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Change the naming for consistency.
While at this, fix the comments in scripts/link-vmlinux.sh.
Signed-off-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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W=1 builds reported warnings regarding files being ignored:
tools/testing/selftests/arm64/tags/.gitignore: warning: ignored by one of the .gitignore files
tools/testing/selftests/arm64/tags/Makefile: warning: ignored by one of the .gitignore files
tools/testing/selftests/arm64/tags/tags_test.c: warning: ignored by one of the .gitignore files
Adjusting the .gitignore entries will prevent these warnings and
ensure a smoother script execution.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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resolve_btfids is used by link-vmlinux.sh.
In contrast to other configuration options and targets no transitive
dependency between resolve_btfids and vmlinux.
Add an explicit one.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Use a helper available in scripts/include/hash.h.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Python3 is necessary for running some scripts such as
drivers/gpu/drm/msm/registers/gen_header.py
Both scripts/package/kernel.spec and scripts/package/PKGBUILD already
list Python as the build dependency.
Do likewise for scripts/package/mkdebian.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
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Modify this function to return earlier when find_symbol() returns NULL,
reducing the level of improve readability.
No functional changes are intended.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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The first error message in device_id_check() is obscure and can be
misleading because the cause of the error is unlikely to be found in
the struct definition in mod_devicetable.h.
This type of error occurs when an array is passed to an incorrect type
of MODULE_DEVICE_TABLE().
[Example 1]
static const struct acpi_device_id foo_ids[] = {
{ "FOO" },
{ /* sentinel */ },
};
MODULE_DEVICE_TABLE(of, foo_ids);
Currently, modpost outputs a meaningless suggestion:
ERROR: modpost: ...: sizeof(struct of_device_id)=200 is not a modulo of the size of section __mod_device_table__of__<identifier>=64.
Fix definition of struct of_device_id in mod_devicetable.h
The root cause here is that MODULE_DEVICE_TABLE(of, ...) is used instead
of the correct MODULE_DEVICE_TABLE(acpi, ...).
This commit provides a more intuitive error message:
ERROR: modpost: ...: type mismatch between foo_ids[] and MODULE_DEVICE_TABLE(of, ...)
The second error message, related to a missing terminator, is too
verbose.
[Example 2]
static const struct acpi_device_id foo_ids[] = {
{ "FOO" },
};
MODULE_DEVICE_TABLE(acpi, foo_ids);
The current error message is overly long, and does not pinpoint the
incorrect array:
...: struct acpi_device_id is 32 bytes. The last of 1 is:
0x46 0x4f 0x4f 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
ERROR: modpost: ...: struct acpi_device_id is not terminated with a NULL entry!
This commit changes it to a more concise error message, sufficient to
identify the incorrect array:
ERROR: modpost: ...: foo_ids[] is not terminated with a NULL entry
Lastly, this commit squashes device_id_check() into do_table() and
changes fatal() into error(), allowing modpost to continue processing
other modules.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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This commit renames the alias symbol, __mod_<type>__<name>_device_table
to __mod_device_table__<type>__<name>.
This change simplifies the code slightly, as there is no longer a need
to check both the prefix and suffix.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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This commit renames the variables in handle_moddevtable() as follows:
name -> type
namelen -> typelen
identifier -> name
These changes align with the definition in include/linux/module.h:
extern typeof(name) __mod_##type##__##name##_device_table
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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This macro is useful in file2alias.c as well.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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do_usb_table() no longer needs to iterate over the usb_device_id array.
Convert it to a generic ->do_entry() handler.
This is the last special case. Clean up handle_moddevtable().
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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do_of_table() no longer needs to iterate over the of_device_id array.
Convert it to a generic ->do_entry() handler.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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do_pnp_device_entry() no longer needs to iterate over the
pnp_device_id array.
Convert it to a generic ->do_entry() handler.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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do_pnp_card_entries() no longer needs to iterate over the
pnp_card_device_id array.
