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Merge pull request #48 from philbudne/master

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sys comments
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philbudne
2016-03-15 06:55:24 -04:00
parent 56f6da9cd8 b94ca04259
commit 8b3ac73639
4 changed files with 164 additions and 140 deletions
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224
src/sys/s2.s
View File

@@ -1,33 +1,38 @@
"** 01-s1.pdf page 7
" s2
" file status (stat) system call
" AC/ pointer to status (inode) buffer (12 words)
" sys status; dir_name_ptr; file_name_ptr
.status:
jms arg
jms arg " fetch directory name pointer
dac .+5
jms arg
jms arg " fetch file name pointer
dac .+6
lac u.cdir
jms namei; ..
jms error
jms namei; ..
jms error
jms iget
lac u.ac
and o17777
jms betwen; o10000; o17762
jms error
dac .+3
jms copy; inode; ..; 12
lac d.i
dac 9 i
lac u.cdir " get current working directory
jms namei; .. " look up source directory
jms error " not found: return error to user
jms namei; .. " look up file
jms error " not found: return error
jms iget " read file inode
lac u.ac " get user buffer pointer
and o17777 " truncate to 13 bits
jms betwen; o10000; o17762 " is user memory (but not last 14 wds)?
jms error " no: error
dac .+3 " save as copy destination
jms copy; inode; ..; 12 " copy inode to user buffer
lac d.i " copy i-num from last dnode read ??
dac 9 i " save thru index 9 (pre-increment) ??
jmp okexit
" capture display?
.capt:
lac u.ac
dac u.dspbuf
jms movdsp
jmp sysexit
" release display?
.rele:
dzm u.dspbuf
law dspbuf
@@ -35,22 +40,22 @@
jmp sysexit
.chmod:
jms isown
lac u.ac
and o17
lmq
lac i.flags
and o777760
omq
dac i.flags
jms iput
jms isown " check if user owns file arg
lac u.ac " get new permissions
and o17 " mask to read/write bits
lmq " save in MQ
lac i.flags " get file flags
and o777760 " clear permissions
omq " or in new permissions from MQ
dac i.flags " save in inode
jms iput " write inode back
jmp okexit
.chown:
jms isown
lac u.ac
dac i.uid
jms iput
jms isown " check if user owns file arg
lac u.ac " get new owner
dac i.uid " save in inode
jms iput " write inode back
jmp okexit
.getuid: " getuid system call
@@ -103,7 +108,7 @@
jms error " Didn't find it
jms namei; 1:0 " In the i-num found by 1st namei,
jms error " search for 2nd argument, err not found
dac u.base
dac u.base " save in user data
jms copy; 2:0; name; 4
lac u.cdir " Search the process' current directory
jms namei; name " for the third argument
@@ -111,11 +116,11 @@
jms error " Error if it already exists
lac d1
dac mode " Save mode bits for access
jms access
jms dslot " ???
lac u.base " ???
jms iget " ???
lac ii " ???
jms access " check access (or return error to user)
jms dslot " allocate directory slot
lac u.base " get source file i-number
jms iget " read inode in
lac ii " get the i-num
dac d.i " Save the i-num in the directory entry
jms copy; name; d.name; 4 " Copy the new link name into the directory entry
lac i.uniq " Copy the i-node unique number into
@@ -129,47 +134,56 @@
jmp okexit " and return OK
.unlink:
jms argname
dac u.base
lac d1 " mode bit 1 (write?)
jms argname " fetch filename, inode
dac u.base " save i-number
lac d1 " write mode bit
dac mode " save for access call
jms access
dac d.i
jms dput
lac u.base
jms iget
isz i.nlks " increment link count
jms access " check access or return error (reads inode)
dzm d.i " clear directory i-num
jms dput " write directory entry back
lac u.base " get i-number back
jms iget " read inode back
isz i.nlks " increment link count (kept as negative count)
jmp 1f " not zero
jms itrunc " zero links: free blocks
dzm i.flags " clear status (free inode)
1:
jms iput
jms iput " write inode back to disk
jmp sysexit
.setuid: " setuid system call
