* [PATCH v2] kbuild: add configurable debug info level @ 2022-08-14 0:20 Dmitrii Bundin 2022-08-14 2:01 ` Masahiro Yamada 0 siblings, 1 reply; 18+ messages in thread From: Dmitrii Bundin @ 2022-08-14 0:20 UTC (permalink / raw) To: masahiroy, akpm Cc: michal.lkml, ndesaulniers, nathan, peterz, keescook, jpoimboe, dan.j.williams, isabbasso, edumazet, vbabka, linux, linux-kernel, linux-kbuild, Dmitrii Bundin Provides a way to configure debug info level (-glevel). Debug level 3 includes extra information such as macro definitions. With level 3 enabled it's possible to expand macros right from the debugging session in gdb simplifying debugging when complicated macros involved. The default level is set to 2 to not change the default build behavior. Signed-off-by: Dmitrii Bundin <dmitrii.bundin.a@gmail.com> --- Changes in v2: https://lore.kernel.org/all/20220804223504.4739-1-dmitrii.bundin.a@gmail.com/ - Replace hardcoded -g3 with a configurable debug info level lib/Kconfig.debug | 11 +++++++++++ scripts/Makefile.debug | 2 +- 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 2e24db4bff19..a17c12c20290 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -304,6 +304,17 @@ config DEBUG_INFO_REDUCED DEBUG_INFO build and compile times are reduced too. Only works with newer gcc versions. +config DEBUG_INFO_LEVEL + int "Debug info level" + range 0 3 + default "2" + help + Sets the level of how much debug information to generate (-glevel). + Level 1 produces minimal debug information without including information + about local variables. Level 3 includes extra information like macro + definitions. Setting up level 3 will require significantly more disk + space and increase built time. Level 0 produces no debug information. + config DEBUG_INFO_COMPRESSED bool "Compressed debugging information" depends on $(cc-option,-gz=zlib) diff --git a/scripts/Makefile.debug b/scripts/Makefile.debug index 9f39b0130551..28beffc42e71 100644 --- a/scripts/Makefile.debug +++ b/scripts/Makefile.debug @@ -3,7 +3,7 @@ DEBUG_CFLAGS := ifdef CONFIG_DEBUG_INFO_SPLIT DEBUG_CFLAGS += -gsplit-dwarf else -DEBUG_CFLAGS += -g +DEBUG_CFLAGS += -g$(CONFIG_DEBUG_INFO_LEVEL) endif ifndef CONFIG_AS_IS_LLVM -- 2.17.1 ^ permalink raw reply related [flat|nested] 18+ messages in thread
* Re: [PATCH v2] kbuild: add configurable debug info level 2022-08-14 0:20 [PATCH v2] kbuild: add configurable debug info level Dmitrii Bundin @ 2022-08-14 2:01 ` Masahiro Yamada 2022-08-14 5:31 ` Fangrui Song 0 siblings, 1 reply; 18+ messages in thread From: Masahiro Yamada @ 2022-08-14 2:01 UTC (permalink / raw) To: Dmitrii Bundin Cc: Andrew Morton, Michal Marek, Nick Desaulniers, Nathan Chancellor, Peter Zijlstra (Intel), Kees Cook, Josh Poimboeuf, Dan Williams, Isabella Basso, Eric Dumazet, Vlastimil Babka, Rasmus Villemoes, Linux Kernel Mailing List, Linux Kbuild mailing list, Fangrui Song +CC: Fangrui Song <maskray@google.com> On Sun, Aug 14, 2022 at 9:25 AM Dmitrii Bundin <dmitrii.bundin.a@gmail.com> wrote: > > Provides a way to configure debug info level (-glevel). > Debug level 3 includes extra information such as macro definitions. With > level 3 enabled it's possible to expand macros right from the debugging > session in gdb simplifying debugging when complicated macros involved. > The default level is set to 2 to not change the default build behavior. > > Signed-off-by: Dmitrii Bundin <dmitrii.bundin.a@gmail.com> > --- > > Changes in v2: https://lore.kernel.org/all/20220804223504.4739-1-dmitrii.bundin.a@gmail.com/ > - Replace hardcoded -g3 with a configurable debug info level > > lib/Kconfig.debug | 11 +++++++++++ > scripts/Makefile.debug | 2 +- > 2 files changed, 12 insertions(+), 1 deletion(-) > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 2e24db4bff19..a17c12c20290 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -304,6 +304,17 @@ config DEBUG_INFO_REDUCED > DEBUG_INFO build and compile times are reduced too. > Only works with newer gcc versions. > > +config DEBUG_INFO_LEVEL > + int "Debug info level" > + range 0 3 > + default "2" > + help > + Sets the level of how much debug information to generate (-glevel). > + Level 1 produces minimal debug information without including information > + about local variables. Level 3 includes extra information like macro > + definitions. Setting up level 3 will require significantly more disk > + space and increase built time. Level 0 produces no debug information. > + We already have CONFIG_DEBUG_INFO_NONE to disable the debug info. The combination of CONFIG_DEBUG_INFO=y and CONFIG_DEBUG_INFO_LEVEL=0 (-g0) would emulate CONFIG_DEBUG_INFO_NONE ? Using 'int' does not look sensible to me. > config DEBUG_INFO_COMPRESSED > bool "Compressed debugging information" > depends on $(cc-option,-gz=zlib) > diff --git a/scripts/Makefile.debug b/scripts/Makefile.debug > index 9f39b0130551..28beffc42e71 100644 > --- a/scripts/Makefile.debug > +++ b/scripts/Makefile.debug > @@ -3,7 +3,7 @@ DEBUG_CFLAGS := > ifdef CONFIG_DEBUG_INFO_SPLIT > DEBUG_CFLAGS += -gsplit-dwarf > else > -DEBUG_CFLAGS += -g > +DEBUG_CFLAGS += -g$(CONFIG_DEBUG_INFO_LEVEL) > endif > > ifndef CONFIG_AS_IS_LLVM > -- > 2.17.1 > I want to consult Fangrui Song for this part. With this Makefile code, CONFIG_DEBUG_INFO_SPLIT takes the presidency over CONFIG_DEBUG_INFO_LEVEL. When CONFIG_DEBUG_INFO_SPLIT is enabled (-gsplit-dwarf), it always uses the default -g2 level. CONFIG_DEBUG_INFO_LEVEL is just ignored silently. It might be sensible in older GCC/Clang behavior because -gsplit-dwarf implied -g2. But, with this commit: https://reviews.llvm.org/D80391 -gsplit-dwarf and -g<level> are orthogonal for GCC 11+/Clang 12+, correct? I think "splitting debug files" and "debug level" should be controlled independently. (but it depends on the compiler version, if I understood correctly) -- Best Regards Masahiro Yamada ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v2] kbuild: add configurable debug info level 2022-08-14 2:01 ` Masahiro Yamada @ 2022-08-14 5:31 ` Fangrui Song 2022-08-14 18:58 ` Masahiro Yamada 2022-08-14 19:17 ` Dmitrii Bundin 0 siblings, 2 replies; 18+ messages in thread From: Fangrui Song @ 2022-08-14 5:31 UTC (permalink / raw) To: Dmitrii Bundin, Masahiro Yamada Cc: Andrew Morton, Michal Marek, Nick Desaulniers, Nathan Chancellor, Peter Zijlstra (Intel), Kees Cook, Josh Poimboeuf, Dan Williams, Isabella Basso, Eric Dumazet, Vlastimil Babka, Rasmus Villemoes, Linux Kernel Mailing List, Linux Kbuild mailing list On 2022-08-14, Masahiro Yamada wrote: >+CC: Fangrui Song <maskray@google.com> > > > > >On Sun, Aug 14, 2022 at 9:25 AM Dmitrii Bundin ><dmitrii.bundin.a@gmail.com> wrote: >> >> Provides a way to configure debug info level (-glevel). >> Debug level 3 includes extra information such as macro definitions. With >> level 3 enabled it's possible to expand macros right from the debugging >> session in gdb simplifying debugging when complicated macros involved. >> The default level is set to 2 to not change the default build behavior. GCC -g3 generates macro information (in the .debug_macro section). In Clang, -g = -g2 = -g3. To