Convert it to a generic ->do_entry() handler.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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The do_*_entry() functions cannot check the length of the given buffer.
Use module_alias_printf() helper consistently for these functions.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Replace the first argument with a pointer to struct module.
'filename' can be replaced with mod->name.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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With the former cleanups in do_pnp_card_entries(), this macro is no
longer used by anyone.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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MODULE_DEVICE_TABLE(pnp_card, ...) may have duplicated IDs. For
instance, snd_ad1816a_pnpids[] in sound/isa/ad1816a/ad1816a.c includes
multiple occurrences of the "ADS7180" string within its .devs fields.
Currently, do_pnp_card_entries() handles deduplication on its own, but
this logic should be moved to a common helper function, as drivers in
other subsystems might also have similar duplication issues.
For example, drivers/media/i2c/s5c73m3/s5c73m3.mod.c contains duplicated
MODULE_ALIAS() entries because both s5c73m3-core.c and s5c73m3-spi.c
define the same compatible string.
This commit eliminates redundant MODULE_ALIAS() entries across all
drivers.
[Before]
$ grep MODULE_ALIAS drivers/media/i2c/s5c73m3/s5c73m3.mod.c
MODULE_ALIAS("i2c:S5C73M3");
MODULE_ALIAS("of:N*T*Csamsung,s5c73m3");
MODULE_ALIAS("of:N*T*Csamsung,s5c73m3C*");
MODULE_ALIAS("of:N*T*Csamsung,s5c73m3");
MODULE_ALIAS("of:N*T*Csamsung,s5c73m3C*");
[After]
$ grep MODULE_ALIAS drivers/media/i2c/s5c73m3/s5c73m3.mod.c
MODULE_ALIAS("i2c:S5C73M3");
MODULE_ALIAS("of:N*T*Csamsung,s5c73m3");
MODULE_ALIAS("of:N*T*Csamsung,s5c73m3C*");
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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The generic ->do_entry() handler is currently limited to returning
a single alias string.
However, this is not flexible enough for several subsystems, which
currently require their own implementations:
- do_usb_table()
- do_of_table()
- do_pnp_device_entry()
- do_pnp_card_entries()
This commit introduces a helper function so that these special cases can
add multiple MODULE_ALIAS() and then migrate to the generic framework.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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The 'id' pointer is never NULL since it has the same address as
'symval'.
Also, checking (*id)[0] is simpler than calling strlen().
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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This function contains multiple bugs after the following commits:
- ac551828993e ("modpost: i2c aliases need no trailing wildcard")
- 6543becf26ff ("mod/file2alias: make modalias generation safe for cross compiling")
Commit ac551828993e inserted the following code to do_eisa_entry():
else
strcat(alias, "*");
This is incorrect because 'alias' is uninitialized. If it is not
NULL-terminated, strcat() could cause a buffer overrun.
Even if 'alias' happens to be zero-filled, it would output:
MODULE_ALIAS("*");
This would match anything. As a result, the module could be loaded by
any unrelated uevent from an unrelated subsystem.
Commit ac551828993e introduced another bug.
Prior to that commit, the conditional check was:
if (eisa->sig[0])
This checked if the first character of eisa_device_id::sig was not '\0'.
However, commit ac551828993e changed it as follows:
if (sig[0])
sig[0] is NOT the first character of the eisa_device_id::sig. The
type of 'sig' is 'char (*)[8]', meaning that the type of 'sig[0]' is
'char [8]' instead of 'char'. 'sig[0]' and 'symval' refer to the same
address, which never becomes NULL.
The correct conversion would have been:
if ((*sig)[0])
However, this if-conditional was meaningless because the earlier change
in commit ac551828993e was incorrect.
This commit removes the entire incorrect code, which should never have
been executed.
