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\ Hypervisor Software File: reenter.fth
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id: @(#)reenter.fth 1.22 07/06/22
copyright: Copyright 2007 Sun Microsystems, Inc. All Rights Reserved
copyright: Use is subject to license terms.
\ Ways to enter the Forth interpreter, and their implications:
\ a) Power up - no autoboot
\ Entry mechanism: prom-cold-code, which is entered from the boot-state
\ reset vector, distinguished this from a watchdog reset by looking
\ at the watchdog bit in the system error register. prom-cold-code
\ then initializes the machine and executes the Forth startup
\ Action: perform the startup initialization sequence, then boot
\ the operating system if autoboot is specified in the configuration.
\ Otherwise enter the text interpreter.
\ b) Power up - abort key
\ Action: Finish initialization procedure, but enter interpreter
\ c) Breakpoint (= single step)
\ Entry mechanism: the trap table entry reads the psr into %l0 and
\ jumps to save-state . save-state saves %l0 into the error-reset-trap
\ field of the cpu-state save area.
\ Signature: The trap type field of the saved tbr indicates the
\ breakpoint trap vector, the error-reset-trap field of the cpu-state save
\ area contains a valid psr value (as opposed to -1; see the
\ "Error reset" case), and no other special conditions are present
\ (see "exittomon", "abortent")
\ Action: perform the action indicated by the "handle-breakpoint"
\ routine; usually disassembles the breakpointed instruction and
\ enters the text interpreter
\ d) Error trap (e.g. Data Access Exception)
\ Entry mechanism: the trap table entry reads the psr into %l0 and
\ jumps to save-state . save-state saves %l0 into the error-reset-trap
\ field of the cpu-state save area.
\ Signature: The trap type field of the saved tbr indicates the
\ breakpoint trap vector, the error-reset-trap field of the cpu-state save
\ area contains a valid psr value (as opposed to -1; see the
\ "Error reset" case), and no other special conditions are present
\ (see "exittomon", "abortent")
\ Action: display exception name and enter text interpreter
\ e) Exittomon - Return from Unix - don't expect to re-enter
\ Entry mechanism: sun4m/machdep.c:halt() calls romp->v_exit_to_mon,
\ which resolves to reenter.fth:reenter . "reenter" executes the
\ breakpoint trap instruction, which proceeds as in the "breakpoint"
\ Signature: This looks almost like the "Breakpoint" case, and is
\ distinguised from that case by the fact that the saved %pc value
\ indicates the address of the trap instruction within the "reenter"
\ Action: Display "Type 'go' to resume", then enter text interpreter
\ Problem: kadb may have usurped the breakpoint trap table entry
\ Idea: Maybe instead of start_mon_clock(), stop_mon_clock(), we should
\ provide romvecs for this, or maybe the monitor should just do it
\ automatically whenever the interpreter is entered or one of the
\ the monitor's I/O routines (maybe just mayget) is called. (No, just
\ mayget() is insufficient, because we could lose characters when
\ Note: Unix displays a message through the PROM's printf routine
\ before calling romp->v_exit_to_mon. The message depends on
\ the reason for the halt:
\ "Halted" Executed from sun4m/machdep.c:boot(), from
\ reboot system call entry (in os/kern_xxx.c),
\ but only if RB_HALT flag from the user's
\ parameters to the system call is set.
\ spl6() is performed before calling halt()
\ "bootflags" The RB_HALT flag was set when Unix parsed the
\ boot flags. Restartable. spl6() NOT called
\ (Is that the right thing?)
\ "system map tables too large"
\ Unix has an internal configuration problem
\ "no memory" Unix was too big for the available phys. memory
\ Note: Unix starts the monitor clock before calling romp->v_exit_to_mon
\ Note: Unix does not intend to be restarted in most cases, but
\ in the "bootflags" case above, restarting is reasonable.
\ Halt() remembers to stop the monitor clock if exit_to_mon returns.
\ f) Abortent - keyboard abort from Unix (L1-A or Break) (continuable)
\ Entry mechanism: either sundev/zs_async.c or sundev/kbd.c calls
\ sun4m/locore.s:montrap(romp->v_abortent), which then calls that
\ abortent routine. Currently, the abortent romvec resolves to
\ reenter.fth:reeenter, the same as for "Exittomon"
\ Signature: Currently, this is indistinguishable from the "Exittomon"
\ case, unless Forth is willing to dig around in the window registers
\ to identify the "montrap()" return address (a silly way to do it;
\ it would be easier to provide a separate "abort-reenter" routine).