generate macro information, specify -fdebug-macro. The different choice is known in the initial implementation https://reviews.llvm.org/D16135 . Not generating macro information for -g3 (i.e. diverging from GCC behavior) makes some sense to me: -fstandalone-debug will probably be more suitable as -g3 (it retains some type debug info for C++ (the code after https://github.com/llvm/llvm-project/blob/b2f31cac28c8a03ceb908b544f5790f4f9f2d9ab/clang/lib/CodeGen/CGDebugInfo.cpp#L2497-L2499). >> Signed-off-by: Dmitrii Bundin <dmitrii.bundin.a@gmail.com> >> --- >> >> Changes in v2: https://lore.kernel.org/all/20220804223504.4739-1-dmitrii.bundin.a@gmail.com/ >> - Replace hardcoded -g3 with a configurable debug info level >> >> lib/Kconfig.debug | 11 +++++++++++ >> scripts/Makefile.debug | 2 +- >> 2 files changed, 12 insertions(+), 1 deletion(-) >> >> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug >> index 2e24db4bff19..a17c12c20290 100644 >> --- a/lib/Kconfig.debug >> +++ b/lib/Kconfig.debug >> @@ -304,6 +304,17 @@ config DEBUG_INFO_REDUCED >> DEBUG_INFO build and compile times are reduced too. >> Only works with newer gcc versions. >> >> +config DEBUG_INFO_LEVEL >> + int "Debug info level" >> + range 0 3 >> + default "2" >> + help >> + Sets the level of how much debug information to generate (-glevel). >> + Level 1 produces minimal debug information without including information >> + about local variables. Level 3 includes extra information like macro >> + definitions. Setting up level 3 will require significantly more disk >> + space and increase built time. Level 0 produces no debug information. >> + > > > >We already have CONFIG_DEBUG_INFO_NONE to >disable the debug info. > > >The combination of CONFIG_DEBUG_INFO=y and >CONFIG_DEBUG_INFO_LEVEL=0 (-g0) >would emulate CONFIG_DEBUG_INFO_NONE ? > > > >Using 'int' does not look sensible to me. > > > > > >> config DEBUG_INFO_COMPRESSED >> bool "Compressed debugging information" >> depends on $(cc-option,-gz=zlib) >> diff --git a/scripts/Makefile.debug b/scripts/Makefile.debug >> index 9f39b0130551..28beffc42e71 100644 >> --- a/scripts/Makefile.debug >> +++ b/scripts/Makefile.debug >> @@ -3,7 +3,7 @@ DEBUG_CFLAGS := >> ifdef CONFIG_DEBUG_INFO_SPLIT >> DEBUG_CFLAGS += -gsplit-dwarf >> else >> -DEBUG_CFLAGS += -g >> +DEBUG_CFLAGS += -g$(CONFIG_DEBUG_INFO_LEVEL) >> endif >> >> ifndef CONFIG_AS_IS_LLVM >> -- >> 2.17.1 >> > > >I want to consult Fangrui Song for this part. > > >With this Makefile code, CONFIG_DEBUG_INFO_SPLIT >takes the presidency over CONFIG_DEBUG_INFO_LEVEL. > > >When CONFIG_DEBUG_INFO_SPLIT is enabled (-gsplit-dwarf), >it always uses the default -g2 level. >CONFIG_DEBUG_INFO_LEVEL is just ignored silently. > > > >It might be sensible in older GCC/Clang behavior because >-gsplit-dwarf implied -g2. > > >But, with this commit: >https://reviews.llvm.org/D80391 > >-gsplit-dwarf and -g<level> are orthogonal >for GCC 11+/Clang 12+, correct? Correct. >I think "splitting debug files" and "debug level" >should be controlled independently. >(but it depends on the compiler version, if I understood correctly) Before GCC 11 and Clang 12, -gsplit-dwarf implied -g2 (older -gsplit-dwarf is like today's `-gsplit-dwarf -g2`). GCC 11 and Clang 12 (https://reviews.llvm.org/D80391) have changed -gsplit-dwarf to not imply -g2. For a group of -g0 -g1 -g2, the last option wins. Therefore, -g0 -gsplit-dwarf => debug info in GCC<11 and Clang<12 -g0 -gsplit-dwarf => no debug info in GCC>=11 and Clang>=12 ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v2] kbuild: add configurable debug info level 2022-08-14 5:31 ` Fangrui Song @ 2022-08-14 18:58 ` Masahiro Yamada 2022-08-14 19:17 ` Dmitrii Bundin 1 sibling, 0 replies; 18+ messages in thread From: Masahiro Yamada @ 2022-08-14 18:58 UTC (permalink / raw) To: Fangrui Song Cc: Dmitrii Bundin, Andrew Morton, Michal Marek, Nick Desaulniers, Nathan Chancellor, Peter Zijlstra (Intel), Kees Cook, Josh Poimboeuf, Dan Williams, Isabella Basso, Eric Dumazet, Vlastimil Babka, Rasmus Villemoes, Linux Kernel Mailing List, Linux Kbuild mailing list On Sun, Aug 14, 2022 at 2:31 PM Fangrui Song <maskray@google.com> wrote: > > On 2022-08-14, Masahiro Yamada wrote: > >+CC: Fangrui Song <maskray@google.com> > > > > > > > > > >On Sun, Aug 14, 2022 at 9:25 AM Dmitrii Bundin > ><dmitrii.bundin.a@gmail.com> wrote: > >> > >> Provides a way to configure debug info level (-glevel). > >> Debug level 3 includes extra information such as macro definitions. With > >> level 3 enabled it's possible to expand macros right from the debugging > >> session in gdb simplifying debugging when complicated macros involved. > >> The default level is set to 2 to not change the default build behavior. > > GCC -g3 generates macro information (in the .debug_macro section). > > In Clang, -g = -g2 = -g3. To generate macro information, > specify -fdebug-macro. > The different choice is known in the initial implementation https://reviews.llvm.org/D16135 . > > Not generating macro information for -g3 (i.e. diverging from GCC > behavior) makes some sense to me: -fstandalone-debug will probably be > more suitable as -g3 (it retains some type debug info for C++ (the code > after https://github.com/llvm/llvm-project/blob/b2f31cac28c8a03ceb908b544f5790f4f9f2d9ab/clang/lib/CodeGen/CGDebugInfo.cpp#L2497-L2499). > > >> Signed-off-by: Dmitrii Bundin <dmitrii.bundin.a@gmail.com> > >> --- > >> > >> Changes in v2: https://lore.kernel.org/all/20220804223504.4739-1-dmitrii.bundin.a@gmail.com/ > >> - Replace hardcoded -g3 with a configurable debug info level > >> > >> lib/Kconfig.debug | 11 +++++++++++ > >> scripts/Makefile.debug | 2 +- > >> 2 files changed, 12 insertions(+), 1 deletion(-) > >> > >> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > >> index 2e24db4bff19..a17c12c20290 100644 > >> --- a/lib/Kconfig.debug > >> +++ b/lib/Kconfig.debug > >> @@ -304,6 +304,17 @@ config DEBUG_INFO_REDUCED > >> DEBUG_INFO build and compile times are reduced too. > >> Only works with newer gcc versions. > >> > >> +config DEBUG_INFO_LEVEL > >> + int "Debug info level" > >> + range 0 3 > >> + default "2" > >> + help > >> + Sets the level of how much debug information to generate (-glevel). > >> + Level 1 produces minimal debug information without including information > >> + about local variables. Level 3 includes extra information like macro > >> + definitions. Setting up level 3 will require significantly more disk > >> + space and increase built time. Level 0 produces no debug information. > >> + > > > > > > > >We already have CONFIG_DEBUG_INFO_NONE to > >disable the debug info. > > > > > >The combination of CONFIG_DEBUG_INFO=y and > >CONFIG_DEBUG_INFO_LEVEL=0 (-g0) > >would emulate CONFIG_DEBUG_INFO_NONE ? > > > > > > > >Using 'int' does not look sensible to me. > > > > > > > > > > > >> config DEBUG_INFO_COMPRESSED > >> bool "Compressed debugging information" > >> depends on $(cc-option,-gz=zlib) > >> diff --git a/scripts/Makefile.debug b/scripts/Makefile.debug > >> index 9f39b0130551..28beffc42e71 100644 > >> --- a/scripts/Makefile.debug > >> +++ b/scripts/Makefile.debug > >> @@ -3,7 +3,7 @@ DEBUG_CFLAGS := > >> ifdef CONFIG_DEBUG_INFO_SPLIT > >> DEBUG_CFLAGS += -gsplit-dwarf > >> else > >> -DEBUG_CFLAGS += -g > >> +DEBUG_CFLAGS += -g$(CONFIG_DEBUG_INFO_LEVEL) > >> endif > >> > >> ifndef CONFIG_AS_IS_LLVM > >> -- > >> 2.17.1 > >> > > > > > >I want to consult Fangrui Song for this part. > > > > > >With this Makefile code, CONFIG_DEBUG_INFO_SPLIT > >takes the presidency over CONFIG_DEBUG_INFO_LEVEL. > > > > > >When CONFIG_DEBUG_INFO_SPLIT is enabled (-gsplit-dwarf), > >it always uses the default -g2 level. > >CONFIG_DEBUG_INFO_LEVEL is just ignored silently. > > > > > > > >It might be sensible in older GCC/Clang behavior because > >-gsplit-dwarf implied -g2. > > > > > >But, with this commit: > >https://reviews.llvm.org/D80391 > > > >-gsplit-dwarf and -g<level> are orthogonal > >for GCC 11+/Clang 12+, correct? > > Correct. > > >I think "splitting debug files" and "debug level" > >should be controlled independently. > >(but it depends on the compiler version, if I understood correctly) > > Before GCC 11 and Clang 12, -gsplit-dwarf implied -g2 (older > -gsplit-dwarf is like today's `-gsplit-dwarf -g2`). > > GCC 11 and Clang 12 (https://reviews.llvm.org/D80391) have changed > -gsplit-dwarf to not imply -g2. > > For a group of -g0 -g1 -g2, the last option wins. Therefore, > > -g0 -gsplit-dwarf => debug info in GCC<11 and Clang<12 > -g0 -gsplit-dwarf => no debug info in GCC>=11 and Clang>=12 Thanks. I tested GCC 9 on Ubuntu 22.04. "-g3 -gsplit-dwarf" produces .debug_macro In old behavior, -gsplit-dwarf upgrades the level, but does not downgrade it, correct? [Old behavior] -g0 -gsplit-dwarf --> level 2 (gsplit-dwarf upgrade 0 to 2) -gsplit-dwarf -g0 --> level 0 (the last -g0 wins) -g3 -gsplit-dwarf --> level 3 (gsplit-dwarf does not downgrade) -g2 -g3 --> level 3 (the last -g3 wins) -g3 -g2 --> level 2 (the last -g2 wins) [New behavior] -g0 -gsplit-dwarf --> level 0 (the options are orthogonal) -gsplit-dwarf -g0 --> level 0 (the options are orthogonal) -g3 -gsplit-dwarf --> level 3 (the options are orthogonal) -g2 -g3 --> level 3 (the last -g3 wins) -g3 -g2 --> level 2 (the last -g2 wins) masahiro@grover:/tmp/foo$ gcc-9 --version gcc-9 (Ubuntu 9.4.0-5ubuntu1) 9.4.0 Copyright (C) 2019 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. masahiro@grover:/tmp/foo$ rm -f *.dwo masahiro@grover:/tmp/foo$ gcc-9 -gsplit-dwarf -o foo foo.c masahiro@grover:/tmp/foo$ readelf -S foo.dwo There are 9 section headers, starting at offset 0x840: Section Headers: [Nr] Name Type Address Offset Size EntSize Flags Link Info Align [ 0] NULL 0000000000000000 00000000 0000000000000000 0000000000000000 0 0 0 [ 1] .debug_info.dwo PROGBITS 0000000000000000 00000040 0000000000000217 0000000000000000 E 0 0 1 [ 2] .debug_abbrev.dwo PROGBITS 0000000000000000 00000257 00000000000000cb 0000000000000000 E 0 0 1 [ 3] .debug_line.dwo PROGBITS 0000000000000000 00000322 00000000000000e5 0000000000000000 E 0 0 1 [ 4] .debug_str_o[...] PROGBITS 0000000000000000 00000407 00000000000000d4 0000000000000000 E 0 0 1 [ 5] .debug_str.dwo PROGBITS 0000000000000000 000004db 00000000000002bd 0000000000000000 E 0 0 1 [ 6] .symtab SYMTAB 0000000000000000 00000798 0000000000000030 0000000000000018 7 2 8 [ 7] .strtab STRTAB 0000000000000000 000007c8 0000000000000001 0000000000000000 0 0 1 [ 8] .shstrtab STRTAB 0000000000000000 000007c9 0000000000000073 0000000000000000 0 0 1 Key to Flags: W (write), A (alloc), X (execute), M (merge), S (strings), I (info), L (link order), O (extra OS processing required), G (group), T (TLS), C (compressed), x (unknown), o (OS specific), E (exclude), D (mbind), l (large), p (processor specific) masahiro@grover:/tmp/foo$ rm -f *.dwo masahiro@grover:/tmp/foo$ gcc-9 -g3 -gsplit-dwarf -o foo foo.c masahiro@grover:/tmp/foo$ readelf -S foo.dwo There are 32 section headers, starting at offset 0x77f8: Section Headers: [Nr] Name Type Address Offset Size EntSize Flags Link Info Align [ 0] NULL 0000000000000000 00000000 0000000000000000 0000000000000000 0 0 0 [ 1] .debug_info.dwo PROGBITS 0000000000000000 00000040 0000000000000245 0000000000000000 E 0 0 1 [ 2] .debug_abbrev.dwo PROGBITS 0000000000000000 00000285 00000000000000ce 0000000000000000 E 0 0 1 [ 3] .debug_macro.dwo PROGBITS 0000000000000000 00000353 000000000000014a 0000000000000000 E 0 0 1 [ 4] .debug_macro.dwo PROGBITS 0000000000000000 0000049d 0000000000000528 0000000000000000 0 0 1 [ 5] .debug_macro.dwo PROGBITS 0000000000000000 000009c5 000000000000001c 0000000000000000 0 0 1 [ 6] .debug_macro.dwo PROGBITS 0000000000000000 000009e1 000000000000000c 0000000000000000 0 0 1 [ 7] .debug_macro.dwo PROGBITS 0000000000000000 000009ed 000000000000010b 0000000000000000 0 0 1 [ 8] .debug_macro.dwo PROGBITS 0000000000000000 00000af8 0000000000000010 0000000000000000 0 0 1 [ 9] .debug_macro.dwo PROGBITS 0000000000000000 00000b08 0000000000000033 0000000000000000 0 0 1 [10] .debug_macro.dwo PROGBITS 0000000000000000 00000b3b 0000000000000143 0000000000000000 0 0 1 [11] .debug_macro.dwo PROGBITS 0000000000000000 00000c7e 0000000000000056 0000000000000000 0 0 1 [12] .debug_macro.dwo PROGBITS 0000000000000000 00000cd4 0000000000000021 0000000000000000 0 0 1 [13] .debug_macro.dwo PROGBITS 0000000000000000 00000cf5 0000000000000037 0000000000000000 0 0 1 [14] .debug_macro.dwo PROGBITS 0000000000000000 00000d2c 000000000000000b 0000000000000000 0 0 1 [15] .debug_macro.dwo PROGBITS 0000000000000000 00000d37 0000000000000068 0000000000000000 0 0 1 [16] .debug_macro.dwo PROGBITS 0000000000000000 00000d9f 000000000000000c 0000000000000000 0 0 1 [17] .debug_macro.dwo PROGBITS 0000000000000000 00000dab 0000000000000048 0000000000000000 0 0 1 [18] .debug_macro.dwo PROGBITS 0000000000000000 00000df3 00000000000000a8 0000000000000000 0 0 1 [19] .debug_macro.dwo PROGBITS 0000000000000000 00000e9b 000000000000000b 0000000000000000 0 0 1 [20] .debug_macro.dwo PROGBITS 0000000000000000 00000ea6 0000000000000023 0000000000000000 0 0 1 [21] .debug_macro.dwo PROGBITS 0000000000000000 00000ec9 0000000000000030 0000000000000000 0 0 1 [22] .debug_macro.dwo PROGBITS 0000000000000000 00000ef9 0000000000000020 0000000000000000 0 0 1 [23] .debug_macro.dwo PROGBITS 0000000000000000 00000f19 000000000000001d 0000000000000000 0 0 1 [24] .debug_macro.dwo PROGBITS 0000000000000000 00000f36 0000000000000020 0000000000000000 0 0 1 [25] .debug_macro.dwo PROGBITS 0000000000000000 00000f56 0000000000000059 0000000000000000 0 0 1 [26] .debug_line.dwo PROGBITS 0000000000000000 00000faf 0000000000000255 0000000000000000 E 0 0 1 [27] .debug_str_o[...] PROGBITS 0000000000000000 00001204 0000000000000bd4 0000000000000000 E 0 0 1 [28] .debug_str.dwo PROGBITS 0000000000000000 00001dd8 0000000000005721 0000000000000000 E 0 0 1 [29] .symtab SYMTAB 0000000000000000 00007500 0000000000000270 0000000000000018 30 26 8 [30] .strtab STRTAB 0000000000000000 00007770 0000000000000001 0000000000000000 0 0 1 [31] .shstrtab STRTAB 0000000000000000 00007771 0000000000000084 0000000000000000 0 0 1 Key to Flags: W (write), A (alloc), X (execute), M (merge), S (strings), I (info), L (link order), O (extra OS processing required), G (group), T (TLS), C (compressed), x (unknown), o (OS specific), E (exclude), D (mbind), l (large), p (processor specific) -- Best Regards Masahiro Yamada ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v2] kbuild: add configurable debug info level 2022-08-14 5:31 ` Fangrui Song 2022-08-14 18:58 ` Masahiro Yamada @ 2022-08-14 19:17 ` Dmitrii Bundin 2022-08-15 1:33 ` [PATCH v3] kbuild: add debug level and macro defs options Dmitrii Bundin 1 sibling, 1 reply; 18+ messages in thread From: Dmitrii Bundin @ 2022-08-14 19:17 UTC (permalink / raw) To: Fangrui Song, masahiroy Cc: Andrew Morton, Michal Marek, Nick Desaulniers, Nathan Chancellor, Peter Zijlstra (Intel), Kees Cook, Josh Poimboeuf, Dan Williams, Isabella Basso, Eric Dumazet, Vlastimil Babka, Rasmus Villemoes, Linux Kernel Mailing List, Linux Kbuild mailing list > We already have CONFIG_DEBUG_INFO_NONE to > disable the debug info. Thanks for pointing this out. Indeed providing another way of disabling debug info does not look reasonable to me. So only it makes sense to set only 1, 2 or 3 debug levels. > Using 'int' does not look sensible to me. Could you please give a hint why? My intention to choose int was to provide a boundary with range on the DEBUG_INFO_LEVEL option to choose only acceptable ones. On Sun, Aug 14, 2022 at 8:31 AM Fangrui Song <maskray@google.com> wrote: > In Clang, -g = -g2 = -g3. To generate macro information, > specify -fdebug-macro. Thanks. I would propose to add another config option like DEBUG_MACRO_DEFINITIONS to turn on macro information for GCC/Clang. For GCC it would be -g3, for Clang -fdebug-macro. > Before GCC 11 and Clang 12, -gsplit-dwarf implied -g2 (older > -gsplit-dwarf is like today's `-gsplit-dwarf -g2`). > > GCC 11 and Clang 12 (https://reviews.llvm.org/D80391) have changed > -gsplit-dwarf to not imply -g2. > > For a group of -g0 -g1 -g2, the last option wins. Therefore, > > -g0 -gsplit-dwarf => debug info in GCC<11 and Clang<12 > -g0 -gsplit-dwarf => no debug info in GCC>=11 and Clang>=12 I would add a note that when selecting -gdwarf-<level> gcc also implicitly sets -g2 (at least in older versions). It seems reasonable to me to put the DEBUG_LEVEL_INFO setting at the very bottom to prevent it from overriding implicitly. What do you think? ^ permalink raw reply [flat|nested] 18+ messages in thread
* [PATCH v3] kbuild: add debug level and macro defs options 2022-08-14 19:17 ` Dmitrii Bundin @ 2022-08-15 1:33 ` Dmitrii Bundin 2022-08-18 4:13 ` Masahiro Yamada 2022-08-19 17:42 ` Nick Desaulniers 0 siblings, 2 replies; 18+ messages in thread From: Dmitrii Bundin @ 2022-08-15 1:33 UTC (permalink / raw) To: masahiroy Cc: akpm, dan.j.williams, edumazet, isabbasso, jpoimboe, keescook, linux-kbuild, linux-kernel, linux, dmitrii.bundin.a, maskray, michal.lkml, nathan, ndesaulniers, peterz, vbabka Adds config options to control debug info level and producing of macro definitions for GCC/Clang. Option DEBUG_INFO_LEVEL is responsible for controlling debug info level. Before GCC 11 and Clang 12 -gsplit-dwarf implicitly uses -g2. To provide a way to override the setting with, e.g. -g1, DEBUG_INFO_LEVEL is set independently from DEBUG_INFO_SPLIT. Option DEBUG_MACRO_DEFINITIONS is responsible for controlling inclusion of macro definitions. Since Clang uses -fdebug-macro to control if macro definitions are produced which is different from GCC, provides a compiler-specific way of handling macro inclusion. The option is handled after DEBUG_INFO_LEVEL since -g3 -g2 implies -g2, but -g2 -g3 implies -g3 and GCC uses -g3 to produce macro definitions. Signed-off-by: Dmitrii Bundin <dmitrii.bundin.a@gmail.com> --- Changes in v2: https://lore.kernel.org/all/20220804223504.4739-1-dmitrii.bundin.a@gmail.com/ - Replace hardcoded -g3 with a configurable debug info level Changes in v3: https://lore.kernel.org/all/20220814002021.16990-1-dmitrii.bundin.a@gmail.com/ - Make -g<level> and -gdwarf-split to be set independently - Add a separate option to control macro definitions for GCC/Clang lib/Kconfig.debug | 20 ++++++++++++++++++++ scripts/Makefile.debug | 12 ++++++++++-- 2 files changed, 30 insertions(+), 2 deletions(-) diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 2e24db4bff19..ace6f2eddb56 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -304,6 +304,26 @@ config DEBUG_INFO_REDUCED DEBUG_INFO build and compile times are reduced too. Only works with newer gcc versions. +config DEBUG_INFO_LEVEL + int "Debug info level" + range 1 3 + default "2" + help + Sets the level of how much debug information to generate (-glevel). + Level 1 produces minimal debug information without including information + about local variables. Level 3 includes extra information like macro + definitions. Setting up level 3 will require significantly more disk + space and increase built time. + +config DEBUG_MACRO_DEFINITIONS + bool "Add macro definitions to debug info" + default n + help + Generates macro definitions to provide a way to expand macros right + in the debugging session. This information can be used with macro expand, + info macro in gdb. This option is equivalent to setting -g3 in GCC and + -fdebug-macro in Clang. + config DEBUG_INFO_COMPRESSED bool "Compressed debugging information" depends on $(cc-option,-gz=zlib) diff --git a/scripts/Makefile.debug b/scripts/Makefile.debug index 9f39b0130551..29cd04234e75 100644 --- a/scripts/Makefile.debug +++ b/scripts/Makefile.debug @@ -2,8 +2,6 @@ DEBUG_CFLAGS := ifdef CONFIG_DEBUG_INFO_SPLIT DEBUG_CFLAGS += -gsplit-dwarf -else -DEBUG_CFLAGS += -g endif ifndef CONFIG_AS_IS_LLVM @@ -16,6 +14,16 @@ dwarf-version-$(CONFIG_DEBUG_INFO_DWARF5) := 5 DEBUG_CFLAGS += -gdwarf-$(dwarf-version-y) endif +DEBUG_CFLAGS += -g$(CONFIG_DEBUG_INFO_LEVEL) +ifdef CONFIG_DEBUG_MACRO_DEFINITIONS +ifdef CONFIG_CC_IS_GCC +DEBUG_CFLAGS += -g3 +endif +ifdef CONFIG_CC_IS_CLANG +DEBUG_CFLAGS += -fdebug-macro +endif +endif + ifdef CONFIG_DEBUG_INFO_REDUCED DEBUG_CFLAGS += -fno-var-tracking ifdef CONFIG_CC_IS_GCC -- 2.17.1 ^ permalink raw reply related [flat|nested] 18+ messages in thread