Fixes: ac551828993e ("modpost: i2c aliases need no trailing wildcard")
Fixes: 6543becf26ff ("mod/file2alias: make modalias generation safe for cross compiling")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Set the -e option to ensure this script fails on any unexpected errors.
Without this change, the kernel build may continue running with an
incorrect string in include/config/kernel.release.
Currently, try_tag() returns 1 when the expected tag is not found as an
ancestor, but this is a case where the script should continue.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Contrary to expectations, passing a single candidate tag to "git
describe" is slower than not passing any --match options.
$ time git describe --debug
...
traversed 10619 commits
...
v6.12-rc5-63-g0fc810ae3ae1
real 0m0.169s
$ time git describe --match=v6.12-rc5 --debug
...
traversed 1310024 commits
v6.12-rc5-63-g0fc810ae3ae1
real 0m1.281s
In fact, the --debug output shows that git traverses all or most of
history. For some repositories and/or git versions, those 1.3s are
actually 10-15 seconds.
This has been acknowledged as a performance bug in git [1], and a fix
is on its way [2]. However, no solution is yet in git.git, and even
when one lands, it will take quite a while before it finds its way to
a release and for $random_kernel_developer to pick that up.
So rewrite the logic to use plumbing commands. For each of the
candidate values of $tag, we ask: (1) is $tag even an annotated
tag? (2) Is it eligible to describe HEAD, i.e. an ancestor of
HEAD? (3) If so, how many commits are in $tag..HEAD?
I have tested that this produces the same output as the current script
for ~700 random commits between v6.9..v6.10. For those 700 commits,
and in my git repo, the 'make -s kernelrelease' command is on average
~4 times faster with this patch applied (geometric mean of ratios).
For the commit mentioned in Josh's original report [3], the
time-consuming part of setlocalversion goes from
$ time git describe --match=v6.12-rc5 c1e939a21eb1
v6.12-rc5-44-gc1e939a21eb1
real 0m1.210s
to
$ time git rev-list --count --left-right v6.12-rc5..c1e939a21eb1
0 44
real 0m0.037s
[1] https://lore.kernel.org/git/20241101113910.GA2301440@coredump.intra.peff.net/
[2] https://lore.kernel.org/git/20241106192236.GC880133@coredump.intra.peff.net/
[3] https://lore.kernel.org/lkml/309549cafdcfe50c4fceac3263220cc3d8b109b2.1730337435.git.jpoimboe@kernel.org/
Reported-by: Sean Christopherson <seanjc@google.com>
Closes: https://lore.kernel.org/lkml/ZPtlxmdIJXOe0sEy@google.com/
Reported-by: Josh Poimboeuf <jpoimboe@kernel.org>
Closes: https://lore.kernel.org/lkml/309549cafdcfe50c4fceac3263220cc3d8b109b2.1730337435.git.jpoimboe@kernel.org/
Tested-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Replace lz4c with lz4 for kernel image compression.
Although lz4 and lz4c are functionally similar, lz4c has been deprecated
upstream since 2018. Since as early as Ubuntu 16.04 and Fedora 25, lz4
and lz4c have been packaged together, making it safe to update the
requirement from lz4c to lz4.
Consequently, some distributions and build systems, such as OpenEmbedded,
have fully transitioned to using lz4. OpenEmbedded core adopted this
change in commit fe167e082cbd ("bitbake.conf: require lz4 instead of
lz4c"), causing compatibility issues when building the mainline kernel
in the latest OpenEmbedded environment, as seen in the errors below.
This change also updates the LZ4 compression commands to make it backward
compatible by replacing stdin and stdout with the '-' option, due to some
unclear reason, the stdout keyword does not work for lz4 and '-' works for
both. In addition, this modifies the legacy '-c1' with '-9' which is also
compatible with both. This fixes the mainline kernel build failures with
the latest master OpenEmbedded builds associated with the mentioned
compatibility issues.
LZ4 arch/arm/boot/compressed/piggy_data
/bin/sh: 1: lz4c: not found
...
