| This is a loose collection of notes for people hacking on simulators. |
| If this document gets big enough it can be prettied up then. |
| |
| Contents |
| |
| - The "common" directory |
| - Common Makefile Support |
| - TAGS support |
| - Generating "configure" files |
| - tconfig.in |
| - C Language Assumptions |
| - "dump" commands under gdb |
| |
| The "common" directory |
| ====================== |
| |
| The common directory contains: |
| |
| - common documentation files (e.g. run.1, and maybe in time .texi files) |
| - common source files (e.g. run.c) |
| - common Makefile fragment and configury (e.g. Make-common.in, aclocal.m4). |
| |
| In addition "common" contains portions of the system call support |
| (e.g. callback.c, nltvals.def). |
| |
| Even though no files are built in this directory, it is still configured |
| so support for regenerating nltvals.def is present. |
| |
| Common Makefile Support |
| ======================= |
| |
| A common configuration framework is available for simulators that want |
| to use it. The common framework exists to remove a lot of duplication |
| in configure.in and Makefile.in, and it also provides a foundation for |
| enhancing the simulators uniformly (e.g. the more they share in common |
| the easier a feature added to one is added to all). |
| |
| The configure.in of a simulator using the common framework should look like: |
| |
| --- snip --- |
| dnl Process this file with autoconf to produce a configure script. |
| sinclude(../common/aclocal.m4) |
| AC_PREREQ(2.5)dnl |
| AC_INIT(Makefile.in) |
| |
| SIM_AC_COMMON |
| |
| ... target specific additions ... |
| |
| SIM_AC_OUTPUT |
| --- snip --- |
| |
| SIM_AC_COMMON: |
| |
| - invokes the autoconf macros most often used by the simulators |
| - defines --enable/--with options usable by all simulators |
| - initializes sim_link_files/sim_link_links as the set of symbolic links |
| to set up |
| |
| SIM_AC_OUTPUT: |
| |
| - creates the symbolic links defined in sim_link_{files,links} |
| - creates config.h |
| - creates the Makefile |
| |
| The Makefile.in of a simulator using the common framework should look like: |
| |
| --- snip --- |
| # Makefile for blah ... |
| # Copyright blah ... |
| |
| ## COMMON_PRE_CONFIG_FRAG |
| |
| # These variables are given default values in COMMON_PRE_CONFIG_FRAG. |
| # We override the ones we need to here. |
| # Not all of these need to be mentioned, only the necessary ones. |
| # In fact it is better to *not* mention ones if the value is the default. |
| |
| # List of object files, less common parts. |
| SIM_OBJS = |
| # List of extra dependencies. |
| # Generally this consists of simulator specific files included by sim-main.h. |
| SIM_EXTRA_DEPS = |
| # List of flags to always pass to $(CC). |
| SIM_EXTRA_CFLAGS = |
| # List of extra libraries to link with. |
| SIM_EXTRA_LIBS = |
| # List of extra program dependencies. |
| SIM_EXTRA_LIBDEPS = |
| # List of main object files for `run'. |
| SIM_RUN_OBJS = run.o |
| # Dependency of `all' to build any extra files. |
| SIM_EXTRA_ALL = |
| # Dependency of `install' to install any extra files. |
| SIM_EXTRA_INSTALL = |
| # Dependency of `clean' to clean any extra files. |
| SIM_EXTRA_CLEAN = |
| |
| ## COMMON_POST_CONFIG_FRAG |
| |
| # Rules need to build $(SIM_OBJS), plus whatever else the target wants. |
| |
| ... target specific rules ... |
| --- snip --- |
| |
| COMMON_{PRE,POST}_CONFIG_FRAG are markers for SIM_AC_OUTPUT to tell it |
| where to insert the two pieces of common/Make-common.in. |
| The resulting Makefile is created by doing autoconf substitions on |
| both the target's Makefile.in and Make-common.in, and inserting |
| the two pieces of Make-common.in into the target's Makefile.in at |
| COMMON_{PRE,POST}_CONFIG_FRAG. |
| |
