diff mbox series

[v5,2/3] Kbuild: make DWARF version a choice

Message ID 20210115210616.404156-3-ndesaulniers@google.com (mailing list archive)
State New
Headers show
Series Kbuild: DWARF v5 support | expand

Commit Message

Nick Desaulniers Jan. 15, 2021, 9:06 p.m. UTC
Modifies CONFIG_DEBUG_INFO_DWARF4 to be a member of a choice. Adds an
explicit CONFIG_DEBUG_INFO_DWARF2, which is the default. Does so in a
way that's forward compatible with existing configs, and makes adding
future versions more straightforward.

Suggested-by: Arvind Sankar <nivedita@alum.mit.edu>
Suggested-by: Fangrui Song <maskray@google.com>
Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 Makefile          | 13 ++++++-------
 lib/Kconfig.debug | 21 ++++++++++++++++-----
 2 files changed, 22 insertions(+), 12 deletions(-)

Comments

Sedat Dilek Jan. 15, 2021, 9:42 p.m. UTC | #1
On Fri, Jan 15, 2021 at 10:06 PM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> Modifies CONFIG_DEBUG_INFO_DWARF4 to be a member of a choice. Adds an
> explicit CONFIG_DEBUG_INFO_DWARF2, which is the default. Does so in a
> way that's forward compatible with existing configs, and makes adding
> future versions more straightforward.
>
> Suggested-by: Arvind Sankar <nivedita@alum.mit.edu>
> Suggested-by: Fangrui Song <maskray@google.com>
> Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
>  Makefile          | 13 ++++++-------
>  lib/Kconfig.debug | 21 ++++++++++++++++-----
>  2 files changed, 22 insertions(+), 12 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index d49c3f39ceb4..4eb3bf7ee974 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -826,13 +826,12 @@ else
>  DEBUG_CFLAGS   += -g
>  endif
>
> -ifneq ($(LLVM_IAS),1)
> -KBUILD_AFLAGS  += -Wa,-gdwarf-2
> -endif
> -
> -ifdef CONFIG_DEBUG_INFO_DWARF4
> -DEBUG_CFLAGS   += -gdwarf-4
> -endif
> +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF2) := 2
> +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4
> +DEBUG_CFLAGS   += -gdwarf-$(dwarf-version-y)
> +# Binutils 2.35+ required for -gdwarf-4+ support.
> +dwarf-aflag    := $(call as-option,-Wa$(comma)-gdwarf-$(dwarf-version-y))
> +KBUILD_AFLAGS  += $(dwarf-aflag)
>
>  ifdef CONFIG_DEBUG_INFO_REDUCED
>  DEBUG_CFLAGS   += $(call cc-option, -femit-struct-debug-baseonly) \
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index dd7d8d35b2a5..e80770fac4f0 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -256,13 +256,24 @@ config DEBUG_INFO_SPLIT
>           to know about the .dwo files and include them.
>           Incompatible with older versions of ccache.
>
> +choice
> +       prompt "DWARF version"

Here you use "DWARF version" so keep this for v2 and v4.

> +       help
> +         Which version of DWARF debug info to emit.
> +
> +config DEBUG_INFO_DWARF2
> +       bool "Generate DWARF Version 2 debuginfo"

s/DWARF Version/DWARF version

> +       help
> +         Generate DWARF v2 debug info.
> +
>  config DEBUG_INFO_DWARF4
> -       bool "Generate dwarf4 debuginfo"
> +       bool "Generate DWARF Version 4 debuginfo"

