| Message ID | 20221002181107.51286-4-masahiroy@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Kconfig.debug: make more efforts to fix CONFIG_DEBUG_INFO for Clang+GAS | expand |
On Mon, Oct 03, 2022 at 03:11:07AM +0900, Masahiro Yamada wrote: > Commit f9b3cd245784 ("Kconfig.debug: make DEBUG_INFO selectable from > a choice") added CONFIG_DEBUG_INFO_NONE into the DWARF version choice, > but it should rather belong to the debug level choice. > > This commit consolidates CONFIG options into two choices: > > - Debug info level (NONE / REDUCED / DEFAULT) > > - DWARF format (DWARF_TOOLCHAIN_DEFAULT / DWARF4 / DWARF5) > > This is more consistent with compilers' policy because the -g0 compiler > flag means "no debug info". > > GCC manual: > > -g<level> > > Request debugging information and also use level to specify how > much information. The default level is 2. > > Level 0 produces no debug information at all. Thus, -g0 negates -g. > > Level 1 produces minimal information, enough for making backtraces > in parts of the program that you don’t plan to debug. This includes > descriptions of functions and external variables, and line number > tables, but no information about local variables. > > Level 3 includes extra information, such as all the macro > definitions present in the program. Some debuggers support macro > expansion when you use -g3. > > Rustc Codegen manual: > > debuginfo > > This flag controls the generation of debug information. It takes > one of the following values: > > 0: no debug info at all (the default). > 1: line tables only. > 2: full debug info. > > I moved CONFIG_DEBUG_INFO_REDUCED into the debug level choice. > > This change will make it easier to add another debug info level if > necessary. > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > Acked-by: Miguel Ojeda <ojeda@kernel.org> As far as I can tell, this will require updating defconfigs again to include an explicit 'CONFIG_DEBUG_INFO_DEFAULT=y', right? It might be nice to do that as part of this change to keep everything working, as there was some fallout from the last time: 92f89ec1b534 ("powerpc: Restore CONFIG_DEBUG_INFO in defconfigs") ddd366bf01de ("ARM: defconfig: address renamed CONFIG_DEBUG_INFO=y") Regardless, I think this is a good change. Reviewed-by: Nathan Chancellor <nathan@kernel.org> > --- > > lib/Kconfig.debug | 59 +++++++++++++++++++++++++++++------------------ > 1 file changed, 36 insertions(+), 23 deletions(-) > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index cc90414d492e..ce1faae1a979 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -234,15 +234,10 @@ config DEBUG_INFO > choice > prompt "Debug information" > depends on DEBUG_KERNEL > + depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502) > 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. > - > - Choose which version of DWARF debug info to emit. If unsure, > - select "Toolchain default". > > config DEBUG_INFO_NONE > bool "Disable debug information" > @@ -250,10 +245,40 @@ config DEBUG_INFO_NONE > Do not build the kernel with debugging information, which will > result in a faster and smaller build. > > +config DEBUG_INFO_REDUCED > + bool "Reduced debugging information" > + select DEBUG_INFO > + help > + If you say Y here compiler is instructed to generate less debugging > + information for structure types. This means that tools that > + need full debugging information (like kgdb or systemtap) won't > + be happy. But if you merely need debugging information to > + resolve line numbers there is no loss. Advantage is that > + build directory object sizes shrink dramatically over a full > + DEBUG_INFO build and compile times are reduced too. > + Only works with newer gcc versions. > + > +config DEBUG_INFO_DEFAULT > + bool "Default-level debugging information" > + select DEBUG_INFO > + help > + If you say Y here compiler is instructed to generate the default > + level of debugging information. > + > + 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. > + > +endchoice # "Debug information" > + > +choice > + prompt "DWARF version" > + depends on DEBUG_INFO > + 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" > - select DEBUG_INFO > - depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502) > help > The implicit default version of DWARF debug info produced by a > toolchain changes over time. > @@ -262,9 +287,10 @@ config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > 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" > - select DEBUG_INFO > depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502) > help > Generate DWARF v4 debug info. This requires gcc 4.5+, binutils 2.35.2 > @@ -276,7 +302,6 @@ config DEBUG_INFO_DWARF4 > > config DEBUG_INFO_DWARF5 > bool "Generate DWARF Version 5 debuginfo" > - select DEBUG_INFO > depends on !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 > @@ -291,22 +316,10 @@ config DEBUG_INFO_DWARF5 > config if they rely on tooling that has not yet been updated to > support DWARF Version 5. > > -endchoice # "Debug information" > +endchoice # "DWARF version" > > if DEBUG_INFO > > -config DEBUG_INFO_REDUCED > - bool "Reduce debugging information" > - help > - If you say Y here gcc is instructed to generate less debugging > - information for structure types. This means that tools that > - need full debugging information (like kgdb or systemtap) won't > - be happy. But if you merely need debugging information to > - resolve line numbers there is no loss. Advantage is that > - build directory object sizes shrink dramatically over a full > - DEBUG_INFO build and compile times are reduced too. > - Only works with newer gcc versions. > - > config DEBUG_INFO_COMPRESSED > bool "Compressed debugging information" > depends on $(cc-option,-gz=zlib) > -- > 2.34.1 >