| Note that SIM_EXTRA_{INSTALL,CLEAN} could be removed and "::" targets |
| could be used instead. However, it's not clear yet whether "::" targets |
| are portable enough. |
| |
| TAGS support |
| ============ |
| |
| Many files generate program symbols at compile time. |
| Such symbols can't be found with grep nor do they normally appear in |
| the TAGS file. To get around this, source files can add the comment |
| |
| /* TAGS: foo1 foo2 */ |
| |
| where foo1, foo2 are program symbols. Symbols found in such comments |
| are greppable and appear in the TAGS file. |
| |
| Generating "configure" files |
| ============================ |
| |
| For targets using the common framework, "configure" can be generated |
| by running `autoconf'. |
| |
| To regenerate the configure files for all targets using the common framework: |
| |
| $ cd devo/sim |
| $ make -f Makefile.in SHELL=/bin/sh autoconf-common |
| |
| To add a change-log entry to the ChangeLog file for each updated |
| directory (WARNING - check the modified new-ChangeLog files before |
| renaming): |
| |
| $ make -f Makefile.in SHELL=/bin/sh autoconf-changelog |
| $ more */new-ChangeLog |
| $ make -f Makefile.in SHELL=/bin/sh autoconf-install |
| |
| In a similar vein, both the configure and config.in files can be |
| updated using the sequence: |
| |
| $ cd devo/sim |
| $ make -f Makefile.in SHELL=/bin/sh autoheader-common |
| $ make -f Makefile.in SHELL=/bin/sh autoheader-changelog |
| $ more */new-ChangeLog |
| $ make -f Makefile.in SHELL=/bin/sh autoheader-install |
| |
| To add the entries to an alternative ChangeLog file, use: |
| |
| $ make ChangeLog=MyChangeLog .... |
| |
| |
| tconfig.in |
| ========== |
| |
| File tconfig.in defines one or more target configuration macros |
| (e.g. a tm.h file). There are very few that need defining. |
| For a list of all of them, see common/tconfig.in. |
| It contains them all, commented out. |
| The intent is that a new port can just copy this file and |
| define the ones it needs. |
| |
| C Language Assumptions |
| ====================== |
| |
| The programmer may assume that the simulator is being built using an |
| ANSI C compiler that supports a 64 bit data type. Consequently: |
| |
| o prototypes can be used (although using |
| PARAMS() and K&R declarations wouldn't |
| go astray). |
| |
| o If sim-types.h is included, the two |
| types signed64 and unsigned64 are |
| available. |
| |
| o The type `unsigned' is valid. |
| |
| However, the user should be aware of the following: |
| |
| o GCC's `<number>LL' is NOT acceptable. |
| Microsoft-C doesn't reconize it. |
| |
| o MSC's `<number>i64' is NOT acceptable. |
| GCC doesn't reconize it. |
| |
| o GCC's `long long' MSC's `_int64' can |
| NOT be used to define 64 bit integer data |
| types. |
| |
| o An empty array (eg int a[0]) is not valid. |
| |
| When building with GCC it is effectivly a requirement that |
| --enable-build-warnings=,-Werror be specified during configuration. |
| |
| "dump" commands under gdb |
| ========================= |
| |
| gdbinit.in contains the following |
| |
| define dump |
| set sim_debug_dump () |
| end |
| |
| Simulators that define the sim_debug_dump function can then have their |
| internal state pretty printed from gdb. |
| |
| FIXME: This can obviously be made more elaborate. As needed it will be. |
| |
| Rebuilding nltvals.def |
| ====================== |
| |
| Checkout a copy of the SIM and LIBGLOSS modules (Unless you've already |
| got one to hand): |
| |
| $ mkdir /tmp/$$ |
| $ cd /tmp/$$ |
| $ cvs checkout sim-no-testsuite libgloss-no-testsuite newlib-no-testsuite |
| |
| Configure things for an arbitrary simulator target (I've d10v for |
| convenience): |
| |
| $ mkdir /tmp/$$/build |
| $ cd /tmp/$$/build |
| $ /tmp/$$/devo/configure --target=d10v-elf |
| |
| In the sim/common directory rebuild the headers: |
