| Message ID | 20221014204210.383380-1-nathan@kernel.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [v2] lib/Kconfig.debug: Add check for non-constant .{s,u}leb128 support to DWARF5 | expand |
On Fri, Oct 14, 2022 at 1:48 PM Nathan Chancellor <nathan@kernel.org> wrote: > > When building with a RISC-V kernel with DWARF5 debug info using clang > and the GNU assembler, several instances of the following error appear: > > /tmp/vgettimeofday-48aa35.s:2963: Error: non-constant .uleb128 is not supported > > Dumping the .s file reveals these .uleb128 directives come from > .debug_loc and .debug_ranges: > > .Ldebug_loc0: > .byte 4 # DW_LLE_offset_pair > .uleb128 .Lfunc_begin0-.Lfunc_begin0 # starting offset > .uleb128 .Ltmp1-.Lfunc_begin0 # ending offset > .byte 1 # Loc expr size > .byte 90 # DW_OP_reg10 > .byte 0 # DW_LLE_end_of_list > > .Ldebug_ranges0: > .byte 4 # DW_RLE_offset_pair > .uleb128 .Ltmp6-.Lfunc_begin0 # starting offset > .uleb128 .Ltmp27-.Lfunc_begin0 # ending offset > .byte 4 # DW_RLE_offset_pair > .uleb128 .Ltmp28-.Lfunc_begin0 # starting offset > .uleb128 .Ltmp30-.Lfunc_begin0 # ending offset > .byte 0 # DW_RLE_end_of_list > > There is an outstanding binutils issue to support a non-constant operand > to .sleb128 and .uleb128 in GAS for RISC-V but there does not appear to > be any movement on it, due to concerns over how it would work with > linker relaxation. > > To avoid these build errors, prevent DWARF5 from being selected when > using clang and an assembler that does not have support for these symbol > deltas, which can be easily checked in Kconfig with as-instr plus the > small test program from the dwz test suite from the binutils issue. > > Link: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 > Link: https://github.com/ClangBuiltLinux/linux/issues/1719 > Signed-off-by: Nathan Chancellor <nathan@kernel.org> Thanks for keeping these LLVM_IAS=0 builds alive a little longer. My hope is the GNU binutils can relax their requirement for debug info sections to improve support for DWARF v5. Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > --- > > v2: > - Rebase on commit bb1435f3f575 ("Kconfig.debug: add toolchain > checks for DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT") from the kbuild > tree. > - Limit CONFIG_AS_HAS_NON_CONST_LEB128 dependency to GNU as. There > is no point to applying this dependency to the integrated > assembler because it will always pass. > - Apply the CONFIG_AS_HAS_NON_CONST_LEB128 dependency to > CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT as well, due to the > aforementioned kbuild change. > - Move comment block to above CONFIG_AS_HAS_NON_CONST_LEB128, as the > configuration is now used in two places. > - Drop Conor's tested by, as the patch is different enough to > potentially require new testing. > > v1: https://lore.kernel.org/20220928182523.3105953-1-nathan@kernel.org/ > > lib/Kconfig.debug | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index db8d9271cabf..5c1c63575895 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -231,6 +231,11 @@ config DEBUG_INFO > in the "Debug information" choice below, indicating that debug > information will be generated for build targets. > > +# Clang is known to generate .{s,u}leb128 with symbol deltas with DWARF5, which > +# some targets may not support: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 > +config AS_HAS_NON_CONST_LEB128 > + def_bool $(as-instr,.uleb128 .Lexpr_end4 - .Lexpr_start3\n.Lexpr_start3:\n.Lexpr_end4:) > + > choice > prompt "Debug information" > depends on DEBUG_KERNEL > @@ -253,7 +258,7 @@ config DEBUG_INFO_NONE > config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > bool "Rely on the toolchain's implicit default DWARF version" > select DEBUG_INFO > - depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502) > + depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) > help > The implicit default version of DWARF debug info produced by a > toolchain changes over time. > @@ -277,7 +282,7 @@ config DEBUG_INFO_DWARF4 > config DEBUG_INFO_DWARF5 > bool "Generate DWARF Version 5 debuginfo" > select DEBUG_INFO > - depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502) > + depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) > help > Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc > 5.0+ accepts the -gdwarf-5 flag but only had partial support for some > > base-commit: bb1435f3f575b5213eaf27434efa3971f51c01de > -- > 2.38.0 > -- Thanks, ~Nick Desaulniers
On Sat, Oct 15, 2022 at 6:52 AM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Fri, Oct 14, 2022 at 1:48 PM Nathan Chancellor <nathan@kernel.org> wrote: > > > > When building with a RISC-V kernel with DWARF5 debug info using clang > > and the GNU assembler, several instances of the following error appear: > > > > /tmp/vgettimeofday-48aa35.s:2963: Error: non-constant .uleb128 is not supported > > > > Dumping the .s file reveals these .uleb128 directives come from > > .debug_loc and .debug_ranges: > > > > .Ldebug_loc0: > > .byte 4 # DW_LLE_offset_pair > > .uleb128 .Lfunc_begin0-.Lfunc_begin0 # starting offset > > .uleb128 .Ltmp1-.Lfunc_begin0 # ending offset > > .byte 1 # Loc expr size > > .byte 90 # DW_OP_reg10 > > .byte 0 # DW_LLE_end_of_list > > > > .Ldebug_ranges0: > > .byte 4 # DW_RLE_offset_pair > > .uleb128 .Ltmp6-.Lfunc_begin0 # starting offset > > .uleb128 .Ltmp27-.Lfunc_begin0 # ending offset > > .byte 4 # DW_RLE_offset_pair > > .uleb128 .Ltmp28-.Lfunc_begin0 # starting offset > > .uleb128 .Ltmp30-.Lfunc_begin0 # ending offset > > .byte 0 # DW_RLE_end_of_list > > > > There is an outstanding binutils issue to support a non-constant operand > > to .sleb128 and .uleb128 in GAS for RISC-V but there does not appear to > > be any movement on it, due to concerns over how it would work with > > linker relaxation. > > > > To avoid these build errors, prevent DWARF5 from being selected when > > using clang and an assembler that does not have support for these symbol > > deltas, which can be easily checked in Kconfig with as-instr plus the > > small test program from the dwz test suite from the binutils issue. > > > > Link: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 > > Link: https://github.com/ClangBuiltLinux/linux/issues/1719 > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > > Thanks for keeping these LLVM_IAS=0 builds alive a little longer. My > hope is the GNU binutils can relax their requirement for debug info > sections to improve support for DWARF v5. > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Applied to linux-kbuild. Thanks. > > --- > > > > v2: > > - Rebase on commit bb1435f3f575 ("Kconfig.debug: add toolchain > > checks for DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT") from the kbuild > > tree. > > - Limit CONFIG_AS_HAS_NON_CONST_LEB128 dependency to GNU as. There > > is no point to applying this dependency to the integrated > > assembler because it will always pass. > > - Apply the CONFIG_AS_HAS_NON_CONST_LEB128 dependency to > > CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT as well, due to the > > aforementioned kbuild change. > > - Move comment block to above CONFIG_AS_HAS_NON_CONST_LEB128, as the > > configuration is now used in two places. > > - Drop Conor's tested by, as the patch is different enough to > > potentially require new testing. > > > > v1: https://lore.kernel.org/20220928182523.3105953-1-nathan@kernel.org/ > > > > lib/Kconfig.debug | 9 +++++++-- > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > index db8d9271cabf..5c1c63575895 100644 > > --- a/lib/Kconfig.debug > > +++ b/lib/Kconfig.debug > > @@ -231,6 +231,11 @@ config DEBUG_INFO > > in the "Debug information" choice below, indicating that debug > > information will be generated for build targets. > > > > +# Clang is known to generate .