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| -rw-r--r-- | Notes | 123 |
1 files changed, 0 insertions, 123 deletions
@@ -1,123 +0,0 @@ -bochs 2.2.6: -./configure --enable-smp --enable-disasm --enable-debugger --enable-all-optimizations --enable-4meg-pages --enable-global-pages --enable-pae --disable-reset-on-triple-fault -bochs CVS after 2.2.6: -./configure --enable-smp --enable-disasm --enable-debugger --enable-all-optimizations --enable-4meg-pages --enable-global-pages --enable-pae - -bootmain.c doesn't work right if the ELF sections aren't -sector-aligned. so you can't use ld -N. and the sections may also need -to be non-zero length, only really matters for tiny "kernels". - -kernel loaded at 1 megabyte. stack same place that bootasm.S left it. - -kinit() should find real mem size - and rescue useable memory below 1 meg - -no paging, no use of page table hardware, just segments - -no user area: no magic kernel stack mapping - so no copying of kernel stack during fork - though there is a kernel stack page for each process - -no kernel malloc(), just kalloc() for user core - -user pointers aren't valid in the kernel - -are interrupts turned on in the kernel? yes. - -pass curproc explicitly, or implicit from cpu #? - e.g. argument to newproc()? - hmm, you need a global curproc[cpu] for trap() &c - -no stack expansion - -test running out of memory, process slots - -we can't really use a separate stack segment, since stack addresses -need to work correctly as ordinary pointers. the same may be true of -data vs text. how can we have a gap between data and stack, so that -both can grow, without committing 4GB of physical memory? does this -mean we need paging? - -perhaps have fixed-size stack, put it in the data segment? - -oops, if kernel stack is in contiguous user phys mem, then moving -users' memory (e.g. to expand it) will wreck any pointers into the -kernel stack. - -do we need to set fs and gs? so user processes can't abuse them? - -setupsegs() may modify current segment table, is that legal? - -trap() ought to lgdt on return, since currently only done in swtch() - -protect hardware interrupt vectors from user INT instructions? - -test out-of-fd cases for creating pipe. -test pipe reader closes then write -test two readers, two writers. -test children being inherited by grandparent &c - -some sleep()s should be interruptible by kill() - -locks - init_lock - sequences CPU startup - proc_table_lock - also protects next_pid - per-fd lock *just* protects count read-modify-write - also maybe freeness? - memory allocator - printf - -in general, the table locks protect both free-ness and - public variables of table elements - in many cases you can use table elements w/o a lock - e.g. if you are the process, or you are using an fd - -lock order - per-pipe lock - proc_table_lock fd_table_lock kalloc_lock - console_lock - -do you have to be holding the mutex in order to call wakeup()? yes - -device interrupts don't clear FL_IF - so a recursive timer interrupt is possible - -what does inode->busy mean? - might be held across disk reads - no-one is allowed to do anything to the inode - protected by inode_table_lock -inode->count counts in-memory pointers to the struct - prevents inode[] element from being re-used - protected by inode_table_lock - -blocks and inodes have ad-hoc sleep-locks - provide a single mechanism? - -kalloc() can return 0; do callers handle this right? - -test: one process unlinks a file while another links to it -test: one process opens a file while another deletes it -test: deadlock d/.. vs ../d, two processes. -test: dup() shared fd->off -test: does echo foo > x truncate x? - -sh: ioredirection incorrect now we have pipes -sh: chain of pipes won't work, also ugly that parent closes fdarray entries too -sh: dynamic memory allocation? -sh: should sh support ; () & -sh: stop stdin on ctrl-d (for cat > y) - -really should have bdwrite() for file content - and make some inode updates async - so soft updates make sense - -disk scheduling -echo foo > bar should truncate bar - so O_CREATE should not truncate - but O_TRUNC should - -make it work on a real machine -release before acquire at end of sleep? -check 2nd disk (i.e. if not in .bochsrc) |