lac u.uid " load current user id
sma " negative?
jms error " no: error!!
sma " negative (super user)
jms error " no: error!!
lac u.ac " load user AC
dac u.uid " save as new uid
jmp sysexit
" rename system call:
" sys rename; old_name_ptr; new_name_ptr
" Questions:
" when is directory entry read??
" is access check on directory or src file??
" check for existing file with new name??
" when is directory entry written back??
.rename:
jms arg
dac 0f
jms arg
dac 1f
lac u.cdir
jms namei; 0:0
jms error
lac d1 " mode bit 1 (write?)
dac mode " save for access call
jms access
jms copy; 1:0; d.name; 4
jms arg " fetch first arg (old name pointer)
dac 0f " save for namei
jms arg " fetch second arg (new name pointer)
dac 1f " save for copy
lac u.cdir " get CWD
jms namei; 0:0 " search for (old) name
jms error " not found: return error
lac d1 " get write mode bit
dac mode " save for access call
jms access " access OK? (or return error to user)
jms copy; 1:0; d.name; 4 " copy new name into directory entry
jmp okexit
" time system call returns line (mains) frequency ticks since boot?
" note: returns uptime!?
" time system call returns line (mains) frequency ticks
" high order bits returned in AC, low order in MQ
" s.tim is located in "system" block (written to disk)
" so this is a running count of uptime since first boot!
" at 60Hz, 36 bits would last 36+ years!
.time:
lac s.tim " load high order bits
@@ -179,14 +193,14 @@
jmp sysexit
.chdir:
jms argname
jms iget
lac i.flags
and o20
sna
jms error
lac ii
dac u.cdir
jms argname " fetch argument as filename
jms iget " (re)read inode(???)
lac i.flags " get flags
and o20 " get directory bit
sna " is a directory?
jms error " no: return error to user
lac ii " yes: get i-number
dac u.cdir " save as current working directory
"** 01-s1.pdf page 10
jmp okexit
@@ -223,27 +237,27 @@
.creat:
lac d1 " mode bit 1 (write)
dac mode " save for access call
jms arg
dac .+2
jms copy; ..; name; 4
jms arg " get name pointer
dac .+2 " save for copy
jms copy; ..; name; 4 " copy filename to "name"
lac u.cdir
jms namei; name
jmp 1f
jms iget
jms access
lac i.flags
and o20
sna
jmp .+4
lac u.uid
sma
jms error
jms itrunc
jms namei; name " look up in current working directory
jmp 1f " not found
jms iget " file exists: read inode
jms access " check access (or return error to user)
lac i.flags " get flags
and o20 " get directory bit
sna " is a directory?
jmp .+4 " no: skip to truncate
lac u.uid " get user
sma " is super user?
jms error " no: error
jms itrunc " yes: truncate
cla
jms dacisize
jms dacisize " clear i.size
jmp open1
1:
jms access
jms access " here if not found
lac u.ac " get access bits from user AC (zero for lock!)
and o17 " mask to permissions
jms icreat
@@ -254,30 +268,30 @@ open1: " common exit for open/creat
"** 01-s1.pdf page 11
.close:
jms finac
dzm f.flags
jms fput
jms finac " get fnode (open file)
dzm f.flags " clear flags
jms fput " write fnode back to u.ofiles
jmp sysexit
.read:
jms arg
and o17777
dac u.base
jms arg
dac u.count
lac u.base
jms betwen; o10000; o17777
jms error
tad u.count
jms betwen; u.base; o17777
jms error
dac u.limit
jms arg " get argument
and o17777 " mask to address
dac u.base " save as I/O base
jms arg " get second argument
dac u.count " save as count
lac u.base " get base
jms betwen; o10000; o17777 " end inside user memory?
jms error " no: error
tad u.count " get end of buffer
jms betwen; u.base; o17777 " inside buffer/user memory?
jms error " no: error
dac u.limit " yes: save as I/O limit
1:
jms finac
lac f.flags
and d1
sza
jms error
jms finac " get fnode for fd in user AC
lac f.flags " get open file flags
and d1 " get write bit
sza " open for write?
jms error " yes: error
lac i.flags " get inode flags
and o40 " get special file bit
sna " special?