{s,u}leb128 with symbol deltas with DWARF5, which > > +# some targets may not support: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 > > +config AS_HAS_NON_CONST_LEB128 > > + def_bool $(as-instr,.uleb128 .Lexpr_end4 - .Lexpr_start3\n.Lexpr_start3:\n.Lexpr_end4:) > > + > > choice > > prompt "Debug information" > > depends on DEBUG_KERNEL > > @@ -253,7 +258,7 @@ config DEBUG_INFO_NONE > > config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > > bool "Rely on the toolchain's implicit default DWARF version" > > select DEBUG_INFO > > - depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502) > > + depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) > > help > > The implicit default version of DWARF debug info produced by a > > toolchain changes over time. > > @@ -277,7 +282,7 @@ config DEBUG_INFO_DWARF4 > > config DEBUG_INFO_DWARF5 > > bool "Generate DWARF Version 5 debuginfo" > > select DEBUG_INFO > > - depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502) > > + depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) > > help > > Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc > > 5.0+ accepts the -gdwarf-5 flag but only had partial support for some > > > > base-commit: bb1435f3f575b5213eaf27434efa3971f51c01de > > -- > > 2.38.0 > > > > > -- > Thanks, > ~Nick Desaulniers -- Best Regards Masahiro Yamada
On Sun, Oct 16, 2022 at 8:04 PM Masahiro Yamada <masahiroy@kernel.org> wrote: > > On Sat, Oct 15, 2022 at 6:52 AM Nick Desaulniers > <ndesaulniers@google.com> wrote: > > > > On Fri, Oct 14, 2022 at 1:48 PM Nathan Chancellor <nathan@kernel.org> wrote: > > > > > > When building with a RISC-V kernel with DWARF5 debug info using clang > > > and the GNU assembler, several instances of the following error appear: > > > > > > /tmp/vgettimeofday-48aa35.s:2963: Error: non-constant .uleb128 is not supported > > > > > > Dumping the .s file reveals these .uleb128 directives come from > > > .debug_loc and .debug_ranges: > > > > > > .Ldebug_loc0: > > > .byte 4 # DW_LLE_offset_pair > > > .uleb128 .Lfunc_begin0-.Lfunc_begin0 # starting offset > > > .uleb128 .Ltmp1-.Lfunc_begin0 # ending offset > > > .byte 1 # Loc expr size > > > .byte 90 # DW_OP_reg10 > > > .byte 0 # DW_LLE_end_of_list > > > > > > .Ldebug_ranges0: > > > .byte 4 # DW_RLE_offset_pair > > > .uleb128 .Ltmp6-.Lfunc_begin0 # starting offset > > > .uleb128 .Ltmp27-.Lfunc_begin0 # ending offset > > > .byte 4 # DW_RLE_offset_pair > > > .uleb128 .Ltmp28-.Lfunc_begin0 # starting offset > > > .uleb128 .Ltmp30-.Lfunc_begin0 # ending offset > > > .byte 0 # DW_RLE_end_of_list > > > > > > There is an outstanding binutils issue to support a non-constant operand > > > to .sleb128 and .uleb128 in GAS for RISC-V but there does not appear to > > > be any movement on it, due to concerns over how it would work with > > > linker relaxation. > > > > > > To avoid these build errors, prevent DWARF5 from being selected when > > > using clang and an assembler that does not have support for these symbol > > > deltas, which can be easily checked in Kconfig with as-instr plus the > > > small test program from the dwz test suite from the binutils issue. > > > > > > Link: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 > > > Link: https://github.com/ClangBuiltLinux/linux/issues/1719 > > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > > > > Thanks for keeping these LLVM_IAS=0 builds alive a little longer. My > > hope is the GNU binutils can relax their requirement for debug info > > sections to improve support for DWARF v5. > > > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > > > Applied to linux-kbuild. > Thanks. > [1] says: "This looks good to me! Feel free to submit with a: Tested-by: Conor Dooley <conor.dooley@microchip.com>" -sed@- [1] https://github.com/ClangBuiltLinux/linux/issues/1719#issuecomment-1261158627 > > > > > --- > > > > > > v2: > > > - Rebase on commit bb1435f3f575 ("Kconfig.debug: add toolchain > > > checks for DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT") from the kbuild > > > tree. > > > - Limit CONFIG_AS_HAS_NON_CONST_LEB128 dependency to GNU as. There > > > is no point to applying this dependency to the integrated > > > assembler because it will always pass. > > > - Apply the CONFIG_AS_HAS_NON_CONST_LEB128 dependency to > > > CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT as well, due to the > > > aforementioned kbuild change. > > > - Move comment block to above CONFIG_AS_HAS_NON_CONST_LEB128, as the > > > configuration is now used in two places. > > > - Drop Conor's tested by, as the patch is different enough to > > > potentially require new testing. > > > > > > v1: https://lore.kernel.org/20220928182523.3105953-1-nathan@kernel.org/ > > > > > > lib/Kconfig.debug | 9 +++++++-- > > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > > index db8d9271cabf..5c1c63575895 100644 > > > --- a/lib/Kconfig.debug > > > +++ b/lib/Kconfig.debug > > > @@ -231,6 +231,11 @@ config DEBUG_INFO > > > in the "Debug information" choice below, indicating that debug > > > information will be generated for build targets. > > > > > > +# Clang is known to generate .{s,u}leb128 with symbol deltas with DWARF5, which > > > +# some targets may not support: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 > > > +config AS_HAS_NON_CONST_LEB128 > > > + def_bool $(as-instr,.uleb128 .Lexpr_end4 - .Lexpr_start3\n.Lexpr_start3:\n.Lexpr_end4:) > > > + > > > choice > > > prompt "Debug information" > > > depends on DEBUG_KERNEL > > > @@ -253,7 +258,7 @@ config DEBUG_INFO_NONE > > > config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > > > bool "Rely on the toolchain's implicit default DWARF version" > > > select DEBUG_INFO > > > - depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502) > > > + depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) > > > help > > > The implicit default version of DWARF debug info produced by a > > > toolchain changes over time. > > > @@ -277,7 +282,7 @@ config DEBUG_INFO_DWARF4 > > > config DEBUG_INFO_DWARF5 > > > bool "Generate DWARF Version 5 debuginfo" > > > select DEBUG_INFO > > > - depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502) > > > + depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) > > > help > > > Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc > > > 5.0+ accepts the -gdwarf-5 flag but only had partial support for some > > > > > > base-commit: bb1435f3f575b5213eaf27434efa3971f51c01de > > > -- > > > 2.38.0 > > > > > > > > > -- > > Thanks, > > ~Nick Desaulniers > > > > -- > Best Regards > Masahiro Yamada
On Sun, Oct 16, 2022 at 08:10:30PM +0200, Sedat Dilek wrote: > On Sun, Oct 16, 2022 at 8:04 PM Masahiro Yamada <masahiroy@kernel.org> wrote: > > > > On Sat, Oct 15, 2022 at 6:52 AM Nick Desaulniers > > <ndesaulniers@google.com> wrote: > > > > > > On Fri, Oct 14, 2022 at 1:48 PM Nathan Chancellor <nathan@kernel.org> wrote: > > > > > > > > When building with a RISC-V kernel with DWARF5 debug info using clang > > > > and the GNU assembler, several instances of the following error appear: > > > > > > > > /tmp/vgettimeofday-48aa35.s:2963: Error: non-constant .uleb128 is not supported > > > > > > > > Dumping the .s file reveals these .uleb128 directives come from > > > > .debug_loc and .debug_ranges: > > > > > > > > .Ldebug_loc0: > > > > .byte 4 # DW_LLE_offset_pair > > > > .uleb128 .Lfunc_begin0-.Lfunc_begin0 # starting offset > > > > .uleb128 .Ltmp1-.Lfunc_begin0 # ending offset > > > > .byte 1 # Loc expr size > > > > .byte 90 # DW_OP_reg10 > > > > .byte 0 # DW_LLE_end_of_list > > > > > > > > .Ldebug_ranges0: > > > > .byte 4 # DW_RLE_offset_pair > > > > .uleb128 .Ltmp6-.Lfunc_begin0 # starting offset > > > > .uleb128 .Ltmp27-.Lfunc_begin0 # ending offset > > > > .byte 4 # DW_RLE_offset_pair > > > > .uleb128 .Ltmp28-.Lfunc_begin0 # starting offset > > > > .uleb128 .Ltmp30-.Lfunc_begin0 # ending offset > > > > .byte 0 # DW_RLE_end_of_list > > > > > > > > There is an outstanding binutils issue to support a non-constant operand > > > > to .sleb128 and .uleb128 in GAS for RISC-V but there does not appear to > > > > be any movement on it, due to concerns over how it would work with > > > > linker relaxation. > > > > > > > > To avoid these build errors, prevent DWARF5 from being selected when > > > > using clang and an assembler that does not have support for these symbol > > > > deltas, which can be easily checked in Kconfig with as-instr plus the > > > > small test program from the dwz test suite from the binutils issue. > > > > > > > > Link: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/1719 > > > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > > > > > > Thanks for keeping these LLVM_IAS=0 builds alive a little longer. My > > > hope is the GNU binutils can relax their requirement for debug info > > > sections to improve support for DWARF v5. > > > > > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > > > > > > Applied to linux-kbuild. > > Thanks. > > > > [1] says: > > "This looks good to me! Feel free to submit with a: > Tested-by: Conor Dooley <conor.dooley@microchip.com>" Hey Sedat, I actually didn't take a proper look at the v2 at all... I didn't realise that Nathan dropped by T-b for v2 since he'd changed the patch enough to feel that he should. I'm not too worried about the removed T-b (espcially since Linus has just merged Masahiro's PR containing this change). Thanks though! Conor. > > -sed@- > > [1] https://github.com/ClangBuiltLinux/linux/issues/1719#issuecomment-1261158627 > > > > > > > > > --- > > > > > > > > v2: > > > > - Rebase on commit bb1435f3f575 ("Kconfig.debug: add toolchain > > > > checks for DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT") from the kbuild > > > > tree. > > > > - Limit CONFIG_AS_HAS_NON_CONST_LEB128 dependency to GNU as. There > > > > is no point to applying this dependency to the integrated > > > > assembler because it will always pass. > > > > - Apply the CONFIG_AS_HAS_NON_CONST_LEB128 dependency to > > > > CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT as well, due to the > > > > aforementioned kbuild change. > > > > - Move comment block to above CONFIG_AS_HAS_NON_CONST_LEB128, as the > > > > configuration is now used in two places. > > > > - Drop Conor's tested by, as the patch is different enough to > > > > potentially require new testing. > > > > > > > > v1: https://lore.kernel.org/20220928182523.3105953-1-nathan@kernel.org/ > > > > > > > > lib/Kconfig.debug | 9 +++++++-- > > > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > > > index db8d9271cabf..5c1c63575895 100644 > > > > --- a/lib/Kconfig.debug > > > > +++ b/lib/Kconfig.debug > > > > @@ -231,6 +231,11 @@ config DEBUG_INFO > > > > in the "Debug information" choice below, indicating that debug > > > > information will be generated for build targets. > > > > > > > > +# Clang is known to generate .{s,u}leb128 with symbol deltas with DWARF5, which > > > > +# some targets may not support: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 > > > > +config AS_HAS_NON_CONST_LEB128 > > > > + def_bool $(as-instr,.uleb128 .Lexpr_end4 - .Lexpr_start3\n.Lexpr_start3:\n.Lexpr_end4:) > > > > + > > > > choice > > > > prompt "Debug information" > > > > depends on DEBUG_KERNEL > > > > @@ -253,7 +258,7 @@ config DEBUG_INFO_NONE > > > > config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > > > > bool "Rely on the toolchain's implicit default DWARF version" > > > > select DEBUG_INFO > > > > - depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502) > > > > + depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) > > > > help > > > > The implicit default version of DWARF debug info produced by a > > > > toolchain changes over time. > > > > @@ -277,7 +282,7 @@ config DEBUG_INFO_DWARF4 > > > > config DEBUG_INFO_DWARF5 > > > > bool "Generate DWARF Version 5 debuginfo" > > > > select DEBUG_INFO > > > > - depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502) > > > > + depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) > > > > help > > > > Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc > > > > 5.0+ accepts the -gdwarf-5 flag but only had partial support for some > > > > > > > > base-commit: bb1435f3f575b5213eaf27434efa3971f51c01de > > > > -- > > > > 2.38.0 > > > > > > > > > > > > > -- > > > Thanks, > > > ~Nick Desaulniers > > > > > > > > -- > > Best Regards > > Masahiro Yamada
On Sun, Oct 16, 2022 at 8:20 PM Conor Dooley <conor@kernel.org> wrote: > > On Sun, Oct 16, 2022 at 08:10:30PM +0200, Sedat Dilek wrote: > > On Sun, Oct 16, 2022 at 8:04 PM Masahiro Yamada <masahiroy@kernel.org> wrote: > > > > > > On Sat, Oct 15, 2022 at 6:52 AM Nick Desaulniers > > > <ndesaulniers@google.com> wrote: > > > > > > > > On Fri, Oct 14, 2022 at 1:48 PM Nathan Chancellor <nathan@kernel.org> wrote: > > > > > > > > > > When building with a RISC-V kernel with DWARF5 debug info using clang > > > > > and the GNU assembler, several instances of the following error appear: > > > > > > > > > > /tmp/vgettimeofday-48aa35.s:2963: Error: non-constant .uleb128 is not supported > > > > > > > > > > Dumping the .s file reveals these .uleb128 directives come from > > > > > .debug_loc and .debug_ranges: > > > > > > > > > > .Ldebug_loc0: > > > > > .byte 4 # DW_LLE_offset_pair > > > > > .uleb128 .Lfunc_begin0-.Lfunc_begin0 # starting offset > > > > > .uleb128 .Ltmp1-.Lfunc_begin0 # ending offset > > > > > .byte 1 # Loc expr size > > > > > .byte 90 # DW_OP_reg10 > > > > > .byte 0 # DW_LLE_end_of_list > > > > > > > > > > .Ldebug_ranges0: > > > > > .byte 4 # DW_RLE_offset_pair > > > > > .uleb128 .Ltmp6-.Lfunc_begin0 # starting offset > > > > > .uleb128 .Ltmp27-.Lfunc_begin0 # ending offset > > > > > .byte 4 # DW_RLE_offset_pair > > > > > .uleb128 .Ltmp28-.Lfunc_begin0 # starting offset > > > > > .uleb128 .Ltmp30-.Lfunc_begin0 # ending offset > > > > > .byte 0 # DW_RLE_end_of_list > > > > > > > > > > There is an outstanding binutils issue to support a non-constant operand > > > > > to .sleb128 and .uleb128 in GAS for RISC-V but there does not appear to > > > > > be any movement on it, due to concerns over how it would work with > > > > > linker relaxation. > > > > > > > > > > To avoid these build errors, prevent DWARF5 from being selected when > > > > > using clang and an assembler that does not have support for these symbol > > > > > deltas, which can be easily checked in Kconfig with as-instr plus the > > > > > small test program from the dwz test suite from the binutils issue. > > > > > > > > > > Link: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 > > > > > Link: https://github.com/ClangBuiltLinux/linux/issues/1719 > > > > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > > > > > > > > Thanks for keeping these LLVM_IAS=0 builds alive a little longer. My > > > > hope is the GNU binutils can relax their requirement for debug info > > > > sections to improve support for DWARF v5. > > > > > > > > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > > > > > > > > > Applied to linux-kbuild. > > > Thanks. > > > > > > > [1] says: > > > > "This looks good to me! Feel free to submit with a: > > Tested-by: Conor Dooley <conor.dooley@microchip.com>" > > Hey Sedat, > > I actually didn't take a proper look at the v2 at all... I didn't realise > that Nathan dropped by T-b for v2 since he'd changed the patch enough to > feel that he should. > > I'm not too worried about the removed T-b (espcially since Linus has > just merged