Same here: s/DWARF Version/DWARF version

- Sedat -

>         help
> -         Generate dwarf4 debug info. This requires recent versions
> -         of gcc and gdb. It makes the debug information larger.
> -         But it significantly improves the success of resolving
> -         variables in gdb on optimized code.
> +         Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
> +         It makes the debug information larger, but it significantly
> +         improves the success of resolving variables in gdb on optimized code.
> +
> +endchoice # "DWARF version"
>
>  config DEBUG_INFO_BTF
>         bool "Generate BTF typeinfo"
> --
> 2.30.0.284.gd98b1dd5eaa7-goog
>
Fangrui Song Jan. 15, 2021, 10:05 p.m. UTC | #2
On 2021-01-15, Sedat Dilek wrote:
>On Fri, Jan 15, 2021 at 10:06 PM Nick Desaulniers
><ndesaulniers@google.com> wrote:
>>
>> Modifies CONFIG_DEBUG_INFO_DWARF4 to be a member of a choice. Adds an
>> explicit CONFIG_DEBUG_INFO_DWARF2, which is the default. Does so in a
>> way that's forward compatible with existing configs, and makes adding
>> future versions more straightforward.
>>
>> Suggested-by: Arvind Sankar <nivedita@alum.mit.edu>
>> Suggested-by: Fangrui Song <maskray@google.com>
>> Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
>> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
>> ---
>>  Makefile          | 13 ++++++-------
>>  lib/Kconfig.debug | 21 ++++++++++++++++-----
>>  2 files changed, 22 insertions(+), 12 deletions(-)
>>
>> diff --git a/Makefile b/Makefile
>> index d49c3f39ceb4..4eb3bf7ee974 100644
>> --- a/Makefile
>> +++ b/Makefile
>> @@ -826,13 +826,12 @@ else
>>  DEBUG_CFLAGS   += -g
>>  endif
>>
>> -ifneq ($(LLVM_IAS),1)
>> -KBUILD_AFLAGS  += -Wa,-gdwarf-2
>> -endif
>> -
>> -ifdef CONFIG_DEBUG_INFO_DWARF4
>> -DEBUG_CFLAGS   += -gdwarf-4
>> -endif
>> +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF2) := 2
>> +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4
>> +DEBUG_CFLAGS   += -gdwarf-$(dwarf-version-y)
>> +# Binutils 2.35+ required for -gdwarf-4+ support.
>> +dwarf-aflag    := $(call as-option,-Wa$(comma)-gdwarf-$(dwarf-version-y))
>> +KBUILD_AFLAGS  += $(dwarf-aflag)
>>
>>  ifdef CONFIG_DEBUG_INFO_REDUCED
>>  DEBUG_CFLAGS   += $(call cc-option, -femit-struct-debug-baseonly) \
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index dd7d8d35b2a5..e80770fac4f0 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -256,13 +256,24 @@ config DEBUG_INFO_SPLIT
>>           to know about the .dwo files and include them.
>>           Incompatible with older versions of ccache.
>>
>> +choice
>> +       prompt "DWARF version"
>
>Here you use "DWARF version" so keep this for v2 and v4.
>
>> +       help
>> +         Which version of DWARF debug info to emit.
>> +
>> +config DEBUG_INFO_DWARF2
>> +       bool "Generate DWARF Version 2 debuginfo"
>
>s/DWARF Version/DWARF version
>
>> +       help
>> +         Generate DWARF v2 debug info.
>> +
>>  config DEBUG_INFO_DWARF4
>> -       bool "Generate dwarf4 debuginfo"
>> +       bool "Generate DWARF Version 4 debuginfo"
>
>Same here: s/DWARF Version/DWARF version

DWARF Version 2 is fine and preferable.

I have checked DWARF Version 2/3/4/5 specifications.
"DWARF Version 2" is the official way that version is referred to...

>
>- Sedat -
>
>>         help
>> -         Generate dwarf4 debug info. This requires recent versions
>> -         of gcc and gdb. It makes the debug information larger.
>> -         But it significantly improves the success of resolving
>> -         variables in gdb on optimized code.
>> +         Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
>> +         It makes the debug information larger, but it significantly
>> +         improves the success of resolving variables in gdb on optimized code.
>> +
>> +endchoice # "DWARF version"
>>
>>  config DEBUG_INFO_BTF
>>         bool "Generate BTF typeinfo"
>> --
>> 2.30.0.284.gd98b1dd5eaa7-goog
>>
Nathan Chancellor Jan. 20, 2021, 8:40 p.m. UTC | #3
On Fri, Jan 15, 2021 at 01:06:15PM -0800, Nick Desaulniers wrote:
> Modifies CONFIG_DEBUG_INFO_DWARF4 to be a member of a choice. Adds an
> explicit CONFIG_DEBUG_INFO_DWARF2, which is the default. Does so in a
> way that's forward compatible with existing configs, and makes adding
> future versions more straightforward.
> 
> Suggested-by: Arvind Sankar <nivedita@alum.mit.edu>
> Suggested-by: Fangrui Song <maskray@google.com>
> Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
> Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> ---
>  Makefile          | 13 ++++++-------
>  lib/Kconfig.debug | 21 ++++++++++++++++-----
>  2 files changed, 22 insertions(+), 12 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index d49c3f39ceb4..4eb3bf7ee974 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -826,13 +826,12 @@ else
>  DEBUG_CFLAGS	+= -g
>  endif
>  
> -ifneq ($(LLVM_IAS),1)
> -KBUILD_AFLAGS	+= -Wa,-gdwarf-2
> -endif

