tjh.dev
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1444073
3
928
Clone this repository
https://tangled.org/tjh.dev/kernel
https://tangled.org/did:plc:65gha4t3avpfpzmvpbwovss7/kernel
git@gordian.tjh.dev:tjh.dev/kernel
git@gordian.tjh.dev:did:plc:65gha4t3avpfpzmvpbwovss7/kernel
For self-hosted knots, clone URLs may differ based on your setup.
Download tar.gz
Geert Uytterhoeven reports a strange side-effect of commit 858805b336be
("kbuild: add $(BASH) to run scripts with bash-extension"), which
inserts the contents of a localversion file in the build directory twice.
[Steps to Reproduce]
$ echo bar > localversion
$ mkdir build
$ cd build/
$ echo foo > localversion
$ make -s -f ../Makefile defconfig include/config/kernel.release
$ cat include/config/kernel.release
5.4.0-rc1foofoobar
This comes down to the behavior change of local variables.
The 'man sh' on my Ubuntu machine, where sh is an alias to dash,
explains as follows:
When a variable is made local, it inherits the initial value and
exported and readonly flags from the variable with the same name
in the surrounding scope, if there is one. Otherwise, the variable
is initially unset.
[Test Code]
foo ()
{
local res
echo "res: $res"
}
res=1
foo
[Result]
$ sh test.sh
res: 1
$ bash test.sh
res:
So, scripts/setlocalversion correctly works only for bash in spite of
its hashbang being #!/bin/sh. Nobody had noticed it before because
CONFIG_SHELL was previously set to bash almost all the time.
Now that CONFIG_SHELL is set to sh, we must write portable and correct
code. I gave the Fixes tag to the commit that uncovered the issue.
Clear the variable 'res' in collect_files() to make it work for sh
(and it also works on distributions where sh is an alias to bash).
Fixes: 858805b336be ("kbuild: add $(BASH) to run scripts with bash-extension")
Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
The namespace.pl script does not work properly if objtree is not set to
an absolute path. The do_nm function is run from within the find
function, which changes directories.
Because of this, appending objtree, $File::Find::dir, and $source, will
return a path which is not valid from the current directory.
This used to work when objtree was set to an absolute path when using
"make namespacecheck". It appears to have not worked when calling
./scripts/namespace.pl directly.
This behavior was changed in 7e1c04779efd ("kbuild: Use relative path
for $(objtree)", 2014-05-14)
Rather than fixing the Makefile to set objtree to an absolute path, just
fix namespace.pl to work when srctree and objtree are relative. Also fix
the script to use an absolute path for these by default.
Use the File::Spec module for this purpose. It's been part of perl
5 since 5.005.
The curdir() function is used to get the current directory when the
objtree and srctree aren't set in the environment.
rel2abs() is used to convert possibly relative objtree and srctree
environment variables to absolute paths.
Finally, the catfile() function is used instead of string appending
paths together, since this is more robust when joining paths together.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Currently, all the logo C files are generated irrespective of the
CONFIG options. Adding them to extra-y is wrong. What we need to do
here is to add them to 'targets' so that if_changed works properly.
Files listed in 'targets' are cleaned, so clean-files is unneeded.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
The pattern *.o is cleaned up globally by the top Makefile.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
The ima/ and evm/ sub-directories contain built-in objects, so
obj-$(CONFIG_...) is the correct way to descend into them.
subdir-$(CONFIG_...) is redundant.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
I guess commit 15ea0e1e3e18 ("efi: Import certificates from UEFI Secure
Boot") attempted to add -fshort-wchar for building load_uefi.o, but it
has never worked as intended.
load_uefi.o is created in the platform_certs/ sub-directory. If you
really want to add -fshort-wchar, the correct code is:
$(obj)/platform_certs/load_uefi.o: KBUILD_CFLAGS += -fshort-wchar
But, you do not need to fix it.
Commit 8c97023cf051 ("Kbuild: use -fshort-wchar globally") had already
added -fshort-wchar globally. This code was unneeded in the first place.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Johannes Berg reports lots of modpost warnings on ARCH=um builds:
WARNING: "rename" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "lseek" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "ftruncate64" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "getuid" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "lseek64" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "unlink" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "pwrite64" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "close" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "opendir" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "pread64" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "syscall" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "readdir" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "readdir64" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "futimes" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "__lxstat" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "write" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "closedir" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "__xstat" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "fsync" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "__lxstat64" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "__fxstat64" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "telldir" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "printf" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "readlink" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "__sprintf_chk" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "link" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "rmdir" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "fdatasync" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "truncate" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "statfs" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "__errno_location" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "__xmknod" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "open64" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "truncate64" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "open" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "read" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "chown" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "chmod" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "utime" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "fchmod" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "seekdir" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "ioctl" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "dup2" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "statfs64" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "utimes" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "mkdir" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "fchown" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "__guard" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "symlink" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "access" [vmlinux] is a static EXPORT_SYMBOL
WARNING: "__stack_smash_handler" [vmlinux] is a static EXPORT_SYMBOL
When you run "make", the modpost is run twice; before linking vmlinux,
and before building modules. All the warnings above are from the second
modpost.
