8148b6ee53
nesting cli/sti: release shouldn't always enable interrupts separate setup of lapic from starting of other cpus, so cpu() works earlier flag to disable locking in console output make locks work even when curproc==0 (still crashes in clock interrupt)
139 lines
4.6 KiB
Text
139 lines
4.6 KiB
Text
bochs 2.2.6:
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./configure --enable-smp --enable-disasm --enable-debugger --enable-all-optimizations --enable-4meg-pages --enable-global-pages --enable-pae --disable-reset-on-triple-fault
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bochs CVS after 2.2.6:
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./configure --enable-smp --enable-disasm --enable-debugger --enable-all-optimizations --enable-4meg-pages --enable-global-pages --enable-pae
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bootmain.c doesn't work right if the ELF sections aren't
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sector-aligned. so you can't use ld -N. and the sections may also need
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to be non-zero length, only really matters for tiny "kernels".
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kernel loaded at 1 megabyte. stack same place that bootasm.S left it.
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kinit() should find real mem size
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and rescue useable memory below 1 meg
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no paging, no use of page table hardware, just segments
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no user area: no magic kernel stack mapping
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so no copying of kernel stack during fork
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though there is a kernel stack page for each process
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no kernel malloc(), just kalloc() for user core
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user pointers aren't valid in the kernel
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setting up first process
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we do want a process zero, as template
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but not runnable
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just set up return-from-trap frame on new kernel stack
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fake user program that calls exec
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map text read-only?
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shared text?
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what's on the stack during a trap or sys call?
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PUSHA before scheduler switch? for callee-saved registers.
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segment contents?
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what does iret need to get out of the kernel?
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how does INT know what kernel stack to use?
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are interrupts turned on in the kernel? probably.
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per-cpu curproc
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one tss per process, or one per cpu?
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one segment array per cpu, or per process?
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pass curproc explicitly, or implicit from cpu #?
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e.g. argument to newproc()?
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hmm, you need a global curproc[cpu] for trap() &c
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test stack expansion
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test running out of memory, process slots
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we can't really use a separate stack segment, since stack addresses
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need to work correctly as ordinary pointers. the same may be true of
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data vs text. how can we have a gap between data and stack, so that
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both can grow, without committing 4GB of physical memory? does this
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mean we need paging?
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what's the simplest way to add the paging we need?
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one page table, re-write it each time we leave the kernel?
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page table per process?
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probably need to use 0-0xffffffff segments, so that
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both data and stack pointers always work
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so is it now worth it to make a process's phys mem contiguous?
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or could use segment limits and 4 meg pages?
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but limits would prevent using stack pointers as data pointers
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how to write-protect text? not important?
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perhaps have fixed-size stack, put it in the data segment?
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oops, if kernel stack is in contiguous user phys mem, then moving
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users' memory (e.g. to expand it) will wreck any pointers into the
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kernel stack.
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do we need to set fs and gs? so user processes can't abuse them?
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setupsegs() may modify current segment table, is that legal?
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trap() ought to lgdt on return, since currently only done in swtch()
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protect hardware interrupt vectors from user INT instructions?
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test out-of-fd cases for creating pipe.
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test pipe reader closes then write
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test two readers, two writers.
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test children being inherited by grandparent &c
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some sleep()s should be interruptible by kill()
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cli/sti in acquire/release should nest!
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in case you acquire two locks
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what would need fixing if we got rid of kernel_lock?
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console output
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proc_exit() needs lock on proc *array* to deallocate
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kill() needs lock on proc *array*
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allocator's free list
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global fd table (really free-ness)
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sys_close() on fd table
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fork on proc list, also next pid
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hold lock until public slots in proc struct initialized
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locks
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init_lock
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sequences CPU startup
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proc_table_lock
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also protects next_pid
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per-fd lock *just* protects count read-modify-write
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also maybe freeness?
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memory allocator
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printf
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wakeup needs proc_table_lock
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so we need recursive locks?
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or you must hold the lock to call wakeup?
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if locks contain proc *, they can't be used at interrupt time
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only proc_table_lock will be used at interrupt time?
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maybe it doesn't matter if we use curproc?
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in general, the table locks protect both free-ness and
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public variables of table elements
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in many cases you can use table elements w/o a lock
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e.g. if you are the process, or you are using an fd
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why can't i get a lock in console code?
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always triple fault
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because release turns on interrupts!
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a bad idea very early in main()
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but mp_init() calls cprintf
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lock code shouldn't call cprintf...
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ide_init doesn't work now?
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and IOAPIC: read from unsupported address
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when running pre-empt user test
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so maybe something wrong with clock interrupts
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no! if one cpu holds lock w/ curproc0=,
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then another cpu can take it, it looks like
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a recursive acquire()
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