...
ERROR: oe_runmake failed
Link: https://github.com/lz4/lz4/pull/553
Suggested-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Signed-off-by: Parth Pancholi <parth.pancholi@toradex.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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This reverts commit 54babdc0343f ("kbuild: Disable KCSAN for
autogenerated *.mod.c intermediaries").
Now that objtool is enabled for *.mod.c, there is no need to filter
out CFLAGS_KCSAN.
I no longer see "Unpatched return thunk in use. This should not happen!"
error with KCSAN when loading a module.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Currently, objtool is disabled in scripts/Makefile.{modfinal,vmlinux}.
This commit moves rule_cc_o_c and rule_as_o_S to scripts/Makefile.lib
and set objtool-enabled to y there.
With this change, *.mod.o, .module-common.o, builtin-dtb.o, and
vmlinux.export.o will now be covered by objtool.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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The cmd_cc_o_c and cmd_as_o_S macros are duplicated in
scripts/Makefile.{build,modfinal,vmlinux}.
This commit factors them out to scripts/Makefile.lib.
No functional changes are intended.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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This rule is unnecessary because you can generate foo/bar.symtypes
as a side effect using:
$ make KBUILD_SYMTYPES=1 foo/bar.o
While compiling *.o is slower than preprocessing, the impact is
negligible. I prioritize keeping the code simpler.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
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There is no need to pass '-r /dev/null', which is no-op.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
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Unless an explicit O= option is provided, external module builds must
start from the kernel directory.
This can be achieved by using the -C option:
$ make -C /path/to/kernel M=/path/to/external/module
This commit allows starting external module builds from any directory,
so you can also do the following:
$ make -f /path/to/kernel/Makefile M=/path/to/external/module
The key difference is that the -C option changes the working directory
and parses the Makefile located there, while the -f option only
specifies the Makefile to use.
As shown in the examples in Documentation/kbuild/modules.rst, external
modules usually have a wrapper Makefile that allows you to build them
without specifying any make arguments. The Makefile typically contains
a rule as follows:
KDIR ?= /path/to/kernel
default:
$(MAKE) -C $(KDIR) M=$(CURDIR) $(MAKECMDGOALS)
The log will appear as follows:
$ make
make -C /path/to/kernel M=/path/to/external/module
make[1]: Entering directory '/path/to/kernel'
make[2]: Entering directory '/path/to/external/module'
CC [M] helloworld.o
MODPOST Module.symvers
CC [M] helloworld.mod.o
CC [M] .module-common.o
LD [M] helloworld.ko
make[2]: Leaving directory '/path/to/external/module'
make[1]: Leaving directory '/path/to/kernel'
This changes the working directory twice because the -C option first
switches to the kernel directory, and then Kbuild internally recurses
back to the external module directory.
With this commit, the wrapper Makefile can directly include the kernel
Makefile:
KDIR ?= /path/to/kernel
export KBUILD_EXTMOD := $(realpath $(dir $(lastword $(MAKEFILE_LIST))))
include $(KDIR)/Makefile
This avoids unnecessary sub-make invocations:
$ make
CC [M] helloworld.o
MODPOST Module.symvers
CC [M] helloworld.mod.o
CC [M] .module-common.o
LD [M] helloworld.ko
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
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When Kbuild starts building in a separate output directory, it generates
a wrapper Makefile, allowing you to invoke 'make' from the output
directory.
This commit makes it more convenient, so you can invoke 'make' without
M= or MO=.
First, you need to build external modules in a separate directory:
$ make M=/path/to/module/source/dir MO=/path/to/module/build/dir
Once the wrapper Makefile is generated in /path/to/module/build/dir,
you can proceed as follows:
$ cd /path/to/module/build/dir
$ make
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
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Keep the consistent behavior when this Makefile is invoked from another
directory.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
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This commit makes -fmacro-prefix-map work for external modules built in
a separate output directory. It improves the reproducibility of external
modules and provides the benefits described in commit a73619a845d5
("kbuild: use -fmacro-prefix-map to make __FILE__ a relative path").
