Since 32ef9e5054ec, -Wa,-gdwarf-2 is no longer used in KBUILD_AFLAGS.
Instead, it includes -g, the appropriate -gdwarf-* flag, and also the
-Wa versions of both of those if building with Clang and GNU as. As a
result, debug info was being generated for the purgatory objects, even
though the intention was that it not be.
Fixes: 32ef9e5054ec ("Makefile.debug: re-enable debug info for .S files")
Signed-off-by: Alyssa Ross <[email protected]>
Cc: [email protected]
Acked-by: Nick Desaulniers <[email protected]>
---
v2: https://lore.kernel.org/r/[email protected]
Difference from v2: replaced asflags-remove-y with every possible
debug flag with asflags-y += -g0, as suggested by Nick Desaulniers.
Additionally, I've CCed the x86 maintainers this time, since Masahiro
said he would like acks from subsystem maintainers, and
get_maintainer.pl didn't pick them the first time around.
arch/riscv/purgatory/Makefile | 7 +------
arch/x86/purgatory/Makefile | 3 +--
2 files changed, 2 insertions(+), 8 deletions(-)
diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile
index d16bf715a586..9c1e71853ee7 100644
--- a/arch/riscv/purgatory/Makefile
+++ b/arch/riscv/purgatory/Makefile
@@ -84,12 +84,7 @@ CFLAGS_string.o += $(PURGATORY_CFLAGS)
CFLAGS_REMOVE_ctype.o += $(PURGATORY_CFLAGS_REMOVE)
CFLAGS_ctype.o += $(PURGATORY_CFLAGS)
-AFLAGS_REMOVE_entry.o += -Wa,-gdwarf-2
-AFLAGS_REMOVE_memcpy.o += -Wa,-gdwarf-2
-AFLAGS_REMOVE_memset.o += -Wa,-gdwarf-2
-AFLAGS_REMOVE_strcmp.o += -Wa,-gdwarf-2
-AFLAGS_REMOVE_strlen.o += -Wa,-gdwarf-2
-AFLAGS_REMOVE_strncmp.o += -Wa,-gdwarf-2
+asflags-y += -g0
$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
$(call if_changed,ld)
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index 17f09dc26381..8e6c81b1c8f7 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -69,8 +69,7 @@ CFLAGS_sha256.o += $(PURGATORY_CFLAGS)
CFLAGS_REMOVE_string.o += $(PURGATORY_CFLAGS_REMOVE)
CFLAGS_string.o += $(PURGATORY_CFLAGS)
-AFLAGS_REMOVE_setup-x86_$(BITS).o += -Wa,-gdwarf-2
-AFLAGS_REMOVE_entry64.o += -Wa,-gdwarf-2
+asflags-y += -g0
$(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
$(call if_changed,ld)
--
2.37.1
On Thu, Mar 30, 2023 at 06:22:24PM +0000, Alyssa Ross wrote:
> Since 32ef9e5054ec, -Wa,-gdwarf-2 is no longer used in KBUILD_AFLAGS.
> Instead, it includes -g, the appropriate -gdwarf-* flag, and also the
> -Wa versions of both of those if building with Clang and GNU as. As a
> result, debug info was being generated for the purgatory objects, even
> though the intention was that it not be.
>
> Fixes: 32ef9e5054ec ("Makefile.debug: re-enable debug info for .S files")
> Signed-off-by: Alyssa Ross <[email protected]>
> Cc: [email protected]
> Acked-by: Nick Desaulniers <[email protected]>
This is definitely more future proof.
Reviewed-by: Nathan Chancellor <[email protected]>
Tested-by: Nathan Chancellor <[email protected]>
> ---
> v2: https://lore.kernel.org/r/[email protected]
>
> Difference from v2: replaced asflags-remove-y with every possible
> debug flag with asflags-y += -g0, as suggested by Nick Desaulniers.
>
> Additionally, I've CCed the x86 maintainers this time, since Masahiro
> said he would like acks from subsystem maintainers, and
> get_maintainer.pl didn't pick them the first time around.
