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Diffstat (limited to 'sim')
| -rw-r--r-- | sim/ChangeLog | 4 | ||||
| -rw-r--r-- | sim/README-HACKING | 245 |
2 files changed, 249 insertions, 0 deletions
diff --git a/sim/ChangeLog b/sim/ChangeLog index ff63166..f0a8287 100644 --- a/sim/ChangeLog +++ b/sim/ChangeLog @@ -1,3 +1,7 @@ +2010-04-12 Mike Frysinger <vapier@gentoo.org> + + * README-HACKING: Add more sections. + 2010-02-11 Doug Evans <dje@sebabeach.org> * cris/cpuv10.h, * cris/cpuv32.h, * cris/cris-desc.c, diff --git a/sim/README-HACKING b/sim/README-HACKING index bee504a..77cad94 100644 --- a/sim/README-HACKING +++ b/sim/README-HACKING @@ -256,4 +256,249 @@ To add a new target: 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 |