On Tue, Nov 03, 2020 at 04:53:43PM -0800, Nick Desaulniers wrote: > DWARF v5 is the latest standard of the DWARF debug info format. > > Feature detection of DWARF5 is onerous, especially given that we've > removed $(AS), so we must query $(CC) for DWARF5 assembler directive > support. GNU `as` only recently gained support for specifying > -gdwarf-5. With gcc, using -gdwarf-5 even without -Wa,--gdwarf-5 results in considerably smaller debug info. gcc does not seem to generate the .file 0 directive that causes older GNU as to barf. Should the assembler support check be restricted to CC_IS_CLANG? > /* Stabs debugging sections. */ > #define STABS_DEBUG \ > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 03c494eefabd..c5b54ba51060 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -274,6 +274,14 @@ config DEBUG_INFO_DWARF4 > It makes the debug information larger, but it significantly > improves the success of resolving variables in gdb on optimized code. > > +config DEBUG_INFO_DWARF5 > + bool "Generate DWARF5 debuginfo" > + depends on $(cc-option,-gdwarf-5) > + depends on $(success,$(srctree)/scripts/test_dwarf5_support.sh $(CC) $(CLANG_FLAGS)) > + help > + Genereate dwarf5 debug info. Requires binutils 2.35+, gcc 5.1+, and > + gdb 8.0+. > + > endchoice # "DWARF version" Perhaps this can be expanded with some description of the advantages of dwarf5 over dwarf4? > > config DEBUG_INFO_BTF > diff --git a/scripts/test_dwarf5_support.sh b/scripts/test_dwarf5_support.sh > new file mode 100755 > index 000000000000..156ad5ec4274 > --- /dev/null > +++ b/scripts/test_dwarf5_support.sh > @@ -0,0 +1,9 @@ > +#!/bin/sh > +# SPDX-License-Identifier: GPL-2.0 > + > +# Test that assembler accepts -gdwarf-5 and .file 0 directives, which were bugs > +# in binutils < 2.35. > +# https://sourceware.org/bugzilla/show_bug.cgi?id=25612 > +# https://sourceware.org/bugzilla/show_bug.cgi?id=25614 > +set -e > +echo '.file 0 "filename"' | $* -Wa,-gdwarf-5 -c -x assembler -o /dev/null - This also actually needs --gdwarf-5 to really check the support for the option, but older versions should error on the .file 0 in any case.