* Re: [PATCH v3] kbuild: add debug level and macro defs options 2022-08-15 1:33 ` [PATCH v3] kbuild: add debug level and macro defs options Dmitrii Bundin @ 2022-08-18 4:13 ` Masahiro Yamada 2022-08-18 18:57 ` Dmitrii Bundin 2022-08-19 17:42 ` Nick Desaulniers 1 sibling, 1 reply; 18+ messages in thread From: Masahiro Yamada @ 2022-08-18 4:13 UTC (permalink / raw) To: Dmitrii Bundin Cc: Andrew Morton, Dan Williams, Eric Dumazet, Isabella Basso, Josh Poimboeuf, Kees Cook, Linux Kbuild mailing list, Linux Kernel Mailing List, Rasmus Villemoes, F���ng-ru��� S���ng, Michal Marek, Nathan Chancellor, Nick Desaulniers, Peter Zijlstra (Intel), Vlastimil Babka On Mon, Aug 15, 2022 at 10:34 AM Dmitrii Bundin <dmitrii.bundin.a@gmail.com> wrote: > > Adds config options to control debug info level and producing of macro > definitions for GCC/Clang. > > Option DEBUG_INFO_LEVEL is responsible for controlling debug info level. > Before GCC 11 and Clang 12 -gsplit-dwarf implicitly uses -g2. To provide > a way to override the setting with, e.g. -g1, DEBUG_INFO_LEVEL is set > independently from DEBUG_INFO_SPLIT. > > Option DEBUG_MACRO_DEFINITIONS is responsible for controlling inclusion > of macro definitions. Since Clang uses -fdebug-macro to control if macro > definitions are produced which is different from GCC, provides a > compiler-specific way of handling macro inclusion. The option is handled > after DEBUG_INFO_LEVEL since -g3 -g2 implies -g2, but -g2 -g3 implies > -g3 and GCC uses -g3 to produce macro definitions. I am not sure if DEBUG_INFO_LEVEL is useful because the macro debug data is now enabled by DEBUG_MACRO_DEFINITIONS. -g1 is only possible via DEBUG_INFO_LEVEL, but presumably it is not your main interest (and not sure if there is anybody interested) because the main motivation for your v1 is to generate macro debug data. BTW, DEBUG_INFO_MACRO might be more consistent (as the others are prefixed DEBUG_INFO_*), but that might be just my personal preference. > > Signed-off-by: Dmitrii Bundin <dmitrii.bundin.a@gmail.com> > --- > > Changes in v2: https://lore.kernel.org/all/20220804223504.4739-1-dmitrii.bundin.a@gmail.com/ > - Replace hardcoded -g3 with a configurable debug info level > > Changes in v3: https://lore.kernel.org/all/20220814002021.16990-1-dmitrii.bundin.a@gmail.com/ > - Make -g<level> and -gdwarf-split to be set independently > - Add a separate option to control macro definitions for GCC/Clang > > lib/Kconfig.debug | 20 ++++++++++++++++++++ > scripts/Makefile.debug | 12 ++++++++++-- > 2 files changed, 30 insertions(+), 2 deletions(-) > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 2e24db4bff19..ace6f2eddb56 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -304,6 +304,26 @@ config DEBUG_INFO_REDUCED > DEBUG_INFO build and compile times are reduced too. > Only works with newer gcc versions. > > +config DEBUG_INFO_LEVEL > + int "Debug info level" > + range 1 3 > + default "2" > + help > + Sets the level of how much debug information to generate (-glevel). > + Level 1 produces minimal debug information without including information > + about local variables. Level 3 includes extra information like macro > + definitions. Setting up level 3 will require significantly more disk > + space and increase built time. > + > +config DEBUG_MACRO_DEFINITIONS > + bool "Add macro definitions to debug info" > + default n > + help > + Generates macro definitions to provide a way to expand macros right > + in the debugging session. This information can be used with macro expand, > + info macro in gdb. This option is equivalent to setting -g3 in GCC and > + -fdebug-macro in Clang. > + > config DEBUG_INFO_COMPRESSED > bool "Compressed debugging information" > depends on $(cc-option,-gz=zlib) > diff --git a/scripts/Makefile.debug b/scripts/Makefile.debug > index 9f39b0130551..29cd04234e75 100644 > --- a/scripts/Makefile.debug > +++ b/scripts/Makefile.debug > @@ -2,8 +2,6 @@ DEBUG_CFLAGS := > > ifdef CONFIG_DEBUG_INFO_SPLIT > DEBUG_CFLAGS += -gsplit-dwarf > -else > -DEBUG_CFLAGS += -g > endif > > ifndef CONFIG_AS_IS_LLVM > @@ -16,6 +14,16 @@ dwarf-version-$(CONFIG_DEBUG_INFO_DWARF5) := 5 > DEBUG_CFLAGS += -gdwarf-$(dwarf-version-y) > endif > > +DEBUG_CFLAGS += -g$(CONFIG_DEBUG_INFO_LEVEL) > +ifdef CONFIG_DEBUG_MACRO_DEFINITIONS > +ifdef CONFIG_CC_IS_GCC > +DEBUG_CFLAGS += -g3 > +endif > +ifdef CONFIG_CC_IS_CLANG > +DEBUG_CFLAGS += -fdebug-macro > +endif > +endif > + > ifdef CONFIG_DEBUG_INFO_REDUCED > DEBUG_CFLAGS += -fno-var-tracking > ifdef CONFIG_CC_IS_GCC > -- > 2.17.1 > -- Best Regards Masahiro Yamada ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] kbuild: add debug level and macro defs options 2022-08-18 4:13 ` Masahiro Yamada @ 2022-08-18 18:57 ` Dmitrii Bundin 0 siblings, 0 replies; 18+ messages in thread From: Dmitrii Bundin @ 2022-08-18 18:57 UTC (permalink / raw) To: Masahiro Yamada Cc: Andrew Morton, Dan Williams, Eric Dumazet, Isabella Basso, Josh Poimboeuf, Kees Cook, Linux Kbuild mailing list, Linux Kernel Mailing List, Rasmus Villemoes, F���ng-ru��� S���ng, Michal Marek, Nathan Chancellor, Nick Desaulniers, Peter Zijlstra (Intel), Vlastimil Babka On Thu, Aug 18, 2022 at 7:14 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > -g1 is only possible via DEBUG_INFO_LEVEL, but > presumably it is not your main interest > (and not sure if there is anybody interested) > because the main motivation for your v1 > is to generate macro debug data. I tested the build process with -g1 and it turned out to generate an image that is 20% lesser in size. This is indeed not really my use-case, but are you sure it might not be helpful in general? The reason to add DEBUG_INFO_LEVEL was also motivated by the GCC11+/Clang12+ behavior of -gsplit-dwarf to provide an orthogonal debug level config. "The later -g<level> wins" behavior in turns works identically for both older and newer compiler versions so such an implementation provides version independent build behavior. Testing on gcc-11, -gdwarf-<level>/-gdwarf still implies -g2. It seemed a clearer way to me to explicitly set a debug level that just wins instead of relying on implicits. Regards Dmitrii ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] kbuild: add debug level and macro defs options 2022-08-15 1:33 ` [PATCH v3] kbuild: add debug level and macro defs options Dmitrii Bundin 2022-08-18 4:13 ` Masahiro Yamada @ 2022-08-19 17:42 ` Nick Desaulniers 2022-08-19 22:52 ` Dmitrii Bundin 1 sibling, 1 reply; 18+ messages in thread From: Nick Desaulniers @ 2022-08-19 17:42 UTC (permalink / raw) To: Dmitrii Bundin Cc: masahiroy, akpm, dan.j.williams, edumazet, isabbasso, jpoimboe, keescook, linux-kbuild, linux-kernel, linux, maskray, michal.lkml, nathan, peterz, vbabka On Sun, Aug 14, 2022 at 6:34 PM Dmitrii Bundin <dmitrii.bundin.a@gmail.com> wrote: > > Adds config options to control debug info level and producing of macro > definitions for GCC/Clang. > > Option DEBUG_INFO_LEVEL is responsible for controlling debug info level. > Before GCC 11 and Clang 12 -gsplit-dwarf implicitly uses -g2. To provide > a way to override the setting with, e.g. -g1, DEBUG_INFO_LEVEL is set > independently from DEBUG_INFO_SPLIT. > > Option DEBUG_MACRO_DEFINITIONS is responsible for controlling inclusion > of macro definitions. Since Clang uses -fdebug-macro to control if macro > definitions are produced which is different from GCC, provides a > compiler-specific way of handling macro inclusion. The option is handled > after DEBUG_INFO_LEVEL since -g3 -g2 implies -g2, but -g2 -g3 implies > -g3 and GCC uses -g3 to produce macro definitions. > > Signed-off-by: Dmitrii Bundin <dmitrii.bundin.a@gmail.com> > --- > > Changes in v2: https://lore.kernel.org/all/20220804223504.4739-1-dmitrii.bundin.a@gmail.com/ Is any of this really necessary? It seems like a great way to bloat vmlinux artifacts built with CONFIG_DEBUG_INFO even further. The above link mentions "when debugging with GDB." In that case, please don't add new Kconfigs for these; just set -g3 when CONFIG_GDB_SCRIPTS=y. -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] kbuild: add debug level and macro defs options 2022-08-19 17:42 ` Nick Desaulniers @ 2022-08-19 22:52 ` Dmitrii Bundin 2022-08-22 16:45 ` Nick Desaulniers 2022-08-23 6:06 ` Peter Zijlstra 0 siblings, 2 replies; 18+ messages in thread From: Dmitrii Bundin @ 2022-08-19 22:52 UTC (permalink / raw) To: Nick Desaulniers Cc: Masahiro Yamada, Andrew Morton, Dan Williams, Eric Dumazet, Isabella Basso, Josh Poimboeuf, Kees Cook, Linux Kbuild mailing list, Linux Kernel Mailing List, Rasmus Villemoes, Fangrui Song, Michal Marek, Nathan Chancellor, Peter Zijlstra (Intel), Vlastimil Babka On Fri, Aug 19, 2022 at 8:42 PM Nick Desaulniers <ndesaulniers@google.com> wrote: > > Is any of this really necessary? Consider the case if CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y. Prior to GCC11/Clang12 -gsplit-dwarf implied -g2. So on newer compilers with -gsplit-dwarf in use there would be no debug symbols produced. -gdwarf-4/5 still implies -g2, but in case CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y neither of the options are set. So it seems like a reasonable choice to provide a debug info level config that would explicitly set the level without relying on implicits. The default value of the config is set to -g2 to not change the build behavior that was before introducing the option. And it works for both older and newer versions of GCC/Clang in the same way. The benefits of the -g1 option are indeed questionable except that it produces an image with ~20% less in size. > It seems like a great way to bloat > vmlinux artifacts built with CONFIG_DEBUG_INFO even further. The defaults were chosen to not change the build behavior that was before introducing the options. Or did you mean something else? > The > above link mentions "when debugging with GDB." In that case, please > don't add new Kconfigs for these; just set -g3 when > CONFIG_GDB_SCRIPTS=y. CONFIG_GDB_SCRIPTS does not necessarily mean that -g3 is wanted, -g2 (default) is usually a reasonable choice. The -g3 option is very useful when debugging macro-intensive code, but requires much more disk space to build. I documented it explicitly in the help section of DEBUG_INFO_LEVEL. GCC and Clang use different options to include macro definitions so it was handled depending on the compiler used. Regards Dmitrii ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] kbuild: add debug level and macro defs options 2022-08-19 22:52 ` Dmitrii Bundin @ 2022-08-22 16:45 ` Nick Desaulniers 2022-08-22 21:36 ` Nick Desaulniers 2022-08-23 6:06 ` Peter Zijlstra 1 sibling, 1 reply; 18+ messages in thread From: Nick Desaulniers @ 2022-08-22 16:45 UTC (permalink / raw) To: Dmitrii Bundin Cc: Masahiro Yamada, Andrew Morton, Dan Williams, Eric Dumazet, Isabella Basso, Josh Poimboeuf, Kees Cook, Linux Kbuild mailing list, Linux Kernel Mailing List, Rasmus Villemoes, Fangrui Song, Michal Marek, Nathan Chancellor, Peter Zijlstra (Intel), Vlastimil Babka On Fri, Aug 19, 2022 at 3:52 PM Dmitrii Bundin <dmitrii.bundin.a@gmail.com> wrote: > > On Fri, Aug 19, 2022 at 8:42 PM Nick Desaulniers > <ndesaulniers@google.com> wrote: > > > > Is any of this really necessary? > > Consider the case if CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y. > Prior to GCC11/Clang12 -gsplit-dwarf implied -g2. So on newer > compilers with -gsplit-dwarf in use there would be no debug symbols > produced. ``` diff --git a/scripts/Makefile.debug b/scripts/Makefile.debug index 9f39b0130551..a881954c1382 100644 --- a/scripts/Makefile.debug +++ b/scripts/Makefile.debug @@ -1,7 +1,7 @@ DEBUG_CFLAGS := ifdef CONFIG_DEBUG_INFO_SPLIT -DEBUG_CFLAGS += -gsplit-dwarf +DEBUG_CFLAGS += -gsplit-dwarf -g2 else DEBUG_CFLAGS += -g endif ``` or perhaps that simply needs to be `-g -gsplit-dwarf`? In which case, that if/else could just be re-arranged. > -gdwarf-4/5 still implies -g2, but in case > CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y neither of the options are > set. -g is set, which has an implicit default level. > So it seems like a reasonable choice to provide a debug info > level config that would explicitly set the level without relying on > implicits. The default value of the config is set to -g2 to not change > the build behavior that was before introducing the option. And it > works for both older and newer versions of GCC/Clang in the same way. > The benefits of the -g1 option are indeed questionable except that it > produces an image with ~20% less in size. Until there's a concrete need, YAGNI. > > > It seems like a great way to bloat > > vmlinux artifacts built with CONFIG_DEBUG_INFO even further. > The defaults were chosen to not change the build behavior that was > before introducing the options. Or did you mean something else? > > > The > > above link mentions "when debugging with GDB." In that case, please > > don't add new Kconfigs for these; just set -g3 when > > CONFIG_GDB_SCRIPTS=y. > > CONFIG_GDB_SCRIPTS does not necessarily mean that -g3 is wanted, -g2 > (default) is usually a reasonable choice. The -g3 option is very > useful when debugging macro-intensive code, but requires much more > disk space to build. I documented it explicitly in the help section of > DEBUG_INFO_LEVEL. GCC and Clang use different options to include macro > definitions so it was handled depending on the compiler used. Honestly, I really don't think we need to be wrapping every compiler command line flag under the sun in a kconfig option. -- Thanks, ~Nick Desaulniers ^ permalink raw reply related [flat|nested] 18+ messages in thread
* Re: [PATCH v3] kbuild: add debug level and macro defs options 2022-08-22 16:45 ` Nick Desaulniers @ 2022-08-22 21:36 ` Nick Desaulniers 2022-08-22 22:42 ` Dmitrii Bundin 0 siblings, 1 reply; 18+ messages in thread From: Nick Desaulniers @ 2022-08-22 21:36 UTC (permalink / raw) To: Dmitrii Bundin Cc: Masahiro Yamada, Andrew Morton, Dan Williams, Eric Dumazet, Isabella Basso, Josh Poimboeuf, Kees Cook, Linux Kbuild mailing list, Linux Kernel Mailing List, Rasmus Villemoes, Fangrui Song, Michal Marek, Nathan Chancellor, Peter Zijlstra (Intel), Vlastimil Babka On Mon, Aug 22, 2022 at 9:45 AM Nick Desaulniers <ndesaulniers@google.com> wrote: > > > So it seems like a reasonable choice to provide a debug info > > level config that would explicitly set the level without relying on > > implicits. The default value of the config is set to -g2 to not change > > the build behavior that was before introducing the option. And it > > works for both older and newer versions of GCC/Clang in the same way. > > The benefits of the -g1 option are indeed questionable except that it > > produces an image with ~20% less in size. > > Until there's a concrete need, YAGNI. Or add -g1 to CONFIG_DEBUG_INFO_REDUCED. -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] kbuild: add debug level and macro defs options 2022-08-22 21:36 ` Nick Desaulniers @ 2022-08-22 22:42 ` Dmitrii Bundin 2022-08-24 23:25 ` Nick Desaulniers 2022-09-29 21:06 ` Masahiro Yamada 0 siblings, 2 replies; 18+ messages in thread From: Dmitrii Bundin @ 2022-08-22 22:42 UTC (permalink / raw) To: Nick