When building_out_of_srctree is not defined (e.g., when the kernel or
external module is built in the source directory), this option is
unnecessary.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
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There has been a long-standing request to support building external
modules in a separate build directory.
This commit introduces a new environment variable, KBUILD_EXTMOD_OUTPUT,
and its shorthand Make variable, MO.
A simple usage:
$ make -C <kernel-dir> M=<module-src-dir> MO=<module-build-dir>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
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With the previous changes, $(extmod_prefix), $(MODORDER), and
$(MODULES_NSDEPS) are constant. (empty, modules.order, and
modules.nsdeps, respectively).
Remove these variables and hard-code their values.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
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Currently, Kbuild always operates in the output directory of the kernel,
even when building external modules. This increases the risk of external
module Makefiles attempting to write to the kernel directory.
This commit switches the working directory to the external module
directory, allowing the removal of the $(KBUILD_EXTMOD)/ prefix from
some build artifacts.
The command for building external modules maintains backward
compatibility, but Makefiles that rely on working in the kernel
directory may break. In such cases, $(objtree) and $(srctree) should
be used to refer to the output and source directories of the kernel.
The appearance of the build log will change as follows:
[Before]
$ make -C /path/to/my/linux M=/path/to/my/externel/module
make: Entering directory '/path/to/my/linux'
CC [M] /path/to/my/externel/module/helloworld.o
MODPOST /path/to/my/externel/module/Module.symvers
CC [M] /path/to/my/externel/module/helloworld.mod.o
CC [M] /path/to/my/externel/module/.module-common.o
LD [M] /path/to/my/externel/module/helloworld.ko
make: Leaving directory '/path/to/my/linux'
[After]
$ make -C /path/to/my/linux M=/path/to/my/externel/module
make: Entering directory '/path/to/my/linux'
make[1]: Entering directory '/path/to/my/externel/module'
CC [M] helloworld.o
MODPOST Module.symvers
CC [M] helloworld.mod.o
CC [M] .module-common.o
LD [M] helloworld.ko
make[1]: Leaving directory '/path/to/my/externel/module'
make: Leaving directory '/path/to/my/linux'
Printing "Entering directory" twice is cumbersome. This will be
addressed later.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
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$(KBUILD_OUTPUT) specifies the output directory of kernel builds.
Use a more generic name, 'output', to better reflect this code hunk in
the context of external module builds.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
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'objtree' refers to the top of the output directory of kernel builds.
Rename abs_objtree to a more generic name, to better reflect its use in
the context of external module builds.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
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$(objtree) refers to the top of the output directory of kernel builds.
This commit adds the explicit $(objtree)/ prefix to build artifacts
needed for building external modules.
This change has no immediate impact, as the top-level Makefile
currently defines:
objtree := .
This commit prepares for supporting the building of external modules
in a different directory.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
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Kbuild changes the working directory until it matches $(abs_objtree).
When $(need-sub-make) is empty, $(abs_objtree) is the same as $(CURDIR).
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <n.schier@avm.de>
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Kernels built without CONFIG_MODULES might still want to create -dbg deb
packages but install_linux_image_dbg() assumes modules.order always
exists. This obviously isn't true if no modules were built, so we should
skip reading modules.order in that case.
Fixes: 16c36f8864e3 ("kbuild: deb-pkg: use build ID instead of debug link for dbg package")
Signed-off-by: Matt Fleming <mfleming@cloudflare.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Commit b1fca27d384e ("kernel debug: support resetting WARN*_ONCE")
added support for clearing the state of once warnings. However,
it is not functional when CONFIG_LD_DEAD_CODE_DATA_ELIMINATION or
CONFIG_LTO_CLANG is enabled, because .data.once matches the
.data.[0-9a-zA-Z_]* pattern in the DATA_MAIN macro.
