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.
The DWARF version of a binary can be validated with: $ llvm-dwarfdump vmlinux | head -n 5 | grep version or $ readelf --debug-dump=info vmlinux 2>/dev/null | grep Version DWARF5 wins significantly in terms of size when mixed with compression (CONFIG_DEBUG_INFO_COMPRESSED). 363M vmlinux.clang12.dwarf5.compressed 434M vmlinux.clang12.dwarf4.compressed 439M vmlinux.clang12.dwarf2.compressed 457M vmlinux.clang12.dwarf5 536M vmlinux.clang12.dwarf4 548M vmlinux.clang12.dwarf2 Link: http://www.dwarfstd.org/doc/DWARF5.pdf Suggested-by: Masahiro Yamada <masahi...@kernel.org> Suggested-by: Jakub Jelinek <ja...@redhat.com> Signed-off-by: Nick Desaulniers <ndesaulni...@google.com> --- Makefile | 1 + include/asm-generic/vmlinux.lds.h | 6 +++++- lib/Kconfig.debug | 8 ++++++++ scripts/test_dwarf5_support.sh | 9 +++++++++ 4 files changed, 23 insertions(+), 1 deletion(-) create mode 100755 scripts/test_dwarf5_support.sh diff --git a/Makefile b/Makefile index e23786a4c1c7..9056bac0ff85 100644 --- a/Makefile +++ b/Makefile @@ -828,6 +828,7 @@ endif dwarf-version-$(CONFIG_DEBUG_INFO_DWARF2) := 2 dwarf-version-$(CONFIG_DEBUG_INFO_DWARF4) := 4 +dwarf-version-$(CONFIG_DEBUG_INFO_DWARF5) := 5 DEBUG_CFLAGS += -gdwarf-$(dwarf-version-y) ifneq ($(dwarf-version-y)$(LLVM_IAS),21) # Binutils 2.35+ required for -gdwarf-4+ support. diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index b2b3d81b1535..76ce62c77029 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -829,7 +829,11 @@ .debug_types 0 : { *(.debug_types) } \ /* DWARF 5 */ \ .debug_macro 0 : { *(.debug_macro) } \ - .debug_addr 0 : { *(.debug_addr) } + .debug_addr 0 : { *(.debug_addr) } \ + .debug_line_str 0 : { *(.debug_line_str) } \ + .debug_loclists 0 : { *(.debug_loclists) } \ + .debug_rnglists 0 : { *(.debug_rnglists) } \ + .debug_str_offsets 0 : { *(.debug_str_offsets) } /* 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" 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 - -- 2.29.1.341.ge80a0c044ae-goog
