Compare commits
No commits in common. "e35bbc1aa2106dc4fa1ab678b148e5bcd5e2441f" and "70bb9ad66d22015495046465fae6fb645a8cb656" have entirely different histories.
e35bbc1aa2
...
70bb9ad66d
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@ -1 +1 @@
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Subproject commit 6a444bd29ea6d474ec98edbc11b27030825b86e2
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Subproject commit 75995422262a192f2c87713d239856e98c799f41
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217
src/vfs.hbasm
217
src/vfs.hbasm
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@ -1,47 +1,12 @@
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-- r255 is used as a bump allocator pointer
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-- r254 is -1
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-- r253 is 33 (the number of bytes in an inode other than its name)
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-- r252 is the root inode address
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-- r251 is `/` (47)
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-- r250 is `\` (92)
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jal r0, r0, start
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start:
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li r255, data
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li r254, -1
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li r253, 33
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li r251, 47
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li r250, 92
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jal r1, r0, create_root
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-- allocate space for the path ("/e")
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cp r8, r255
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addi r255, r255, 2
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li r9, 101
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-- store the path
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st r251, r8, 0, 1
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st r9, r8, 1, 1
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li r9, 2
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li r10, 0
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cp r32, r8 -- copy r8 to use the path again later
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jal r2, r0, create_inode
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cp r33, r8 -- copy r8 to compare against
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-- find `e` in /
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cp r8, r32
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addi r8, r8, 1
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li r9, 1
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ld r10, r252, 17, 8
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jal r3, r0, find_inode
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cp r34, r8
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-- at this point r33 is the address we created /e at, and r34 is the address we found it at
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ecall
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-- Reads the file at the path pointed to by `name_addr`
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--
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@ -88,80 +53,74 @@ write:
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-- r8: addr
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-- returns to r1
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mount:
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jal r0, r1, 0 -- do nothing for now
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-- Creates the root inode `/`
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-- This should be run at the start of execution, before any other inodes are made
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--
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-- returns to r1
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-- sets 252 to root inode's address
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create_root:
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cp r252, r255
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add r255, r255, r253 -- bump allocator past this inode
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st r0, r252, 0, 8 -- `next`
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li r8, 2
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st r8, r252, 8, 1 -- put 2 in `flags`
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st r0, r252, 9, 8 -- 0 `size` for now
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st r0, r252, 17, 8 -- 0 `addr` too
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st r0, r252, 25, 8 -- 0 `name_len`
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jal r0, r1, 0
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-- Creates a new inode with a chosen path
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--
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-- inputs:
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-- r8: path_addr
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-- r9: path_len
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-- r10: flags
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-- r10: dir
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-- outputs:
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-- r8: addr
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-- 1 if the path doesn't begin with a slash
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-- 2 if a parent doesn't exist
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-- 3 if a parent is a file
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-- returns to r2
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-- modifies r8-r17
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-- indirectly modifies r19-r27
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create_inode:
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cp r16, r9 -- copy `path_len` so we can use r9
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cp r17, r10 -- same with `flags` and r10
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-- r8 will store the address of the next bytes
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cp r17, r10 -- same with `dir` and r10
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-- r8 will store the address of the next byte
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li r9, 0 -- r9 will store the parsed length of the current part
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li r10, data -- r10 will be used to refer to the current parent inode, so we'll start it at the root
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cp r11, r8 -- r11 will store the base of the current part
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li r12, 0 -- r12 will store the total length of the parsed path for comparing to `path_len`
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-- r9 becomes the address of the end name
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-- r10 becomes the address of the direct parent, or an error code
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-- r11 becomes the length of the end name
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jal r4, r0, follow_path
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li r24, 10
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jltu r10, r24, create_inode_fail
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-- store slash character bytes to compare to
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li r14, 42 -- `/` is ascii 47
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li r15, 97 -- `\` is ascii 92
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create_parse_path:
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-- we have the start address, now we need the length of the part
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-- the next byte goes in r13
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ld r13, r8, 0, 8
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-- try to enter the inode if a slash was found
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jeq r13, r14, create_enter_inode
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jeq r13, r15, create_enter_inode
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-- increment the byte pointer and check the next one
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addi r8, r8, 1
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addi r9, r9, 1
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jeq r12, r16, creation -- create the inode if this is the last part
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jal r0, r0, create_parse_path
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create_enter_inode:
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cp r8, r11 -- for `find_inode` argument
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jal r3, r0, find_inode -- this will put the inode address in r8, or 0 if not found
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jeq r8, r0, create_inode_return -- return if the inode wasn't found
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cp r10, r8
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add r11, r11, r9 -- skip to the next path part
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addi r11, r10, 1 -- also skip the slash
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cp r8, r11
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add r12, r12, r9 -- increase the parsed length
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addi r12, r12, 1
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li r9, 0
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jal r0, r0, create_parse_path
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creation:
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cp r8, r255 -- set the base address of this inode
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add r255, r255, r253 -- bump allocator past this inode
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add r255, r255, r9 -- and its name
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-- get the first entry under the parent inode
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addi r24, r10, 17 -- r24 is now at the `addr` field of the parent
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st r24, r8, 0, 8 -- make this inode's `next` field point to the previous first child
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st r8, r10, 17, 8 -- point the parent's `addr` to this inode
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st r17, r8, 8, 1 -- store `flags`
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st r0, r8, 9, 8 -- store 0 for `size` until something gets added
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st r0, r8, 17, 8 -- same for `addr`
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st r9, r8, 25, 8 -- store `name_len`
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add r255, r255, r9 --
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add r255, r255, r253 -- bump allocator past this inode
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st r9, r8, 0, 8 -- store name_len
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-- copy the name into the inode
