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Kconfig.debug: make DEBUG_INFO selectable from a choice
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Currently it's not possible to enable DEBUG_INFO for an all*config
build, since it is marked as "depends on !COMPILE_TEST".

This generally makes sense because a debug build of an all*config target
ends up taking much longer and the output is much larger.  Having this
be "default off" makes sense.

However, there are cases where enabling DEBUG_INFO for such builds is
useful for doing treewide A/B comparisons of build options, etc.

Make DEBUG_INFO selectable from any of the DWARF version choice options,
with DEBUG_INFO_NONE being the default for COMPILE_TEST.

The mutually exclusive relationship between DWARF5 and BTF must be
inverted, but the result remains the same.  Additionally moves
DEBUG_KERNEL and DEBUG_MISC up to the top of the menu because they were
enabling features _above_ it, making it weird to navigate menuconfig.

[[email protected]: make DEBUG_INFO always default=n]
  Link: https://lkml.kernel.org/r/[email protected]
  Link: https://lore.kernel.org/lkml/[email protected]

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Kees Cook <[email protected]>
Suggested-by: Arnd Bergmann <[email protected]>
Reviewed-by: Arnd Bergmann <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Tested-by: Nick Desaulniers <[email protected]>
Reviewed-by: Masahiro Yamada <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Cc: Tetsuo Handa <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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@kees @torvalds
kees authored and torvalds committed Mar 24, 2022
1 parent a7cd9a5 commit f9b3cd2
Showing 1 changed file with 74 additions and 65 deletions.
139 changes: 74 additions & 65 deletions lib/Kconfig.debug
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Original file line number Diff line number Diff line change
Expand Up @@ -208,20 +208,87 @@ config DEBUG_BUGVERBOSE

endmenu # "printk and dmesg options"

config DEBUG_KERNEL
bool "Kernel debugging"
help
Say Y here if you are developing drivers or trying to debug and
identify kernel problems.

config DEBUG_MISC
bool "Miscellaneous debug code"
default DEBUG_KERNEL
depends on DEBUG_KERNEL
help
Say Y here if you need to enable miscellaneous debug code that should
be under a more specific debug option but isn't.

menu "Compile-time checks and compiler options"

config DEBUG_INFO
bool "Compile the kernel with debug info"
depends on DEBUG_KERNEL && !COMPILE_TEST
bool
help
If you say Y here the resulting kernel image will include
debugging info resulting in a larger kernel image.
A kernel debug info option other than "None" has been selected
in the "Debug information" choice below, indicating that debug
information will be generated for build targets.

choice
prompt "Debug information"
depends on DEBUG_KERNEL
help
Selecting something other than "None" results in a kernel image
that will include debugging info resulting in a larger kernel image.
This adds debug symbols to the kernel and modules (gcc -g), and
is needed if you intend to use kernel crashdump or binary object
tools like crash, kgdb, LKCD, gdb, etc on the kernel.
Say Y here only if you plan to debug the kernel.

If unsure, say N.
Choose which version of DWARF debug info to emit. If unsure,
select "Toolchain default".

config DEBUG_INFO_NONE
bool "Disable debug information"
help
Do not build the kernel with debugging information, which will
result in a faster and smaller build.

config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
bool "Rely on the toolchain's implicit default DWARF version"
select DEBUG_INFO
help
The implicit default version of DWARF debug info produced by a
toolchain changes over time.

This can break consumers of the debug info that haven't upgraded to
support newer revisions, and prevent testing newer versions, but
those should be less common scenarios.

config DEBUG_INFO_DWARF4
bool "Generate DWARF Version 4 debuginfo"
select DEBUG_INFO
help
Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.

If you have consumers of DWARF debug info that are not ready for
newer revisions of DWARF, you may wish to choose this or have your
config select this.

config DEBUG_INFO_DWARF5
bool "Generate DWARF Version 5 debuginfo"
select DEBUG_INFO
depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
help
Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
5.0+ accepts the -gdwarf-5 flag but only had partial support for some
draft features until 7.0), and gdb 8.0+.

Changes to the structure of debug info in Version 5 allow for around
15-18% savings in resulting image and debug info section sizes as
compared to DWARF Version 4. DWARF Version 5 standardizes previous
extensions such as accelerators for symbol indexing and the format
for fission (.dwo/.dwp) files. Users may not want to select this
config if they rely on tooling that has not yet been updated to
support DWARF Version 5.

endchoice # "Debug information"

if DEBUG_INFO

Expand Down Expand Up @@ -267,56 +334,12 @@ config DEBUG_INFO_SPLIT
to know about the .dwo files and include them.
Incompatible with older versions of ccache.

choice
prompt "DWARF version"
help
Which version of DWARF debug info to emit.

config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT
bool "Rely on the toolchain's implicit default DWARF version"
help
The implicit default version of DWARF debug info produced by a
toolchain changes over time.

This can break consumers of the debug info that haven't upgraded to
support newer revisions, and prevent testing newer versions, but
those should be less common scenarios.

If unsure, say Y.

config DEBUG_INFO_DWARF4
bool "Generate DWARF Version 4 debuginfo"
help
Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.

If you have consumers of DWARF debug info that are not ready for
newer revisions of DWARF, you may wish to choose this or have your
config select this.

config DEBUG_INFO_DWARF5
bool "Generate DWARF Version 5 debuginfo"
depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
depends on !DEBUG_INFO_BTF
help
Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
5.0+ accepts the -gdwarf-5 flag but only had partial support for some
draft features until 7.0), and gdb 8.0+.

Changes to the structure of debug info in Version 5 allow for around
15-18% savings in resulting image and debug info section sizes as
compared to DWARF Version 4. DWARF Version 5 standardizes previous
extensions such as accelerators for symbol indexing and the format
for fission (.dwo/.dwp) files. Users may not want to select this
config if they rely on tooling that has not yet been updated to
support DWARF Version 5.

endchoice # "DWARF version"

config DEBUG_INFO_BTF
bool "Generate BTF typeinfo"
depends on !DEBUG_INFO_SPLIT && !DEBUG_INFO_REDUCED
depends on !GCC_PLUGIN_RANDSTRUCT || COMPILE_TEST
depends on BPF_SYSCALL
depends on !DEBUG_INFO_DWARF5
help
Generate deduplicated BTF type information from DWARF debug info.
Turning this on expects presence of pahole tool, which will convert
Expand Down Expand Up @@ -585,20 +608,6 @@ source "lib/Kconfig.kcsan"

endmenu

config DEBUG_KERNEL
bool "Kernel debugging"
help
Say Y here if you are developing drivers or trying to debug and
identify kernel problems.

config DEBUG_MISC
bool "Miscellaneous debug code"
default DEBUG_KERNEL
depends on DEBUG_KERNEL
help
Say Y here if you need to enable miscellaneous debug code that should
be under a more specific debug option but isn't.

menu "Networking Debugging"

source "net/Kconfig.debug"
Expand Down

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