Commit cb87481ee89d ("kbuild: linker script do not match C names unless
LD_DEAD_CODE_DATA_ELIMINATION is configured") was introduced to suppress
the issue for the default CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=n case,
providing a minimal fix for stable backporting. We were aware this did
not address the issue for CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y. The
plan was to apply correct fixes and then revert cb87481ee89d. [1]
Seven years have passed since then, yet the #ifdef workaround remains in
place. Meanwhile, commit b1fca27d384e introduced the .data.once section,
and commit dc5723b02e52 ("kbuild: add support for Clang LTO") extended
the #ifdef.
Using a ".." separator in the section name fixes the issue for
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION and CONFIG_LTO_CLANG.
[1]: https://lore.kernel.org/linux-kbuild/CAK7LNASck6BfdLnESxXUeECYL26yUDm0cwRZuM4gmaWUkxjL5g@mail.gmail.com/
Fixes: b1fca27d384e ("kernel debug: support resetting WARN*_ONCE")
Fixes: dc5723b02e52 ("kbuild: add support for Clang LTO")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Commit 7ccaba5314ca ("consolidate WARN_...ONCE() static variables")
was intended to collect all .data.unlikely sections into one chunk.
However, this has not worked when CONFIG_LD_DEAD_CODE_DATA_ELIMINATION
or CONFIG_LTO_CLANG is enabled, because .data.unlikely matches the
.data.[0-9a-zA-Z_]* pattern in the DATA_MAIN macro.
Commit cb87481ee89d ("kbuild: linker script do not match C names unless
LD_DEAD_CODE_DATA_ELIMINATION is configured") was introduced to suppress
the issue for the default CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=n case,
providing a minimal fix for stable backporting. We were aware this did
not address the issue for CONFIG_LD_DEAD_CODE_DATA_ELIMINATION=y. The
plan was to apply correct fixes and then revert cb87481ee89d. [1]
Seven years have passed since then, yet the #ifdef workaround remains in
place.
Using a ".." separator in the section name fixes the issue for
CONFIG_LD_DEAD_CODE_DATA_ELIMINATION and CONFIG_LTO_CLANG.
[1]: https://lore.kernel.org/linux-kbuild/CAK7LNASck6BfdLnESxXUeECYL26yUDm0cwRZuM4gmaWUkxjL5g@mail.gmail.com/
Fixes: cb87481ee89d ("kbuild: linker script do not match C names unless LD_DEAD_CODE_DATA_ELIMINATION is configured")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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The '-fbasic-block-sections=labels' option has been deprecated in tip
of tree clang (20.0.0) [1]. While the option still works, a warning is
emitted:
clang: warning: argument '-fbasic-block-sections=labels' is deprecated, use '-fbasic-block-address-map' instead [-Wdeprecated]
Add a version check to set the proper option.
Link: https://github.com/llvm/llvm-project/pull/110039 [1]
Signed-off-by: Rong Xu <xur@google.com>
Reported-by: Nathan Chancellor <nathan@kernel.org>
Suggested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Add the build support for using Clang's Propeller optimizer. Like
AutoFDO, Propeller uses hardware sampling to gather information
about the frequency of execution of different code paths within a
binary. This information is then used to guide the compiler's
optimization decisions, resulting in a more efficient binary.
The support requires a Clang compiler LLVM 19 or later, and the
create_llvm_prof tool
(https://github.com/google/autofdo/releases/tag/v0.30.1). This
commit is limited to x86 platforms that support PMU features
like LBR on Intel machines and AMD Zen3 BRS.