Aren't you regressing this with this patch? Why is the hunk from 3/3
that adds

ifdef CONFIG_CC_IS_CLANG
ifneq ($(LLVM_IAS),1)

not in this patch?

> -ifdef CONFIG_DEBUG_INFO_DWARF4
> -DEBUG_CFLAGS	+= -gdwarf-4
> -endif
> +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF2) := 2
> +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4
> +DEBUG_CFLAGS	+= -gdwarf-$(dwarf-version-y)
> +# Binutils 2.35+ required for -gdwarf-4+ support.
> +dwarf-aflag	:= $(call as-option,-Wa$(comma)-gdwarf-$(dwarf-version-y))
> +KBUILD_AFLAGS	+= $(dwarf-aflag)
>  
>  ifdef CONFIG_DEBUG_INFO_REDUCED
>  DEBUG_CFLAGS	+= $(call cc-option, -femit-struct-debug-baseonly) \
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index dd7d8d35b2a5..e80770fac4f0 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -256,13 +256,24 @@ 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_DWARF2
> +	bool "Generate DWARF Version 2 debuginfo"
> +	help
> +	  Generate DWARF v2 debug info.
> +
>  config DEBUG_INFO_DWARF4
> -	bool "Generate dwarf4 debuginfo"
> +	bool "Generate DWARF Version 4 debuginfo"
>  	help
> -	  Generate dwarf4 debug info. This requires recent versions
> -	  of gcc and gdb. It makes the debug information larger.
> -	  But it significantly improves the success of resolving
> -	  variables in gdb on optimized code.
> +	  Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
> +	  It makes the debug information larger, but it significantly
> +	  improves the success of resolving variables in gdb on optimized code.
> +
> +endchoice # "DWARF version"
>  
>  config DEBUG_INFO_BTF
>  	bool "Generate BTF typeinfo"
> -- 
> 2.30.0.284.gd98b1dd5eaa7-goog
>
Sedat Dilek Jan. 21, 2021, 2:35 a.m. UTC | #4
On Wed, Jan 20, 2021 at 9:40 PM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> On Fri, Jan 15, 2021 at 01:06:15PM -0800, Nick Desaulniers wrote:
> > Modifies CONFIG_DEBUG_INFO_DWARF4 to be a member of a choice. Adds an
> > explicit CONFIG_DEBUG_INFO_DWARF2, which is the default. Does so in a
> > way that's forward compatible with existing configs, and makes adding
> > future versions more straightforward.
> >
> > Suggested-by: Arvind Sankar <nivedita@alum.mit.edu>
> > Suggested-by: Fangrui Song <maskray@google.com>
> > Suggested-by: Masahiro Yamada <masahiroy@kernel.org>
> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> > ---
> >  Makefile          | 13 ++++++-------
> >  lib/Kconfig.debug | 21 ++++++++++++++++-----
> >  2 files changed, 22 insertions(+), 12 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index d49c3f39ceb4..4eb3bf7ee974 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -826,13 +826,12 @@ else
> >  DEBUG_CFLAGS += -g
> >  endif
> >
> > -ifneq ($(LLVM_IAS),1)
> > -KBUILD_AFLAGS        += -Wa,-gdwarf-2
> > -endif
>
> Aren't you regressing this with this patch? Why is the hunk from 3/3
> that adds
>
> ifdef CONFIG_CC_IS_CLANG
> ifneq ($(LLVM_IAS),1)
>
> not in this patch?
>

Nice catch Nathan.

Just FYI:

The patch...

