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498 lines
12 KiB
498 lines
12 KiB
3 years ago
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<HTML
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><HEAD
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><TITLE
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>Emulator Objects</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
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REL="HOME"
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TITLE="Bochs Developers Guide"
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HREF="index.html"><LINK
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REL="UP"
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TITLE="About the code"
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HREF="about-the-code.html"><LINK
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REL="PREVIOUS"
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TITLE="Directory Structure"
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HREF="directory-structure.html"><LINK
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REL="NEXT"
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TITLE="Configure Scripting"
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HREF="configure-scripting.html"></HEAD
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><BODY
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CLASS="SECTION"
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#840084"
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ALINK="#0000FF"
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><DIV
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CLASS="NAVHEADER"
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><TABLE
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SUMMARY="Header navigation table"
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>Bochs Developers Guide</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="directory-structure.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 2. About the code</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="configure-scripting.html"
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ACCESSKEY="N"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="SECTION"
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><H1
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CLASS="SECTION"
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><A
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NAME="EMULATOR-OBJECTS"
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>2.3. Emulator Objects</A
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></H1
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><DIV
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CLASS="SECTION"
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><H2
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CLASS="SECTION"
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><A
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NAME="AEN175"
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>2.3.1. Weird macros and other mysteries</A
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></H2
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><P
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>Bochs has many macros with inscrutable names. One might even go as far as to
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say that Bochs is macro infested.
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Some of them are gross speed hacks, to cover up the slow speed that C++ causes.
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Others paper over differences between the simulated PC configurations.
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Many of the macros exhibit the same problem as C++ does: too much stuff happens
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behind the programmer's back. More explicitness would be a big win.</P
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></DIV
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><DIV
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CLASS="SECTION"
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><H2
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CLASS="SECTION"
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><A
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NAME="STATIC-METHODS-HACK"
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>2.3.2. Static methods hack</A
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></H2
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><P
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>C++ methods have an invisible parameter called the this pointer - otherwise the
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method wouldn't know which object to operate on. In many cases in Bochs, there
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will only ever be one object - so this flexibility is unnecessary. There is a
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hack that can be enabled by #defining BX_USE_CPU_SMF to 1 in <TT
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CLASS="FILENAME"
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>config.h</TT
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> that makes most methods static, which means they have a "special
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relationship" with the class they are declared in but apart from that are
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normal C functions with no hidden parameters. Of course they still need access
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to the internals of an object, so the single object of their class has a globally
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visible name that these functions use. It is all hidden with macros.</P
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><P
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>Declaration of a class, from iodev/pic.h:</P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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>...
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#if BX_USE_PIC_SMF
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# define BX_PIC_SMF static
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# define BX_PIC_THIS thePic->
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#else
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# define BX_PIC_SMF
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# define BX_PIC_THIS this->
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#endif
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...
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class bx_pic_c : public bx_pic_stub_c {
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public:
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bx_pic_c(void);
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~bx_pic_c(void);
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...
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BX_PIC_SMF void service_master_pic(void);
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BX_PIC_SMF void service_slave_pic(void);
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BX_PIC_SMF void clear_highest_interrupt(bx_pic_t *pic);
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};</PRE
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></TD
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></TR
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></TABLE
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><P
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>And iodev/pic.cc:</P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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>...
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#define LOG_THIS thePic->
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...
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bx_pic_c *thePic = NULL;
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...
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void
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bx_pic_c::service_master_pic(void)
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{
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Bit8u unmasked_requests;
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int irq;
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Bit8u isr, max_irq;
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Bit8u highest_priority = BX_PIC_THIS s.master_pic.lowest_priority + 1;
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if(highest_priority > 7)
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highest_priority = 0;
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if (BX_PIC_THIS s.master_pic.INT) { /* last interrupt still not acknowleged */
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return;
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}
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if (BX_PIC_THIS s.master_pic.special_mask) {
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/* all priorities may be enabled. check all IRR bits except ones
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* which have corresponding ISR bits set
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*/
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max_irq = highest_priority;
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}
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else { /* normal mode */
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/* Find the highest priority IRQ that is enabled due to current ISR */
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isr = BX_PIC_THIS s.master_pic.isr;
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...