Masahiro's PR containing this change). > > Thanks though! > Conor. > Yes, just saw the update on https://github.com/torvalds/linux/commits/master first. -Sedat- > > > > -sed@- > > > > [1] https://github.com/ClangBuiltLinux/linux/issues/1719#issuecomment-1261158627 > > > > > > > > > > > > > --- > > > > > > > > > > v2: > > > > > - Rebase on commit bb1435f3f575 ("Kconfig.debug: add toolchain > > > > > checks for DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT") from the kbuild > > > > > tree. > > > > > - Limit CONFIG_AS_HAS_NON_CONST_LEB128 dependency to GNU as. There > > > > > is no point to applying this dependency to the integrated > > > > > assembler because it will always pass. > > > > > - Apply the CONFIG_AS_HAS_NON_CONST_LEB128 dependency to > > > > > CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT as well, due to the > > > > > aforementioned kbuild change. > > > > > - Move comment block to above CONFIG_AS_HAS_NON_CONST_LEB128, as the > > > > > configuration is now used in two places. > > > > > - Drop Conor's tested by, as the patch is different enough to > > > > > potentially require new testing. > > > > > > > > > > v1: https://lore.kernel.org/20220928182523.3105953-1-nathan@kernel.org/ > > > > > > > > > > lib/Kconfig.debug | 9 +++++++-- > > > > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > > > > > > > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > > > > > index db8d9271cabf..5c1c63575895 100644 > > > > > --- a/lib/Kconfig.debug > > > > > +++ b/lib/Kconfig.debug > > > > > @@ -231,6 +231,11 @@ config DEBUG_INFO > > > > > in the "Debug information" choice below, indicating that debug > > > > > information will be generated for build targets. > > > > > > > > > > +# Clang is known to generate .{s,u}leb128 with symbol deltas with DWARF5, which > > > > > +# some targets may not support: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 > > > > > +config AS_HAS_NON_CONST_LEB128 > > > > > + def_bool $(as-instr,.uleb128 .Lexpr_end4 - .Lexpr_start3\n.Lexpr_start3:\n.Lexpr_end4:) > > > > > + > > > > > choice > > > > > prompt "Debug information" > > > > > depends on DEBUG_KERNEL > > > > > @@ -253,7 +258,7 @@ config DEBUG_INFO_NONE > > > > > config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT > > > > > bool "Rely on the toolchain's implicit default DWARF version" > > > > > select DEBUG_INFO > > > > > - depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502) > > > > > + depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) > > > > > help > > > > > The implicit default version of DWARF debug info produced by a > > > > > toolchain changes over time. > > > > > @@ -277,7 +282,7 @@ config DEBUG_INFO_DWARF4 > > > > > config DEBUG_INFO_DWARF5 > > > > > bool "Generate DWARF Version 5 debuginfo" > > > > > select DEBUG_INFO > > > > > - depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502) > > > > > + depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) > > > > > help > > > > > Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc > > > > > 5.0+ accepts the -gdwarf-5 flag but only had partial support for some > > > > > > > > > > base-commit: bb1435f3f575b5213eaf27434efa3971f51c01de > > > > > -- > > > > > 2.38.0 > > > > > > > > > > > > > > > > > -- > > > > Thanks, > > > > ~Nick Desaulniers > > > > > > > > > > > > -- > > > Best Regards > > > Masahiro Yamada
On Fri, 14 Oct 2022 13:42:11 -0700 Nathan Chancellor <nathan@kernel.org> wrote: > When building with a RISC-V kernel with DWARF5 debug info using clang > and the GNU assembler, several instances of the following error appear: > > /tmp/vgettimeofday-48aa35.s:2963: Error: non-constant .uleb128 is not supported hm, which kernels want this? I could merge it for 6.1, which seems suitable. If we want it backported into earlier kernels then a Fixes: would be nice, to prevent it from being ported back further than necessary.