41
src/sys/s5.s
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@@ -17,15 +17,15 @@ dskswap: 0
t = t+1
access: 0
lac i.flags
lac i.flags " get inode flags
lmq " save in MQ
lac u.uid " get user id
spa " negative?
jmp access i " yes: super user, return
sad i.uid " compare to file owner
lrs 2 " same: shift flags down two
lacq " get flags back
and mode " mode from system call
lacq " get inode flags back
and mode " AND with mode from system call
sza " access allowed?
jmp access i " yes: return
jms error " no: return error from system call
@@ -256,18 +256,24 @@ movdsp: 0
ion
jmp movdsp i
" fetch user argument from word after "sys" call, return in AC
arg: 0
lac u.rq+8 i
isz u.rq+8
lac u.rq+8 i " fetch word after return PC
isz u.rq+8 " bump PC
jmp arg i
" fetch user pathname argument from pointer word after "sys" call
" into "name" and look it up (in current working directory)
" if lookup fails: returns error to user (not caller)
" if lookup OK: returns with file i-inode read (into "inode")
" and i-number in AC
argname: 0
jms arg
dac .+2
jms copy; ..; name; 4
lac u.cdir
jms namei; name
jms error
jms arg " fetch name pointer
dac .+2 " save as copy source
jms copy; ..; name; 4 " copy to "name"
lac u.cdir " get CWD
jms namei; name " look up file
jms error " failed: return error directly to user
jmp argname i
seektell: 0
@@ -288,13 +294,16 @@ seektell: 0
lac f.badd
jmp seektell i
" system call helper
" fetch system call argument name pointer from after "sys" call
" read inode; if current user is not owner, return error to user
isown: 0
jms argname
jms iget
lac u.uid
sma
sad i.uid
skp
jms error
lac u.uid " get user id
sma " super user?
sad i.uid " no: does user own file?
skp " yes, or super user
jms error " not super user, not owner: return error
jmp isown i

37
src/sys/s6.s
View File

@@ -43,24 +43,25 @@ t = t+4
" Given a pointer to a 4-word filename after
" the jms to namei, and with AC holding the
" i-num of the directory it is in, return the
" i-number of the filename, or 0 if not found
" i-number of the filename (and skip)
" return zero in AC if not found (no skip)
namei: 0
jms iget " Get the inode from the i-num in the AC
-1
tad namei i
dac 9f+t+1
isz namei
tad namei i " get argptr-1
dac 9f+t+1 " save in t1
isz namei " skip over argument
lac i.flags
and o20 " Is this a directory?
sna
jmp namei i " No, loop back
and o20 " get directory bit
sna " Is this a directory?
jmp namei i " no: return without skip
-8
tad i.size " Subtract 8 from the file's size
cma
lrss 3
dac 9f+t
sna
jmp namei i
dac 9f+t " negative count of directory entries in t0
sna " any?
jmp namei i " no: return without skip
dzm di " Store zero in di
1:
lac di
@@ -68,10 +69,10 @@ namei: 0
"** 01-s1.pdf page 35
jms dget " Get a directory entry from the dirblock
lac d.i
sna
jmp 2f
lac 9f+t+1
lac d.i " get i-num
sna " in use?
jmp 2f " no
lac 9f+t+1 " get argptr-1
dac 8
lac d.name " Compare the four words of the filename in the
sad 8 i " directory entry with the argument to namei
@@ -90,13 +91,13 @@ namei: 0
skp
jmp 2f " No match
lac d.i " A match. Get the i-number into AC
isz namei " Skip over the argument and return
isz namei " give skip return
jmp namei i
2:
isz di " No match, move up to the next direntry
isz 9f+t
jmp 1b
jmp namei i " Didn't find it, return zero in AC
isz 9f+t " any left?
jmp 1b " yes: keep going
jmp namei i " Didn't find it, return zero in AC (without skip)
t = t+2
" Given an i-number in AC, fetch that i-node
" from disk and store it in the inode buffer

2
src/sys/sop.s
View File

@@ -77,7 +77,7 @@ rrb = 0700112 " PTR: clear flag, or read buffer
psf = 0700201 " PTP: skip if flag set
pcf = 0700202 " PTP: clear flag
psa = 0700204 " PTP: alphanumeric mode
cdf = 0700501 " ???
cdf = 0700501 " G-2: clear display flags
lds = 0701052 " G-2: load display status
lda = 0701012 " G-2: load display address
wcga = 0704206 " G-2: ???