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}
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...</PRE
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></TD
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></TR
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></TABLE
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><P
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>Ugly, isn't it? If we use static methods, methods prefixed with BX_PIC_SMF are
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declared static and references to fields inside the object, which are prefixed
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with BX_PIC_THIS, will use the globally visible object, thePic->. If we don't
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use static methods, BX_PIC_SMF evaluates to nothing and BX_PIC_THIS becomes this->.
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Making it evaluate to nothing would be a lot cleaner, but then the scoping rules
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would change slightly between the two Bochs configurations, which would be a load
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of bugs just waiting to happen. Some classes use BX_SMF, others have their own
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version of the macro, like BX_PIC_SMF above.</P
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></DIV
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><DIV
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CLASS="SECTION"
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><H2
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CLASS="SECTION"
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><A
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NAME="CPU-MEM-OBJECTS"
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>2.3.3. CPU und memory objects in UP/SMP configurations</A
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></H2
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><P
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>The CPU class is a special case of the above: if Bochs is simulating a uni-
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processor machine then there is obviously only one bx_cpu_c object and the
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static methods trick can be used. If, on the other hand, Bochs is simulating an
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smp machine then we can't use the trick. The same seems to be true for memory:
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for some reason, we have a memory object for each CPU object. This might become
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relevant for NUMA machines, but they are not all that common -- and even the
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existing IA-32 NUMA machines bend over backwards to hide that fact: it should
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only be visible in slightly worse timing for non-local memory and non-local
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peripherals. Other than that, the memory map and device map presented to each
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CPU will be identical.</P
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><P
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>In a UP configuration, the CPU object is declared as bx_cpu. In an SMP
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configuration it will be an array of pointers to CPU objects (bx_cpu_array[]).
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For memory that would be bx_mem and bx_mem_array[], respectively.
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Each CPU object contains a pointer to its associated memory object.
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Access of a CPU object often goes through the BX_CPU(x) macro, which either
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ignores the parameter and evaluates to &bx_cpu, or evaluates to bx_cpu_array
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[n], so the result will always be a pointer. The same goes for BX_MEM(x).
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If static methods are used then BX_CPU_THIS_PTR evaluates to BX_CPU(0)->. Ugly,
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isn't it?</P
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></DIV
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><DIV
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CLASS="SECTION"
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><H2
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CLASS="SECTION"
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><A
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NAME="CONFIG-PARAMETER-TREE"
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>2.3.4. The configuration parameter tree</A
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></H2
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><P
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>Starting with version 1.3, the Bochs configuration parameters are stored in parameter
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objects. These objects have get/set methods with min/max checks and it is possible
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to define parameter handlers to perform side effects and to override settings.
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Each parameter type has it's own object type with specific features (numeric,
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boolean, enum, string and file name). A special object type containing a list of
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parameters is designed for building and managing configuration menus or dialogs
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automatically. In the original implementation the parameters could be accessed
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only with their unique id from a static list or a special structure containing
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pointers to all parameters.</P
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><P
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>Starting with version 2.3, the Bochs parameter object handling has been rewritten
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to a parameter tree. There is now a root list containing child lists, and these
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lists can contain lists or parameters and so on. The parameters are now accessed
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by a name build from all the list names in the path and finally the parameter
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name separated by periods.
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<TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="SCREEN"
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>Bit32u megs = SIM->get_param_num("memory.standard.ram.size")->get();</PRE
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></TD
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></TR
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></TABLE
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></P
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><P
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>The example above shows how to get the memory size in megabytes from the simulator
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interface. In the root list (".") there is child list named "memory" containing
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a child list "standard". It's child list "ram" contains the numeric parameter type
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"size". The SIM->get_param_num() methods returns the object pointer and the get()
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method returns the parameter value.</P
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><P
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>The table below shows all parameter types used by the Bochs configuration interface.