>
> arch/riscv/purgatory/Makefile | 7 +------
> arch/x86/purgatory/Makefile | 3 +--
> 2 files changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/arch/riscv/purgatory/Makefile b/arch/riscv/purgatory/Makefile
> index d16bf715a586..9c1e71853ee7 100644
> --- a/arch/riscv/purgatory/Makefile
> +++ b/arch/riscv/purgatory/Makefile
> @@ -84,12 +84,7 @@ CFLAGS_string.o += $(PURGATORY_CFLAGS)
> CFLAGS_REMOVE_ctype.o += $(PURGATORY_CFLAGS_REMOVE)
> CFLAGS_ctype.o += $(PURGATORY_CFLAGS)
>
> -AFLAGS_REMOVE_entry.o += -Wa,-gdwarf-2
> -AFLAGS_REMOVE_memcpy.o += -Wa,-gdwarf-2
> -AFLAGS_REMOVE_memset.o += -Wa,-gdwarf-2
> -AFLAGS_REMOVE_strcmp.o += -Wa,-gdwarf-2
> -AFLAGS_REMOVE_strlen.o += -Wa,-gdwarf-2
> -AFLAGS_REMOVE_strncmp.o += -Wa,-gdwarf-2
> +asflags-y += -g0
>
> $(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
> $(call if_changed,ld)
> diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
> index 17f09dc26381..8e6c81b1c8f7 100644
> --- a/arch/x86/purgatory/Makefile
> +++ b/arch/x86/purgatory/Makefile
> @@ -69,8 +69,7 @@ CFLAGS_sha256.o += $(PURGATORY_CFLAGS)
> CFLAGS_REMOVE_string.o += $(PURGATORY_CFLAGS_REMOVE)
> CFLAGS_string.o += $(PURGATORY_CFLAGS)
>
> -AFLAGS_REMOVE_setup-x86_$(BITS).o += -Wa,-gdwarf-2
> -AFLAGS_REMOVE_entry64.o += -Wa,-gdwarf-2
> +asflags-y += -g0
>
> $(obj)/purgatory.ro: $(PURGATORY_OBJS) FORCE
> $(call if_changed,ld)
> --
> 2.37.1
>
>
On Fri, Mar 31, 2023 at 7:29 AM Nathan Chancellor <[email protected]> wrote:
>
> On Thu, Mar 30, 2023 at 06:22:24PM +0000, Alyssa Ross wrote:
> > Since 32ef9e5054ec, -Wa,-gdwarf-2 is no longer used in KBUILD_AFLAGS.
> > Instead, it includes -g, the appropriate -gdwarf-* flag, and also the
> > -Wa versions of both of those if building with Clang and GNU as. As a
> > result, debug info was being generated for the purgatory objects, even
> > though the intention was that it not be.
> >
> > Fixes: 32ef9e5054ec ("Makefile.debug: re-enable debug info for .S files")
> > Signed-off-by: Alyssa Ross <[email protected]>
> > Cc: [email protected]
> > Acked-by: Nick Desaulniers <[email protected]>
>
> This is definitely more future proof.
>
> Reviewed-by: Nathan Chancellor <[email protected]>
> Tested-by: Nathan Chancellor <[email protected]>
I prefer v3 since it is cleaner, but unfortunately
it does not work for Clang+GAS.
With v3 applied, I still see the debug info.
$ make LLVM=1 LLVM_IAS=0 arch/x86/purgatory/setup-x86_64.o
UPD include/config/kernel.release
UPD include/generated/utsrelease.h
CALL scripts/checksyscalls.sh
DESCEND objtool
INSTALL libsubcmd_headers
AS arch/x86/purgatory/setup-x86_64.o
$ readelf -S arch/x86/purgatory/setup-x86_64.o
There are 18 section headers, starting at offset 0x14d8:
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .text PROGBITS 0000000000000000 00000040
0000000000000027 0000000000000000 AX 0 0 16
[ 2] .rela.text RELA 0000000000000000 000012f8
0000000000000060 0000000000000018 I 15 1 8
[ 3] .data PROGBITS 0000000000000000 00000067
0000000000000000 0000000000000000 WA 0 0 1
[ 4] .bss NOBITS 0000000000000000 00001000
0000000000001000 0000000000000000 WA 0 0 4096
[ 5] .rodata PROGBITS 0000000000000000 00001000
0000000000000020 0000000000000000 A 0 0 16
[ 6] .rela.rodata RELA 0000000000000000 00001358
0000000000000018 0000000000000018 I 15 5 8
[ 7] .debug_line PROGBITS 0000000000000000 00001020
000000000000005f 0000000000000000 0 0 1
[ 8] .rela.debug_line RELA 0000000000000000 00001370
0000000000000018 0000000000000018 I 15 7 8
[ 9] .debug_info PROGBITS 0000000000000000 0000107f
0000000000000027 0000000000000000 0 0 1
[10] .rela.debug_info RELA 0000000000000000 00001388
0000000000000090 0000000000000018 I 15 9 8
[11] .debug_abbrev PROGBITS 0000000000000000 000010a6
0000000000000014 0000000000000000 0 0 1
[12] .debug_aranges PROGBITS 0000000000000000 000010c0
0000000000000030 0000000000000000 0 0 16
[13] .rela.debug_[...] RELA 0000000000000000 00001418
0000000000000030 0000000000000018 I 15 12 8
[14] .debug_str PROGBITS 0000000000000000 000010f0
0000000000000054 0000000000000001 MS 0 0 1
[15] .symtab SYMTAB 0000000000000000 00001148
0000000000000168 0000000000000018 16 12 8
[16] .strtab STRTAB 0000000000000000 000012b0
0000000000000041 0000000000000000 0 0 1
[17] .shstrtab STRTAB 0000000000000000 00001448
000000000000008d 0000000000000000 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
L (link order), O (extra OS processing required), G (group), T (TLS),
C (compressed), x (unknown), o (OS specific), E (exclude),
D (mbind), l (large), p (processor specific)
With -g0 given, GCC stops passing -g -gdwarf-4 down to GAS.