Desaulniers Cc: Masahiro Yamada, Andrew Morton, Dan Williams, Eric Dumazet, Isabella Basso, Josh Poimboeuf, Kees Cook, Linux Kbuild mailing list, Linux Kernel Mailing List, Rasmus Villemoes, Fangrui Song, Michal Marek, Nathan Chancellor, Peter Zijlstra (Intel), Vlastimil Babka On Tue, Aug 23, 2022 at 12:36 AM Nick Desaulniers <ndesaulniers@google.com> wrote: > > or perhaps that simply needs to be `-g -gsplit-dwarf`? In which case, > that if/else could just be re-arranged. How about simply assigning DEBUG_CFLAGS := -g at the very beginning without any conditions? This would provide the default with the possibility of overriding later and -gsplit-dwarf does not necessarily come with -g implicitly. > Honestly, I really don't think we need to be wrapping every compiler > command line flag under the sun in a kconfig option. This indeed sounds reasonable to me. So the key point here is to not bloat the kconfig with options related to every compiler flag. But I think it still might be useful to provide some option that would include sort of full debug information compilers may produce. With this approach there would be, in fact 3 different levels of debug information supported by Kconfig: reduced, default and full. The full level would increase everything like -g3, and -fdebug-macro for Clang, and probably others. > Or add -g1 to CONFIG_DEBUG_INFO_REDUCED. I ran some tests and there was indeed some decrease in size. That combination probably might be useful. Any thoughts? Regards Dmitrii ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] kbuild: add debug level and macro defs options 2022-08-22 22:42 ` Dmitrii Bundin @ 2022-08-24 23:25 ` Nick Desaulniers 2022-09-29 21:06 ` Masahiro Yamada 1 sibling, 0 replies; 18+ messages in thread From: Nick Desaulniers @ 2022-08-24 23:25 UTC (permalink / raw) To: Dmitrii Bundin Cc: Masahiro Yamada, Andrew Morton, Dan Williams, Eric Dumazet, Isabella Basso, Josh Poimboeuf, Kees Cook, Linux Kbuild mailing list, Linux Kernel Mailing List, Rasmus Villemoes, Fangrui Song, Michal Marek, Nathan Chancellor, Peter Zijlstra (Intel), Vlastimil Babka, Doug Anderson On Mon, Aug 22, 2022 at 3:42 PM Dmitrii Bundin <dmitrii.bundin.a@gmail.com> wrote: > > On Tue, Aug 23, 2022 at 12:36 AM Nick Desaulniers > <ndesaulniers@google.com> wrote: > > > > or perhaps that simply needs to be `-g -gsplit-dwarf`? In which case, > > that if/else could just be re-arranged. > > How about simply assigning DEBUG_CFLAGS := -g at the very beginning > without any conditions? This would provide the default with the > possibility of overriding later and -gsplit-dwarf does not necessarily > come with -g implicitly. SGTM; I'd accept such a patch. > > Honestly, I really don't think we need to be wrapping every compiler > > command line flag under the sun in a kconfig option. > > This indeed sounds reasonable to me. So the key point here is to not > bloat the kconfig with options related to every compiler flag. But I > think it still might be useful to provide some option that would > include sort of full debug information compilers may produce. With > this approach there would be, in fact 3 different levels of debug > information supported by Kconfig: reduced, default and full. The full > level would increase everything like -g3, and -fdebug-macro for Clang, > and probably others. Has anyone asked for that though? It seems like your intent with this patch is to fix the surprising+user hostile behavior of compilers requiring -g to be used when -gsplit-dwarf is used. If someone using GDB_SCRIPTS or KGDB was like "man, I wish I could debug macros" then sure I'd be more likely to accept this. Without the need, this is just wrapping every compiler option in a kconfig, which frustrates randconfig testing bots. This will slow them down and bloat their artifacts when randconfig selects -g3, so I'd like someone to come forward saying they need this and why. > > > Or add -g1 to CONFIG_DEBUG_INFO_REDUCED. > > I ran some tests and there was indeed some decrease in size. That > combination probably might be useful. > > Any thoughts? I think there's also -gmlt; when that is preferable to -g1 IDK. Why either of those weren't used in the first place, IDK. The help text in DEBUG_INFO_REDUCED in lib/Kconfig.debug makes it sound like -gmlt is what is wanted. Maybe that should be updated. But I think DEBUG_INFO_REDUCED is redundant if we were to accept DEBUG_INFO_LEVEL. Both don't need to exist IMO. -- Thanks, ~Nick Desaulniers ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] kbuild: add debug level and macro defs options 2022-08-22 22:42 ` Dmitrii Bundin 2022-08-24 23:25 ` Nick Desaulniers @ 2022-09-29 21:06 ` Masahiro Yamada 2022-09-30 9:11 ` Masahiro Yamada 1 sibling, 1 reply; 18+ messages in thread From: Masahiro Yamada @ 2022-09-29 21:06 UTC (permalink / raw) To: Dmitrii Bundin Cc: Nick Desaulniers, Andrew Morton, Dan Williams, Eric Dumazet, Isabella Basso, Josh Poimboeuf, Kees Cook, Linux Kbuild mailing list, Linux Kernel Mailing List, Rasmus Villemoes, Fangrui Song, Michal Marek, Nathan Chancellor, Peter Zijlstra (Intel), Vlastimil Babka On Tue, Aug 23, 2022 at 7:42 AM Dmitrii Bundin <dmitrii.bundin.a@gmail.com> wrote: > > On Tue, Aug 23, 2022 at 12:36 AM Nick Desaulniers > <ndesaulniers@google.com> wrote: > > > > or perhaps that simply needs to be `-g -gsplit-dwarf`? In which case, > > that if/else could just be re-arranged. > > How about simply assigning DEBUG_CFLAGS := -g at the very beginning > without any conditions? This would provide the default with the > possibility of overriding later and -gsplit-dwarf does not necessarily > come with -g implicitly. This was fixed by commit 32ef9e5054ec0321b9336058c58ec749e9c6b0fe, which is now in the mainline. > > Honestly, I really don't think we need to be wrapping every compiler > > command line flag under the sun in a kconfig option. > > This indeed sounds reasonable to me. So the key point here is to not > bloat the kconfig with options related to every compiler flag. But I > think it still might be useful to provide some option that would > include sort of full debug information compilers may produce. With > this approach there would be, in fact 3 different levels of debug > information supported by Kconfig: reduced, default and full. The full > level would increase everything like -g3, and -fdebug-macro for Clang, > and probably others. I think that would be much saner than this patch. CONFIG_DEBUG_INFO_LEVEL is a direct way to specify the debug level. CONFIG_DEBUG_MACRO_DEFINITIONS is feature-driven. Do not mix two different ways. CONFIG_DEBUG_INFO_LEVEL is here just because Andrew Morton suggested that. The debug level is compiler-specific. There is no guarantee that there is a common range. The debug level range of GCC is 0-3. Clang accepts 3, but -g3 has no effect. The debug level range of Rustc is 0-2. See how badly scripts/Makefile.debug looks in linux-next. How should Rustc behave for CONFIG_DEBUG_INFO_LEVEL=3 ? -Cdebuginfo=3 is a compile error. RUSTC L rust/core.o error: debug info level needs to be between 0-2 (instead was `3`) You cannot