On Tue, Oct 4, 2022 at 2:20 AM Nathan Chancellor <nathan@kernel.org> wrote: > > On Mon, Oct 03, 2022 at 03:11:07AM +0900, Masahiro Yamada wrote: > > Commit f9b3cd245784 ("Kconfig.debug: make DEBUG_INFO selectable from > > a choice") added CONFIG_DEBUG_INFO_NONE into the DWARF version choice, > > but it should rather belong to the debug level choice. > > > > This commit consolidates CONFIG options into two choices: > > > > - Debug info level (NONE / REDUCED / DEFAULT) > > > > - DWARF format (DWARF_TOOLCHAIN_DEFAULT / DWARF4 / DWARF5) > > > > This is more consistent with compilers' policy because the -g0 compiler > > flag means "no debug info". > > > > GCC manual: > > > > -g<level> > > > > Request debugging information and also use level to specify how > > much information. The default level is 2. > > > > Level 0 produces no debug information at all. Thus, -g0 negates -g. > > > > Level 1 produces minimal information, enough for making backtraces > > in parts of the program that you don’t plan to debug. This includes > > descriptions of functions and external variables, and line number > > tables, but no information about local variables. > > > > Level 3 includes extra information, such as all the macro > > definitions present in the program. Some debuggers support macro > > expansion when you use -g3. > > > > Rustc Codegen manual: > > > > debuginfo > > > > This flag controls the generation of debug information. It takes > > one of the following values: > > > > 0: no debug info at all (the default). > > 1: line tables only. > > 2: full debug info. > > > > I moved CONFIG_DEBUG_INFO_REDUCED into the debug level choice. > > > > This change will make it easier to add another debug info level if > > necessary. > > > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > > Acked-by: Miguel Ojeda <ojeda@kernel.org> > > As far as I can tell, this will require updating defconfigs again to > include an explicit 'CONFIG_DEBUG_INFO_DEFAULT=y', right? It might be > nice to do that as part of this change to keep everything working, as > there was some fallout from the last time: > > 92f89ec1b534 ("powerpc: Restore CONFIG_DEBUG_INFO in defconfigs") > ddd366bf01de ("ARM: defconfig: address renamed CONFIG_DEBUG_INFO=y") > > Regardless, I think this is a good change. Thanks. I will do that in v2.
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index cc90414d492e..ce1faae1a979 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -234,15 +234,10 @@ config DEBUG_INFO choice prompt "Debug information" depends on DEBUG_KERNEL + depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502) 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. - - Choose which version of DWARF debug info to emit. If unsure, - select "Toolchain default". config DEBUG_INFO_NONE bool "Disable debug information" @@ -250,10 +245,40 @@ config DEBUG_INFO_NONE Do not build the kernel with debugging information, which will result in a faster and smaller build. +config DEBUG_INFO_REDUCED + bool "Reduced debugging information" + select DEBUG_INFO + help + If you say Y here compiler is instructed to generate less debugging + information for structure types. This means that tools that + need full debugging information (like kgdb or systemtap) won't + be happy. But if you merely need debugging information to + resolve line numbers there is no loss. Advantage is that + build directory object sizes shrink dramatically over a full + DEBUG_INFO build and compile times are reduced too. + Only works with newer gcc versions. + +config DEBUG_INFO_DEFAULT + bool "Default-level debugging information" + select DEBUG_INFO + help + If you say Y here compiler is instructed to generate the default + level of debugging information. + + 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. + +endchoice # "Debug information" + +choice + prompt "DWARF version" + depends on DEBUG_INFO + 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" - select DEBUG_INFO - depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502) help The implicit default version of DWARF debug info produced by a toolchain changes over time. @@ -262,9 +287,10 @@ config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT 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" - select DEBUG_INFO depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502) help Generate DWARF v4 debug info. This requires gcc 4.5+, binutils 2.35.2 @@ -276,7 +302,6 @@ config DEBUG_INFO_DWARF4 config DEBUG_INFO_DWARF5 bool "Generate DWARF Version 5 debuginfo" - select DEBUG_INFO depends on !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 @@ -291,22 +316,10 @@ config DEBUG_INFO_DWARF5 config if they rely on tooling that has not yet been updated to support DWARF Version 5. -endchoice # "Debug information" +endchoice # "DWARF version" if DEBUG_INFO -config DEBUG_INFO_REDUCED - bool "Reduce debugging information" - help - If you say Y here gcc is instructed to generate less debugging - information for structure types. This means that tools that - need full debugging information (like kgdb or systemtap) won't - be happy. But if you merely need debugging information to - resolve line numbers there is no loss. Advantage is that - build directory object sizes shrink dramatically over a full - DEBUG_INFO build and compile times are reduced too. - Only works with newer gcc versions. - config DEBUG_INFO_COMPRESSED bool "Compressed debugging information" depends on $(cc-option,-gz=zlib)
Commit f9b3cd245784 ("Kconfig.debug: make DEBUG_INFO selectable from a choice") added CONFIG_DEBUG_INFO_NONE into the DWARF version choice, but it should rather belong to the debug level choice. This commit consolidates CONFIG options into two choices: - Debug info level (NONE / REDUCED / DEFAULT) - DWARF format (DWARF_TOOLCHAIN_DEFAULT / DWARF4 / DWARF5) This is more consistent with compilers' policy because the -g0 compiler flag means "no debug info". GCC manual: -g<level> Request debugging information and also use level to specify how much information. The default level is 2. Level 0 produces no debug information at all. Thus, -g0 negates -g. Level 1 produces minimal information, enough for making backtraces in parts of the program that you don’t plan to debug. This includes descriptions of functions and external variables, and line number tables, but no information about local variables. Level 3 includes extra information, such as all the macro definitions present in the program. Some debuggers support macro expansion when you use -g3. Rustc Codegen manual: debuginfo This flag controls the generation of debug information. It takes one of the following values: 0: no debug info at all (the default). 1: line tables only. 2: full debug info. I moved CONFIG_DEBUG_INFO_REDUCED into the debug level choice. This change will make it easier to add another debug info level if necessary. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Acked-by: Miguel Ojeda <ojeda@kernel.org> --- lib/Kconfig.debug | 59 +++++++++++++++++++++++++++++------------------ 1 file changed, 36 insertions(+), 23 deletions(-)