\ Action: Currently the same as for "Exittomon"
\ Suggestion: the action should be similar to "L1-A when Forth running"
\ Note: if kadb is installed (Unix saw "-d" flag), kadb is entered
\ instead of the monitor.
\ Note: Execution of Unix is frequently resumed after this kind of abort
\ Note: Unix does NOT start the monitor clock before calling
\ g) Bootme - return from Unix with auto-reboot
\ Entry mechanism: sun4m/machdep.c:boot(), which is called from the
\ reboot system call code in os/kern_xxx.c. boot() calls
\ romp->v_boot_me, which calls a Forth entry resolving to
\ Note: Never returns to Unix; instead reboots the system
\ Note: Monitor clock has been started at spl6() (pil 13).
\ Note: Argument is a C string which is either "", "-s", or the argument
\ to the reboot user command
\ Note: Doesn't enter the Forth text interpreter
\ h) Callvec - call Unix subroutine which then returns back to Forth
\ Entry mechanism: Forth calls a subroutine whose address has been
\ exported by Unix. That subroutine returns, reentering the
\ Forth word (callvec or sync) from which it was called.
\ Note: Unix doesn't do anything to restore it's state. Maybe this is
\ wrong. Perhaps Unix should be in charge of setting up its own
\ stack, context, trap table, and interrupts again?
\ Note: This is usually executed after a keyboard abort or a watchdog.
\ i) fwritestr - terminal emulator called from Unix
\ Entry mechanism: Unix calls either "putchar()", "mayput()", or
\ "fwritestr()". putchar() and mayput() are C subroutines which
\ themselves call "fwritestr()". fwritestr() is a C to Forth entry
\ point, which establishes a temporary Forth environment on the
\ C stack, then calls a Forth word.
\ Note: When executing fwritestr(), we can lose keyboard characters
\ if Unix has disabled the Forth level 14 clock handler. We need
\ to make sure that Unix leaves that handler enabled during startup
\ up until the point where Unix takes over the keyboard.
\ j) L1-A or break from keyboard when Forth is running
\ Entry mechanism: The level 14 clock interrupt handler checks for an
\ abort (L1-A from the keyboard or break from a tty) and sets the
\ "aborted?" variable if one is seen. Just before the assembly
\ language part of the interrupt handler returns, it checks
\ "aborted?", and if it is set, the handler jumps to save-state
\ instead of returning. The CPU state at that point has been
\ restored to the same state that existed just when the interrupt
\ handler was entered, i.e. as if the trap had directly vectored
\ to "save-state" instead of to the interrupt handler. That way,
\ the user does not see any artifacts of the interrupt handler itself.
\ Signature: The "aborted?" variable is set. Otherwise looks like a
\ Action: Displays "Keyboard abort. Type 'go' to resume"
\ k) L1-A from keyboard with interrupts off and polling mayget()
\ Entry mechanism: an application is calling the PROM's mayget()
\ routine in order to get a characters. Level 14 interrupts are
\ turned off. The input device is the Sun keyboard. mayget()
\ call key_check() to poll the keyboard. The key is determined
\ to be the A of an L1-A sequence. key_check() calls _enterforth
\ == reenter , which sets the establishes Forth's trap table and
\ executes a trap #7f instruction.
\ Signature: This looks like the "Abortent" case above. If necessary
\ it could be distinguished by looking on the C stack to see the
\ interruption of the key_check routine.
\ Action: Displays "Type 'go' to resume"
\ l) From a watchdog reset
\ Entry mechanism: prom-cold-code, which is entered from the boot-state
\ reset vector, destinguished this from a power-on reset by looking
\ at the watchdog bit in the system error register. prom-cold-code
\ then puts a discernable value (-1) in %l0, jumps to save-state,
\ and save-state saves %l0 in the cpu-state area.
\ Signature: the "error-reset-trap" field in the cpu-state area contains -1.
\ Otherwise looks like a breakpoint.
\ Action: If watchdog-reboot? is set, execute the autoboot sequence,
\ otherwise enter the text interpreter.