Here is an example workflow for building an AutoFDO+Propeller
optimized kernel:
1) Build the kernel on the host machine, with AutoFDO and Propeller
build config
CONFIG_AUTOFDO_CLANG=y
CONFIG_PROPELLER_CLANG=y
then
$ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo_profile>
“<autofdo_profile>” is the profile collected when doing a non-Propeller
AutoFDO build. This step builds a kernel that has the same optimization
level as AutoFDO, plus a metadata section that records basic block
information. This kernel image runs as fast as an AutoFDO optimized
kernel.
2) Install the kernel on test/production machines.
3) Run the load tests. The '-c' option in perf specifies the sample
event period. We suggest using a suitable prime number,
like 500009, for this purpose.
For Intel platforms:
$ perf record -e BR_INST_RETIRED.NEAR_TAKEN:k -a -N -b -c <count> \
-o <perf_file> -- <loadtest>
For AMD platforms:
The supported system are: Zen3 with BRS, or Zen4 with amd_lbr_v2
# To see if Zen3 support LBR:
$ cat proc/cpuinfo | grep " brs"
# To see if Zen4 support LBR:
$ cat proc/cpuinfo | grep amd_lbr_v2
# If the result is yes, then collect the profile using:
$ perf record --pfm-events RETIRED_TAKEN_BRANCH_INSTRUCTIONS:k -a \
-N -b -c <count> -o <perf_file> -- <loadtest>
4) (Optional) Download the raw perf file to the host machine.
5) Generate Propeller profile:
$ create_llvm_prof --binary=<vmlinux> --profile=<perf_file> \
--format=propeller --propeller_output_module_name \
--out=<propeller_profile_prefix>_cc_profile.txt \
--propeller_symorder=<propeller_profile_prefix>_ld_profile.txt
“create_llvm_prof” is the profile conversion tool, and a prebuilt
binary for linux can be found on
https://github.com/google/autofdo/releases/tag/v0.30.1 (can also build
from source).
"<propeller_profile_prefix>" can be something like
"/home/user/dir/any_string".
This command generates a pair of Propeller profiles:
"<propeller_profile_prefix>_cc_profile.txt" and
"<propeller_profile_prefix>_ld_profile.txt".
6) Rebuild the kernel using the AutoFDO and Propeller profile files.
CONFIG_AUTOFDO_CLANG=y
CONFIG_PROPELLER_CLANG=y
and
$ make LLVM=1 CLANG_AUTOFDO_PROFILE=<autofdo_profile> \
CLANG_PROPELLER_PROFILE_PREFIX=<propeller_profile_prefix>
Co-developed-by: Han Shen <shenhan@google.com>
Signed-off-by: Han Shen <shenhan@google.com>
Signed-off-by: Rong Xu <xur@google.com>
Suggested-by: Sriraman Tallam <tmsriram@google.com>
Suggested-by: Krzysztof Pszeniczny <kpszeniczny@google.com>
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Suggested-by: Stephane Eranian <eranian@google.com>
Tested-by: Yonghong Song <yonghong.song@linux.dev>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Enable the machine function split optimization for AutoFDO in Clang.
Machine function split (MFS) is a pass in the Clang compiler that
splits a function into hot and cold parts. The linker groups all
cold blocks across functions together. This decreases hot code
fragmentation and improves iCache and iTLB utilization.
MFS requires a profile so this is enabled only for the AutoFDO builds.
Co-developed-by: Han Shen <shenhan@google.com>
Signed-off-by: Han Shen <shenhan@google.com>
Signed-off-by: Rong Xu <xur@google.com>
Suggested-by: Sriraman Tallam <tmsriram@google.com>
Suggested-by: Krzysztof Pszeniczny <kpszeniczny@google.com>
Tested-by: Yonghong Song <yonghong.song@linux.dev>
Tested-by: Yabin Cui <yabinc@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Enable -ffunction-sections by default for the AutoFDO build.
With -ffunction-sections, the compiler places each function in its own
section named .text.function_name instead of placing all functions in
the .text section. In the AutoFDO build, this allows the linker to
utilize profile information to reorganize functions for improved
utilization of iCache and iTLB.
