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