\ Enter the monitor with no complaints or error messages.
only forth also hidden also forth definitions
code reclaim-machine ( -- )
%g0 h# 14 wrpstate \ IE=0, FPU=1, PRIV=1
%g0 h# 20 %o5 add \ MMU_TSB_CTX0
%g0 h# 21 %o5 add \ MMU_TSB_CTXNON0
%g0 h# 16 wrpstate \ IE=1, FPU=1, PRIV=1
\ Undo the effects of "fentry" because
\ of the Client Interface Service EXIT
\ We don't want to depend on the data
\ stack pointer being the same, because
\ the routine may have left a return value
%o6 V9_SP_BIAS d# 16 na+ sp nget
%o6 V9_SP_BIAS d# 24 na+ rp nget
\ Restore these in case of multiple levels of cross-language calls;
\ if the Forth word that was just executed called a C subroutine,
\ then saved-sp and saved-rp could have been changed.
%o6 V9_SP_BIAS d# 17 na+ %g1 nget
%o6 V9_SP_BIAS d# 18 na+ %g2 nget
%o6 V9_SP_BIAS d# 19 na+ %g3 nget
%o6 V9_SP_BIAS d# 20 na+ %g4 nget
%o6 V9_SP_BIAS d# 21 na+ %g5 nget
%o6 V9_SP_BIAS d# 22 na+ %g6 nget
%o6 V9_SP_BIAS d# 23 na+ %g7 nget
\ Back to the previous frame
\ Save the client program's trap base register
\ Set the trap base register to Forth's trap table
again \ Not restartable; keep exiting
\ Undo the effects of "fentry" because
\ of the Client Interface Service ENTER
\ We don't want to depend on the data
\ stack pointer being the same, because
\ the routine may have left a return value
%o6 V9_SP_BIAS d# 16 na+ sp nget
%o6 V9_SP_BIAS d# 24 na+ rp nget
\ Restore these in case of multiple levels of cross-language calls;
\ if the Forth word that was just executed called a C subroutine,
\ then saved-sp and saved-rp could have been changed.
%o6 V9_SP_BIAS d# 17 na+ %g1 nget
%o6 V9_SP_BIAS d# 18 na+ %g2 nget
%o6 V9_SP_BIAS d# 19 na+ %g3 nget
%o6 V9_SP_BIAS d# 20 na+ %g4 nget
%o6 V9_SP_BIAS d# 21 na+ %g5 nget
%o6 V9_SP_BIAS d# 22 na+ %g6 nget
%o6 V9_SP_BIAS d# 23 na+ %g7 nget
\ Back to the previous frame
\ Save the client program's trap base register
\ Set the trap base register to Forth's trap table
\ Restore the client's trap base register
\ Restarting is only possible if the state that was first saved
\ is from a restartable exception.
state-valid @ -1 = already-go? and if
['] interpret behavior ['] (interpret = if
." Type 'go' to resume" cr
0 >debugger-hook per-cpu-defer: debugger-hook
\ KADB uses this *and* the per cpu version!
: init-debugger-hook ( xt -- ) ['] debugger-hook 3 perform-action ;
stand-init: Init debugger-hook
['] noop init-debugger-hook
defer rearm-alarms ' noop is rearm-alarms
: reset-debugger-hook ( -- ) ['] noop to debugger-hook ;
addr debugger-hook token@ reset-debugger-hook execute
: is-xir-trap? ( -- flag ) last-trap# xir-trap# = ;
: is-breakpoint-trap? ( -- flag ) last-trap# breakpoint-trap# = ;
: inside? ( label end -- flag ) %pc -rot within ;
\ Hooks to take care of special platform specific handling.
defer xir-trap-hook ' noop is xir-trap-hook
defer exittomon-hook ' noop is exittomon-hook
defer reenter-hook ( -- ) ' noop is reenter-hook
talign \ Hack; recover in case dp is misaligned
aborted? off rearm-alarms
enter-debugger hex cr .go-message exit
is-breakpoint-trap? 0= if
enter-debugger (do-last-trap) exit
\ We want to stay at the 'ok' prompt
\ so, uninstall the debugger-hook
exittomon exittomon-end inside? if
obp-control-relinquished? if
\ Client program dropped to ok-prompt by unsuccessful boot
false to obp-control-relinquished?
." Program terminated" cr exit
reenter reenter-end inside? if
\ If the PC is pointing to the trap instruction in "reenter",
\ adjust %pc and %npc to skip that trap instruction.
reenter reenter-end inside? if
mid@ <# ascii } hold u#s ascii { hold u#> type ." ok "
-1 max-mondo-target# 0 ?do
i >cpu-struct >cpu-status @ if 1+ then
mp-system? if ['] mp-ok is (ok) then
stand-init: Install .exception
only forth also definitions
projects / OpenSPARC-T2-SAM / blob