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cp r24, r11
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cp r25, r9
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cp r26, r8
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add r26, r26, r253
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-- increase the parent's size
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ld r24, r10, 9, 1
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addi r24, r24, 1
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st r24, r10, 9, 1
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addi r26, r253
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jal r4, r0, copy_buf
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-- get the first entry under the parent inode
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addi r25, r25, -- now r25 is at the `addr` field of the parent
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create_inode_return:
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jal r0, r2, 0
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create_inode_fail:
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cp r8, r10
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jal r0, r2, 0
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-- Finds an inode address by name within a parent inode
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-- Returns with 0 in `r8` if there is no inode with the passed name
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--
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@ -171,20 +130,12 @@ create_inode:
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-- r10: current_addr
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-- outputs:
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-- r8: addr
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-- 1 if the inode doesn't exist
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-- returns to r3
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-- modifies r10 and r19-r27
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find_inode:
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ld r19, r10, 25, 8 -- load the name length to compare
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ld r20, r10, 0, 8 -- load the `next` field of this inode
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ld r20, r27, 0, 8 -- load the `next` field of this inode
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jeq r9, r19, find_compare -- only compare names if they're the same length
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ld r64, r10, 0, 8
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ld r65, r10, 8, 1
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ld r66, r10, 9, 24
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ecall
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jeq r10, r20, find_inode_fail -- fail if this is the last one
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cp r10, r20
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jal r0, r0, find_inode -- else try the next inode
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@ -206,19 +157,19 @@ find_inode:
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cmp_4:
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ld r26, r19, 0, 4
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ld r24, r25, 0, 4
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addi r21, r21, 4
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add r21, r21, 4
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jal r0, r0, cmp_end
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cmp_2:
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ld r26, r19, 0, 2 -- first 2 bytes
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ld r24, r25, 0, 2
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addi r21, r21, 2
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add r21, r21, 2
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jal r0, r0, cmp_end
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cmp_1:
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ld r26, r19, 0, 1 -- get the byte to compare
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ld r24, r25, 0, 1 -- and the byte to compare with
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addi r21, r21, 1
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add r21, r21, 1
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cmp_end:
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jeq r26, r24, find_compare_loop -- continue if this set matches
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@ -229,10 +180,6 @@ find_inode:
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find_inode_return:
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jal r0, r3, 0
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find_inode_fail:
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li r8, 1
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jal r0, r3, 0
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-- Copies a buffer
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--
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-- inputs:
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@ -252,7 +199,7 @@ copy_buf:
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jeq r27, r0, copy_end
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addi r24, r24, 4
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addi r26, r26, 4
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addi r25, r25, -4
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addi r25, -4
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jal r0, r0, copy_buf
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copy_2:
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@ -260,7 +207,7 @@ copy_buf:
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jeq r27, r0, copy_end
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addi r24, r24, 2
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addi r26, r26, 2
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addi r25, r25, -2
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addi r25, -2
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jal r0, r0, copy_buf
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copy_1:
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@ -269,72 +216,6 @@ copy_buf:
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copy_end:
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jal r0, r4, 0
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-- Parses a path, returning the address of the direct parent
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--
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-- inputs:
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-- r8: path_addr
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-- r16: path_len
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-- outputs:
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-- r9: name_len
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-- r10: parent_addr
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-- 1 if the direct parent wasn't found
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-- 2 if a parent is a file
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-- r11: name_addr
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-- returns to r4
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-- modifies r12-r13
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follow_path:
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li r9, 0 -- r9 will store the parsed length of the current part
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cp r10, r252 -- r10 will be used to refer to the current parent inode, so we'll start it at the root
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cp r11, r8 -- r11 will store the base of the current part
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li r12, 0 -- r12 will store the total length of the parsed path for comparing to `path_len`
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-- skip leading slash if it exists
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ld r13, r8, 0, 1
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jeq r13, r14, skip_leading
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jeq r13, r15, skip_leading
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li r8, 1 -- return with a 1 in r8
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jal r0, r0, parse_return
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skip_leading:
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addi r8, r8, 1
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addi r9, r9, 1
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parse_loop:
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-- we have the start address, now we need the length of the part
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-- the next byte goes in r13
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ld r13, r8, 0, 1
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-- try to enter the inode if a slash was found
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jeq r13, r251, enter_inode
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jeq r13, r250, enter_inode
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-- increment the byte pointer and check the next one
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addi r8, r8, 1
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addi r9, r9, 1
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jeq r12, r16, parse_return -- return inode if this is the last part
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jal r0, r0, parse_loop
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enter_inode:
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cp r8, r11 -- for `find_inode` argument
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jal r3, r0, find_inode -- this will put the inode address in r8, or 0 if not found
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jeq r8, r0, parse_fail -- fail if the inode wasn't found
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cp r10, r8
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add r11, r11, r9 -- skip to the next path part
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addi r11, r11, 1 -- also skip the slash
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cp r8, r11
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add r12, r12, r9 -- increase the parsed length
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addi r12, r12, 1 -- including the slash
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li r9, 0
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jal r0, r0, parse_loop
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parse_return:
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jal r0, r4, 0
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parse_fail:
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li r10, 1
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jal r0, r4, 0
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parse_parent_file:
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li r10, 2
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jal r0, r4, 0
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-- This is where all the VFS and FS data will be stored
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-- VFS comes first, and FS starts at `data + 2048`
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