [count]

  Ctrl-C                      stop execution, and return to command line prompt
  Ctrl-D                      if at empty line on command line, exit

  q                           quit debugger and execution
  quit
  exit

8.13.2. BreakPoints

  NOTE: The format of 'seg', 'off', and 'addr' in these descriptions,
        are as follows.  I don't have any way to set the current radix.

        hexidecimal:    0xcdef0123
        decimal:        123456789
        octal:          01234567

  vbreak seg:off              Set a virtual address instruction breakpoint
  vb     seg:off

  lbreak addr                 Set a linear address instruction breakpoint
  lb     addr

  pbreak [*] addr             Set a physical address instruction breakpoint
  pb     [*] addr             (the '*' is optional for GDB compatibility)
  break  [*] addr
  b      [*] addr

  info break                  Display state of all current breakpoints
  bpe    n                    Enable a breakpoint
  bpd    n                    Disable a breakpoint
  delete n                    Delete a breakpoint
  del    n
  d      n

8.13.3. Memory WatchPoints

  watch read  addr            Insert a read watch point at physical address addr
  watch r     addr            Insert a read watch point at physical address addr

  watch write addr            Insert a write watch point at physical address addr
  watch w     addr            Insert a write watch point at physical address addr

  watch                       Display state of current memory watchpoints

  watch stop                  Stop simulation when a watchpoint is encountered (default)
  watch continue              Do not stop simulation when a watchpoint is encountered

  unwatch addr                Remove watchpoint to specific physical address
  unwatch                     Remove all watch points

  trace-mem on/off            Enable/Disable memory access tracing

8.13.4. Manipulating Memory

  x  /nuf addr      Examine memory at linear address addr
  xp /nuf addr      Examine memory at physical address addr
     n              Count of how many units to display
     u              Unit size; one of
                      b Individual bytes
                      h Halfwords (2 bytes)
                      w Words (4 bytes)
                      g Giant words (8 bytes)
                      NOTE: these are *not* typical Intel nomenclature sizes,
                            but they are consistent with GDB convention.
     f              Printing format.  one of
                      x Print in hexadecimal
                      d Print in decimal
                      u Print in unsigned decimal
                      o Print in octal
                      t Print in binary

    n, f, and u are optional parameters.  u and f default to the last values
    you used, or to w(words) and x(hex) if none have been supplied.
    n currently defaults to 1.  If none of these optional parameters are
    used, no slash should be typed.  addr is also optional.  If you don't
    specify it, it will be the value the next address (as if you had
    specified n+1 in the last x command).

  setpmem addr datasize val    Set physical memory location of size
                               datasize to value val.

  writemem                     dump a number of bytes of virtual memory starting from
                               the specified linear address into a file

  crc  addr1  addr2            Show CRC32 for physical memory range addr1..addr2

8.13.5. Info commands

  r|reg|regs|registers         List of CPU integer registers and their contents
  fp|fpu                       List of all FPU registers and their contents
  mmx                          List of all MMX registers and their contents
  sse|xmm                      List of all SSE registers and their contents
  ymm                          List of all AVX registers and their contents
  sreg                         Show segment registers and their contents
  dreg                         Show debug registers and their contents
  creg                         Show control registers and their contents

  info cpu                     List of all CPU registers and their contents
  info eflags                  Show decoded EFLAGS register
  info break                   Information about current breakpoint status
  info tab                     Show paging address translation
  info device                  Show state of the specified device

8.13.6. Manipulating CPU Registers

  set reg = expr    Change a CPU register to value of expression.
                    Currently only general purpose registers and instruction pointer
                    are supported. You may not change eflags, segment registers,
                    floating point or SIMD registers.