The offending symbols are defined not in vmlinux, but in the C library.
The first modpost is run against the relocatable vmlinux.o, and those
warnings are nicely suppressed because the SH_UNDEF entries from the
symbol table clear the ->is_static flag.
The second modpost is run against the executable vmlinux (+ modules),
where those symbols have been resolved, but the definitions do not
exist.
This commit fixes it in a straightforward way; suppress the static
EXPORT_SYMBOL warnings from "vmlinux".
Without this commit, we see valid warnings twice anyway. For example,
ARCH=arm64 defconfig shows the following warning twice:
WARNING: "HYPERVISOR_platform_op" [vmlinux] is a static EXPORT_SYMBOL_GPL
So, it is reasonable to suppress the second one.
Fixes: 15bfc2348d54 ("modpost: check for static EXPORT_SYMBOL* functions")
Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Johannes Berg <johannes@sipsolutions.net>
Tested-by: Denis Efremov <efremov@linux.com>
Minor formatting fixup.
Fixes: cd238effefa2 ("docs: kbuild: convert docs to ReST and rename to *.rst")
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: Matthew Garrett <mjg59@google.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Linux 5.3 is out. Remove the SUBDIRS support.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Commit 40df759e2b9e ("kbuild: Fix build with binutils <= 2.19")
introduced ar-option and KBUILD_ARFLAGS to deal with old binutils.
According to Documentation/process/changes.rst, the current minimal
supported version of binutils is 2.21 so you can assume the 'D' option
is always supported. Not only GNU ar but also llvm-ar supports it.
With the 'D' option hard-coded, there is no more user of ar-option
or KBUILD_ARFLAGS.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Pull btrfs fixes from David Sterba:
"A bunch of fixes that accumulated in recent weeks, mostly material for
stable.
Summary:
- fix for regression from 5.3 that prevents to use balance convert
with single profile
- qgroup fixes: rescan race, accounting leak with multiple writers,
potential leak after io failure recovery
- fix for use after free in relocation (reported by KASAN)
- other error handling fixups"
* tag 'for-5.4-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
btrfs: qgroup: Fix reserved data space leak if we have multiple reserve calls
btrfs: qgroup: Fix the wrong target io_tree when freeing reserved data space
btrfs: Fix a regression which we can't convert to SINGLE profile
btrfs: relocation: fix use-after-free on dead relocation roots
Btrfs: fix race setting up and completing qgroup rescan workers
Btrfs: fix missing error return if writeback for extent buffer never started
btrfs: adjust dirty_metadata_bytes after writeback failure of extent buffer
Btrfs: fix selftests failure due to uninitialized i_mode in test inodes
Pull csky updates from Guo Ren:
"This round of csky subsystem just some fixups:
- Fix mb() synchronization problem
- Fix dma_alloc_coherent with PAGE_SO attribute
- Fix cache_op failed when cross memory ZONEs
- Optimize arch_sync_dma_for_cpu/device with dma_inv_range
- Fix ioremap function losing
- Fix arch_get_unmapped_area() implementation
- Fix defer cache flush for 610
- Support kernel non-aligned access
- Fix 610 vipt cache flush mechanism
- Fix add zero_fp fixup perf backtrace panic
- Move static keyword to the front of declaration
- Fix csky_pmu.max_period assignment
- Use generic free_initrd_mem()
- entry: Remove unneeded need_resched() loop"
* tag 'csky-for-linus-5.4-rc1' of git://github.com/c-sky/csky-linux:
csky: Move static keyword to the front of declaration
csky: entry: Remove unneeded need_resched() loop
csky: Fixup csky_pmu.max_period assignment
csky: Fixup add zero_fp fixup perf backtrace panic
csky: Use generic free_initrd_mem()
csky: Fixup 610 vipt cache flush mechanism
csky: Support kernel non-aligned access
csky: Fixup defer cache flush for 610
csky: Fixup arch_get_unmapped_area() implementation
csky: Fixup ioremap function losing
csky: Optimize arch_sync_dma_for_cpu/device with dma_inv_range
csky/dma: Fixup cache_op failed when cross memory ZONEs
csky: Fixup dma_alloc_coherent with PAGE_SO attribute
csky: Fixup mb() synchronization problem
README