Hi Andrew, On Sun, Oct 16, 2022 at 05:28:15PM -0700, Andrew Morton wrote: > On Fri, 14 Oct 2022 13:42:11 -0700 Nathan Chancellor <nathan@kernel.org> wrote: > > > When building with a RISC-V kernel with DWARF5 debug info using clang > > and the GNU assembler, several instances of the following error appear: > > > > /tmp/vgettimeofday-48aa35.s:2963: Error: non-constant .uleb128 is not supported > > hm, which kernels want this? > > I could merge it for 6.1, which seems suitable. If we want it > backported into earlier kernels then a Fixes: would be nice, to prevent > it from being ported back further than necessary. Masahiro took this for 6.1 via the kbuild tree, it is now in mainline as commit 0a6de78cff60 ("lib/Kconfig.debug: Add check for non-constant .{s,u}leb128 support to DWARF5"). It does need to go to stable but it needs a few prerequisite changes to cover all cases and I did not want to try and describe those dependencies in the patch itself. I should be able to handle the backports manually tomorrow. Cheers, Nathan
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index db8d9271cabf..5c1c63575895 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -231,6 +231,11 @@ config DEBUG_INFO in the "Debug information" choice below, indicating that debug information will be generated for build targets. +# Clang is known to generate .{s,u}leb128 with symbol deltas with DWARF5, which +# some targets may not support: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 +config AS_HAS_NON_CONST_LEB128 + def_bool $(as-instr,.uleb128 .Lexpr_end4 - .Lexpr_start3\n.Lexpr_start3:\n.Lexpr_end4:) + choice prompt "Debug information" depends on DEBUG_KERNEL @@ -253,7 +258,7 @@ config DEBUG_INFO_NONE config DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT bool "Rely on the toolchain's implicit default DWARF version" select DEBUG_INFO - depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502) + depends on !CC_IS_CLANG || AS_IS_LLVM || CLANG_VERSION < 140000 || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) help The implicit default version of DWARF debug info produced by a toolchain changes over time. @@ -277,7 +282,7 @@ config DEBUG_INFO_DWARF4 config DEBUG_INFO_DWARF5 bool "Generate DWARF Version 5 debuginfo" select DEBUG_INFO - depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502) + depends on !CC_IS_CLANG || AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502 && AS_HAS_NON_CONST_LEB128) help Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc 5.0+ accepts the -gdwarf-5 flag but only had partial support for some
When building with a RISC-V kernel with DWARF5 debug info using clang and the GNU assembler, several instances of the following error appear: /tmp/vgettimeofday-48aa35.s:2963: Error: non-constant .uleb128 is not supported Dumping the .s file reveals these .uleb128 directives come from .debug_loc and .debug_ranges: .Ldebug_loc0: .byte 4 # DW_LLE_offset_pair .uleb128 .Lfunc_begin0-.Lfunc_begin0 # starting offset .uleb128 .Ltmp1-.Lfunc_begin0 # ending offset .byte 1 # Loc expr size .byte 90 # DW_OP_reg10 .byte 0 # DW_LLE_end_of_list .Ldebug_ranges0: .byte 4 # DW_RLE_offset_pair .uleb128 .Ltmp6-.Lfunc_begin0 # starting offset .uleb128 .Ltmp27-.Lfunc_begin0 # ending offset .byte 4 # DW_RLE_offset_pair .uleb128 .Ltmp28-.Lfunc_begin0 # starting offset .uleb128 .Ltmp30-.Lfunc_begin0 # ending offset .byte 0 # DW_RLE_end_of_list There is an outstanding binutils issue to support a non-constant operand to .sleb128 and .uleb128 in GAS for RISC-V but there does not appear to be any movement on it, due to concerns over how it would work with linker relaxation. To avoid these build errors, prevent DWARF5 from being selected when using clang and an assembler that does not have support for these symbol deltas, which can be easily checked in Kconfig with as-instr plus the small test program from the dwz test suite from the binutils issue. Link: https://sourceware.org/bugzilla/show_bug.cgi?id=27215 Link: https://github.com/ClangBuiltLinux/linux/issues/1719 Signed-off-by: Nathan Chancellor <nathan@kernel.org> --- v2: - Rebase on commit bb1435f3f575 ("Kconfig.debug: add toolchain checks for DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT") from the kbuild tree. - Limit CONFIG_AS_HAS_NON_CONST_LEB128 dependency to GNU as. There is no point to applying this dependency to the integrated assembler because it will always pass. - Apply the CONFIG_AS_HAS_NON_CONST_LEB128 dependency to CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT as well, due to the aforementioned kbuild change. - Move comment block to above CONFIG_AS_HAS_NON_CONST_LEB128, as the configuration is now used in two places. - Drop Conor's tested by, as the patch is different enough to potentially require new testing. v1: https://lore.kernel.org/20220928182523.3105953-1-nathan@kernel.org/ lib/Kconfig.debug | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) base-commit: bb1435f3f575b5213eaf27434efa3971f51c01de