| |
| $ cd sim/common |
| $ make headers |
| |
| To add a new target: |
| |
| devo/sim/common/gennltvals.sh |
| |
| Add your new processor target (you'll need to grub |
| around to find where your syscall.h lives). |
| |
| devo/sim/<processor>/Makefile.in |
| |
| Add the definition: |
| |
| ``NL_TARGET = -DNL_TARGET_d10v'' |
| |
| just before the line COMMON_POST_CONFIG_FRAG. |
| |
| devo/sim/<processor>/*.[ch] |
| |
| Include targ-vals.h instead of syscall.h. |
| |
| Tracing |
| ======= |
| |
| For ports based on CGEN, tracing instrumentation should largely be for free, |
| so we will cover the basic non-CGEN setup here. The assumption is that your |
| target is using the common autoconf macros and so the build system already |
| includes the sim-trace configure flag. |
| |
| The full tracing API is covered in sim-trace.h, so this section is an overview. |
| |
| Before calling any trace function, you should make a call to the trace_prefix() |
| function. This is usually done in the main sim_engine_run() loop before |
| simulating the next instruction. You should make this call before every |
| simulated insn. You can probably copy & paste this: |
| if (TRACE_ANY_P (cpu)) |
| trace_prefix (sd, cpu, NULL_CIA, oldpc, TRACE_LINENUM_P (cpu), NULL, 0, ""); |
| |
| You will then need to instrument your simulator code with calls to the |
| trace_generic() function with the appropriate trace index. Typically, this |
| will take a form similar to the above snippet. So to trace instructions, you |
| would use something like: |
| if (TRACE_INSN_P (cpu)) |
| trace_generic (sd, cpu, TRACE_INSN_IDX, "NOP;"); |
| |
| The exact output format is up to you. See the trace index enum in sim-trace.h |
| to see the different tracing info available. |
| |
| To utilize the tracing features at runtime, simply use the --trace-xxx flags. |
| run --trace-insn ./some-program |
| |
| Profiling |
| ========= |
| |
| Similar to the tracing section, this is merely an overview for non-CGEN based |
| ports. The full API may be found in sim-profile.h. Its API is also similar |
| to the tracing API. |
| |
| Note that unlike the tracing command line options, in addition to the profile |
| flags, you have to use the --verbose option to view the summary report after |
| execution. Tracing output is displayed on the fly, but the profile output is |
| only summarized. |
| |
| To profile core accesses (such as data reads/writes and insn fetches), add |
| calls to PROFILE_COUNT_CORE() to your read/write functions. So in your data |
| fetch function, you'd use something like: |
| PROFILE_COUNT_CORE (cpu, target_addr, size_in_bytes, map_read); |
| Then in your data write function: |
| PROFILE_COUNT_CORE (cpu, target_addr, size_in_bytes, map_write); |
| And in your insn fetcher: |
| PROFILE_COUNT_CORE (cpu, target_addr, size_in_bytes, map_exec); |
| |
| To use the PC profiling code, you simply have to tell the system where to find |
| your simulator's PC and its size. So in your sim_open() function: |
| STATE_WATCHPOINTS (sd)->pc = address_of_cpu0_pc; |
| STATE_WATCHPOINTS (sd)->sizeof_pc = number_of_bytes_for_pc_storage; |
| In a typical 32bit system, the sizeof_pc will be 4 bytes. |
| |
| To profile branches, in every location where a branch insn is executed, call |
| one of the related helpers: |
| PROFILE_BRANCH_TAKEN (cpu); |
| PROFILE_BRANCH_UNTAKEN (cpu); |
| If you have stall information, you can utilize the other helpers too. |
| |
| Environment Simulation |
| ====================== |
| |
| The simplest simulator doesn't include environment support -- it merely |
| simulates the Instruction Set Architecture (ISA). Once you're ready to move |
| on to the next level, call the common macro in your configure.ac: |
| SIM_AC_OPTION_ENVIRONMENT |
| |