Co-developed-by: Han Shen <shenhan@google.com>
Signed-off-by: Han Shen <shenhan@google.com>
Signed-off-by: Rong Xu <xur@google.com>
Suggested-by: Sriraman Tallam <tmsriram@google.com>
Tested-by: Yonghong Song <yonghong.song@linux.dev>
Tested-by: Yabin Cui <yabinc@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Add markers like __hot_text_start, __hot_text_end, __unlikely_text_start,
and __unlikely_text_end which will be included in System.map. These markers
indicate how the compiler groups functions, providing valuable information
to developers about the layout and optimization of the code.
Co-developed-by: Han Shen <shenhan@google.com>
Signed-off-by: Han Shen <shenhan@google.com>
Signed-off-by: Rong Xu <xur@google.com>
Suggested-by: Sriraman Tallam <tmsriram@google.com>
Tested-by: Yonghong Song <yonghong.song@linux.dev>
Tested-by: Yabin Cui <yabinc@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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When the -ffunction-sections compiler option is enabled, each function
is placed in a separate section named .text.function_name rather than
putting all functions in a single .text section.
However, using -function-sections can cause problems with the
linker script. The comments included in include/asm-generic/vmlinux.lds.h
note these issues.:
“TEXT_MAIN here will match .text.fixup and .text.unlikely if dead
code elimination is enabled, so these sections should be converted
to use ".." first.”
It is unclear whether there is a straightforward method for converting
a suffix to "..".
This patch modifies the order of subsections within the text output
section. Specifically, it changes current order:
.text.hot, .text, .text_unlikely, .text.unknown, .text.asan
to the new order:
.text.asan, .text.unknown, .text_unlikely, .text.hot, .text
Here is the rationale behind the new layout:
The majority of the code resides in three sections: .text.hot, .text,
and .text.unlikely, with .text.unknown containing a negligible amount.
.text.asan is only generated in ASAN builds.
The primary goal is to group code segments based on their execution
frequency (hotness).
First, we want to place .text.hot adjacent to .text. Since we cannot put
.text.hot after .text (Due to constraints with -ffunction-sections,
placing .text.hot after .text is problematic), we need to put
.text.hot before .text.
Then it comes to .text.unlikely, we cannot put it after .text (same
-ffunction-sections issue) . Therefore, we position .text.unlikely
before .text.hot.
.text.unknown and .tex.asan follow the same logic.
This revised ordering effectively reverses the original arrangement (for
.text.unlikely, .text.unknown, and .tex.asan), maintaining a similar level
of affinity between sections.
It also places .text.hot section at the beginning of a page to better
utilize the TLB entry.
Note that the limitation arises because the linker script employs glob
patterns instead of regular expressions for string matching. While there
is a method to maintain the current order using complex patterns, this
significantly complicates the pattern and increases the likelihood of
errors.
This patch also changes vmlinux.lds.S for the sparc64 architecture to
accommodate specific symbol placement requirements.
Co-developed-by: Han Shen <shenhan@google.com>
Signed-off-by: Han Shen <shenhan@google.com>
Signed-off-by: Rong Xu <xur@google.com>
Suggested-by: Sriraman Tallam <tmsriram@google.com>
Suggested-by: Krzysztof Pszeniczny <kpszeniczny@google.com>
Tested-by: Yonghong Song <yonghong.song@linux.dev>
Tested-by: Yabin Cui <yabinc@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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Mark __kernel_entry as ".head.text" and place HEAD_TEXT before
TEXT_TEXT in the linker script. This ensures that __kernel_entry
will be placed at the beginning of text section.
Drop mips from scripts/head-object-list.txt.
Signed-off-by: Rong Xu <xur@google.com>
Reported-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Closes: https://lore.kernel.org/lkml/c6719149-8531-4174-824e-a3caf4bc6d0e@alliedtelesis.co.nz/T/
Tested-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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