    Examples: set eax = 2+2/2
              set esi = 2*eax+ebx

  registers         List of CPU registers and their contents
  regs
  reg
  r

8.13.7. Disassembly commands

  disassemble start end       Disassemble instructions in given linear address
                              range, inclusive of start, exclusive of end.
                              Use "set $disassemble_size =" to tell
                              debugger desired segment size.  Use a value for
                              end of less than start (or zero) if you only
                              want the first instruction disassembled.

  disassemble switch-mode     Switch between Intel and AT&T disassebly styles
                              for debugger disassembler.

  disassemble size = n        Tell debugger what segment size to use when
                              the "disassemble" command is used.  Use values
                              of 0, 16 or 32 for n.  Value of 0 means
         "use segment size specified by current CS
         segment". Default is 0.

  set $auto_disassemble = n   Cause debugger to disassemble current instruction
                              every time execution stops if n=1.  Default is 0.
                              Segment size of current CPU context is used for
                              disassembly, so the "disassemble size" variable is
                              ignored.

  set disassemble on          The same as 'set $auto_disassemble = 1'
  set disassemble off         The same as 'set $auto_disassemble = 0'

8.13.8. Instruction tracing

  trace on                    Disassemble every executed instruction. Note
                              that instructions which caused exceptions are
                              not really executed, and therefore not traced.

  trace off                   Disable instruction tracing.

8.13.9. Instrumentation

To use instrumentation features in bochs, you must compile in support for it. You should build a custom instrumentation library in a separate directory in the "instrument/" directory. To tell configure which instrumentation library you want to use, use the --enable-instrumentation option. The default library consists of a set of stubs, and the following are equivalent:
  ./configure [...] --enable-instrumentation
  ./configure [...] --enable-instrumentation="instrument/stubs"
You could make a separate directory with your custom library, for example "instrument/myinstrument", copy the contents of the "instrument/stubs" directory to it, then customize it. Use:
  ./configure [...] --enable-instrumentation="instrument/myinstrument"

8.13.10. Instrumentation commands

  instrument [command]        calls BX_INSTR_DEBUG_CMD instrumentation callback with [command]

8.13.11. Other Commands

ptime
Print the current time (number of ticks since start of simulation).
sb delta
Insert a time break point "delta" instructions into the future ("delta" is a 64-bit integer followed by "L", for example 1000L).
sba time
Insert a time break point at "time" ("time" is a 64-bit integer followed by "L", for example 1000L).
print-stack [num words]
Print the num words top 16-bit words on the stack. Num words defaults to 16. Only works reliably in protected mode when the base address of the stack segment is zero.
modebp
Toggles CPU mode switch breakpoint.
ldsym [global] filename [offset]
Load symbols from file filename. If the global keyword is added, then the the symbols will be visible in all contexts for which symbols have not been loaded. Offset (default is 0) is added to every symbol entry. The symbols are loaded in the current (executing) context.The symbol file consists of zero or more lines of the format
"%x %s"
.
show [string]
  Toggles show symbolic info (calls to begin with).
  show - shows current show mode
  show mode     - show, when processor switch mode
  show int      - show, when interrupt is happens
  show call     - show, when call is happens
  show ret      - show, when iret is happens
  show off      - toggles off symbolic info
  show dbg-all  - turn on all show flags
  show dbg-none - turn off all show flags

8.13.12. The Bochs debugger gui

The graphical front-end for the Bochs command line debugger is available for Windows and GTK2 hosts.
To use the gui debugger, you must configure Bochs with the default debugger switches and the --enable-debugger-gui flag. For example:
  ./configure --enable-debugger --enable-disasm --enable-debugger-gui
At runtime you need to add the value gui_debug to the display_library options parameter in order to use the gui instead of the command line debugger. This example shows how to use it with the 'x' gui:
display_library: x, options="gui_debug"
The gui debugger consists of a gui window with a menu bar, a button bar and some child windows that show the cpu registers, disassembler output, memory dump and the internal debugger output. A command prompt for entering debugger commands is also available.
 List the features here.
Most of the gui debugger settings are now saved to an INI file on exit and restored at the next run.

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