| This will support for the user, virtual, and operating environments. See the |
| sim-config.h header for a more detailed description of them. The former are |
| pretty straight forward as things like exceptions (making system calls) are |
| handled in the simulator. Which is to say, an exception does not trigger an |
| exception handler in the simulator target -- that is what the operating env |
| is about. See the following userspace section for more information. |
| |
| Userspace System Calls |
| ====================== |
| |
| By default, the libgloss userspace is simulated. That means the system call |
| numbers and calling convention matches that of libgloss. Simulating other |
| userspaces (such as Linux) is pretty straightforward, but let's first focus |
| on the basics. The basic API is covered in include/gdb/callback.h. |
| |
| When an instruction is simulated that invokes the system call method (such as |
| forcing a hardware trap or exception), your simulator code should set up the |
| CB_SYSCALL data structure before calling the common cb_syscall() function. |
| For example: |
| static int |
| syscall_read_mem (host_callback *cb, struct cb_syscall *sc, |
| unsigned long taddr, char *buf, int bytes) |
| { |
| SIM_DESC sd = (SIM_DESC) sc->p1; |
| SIM_CPU *cpu = (SIM_CPU *) sc->p2; |
| return sim_core_read_buffer (sd, cpu, read_map, buf, taddr, bytes); |
| } |
| static int |
| syscall_write_mem (host_callback *cb, struct cb_syscall *sc, |
| unsigned long taddr, const char *buf, int bytes) |
| { |
| SIM_DESC sd = (SIM_DESC) sc->p1; |
| SIM_CPU *cpu = (SIM_CPU *) sc->p2; |
| return sim_core_write_buffer (sd, cpu, write_map, buf, taddr, bytes); |
| } |
| void target_sim_syscall (SIM_CPU *cpu) |
| { |
| SIM_DESC sd = CPU_STATE (cpu); |
| host_callback *cb = STATE_CALLBACK (sd); |
| CB_SYSCALL sc; |
| |
| CB_SYSCALL_INIT (&sc); |
| |
| sc.func = <fetch system call number>; |
| sc.arg1 = <fetch first system call argument>; |
| sc.arg2 = <fetch second system call argument>; |
| sc.arg3 = <fetch third system call argument>; |
| sc.arg4 = <fetch fourth system call argument>; |
| sc.p1 = (PTR) sd; |
| sc.p2 = (PTR) cpu; |
| sc.read_mem = syscall_read_mem; |
| sc.write_mem = syscall_write_mem; |
| |
| cb_syscall (cb, &sc); |
| |
| <store system call result from sc.result>; |
| <store system call error from sc.errcode>; |
| } |
| Some targets store the result and error code in different places, while others |
| only store the error code when the result is an error. |
| |
| Keep in mind that the CB_SYS_xxx defines are normalized values with no real |
| meaning with respect to the target. They provide a unique map on the host so |
| that it can parse things sanely. For libgloss, the common/nltvals.def file |
| creates the target's system call numbers to the CB_SYS_xxx values. |
| |
| To simulate other userspace targets, you really only need to update the maps |
| pointers that are part of the callback interface. So create CB_TARGET_DEFS_MAP |
| arrays for each set (system calls, errnos, open bits, etc...) and in a place |
| you find useful, do something like: |
| |
| ... |
| static CB_TARGET_DEFS_MAP cb_linux_syscall_map[] = { |
| # define TARGET_LINUX_SYS_open 5 |
| { CB_SYS_open, TARGET_LINUX_SYS_open }, |
| ... |
| { -1, -1 }, |
| }; |
| ... |
| host_callback *cb = STATE_CALLBACK (sd); |
| cb->syscall_map = cb_linux_syscall_map; |
| cb->errno_map = cb_linux_errno_map; |
| cb->open_map = cb_linux_open_map; |
| cb->signal_map = cb_linux_signal_map; |
| cb->stat_map = cb_linux_stat_map; |
| ... |
| |
| Each of these cb_linux_*_map's are manually declared by the arch target. |
| |
| The target_sim_syscall() example above will then work unchanged (ignoring the |
| system call convention) because all of the callback functions go through these |
| mapping arrays. |
| |
| Events |