"kbuild: Remove $(cc-option,-gdwarf-4) dependency from DEBUG_INFO_DWARF4"

... has now entered kbuild-next.
( This patch is included in this patch-series. )

So should we point to this one and add a comment?
Thinking of a next version of this DWARF5 support patch-series.

- Sedat -

[1] https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/commit/?h=kbuild&id=3f4d8ce271c7082be75bacbcbd2048aa78ce2b44

> > -ifdef CONFIG_DEBUG_INFO_DWARF4
> > -DEBUG_CFLAGS += -gdwarf-4
> > -endif
> > +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF2) := 2
> > +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4
> > +DEBUG_CFLAGS += -gdwarf-$(dwarf-version-y)
> > +# Binutils 2.35+ required for -gdwarf-4+ support.
> > +dwarf-aflag  := $(call as-option,-Wa$(comma)-gdwarf-$(dwarf-version-y))
> > +KBUILD_AFLAGS        += $(dwarf-aflag)
> >
> >  ifdef CONFIG_DEBUG_INFO_REDUCED
> >  DEBUG_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly) \
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index dd7d8d35b2a5..e80770fac4f0 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -256,13 +256,24 @@ 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_DWARF2
> > +     bool "Generate DWARF Version 2 debuginfo"
> > +     help
> > +       Generate DWARF v2 debug info.
> > +
> >  config DEBUG_INFO_DWARF4
> > -     bool "Generate dwarf4 debuginfo"
> > +     bool "Generate DWARF Version 4 debuginfo"
> >       help
> > -       Generate dwarf4 debug info. This requires recent versions
> > -       of gcc and gdb. It makes the debug information larger.
> > -       But it significantly improves the success of resolving
> > -       variables in gdb on optimized code.
> > +       Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
> > +       It makes the debug information larger, but it significantly
> > +       improves the success of resolving variables in gdb on optimized code.
> > +
> > +endchoice # "DWARF version"
> >
> >  config DEBUG_INFO_BTF
> >       bool "Generate BTF typeinfo"
> > --
> > 2.30.0.284.gd98b1dd5eaa7-goog
> >
diff mbox series

Patch

diff --git a/Makefile b/Makefile
index d49c3f39ceb4..4eb3bf7ee974 100644
--- a/Makefile
+++ b/Makefile
@@ -826,13 +826,12 @@  else
 DEBUG_CFLAGS	+= -g
 endif
 
-ifneq ($(LLVM_IAS),1)
-KBUILD_AFLAGS	+= -Wa,-gdwarf-2
-endif
-
-ifdef CONFIG_DEBUG_INFO_DWARF4
-DEBUG_CFLAGS	+= -gdwarf-4
-endif
+dwarf-version-$(CONFIG_DEBUG_INFO_DWARF2) := 2
+dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4
+DEBUG_CFLAGS	+= -gdwarf-$(dwarf-version-y)
+# Binutils 2.35+ required for -gdwarf-4+ support.
+dwarf-aflag	:= $(call as-option,-Wa$(comma)-gdwarf-$(dwarf-version-y))
+KBUILD_AFLAGS	+= $(dwarf-aflag)
 
 ifdef CONFIG_DEBUG_INFO_REDUCED
 DEBUG_CFLAGS	+= $(call cc-option, -femit-struct-debug-baseonly) \
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index dd7d8d35b2a5..e80770fac4f0 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -256,13 +256,24 @@  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_DWARF2
+	bool "Generate DWARF Version 2 debuginfo"
+	help
+	  Generate DWARF v2 debug info.
+
 config DEBUG_INFO_DWARF4
-	bool "Generate dwarf4 debuginfo"
+	bool "Generate DWARF Version 4 debuginfo"
 	help
-	  Generate dwarf4 debug info. This requires recent versions
-	  of gcc and gdb. It makes the debug information larger.
-	  But it significantly improves the success of resolving
-	  variables in gdb on optimized code.
+	  Generate DWARF v4 debug info. This requires gcc 4.5+ and gdb 7.0+.
+	  It makes the debug information larger, but it significantly
+	  improves the success of resolving variables in gdb on optimized code.
+
+endchoice # "DWARF version"
 
 config DEBUG_INFO_BTF
 	bool "Generate BTF typeinfo"