Clang does not do anything about -g0 for the external assembler.
I was thinking of dropping LLVM_IAS=0 support.
When we decide to give up -fno-integrated-as,
we can clean up the code in various places.
Anyway, v3 does not work in the current situation.
V2 works for all usecases.
--
Best Regards
Masahiro Yamada
On Sat, Apr 01, 2023 at 12:42:13AM +0900, Masahiro Yamada wrote:
> On Fri, Mar 31, 2023 at 7:29 AM Nathan Chancellor <[email protected]> wrote:
> >
> > On Thu, Mar 30, 2023 at 06:22:24PM +0000, Alyssa Ross wrote:
> > > Since 32ef9e5054ec, -Wa,-gdwarf-2 is no longer used in KBUILD_AFLAGS.
> > > Instead, it includes -g, the appropriate -gdwarf-* flag, and also the
> > > -Wa versions of both of those if building with Clang and GNU as. As a
> > > result, debug info was being generated for the purgatory objects, even
> > > though the intention was that it not be.
> > >
> > > Fixes: 32ef9e5054ec ("Makefile.debug: re-enable debug info for .S files")
> > > Signed-off-by: Alyssa Ross <[email protected]>
> > > Cc: [email protected]
> > > Acked-by: Nick Desaulniers <[email protected]>
> >
> > This is definitely more future proof.
> >
> > Reviewed-by: Nathan Chancellor <[email protected]>
> > Tested-by: Nathan Chancellor <[email protected]>
>
>
>
> I prefer v3 since it is cleaner, but unfortunately
> it does not work for Clang+GAS.
>
>
> With v3 applied, I still see the debug info.
>
>
>
> $ make LLVM=1 LLVM_IAS=0 arch/x86/purgatory/setup-x86_64.o
> UPD include/config/kernel.release
> UPD include/generated/utsrelease.h
> CALL scripts/checksyscalls.sh
> DESCEND objtool
> INSTALL libsubcmd_headers
> AS arch/x86/purgatory/setup-x86_64.o
> $ readelf -S arch/x86/purgatory/setup-x86_64.o
> There are 18 section headers, starting at offset 0x14d8:
>
> Section Headers:
> [Nr] Name Type Address Offset
> Size EntSize Flags Link Info Align
> [ 0] NULL 0000000000000000 00000000
> 0000000000000000 0000000000000000 0 0 0
> [ 1] .text PROGBITS 0000000000000000 00000040
> 0000000000000027 0000000000000000 AX 0 0 16
> [ 2] .rela.text RELA 0000000000000000 000012f8
> 0000000000000060 0000000000000018 I 15 1 8
> [ 3] .data PROGBITS 0000000000000000 00000067
> 0000000000000000 0000000000000000 WA 0 0 1
> [ 4] .bss NOBITS 0000000000000000 00001000
> 0000000000001000 0000000000000000 WA 0 0 4096
> [ 5] .rodata PROGBITS 0000000000000000 00001000
> 0000000000000020 0000000000000000 A 0 0 16
> [ 6] .rela.rodata RELA 0000000000000000 00001358
> 0000000000000018 0000000000000018 I 15 5 8
> [ 7] .debug_line PROGBITS 0000000000000000 00001020
> 000000000000005f 0000000000000000 0 0 1
> [ 8] .rela.debug_line RELA 0000000000000000 00001370
> 0000000000000018 0000000000000018 I 15 7 8
> [ 9] .debug_info PROGBITS 0000000000000000 0000107f
> 0000000000000027 0000000000000000 0 0 1
> [10] .rela.debug_info RELA 0000000000000000 00001388
> 0000000000000090 0000000000000018 I 15 9 8
> [11] .debug_abbrev PROGBITS 0000000000000000 000010a6
> 0000000000000014 0000000000000000 0 0 1
> [12] .debug_aranges PROGBITS 0000000000000000 000010c0
> 0000000000000030 0000000000000000 0 0 16
> [13] .rela.debug_[...] RELA 0000000000000000 00001418
> 0000000000000030 0000000000000018 I 15 12 8
> [14] .debug_str PROGBITS 0000000000000000 000010f0
> 0000000000000054 0000000000000001 MS 0 0 1
> [15] .symtab SYMTAB 0000000000000000 00001148
> 0000000000000168 0000000000000018 16 12 8
> [16] .strtab STRTAB 0000000000000000 000012b0
> 0000000000000041 0000000000000000 0 0 1
> [17] .shstrtab STRTAB 0000000000000000 00001448
> 000000000000008d 0000000000000000 0 0 1
> Key to Flags:
> W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
> L (link order), O (extra OS processing required), G (group), T (TLS),
> C (compressed), x (unknown), o (OS specific), E (exclude),
> D (mbind), l (large), p (processor specific)
>
>
>
>
>
>
> With -g0 given, GCC stops passing -g -gdwarf-4 down to GAS.
>
>
> