On Wed, Aug 26, 2020 at 2:11 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > > On Sun, Aug 16, 2020 at 2:14 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > > > > Hi Masahiro, > > > > I wondered why my generated linux-image-db Debian packages were so big > > when I use GCC toolchain instead of LLVM toolchain. > > > > It turned out I mixed both... > > > > KBUILD_AFLAGS += -Wa,-gdwarf-2 > > > > ...together with... > > > > DEBUG_CFLAGS += -gdwarf-4 > > > > ...when CONFIG_DEBUG_INFO_DWARF4=y is set. > > > > So I hacked up something like the following to prevent this: > > > > diff --git a/Makefile b/Makefile > > index 24a4c1b97bb0..e7a8e47b0e34 100644 > > --- a/Makefile > > +++ b/Makefile > > @@ -815,7 +815,11 @@ DEBUG_CFLAGS += -gsplit-dwarf > > else > > DEBUG_CFLAGS += -g > > endif > > +ifdef CONFIG_DEBUG_INFO_AS_DWARF2 > > KBUILD_AFLAGS += -Wa,-gdwarf-2 > > +else ifdef CONFIG_DEBUG_INFO_AS_DWARF4 > > +KBUILD_AFLAGS += -Wa,-gdwarf-4 > > +endif > > endif > > ifdef CONFIG_DEBUG_INFO_DWARF4 > > DEBUG_CFLAGS += -gdwarf-4 > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > index 9ad9210d70a1..9f11fc71462c 100644 > > --- a/lib/Kconfig.debug > > +++ b/lib/Kconfig.debug > > @@ -257,10 +257,23 @@ config DEBUG_INFO_SPLIT > > to know about the .dwo files and include them. > > Incompatible with older versions of ccache. > > > > +config DEBUG_INFO_AS_DWARF2 > > + bool "Use DWARF-2 assembler option with debuginfo" > > + depends on $(cc-option,-Wa$(comma)-gdwarf-2) > > + help > > + Set DWARF-2 assembler option with debuginfo > > + > > +config DEBUG_INFO_AS_DWARF4 > > + bool "Use DWARF-4 assembler option with debuginfo" > > + depends on $(cc-option,-Wa$(comma)-gdwarf-4) > > + help > > + Set DWARF-4 assembler option with debuginfo > > + > > config DEBUG_INFO_DWARF4 > > bool "Generate dwarf4 debuginfo" > > depends on DEBUG_INFO > > depends on $(cc-option,-gdwarf-4) > > + select DEBUG_INFO_AS_DWARF4 > > help > > Generate dwarf4 debug info. This requires recent versions > > of gcc and gdb. It makes the debug information larger. > > > > NOTE: This is on top of Linux v5.8 vanilla. > > > > NOTE-2: When building with LLVM toolchain v11.0.0-rc1+ and especially > > with LLVM_IAS=1 (and LLVM=1) DWARF version 4 is a good choice. > > > > For details see below links. > > > > Thoughts? > > > > Regards, > > - Sedat - > > > > [1] https://github.com/ClangBuiltLinux/linux/issues/1086 > > [2] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-674503335 > > [3] https://github.com/ClangBuiltLinux/linux/issues/1086#issuecomment-674517876 > > [ CC Sami ] > > Hi, > > while playing with Clang-CFI I needed this patch to fix these warnings: > > $ grep DWARF BROKEN_DWARF2-only-supports-one-section-per-compilation-unit.txt > arch/x86/crypto/twofish-avx-x86_64-asm_64.S:17:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/twofish-avx-x86_64-asm_64.S:22:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/serpent-avx-x86_64-asm_64.S:17:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/serpent-avx-x86_64-asm_64.S:21:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/serpent-avx2-asm_64.S:18:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/serpent-avx2-asm_64.S:23:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/serpent-avx2-asm_64.S:28:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/des3_ede-asm_64.S:534:1: warning: DWARF2 only supports > one section per compilation unit > arch/x86/crypto/camellia-aesni-avx-asm_64.S:577:1: warning: DWARF2 > only supports one section per compilation unit > arch/x86/crypto/camellia-aesni-avx-asm_64.S:717:1: warning: DWARF2 > only supports one section per compilation unit > <instantiation>:2:2: warning: DWARF2 only supports one section per > compilation unit > <instantiation>:8:2: warning: DWARF2 only supports one section per > compilation unit > <instantiation>:13:2: warning: DWARF2 only supports one section per > compilation unit > arch/x86/crypto/camellia-aesni-avx2-asm_64.S:610:1: warning: DWARF2 > only supports one section per compilation unit > arch/x86/crypto/camellia-aesni-avx2-asm_64.S:618:1: warning: DWARF2 > only supports one section per compilation unit > arch/x86/crypto/camellia-aesni-avx2-asm_64.S:625:1: warning: DWARF2 > only supports one section per compilation unit > arch/x86/crypto/camellia-aesni-avx2-asm_64.S:754:1: warning: DWARF2 > only supports one section per compilation unit > <instantiation>:2:2: warning: DWARF2 only supports one section per > compilation unit > <instantiation>:8:2: warning: DWARF2 only supports one section per > compilation unit > <instantiation>:13:2: warning: DWARF2 only supports one section per > compilation unit > arch/x86/crypto/cast5-avx-x86_64-asm_64.S:183:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/cast5-avx-x86_64-asm_64.S:187:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/cast5-avx-x86_64-asm_64.S:191:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/cast5-avx-x86_64-asm_64.S:196:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/cast5-avx-x86_64-asm_64.S:200:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/cast5-avx-x86_64-asm_64.S:204:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/cast6-avx-x86_64-asm_64.S:213:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/cast6-avx-x86_64-asm_64.S:232:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/cast6-avx-x86_64-asm_64.S:237:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/cast6-avx-x86_64-asm_64.S:242:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/aegis128-aesni-asm.S:27:1: warning: DWARF2 only > supports one section per compilation unit > arch/x86/crypto/aegis128-aesni-asm.S:36:1: warning: DWARF2 only > supports one section per compilation unit > > Can you please review? > > Thanks. > > Regards, > - Sedat - > > P.S.: With the help of Sami I can now build and boot into Linux-kernel > with Clang-CFI support enabled. > > [1] https://github.com/samitolvanen/linux/commits/clang-cfi Some more informations to clarify this is really needed. I switched over to DWARF version 4 when dealing with Clang-IAS (integrated assembler). And saw similar problems. This was always with... CONFIG_DEBUG_INFO_DWARF4=y There are 156 places here on x86 64bit... [ Clang-CFI ] $ grep '\-Wa,-gdwarf-4' build-log_5.9.0-rc2-5-amd64-llvm11-cfi.txt | wc -l 156 [ Clang-LTO ] $ grep '\-Wa,-gdwarf-4' build-log_5.9.0-rc2-6-amd64-clang-lto.txt | wc -l 156 - Sedat -