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<DIV
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CLASS="TABLE"
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><A
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NAME="AEN198"
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></A
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><P
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><B
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>Table 2-2. Parameter types</B
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></P
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><TABLE
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BORDER="1"
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CLASS="CALSTABLE"
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><COL><COL><THEAD
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><TR
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><TH
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>Type</TH
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><TH
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>Description</TH
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></TR
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></THEAD
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><TBODY
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><TR
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><TD
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>bx_object_c</TD
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><TD
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>Base class for all the other parameter types. It contains the unique parameter id and the object type value.</TD
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></TR
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><TR
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><TD
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>bx_param_c</TD
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><TD
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>Generic parameter class. It contains the name, label, description and the input/output formats.</TD
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></TR
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><TR
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><TD
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>bx_param_num_c</TD
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><TD
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>Numerical (decimal/hex) config settings are stored in this parameter type.</TD
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></TR
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><TR
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><TD
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>bx_param_bool_c</TD
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><TD
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>This parameter type is based on bx_param_num_c, but it is designed for boolean values. A dependency
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list can be defined to enable/disable other parameters depending on the value change.</TD
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></TR
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><TR
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><TD
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>bx_param_enum_c</TD
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><TD
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>Based on bx_param_num_c this parameter type contains a list of valid values.</TD
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></TR
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><TR
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><TD
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>bx_param_string_c</TD
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><TD
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>Configuration strings are stored in this type of parameter.</TD
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></TR
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><TR
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><TD
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>bx_param_filename_c</TD
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><TD
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>Based on bx_param_string_c this parameter type is used for file names.</TD
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></TR
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><TR
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><TD
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||
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>bx_list_c</TD
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||
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><TD
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||
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>Contains a list of pointers to parameters (bx_param_*_c and bx_list_c).
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In the config interface it is used for menus/dialogs.</TD
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||
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></TR
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||
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></TBODY
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||
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></TABLE
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||
|
|
></DIV
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||
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></P
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||
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></DIV
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||
|
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><DIV
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||
|
|
CLASS="SECTION"
|
||
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><H2
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CLASS="SECTION"
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||
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><A
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||
|
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NAME="SAVE-RESTORE"
|
||
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>2.3.5. The save/restore feature</A
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||
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></H2
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||
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><P
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||
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>The save/restore feature is based on an extension to the parameter tree concept.
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A subtree (list) called "bochs" appears in the root of the parameter tree
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and some new "shadow" parameter types store pointers to values instead of the values
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itself. All the hardware objects have register_state() methods to register pointers
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to the device registers and switches that need to be saved. The simulator interface
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||
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saves the registered data in text format to the specified folder (usually one file
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per item in the save/restore list). Large binary arrays are registered with a
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special parameter type, so they are saved as separate files.</P
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||
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><P
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||
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>The table below shows the additional parameter types for save/restore.
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||
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<DIV
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||
|
|
CLASS="TABLE"
|
||
|
|
><A
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||
|
|
NAME="AEN234"
|
||
|
|
></A
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||
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><P
|
||
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><B
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>Table 2-3. Save/restore parameter types</B
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></P
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><TABLE
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BORDER="1"
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CLASS="CALSTABLE"
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><COL><COL><THEAD
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><TR
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><TH
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>Type</TH
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><TH
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>Description</TH
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></TR
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></THEAD
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><TBODY
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><TR
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><TD
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>bx_shadow_num_c</TD
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><TD
|
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>Based on bx_param_num_c this type stores a pointer to a numerical variable.</TD
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></TR
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><TR
|
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><TD
|
||
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>bx_shadow_bool_c</TD
|
||
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><TD
|
||
|
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>This parameter type stores a pointer to a boolean variable.</TD
|
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></TR
|
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><TR
|
||
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><TD
|
||
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>bx_shadow_data_c</TD
|
||
|
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><TD
|
||
|
|
>This special parameter type stores pointer size of a binary array.</TD
|
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></TR
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></TBODY
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></TABLE
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></DIV
|
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>
|
||
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It is also possible to use the bx_param_num_c object with parameter save/restore
|
||
|
|
handlers. With this special way several device settings can be save to and restored
|
||
|
|
from one single parameter.</P
|
||
|
|
><P
|
||
|
|
>All devices can uses these two save/restore specific methods:
|
||
|
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<P
|
||
|
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></P
|
||
|
|
><UL
|
||
|
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><LI
|
||
|
|
><P
|
||
|
|
>register_state() is called after the device init() to register the device members for save/restore</P
|
||
|
|
></LI
|
||
|
|
><LI
|
||
|
|
><P
|
||
|
|
>after_restore_state() is an optional method to do things directly after restore</P
|
||
|
|
></LI
|
||
|
|
></UL
|
||
|
|
></P
|
||
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|
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