109 lines
3.9 KiB
Text
109 lines
3.9 KiB
Text
This is Task 16 of the Eudyptula Challenge
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------------------------------------------
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Good job with the new syscall. The odds of you ever having to write a
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new syscall is pretty rare, but now you know where to look them up, and
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what the code involved in creating one looks like, which is useful when
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you try to debug things.
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Let's take a breather after all of that code, and go back to doing a bit
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of reading, and learn some more about some common kernel tools.
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Go install the tool 'sparse'. It was started by Linus as a
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static-analysis tool that acts much like a compiler. The kernel build
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system is set up to have it run if you ask it to, and it will report a
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bunch of issues in C code that are really specific to the kernel.
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When you build the kernel, pass the "C=1" option to the build, to have
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sparse run on the .c file before gcc is run. Depending on the file,
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nothing might be printed out, or something might. Here's an example of
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it being run on the ext4 code:
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$ make C=1 M=fs/ext4
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CHECK fs/ext4/balloc.c
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CC fs/ext4/balloc.o
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CHECK fs/ext4/bitmap.c
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CC fs/ext4/bitmap.o
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CHECK fs/ext4/dir.c
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CC fs/ext4/dir.o
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CHECK fs/ext4/file.c
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CC fs/ext4/file.o
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CHECK fs/ext4/fsync.c
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CC fs/ext4/fsync.o
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CHECK fs/ext4/ialloc.c
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CC fs/ext4/ialloc.o
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CHECK fs/ext4/inode.c
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CC fs/ext4/inode.o
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CHECK fs/ext4/page-io.c
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CC fs/ext4/page-io.o
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CHECK fs/ext4/ioctl.c
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CC fs/ext4/ioctl.o
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CHECK fs/ext4/namei.c
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CC fs/ext4/namei.o
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CHECK fs/ext4/super.c
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CC fs/ext4/super.o
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CHECK fs/ext4/symlink.c
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CC fs/ext4/symlink.o
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CHECK fs/ext4/hash.c
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CC fs/ext4/hash.o
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CHECK fs/ext4/resize.c
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CC fs/ext4/resize.o
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CHECK fs/ext4/extents.c
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CC fs/ext4/extents.o
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CHECK fs/ext4/ext4_jbd2.c
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CC fs/ext4/ext4_jbd2.o
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CHECK fs/ext4/migrate.c
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CC fs/ext4/migrate.o
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CHECK fs/ext4/mballoc.c
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fs/ext4/mballoc.c:5018:9: warning: context imbalance in 'ext4_trim_extent' - unexpected unlock
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CC fs/ext4/mballoc.o
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CHECK fs/ext4/block_validity.c
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CC fs/ext4/block_validity.o
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CHECK fs/ext4/move_extent.c
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CC fs/ext4/move_extent.o
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CHECK fs/ext4/mmp.c
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CC fs/ext4/mmp.o
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CHECK fs/ext4/indirect.c
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CC fs/ext4/indirect.o
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CHECK fs/ext4/extents_status.c
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CC fs/ext4/extents_status.o
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CHECK fs/ext4/xattr.c
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CC fs/ext4/xattr.o
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CHECK fs/ext4/xattr_user.c
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CC fs/ext4/xattr_user.o
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CHECK fs/ext4/xattr_trusted.c
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CC fs/ext4/xattr_trusted.o
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CHECK fs/ext4/inline.c
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CC fs/ext4/inline.o
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CHECK fs/ext4/acl.c
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CC fs/ext4/acl.o
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CHECK fs/ext4/xattr_security.c
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CC fs/ext4/xattr_security.o
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LD fs/ext4/ext4.o
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LD fs/ext4/built-in.o
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Building modules, stage 2.
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MODPOST 0 modules
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As you can see, only one warning was found here, and odds are, it is a
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false-positive, as I'm sure those ext4 developers know what they are
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doing with their locking functions, right?
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Anyway the task this time is:
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- Run sparse on the drivers/staging/ directory, yes, that horrible
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code again, sorry.
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- Find one warning that looks interesting.
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- Write a patch that resolves the issue.
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- Make sure the patch is correct by running it through
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scripts/checkpatch.pl
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- Submit the code to the maintainer of the driver/subsystem, finding
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the proper name and mailing lists to send it to by running the tool,
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scripts/get_maintainer.pl on your patch.
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- Work with the maintainer to get the patch accepted into their tree.
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- Send a web link back to me of your patch in the public mailing list
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archive (don't cc: me on the patch, that will only confuse me and
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everyone in the kernel development community) as well as a pointer
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to the patch in the maintainer's public git tree.
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That's it, much like task 10 was, but this time you are fixing logical
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issues, not just pesky coding style issues. You are a real developer
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now, fixing real bugs!
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