| ====== |
| |
| Events are scheduled and executed on behalf of either a cpu or hardware devices. |
| The API is pretty much the same and can be found in common/sim-events.h and |
| common/hw-events.h. |
| |
| For simulator targets, you really just have to worry about the schedule and |
| deschedule functions. |
| |
| Device Trees |
| ============ |
| |
| The device tree model is based on the OpenBoot specification. Since this is |
| largely inherited from the psim code, consult the existing psim documentation |
| for some in-depth details. |
| http://sourceware.org/psim/manual/ |
| |
| Hardware Devices |
| ================ |
| |
| The simplest simulator doesn't include hardware device support. Once you're |
| ready to move on to the next level, call the common macro in your configure.ac: |
| SIM_AC_OPTION_HARDWARE(yes,,devone devtwo devthree) |
| |
| The basic hardware API is documented in common/hw-device.h. |
| |
| Each device has to have a matching file name with a "dv-" prefix. So there has |
| to be a dv-devone.c, dv-devtwo.c, and dv-devthree.c files. Further, each file |
| has to have a matching hw_descriptor structure. So the dv-devone.c file has to |
| have something like: |
| const struct hw_descriptor dv_devone_descriptor[] = { |
| {"devone", devone_finish,}, |
| {NULL, NULL}, |
| }; |
| |
| The "devone" string as well as the "devone_finish" function are not hard |
| requirements, just common conventions. The structure name is a hard |
| requirement. |
| |
| The devone_finish() callback function is used to instantiate this device by |
| parsing the corresponding properties in the device tree. |
| |
| Hardware devices typically attach address ranges to themselves. Then when |
| accesses to those addresses are made, the hardware will have its callback |
| invoked. The exact callback could be a normal I/O read/write access, as |
| well as a DMA access. This makes it easy to simulate memory mapped registers. |
| |
| Keep in mind that like a proper device driver, it may be instantiated many |
| times over. So any device state it needs to be maintained should be allocated |
| during the finish callback and attached to the hardware device via set_hw_data. |
| Any hardware functions can access this private data via the hw_data function. |
| |
| Ports (Interrupts / IRQs) |
| ========================= |
| |
| First, a note on terminology. A "port" is an aspect of a hardware device that |
| accepts or generates interrupts. So devices with input ports may be the target |
| of an interrupt (accept it), and/or they have output ports so that they may be |
| the source of an interrupt (generate it). |
| |
| Each port has a symbolic name and a unique number. These are used to identify |
| the port in different contexts. The output port name has no hard relationship |
| to the input port name (same for the unique number). The callback that accepts |
| the interrupt uses the name/id of its input port, while the generator function |
| uses the name/id of its output port. |
| |
| The device tree is used to connect the output port of a device to the input |
| port of another device. There are no limits on the number of inputs connected |
| to an output, or outputs to an input, or the devices attached to the ports. |
| In other words, the input port and output port could be the same device. |
| |
| The basics are: |
| - each hardware device declares an array of ports (hw_port_descriptor). |
| any mix of input and output ports is allowed. |
| - when setting up the device, attach the array (set_hw_ports). |
| - if the device accepts interrupts, it will have to attach a port callback |
| function (set_hw_port_event) |
| - connect ports with the device tree |
| - handle incoming interrupts with the callback |
| - generate outgoing interrupts with hw_port_event |