directly specify the debug level number given that we support multiple compilers with different policy for debug level options. > > Or add -g1 to CONFIG_DEBUG_INFO_REDUCED. > > I ran some tests and there was indeed some decrease in size. That > combination probably might be useful. > > Any thoughts? > > Regards > Dmitrii -- Best Regards Masahiro Yamada ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] kbuild: add debug level and macro defs options 2022-09-29 21:06 ` Masahiro Yamada @ 2022-09-30 9:11 ` Masahiro Yamada 2022-10-08 7:24 ` Dmitrii Bundin 0 siblings, 1 reply; 18+ messages in thread From: Masahiro Yamada @ 2022-09-30 9:11 UTC (permalink / raw) To: Dmitrii Bundin Cc: Nick Desaulniers, Andrew Morton, Dan Williams, Eric Dumazet, Isabella Basso, Josh Poimboeuf, Kees Cook, Linux Kbuild mailing list, Linux Kernel Mailing List, Rasmus Villemoes, Fangrui Song, Michal Marek, Nathan Chancellor, Peter Zijlstra (Intel), Vlastimil Babka On Fri, Sep 30, 2022 at 6:06 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > On Tue, Aug 23, 2022 at 7:42 AM Dmitrii Bundin > <dmitrii.bundin.a@gmail.com> wrote: > > > > On Tue, Aug 23, 2022 at 12:36 AM Nick Desaulniers > > <ndesaulniers@google.com> wrote: > > > > > > or perhaps that simply needs to be `-g -gsplit-dwarf`? In which case, > > > that if/else could just be re-arranged. > > > > How about simply assigning DEBUG_CFLAGS := -g at the very beginning > > without any conditions? This would provide the default with the > > possibility of overriding later and -gsplit-dwarf does not necessarily > > come with -g implicitly. > > This was fixed by commit 32ef9e5054ec0321b9336058c58ec749e9c6b0fe, > which is now in the mainline. > > > > > > > Honestly, I really don't think we need to be wrapping every compiler > > > command line flag under the sun in a kconfig option. > > > > This indeed sounds reasonable to me. So the key point here is to not > > bloat the kconfig with options related to every compiler flag. But I > > think it still might be useful to provide some option that would > > include sort of full debug information compilers may produce. With > > this approach there would be, in fact 3 different levels of debug > > information supported by Kconfig: reduced, default and full. The full > > level would increase everything like -g3, and -fdebug-macro for Clang, > > and probably others. > > > I think that would be much saner than this patch. > > > > CONFIG_DEBUG_INFO_LEVEL is a direct way to specify the debug level. > > CONFIG_DEBUG_MACRO_DEFINITIONS is feature-driven. > > Do not mix two different ways. > > > > > > > CONFIG_DEBUG_INFO_LEVEL is here just because Andrew Morton suggested that. > > > The debug level is compiler-specific. There is no guarantee > that there is a common range. > > > The debug level range of GCC is 0-3. > Clang accepts 3, but -g3 has no effect. > The debug level range of Rustc is 0-2. > > See how badly scripts/Makefile.debug looks in linux-next. > > > > > > How should Rustc behave for CONFIG_DEBUG_INFO_LEVEL=3 ? > > -Cdebuginfo=3 is a compile error. > > RUSTC L rust/core.o > error: debug info level needs to be between 0-2 (instead was `3`) > > > > You cannot directly specify the debug level number given that > we support multiple compilers with different policy for > debug level options. > > > > > > > > > Or add -g1 to CONFIG_DEBUG_INFO_REDUCED. > > > > I ran some tests and there was indeed some decrease in size. That > > combination probably might be useful. > > > > Any thoughts? > > > > Regards > > Dmitrii > > > > > > -- > Best Regards > Masahiro Yamada I proposed to do a ground-work like the following first. https://patchwork.kernel.org/project/linux-kbuild/patch/20220930085351.2648034-1-masahiroy@kernel.org/ On top of that, it is easier to add CONFIG_DEBUG_INFO_FULL or whatever. And, -g1 for CONFIG_DEBUG_INFO_REDUCED if you think it is worthwhile. -- Best Regards Masahiro Yamada ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] kbuild: add debug level and macro defs options 2022-09-30 9:11 ` Masahiro Yamada @ 2022-10-08 7:24 ` Dmitrii Bundin 0 siblings, 0 replies; 18+ messages in thread From: Dmitrii Bundin @ 2022-10-08 7:24 UTC (permalink / raw) To: Masahiro Yamada Cc: Nick Desaulniers, Andrew Morton, Dan Williams, Eric Dumazet, Isabella Basso, Josh Poimboeuf, Kees Cook, Linux Kbuild mailing list, Linux Kernel Mailing List, Rasmus Villemoes, Fangrui Song, Michal Marek, Nathan Chancellor, Peter Zijlstra (Intel), Vlastimil Babka Hi Masahiro, > On top of that, it is easier to add CONFIG_DEBUG_INFO_FULL or whatever. As per the prior discussion, Nick has convinced me that configuring an additional choice for a full debug info might cause more problems that it solves in general. >And, -g1 for CONFIG_DEBUG_INFO_REDUCED if you think it is worthwhile. This indeed would shrink the image size, but with this option enabled there would be no information about local variables which might surprise users of the option. So I don't really think it is worthwhile. Regards, Dmitrii. ^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH v3] kbuild: add debug level and macro defs options 2022-08-19 22:52 ` Dmitrii Bundin 2022-08-22 16:45 ` Nick Desaulniers @ 2022-08-23 6:06 ` Peter Zijlstra 1 sibling, 0 replies; 18+ messages in thread From: Peter Zijlstra @ 2022-08-23 6:06 UTC (permalink / raw) To: Dmitrii Bundin Cc: Nick Desaulniers, Masahiro Yamada, Andrew Morton, Dan Williams, Eric Dumazet, Isabella Basso, Josh Poimboeuf, Kees Cook, Linux Kbuild mailing list, Linux Kernel Mailing List, Rasmus Villemoes, Fangrui Song, Michal Marek, Nathan Chancellor, Vlastimil Babka On Sat, Aug 20, 2022 at 01:52:04AM +0300, Dmitrii Bundin wrote: > On Fri, Aug 19, 2022 at 8:42 PM Nick Desaulniers > <ndesaulniers@google.com> wrote: > > > > Is any of this really necessary? > > Consider the case if CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT=y. Can I just say I *HATE* that thing? It uesd to be I could do: ../scripts/config --enable DEBUG_INFO and I'd get a debug-info build, now I gotta use that horrible piece of crap you just mentioned which I mis-type at least once every single time. ^ permalink raw reply [flat|nested] 18+ messages in thread
end of thread, other threads:[~2022-10-08 7:24 UTC | newest] Thread overview: 18+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-08-14 0:20 [PATCH v2] kbuild: add configurable debug info level Dmitrii Bundin 2022-08-14 2:01 ` Masahiro Yamada 2022-08-14 5:31 ` Fangrui Song 2022-08-14 18:58 ` Masahiro Yamada 2022-08-14 19:17 ` Dmitrii Bundin 2022-08-15 1:33 ` [PATCH v3] kbuild: add debug level and macro defs options Dmitrii Bundin 2022-08-18 4:13 ` Masahiro Yamada 2022-08-18 18:57 ` Dmitrii Bundin 2022-08-19 17:42 ` Nick Desaulniers 2022-08-19 22:52 ` Dmitrii Bundin 2022-08-22 16:45 ` Nick Desaulniers 2022-08-22 21:36 ` Nick Desaulniers 2022-08-22 22:42 ` Dmitrii Bundin 2022-08-24 23:25 ` Nick Desaulniers 2022-09-29 21:06 ` Masahiro Yamada 2022-09-30 9:11 ` Masahiro Yamada 2022-10-08 7:24 ` Dmitrii Bundin 2022-08-23 6:06 ` Peter Zijlstra
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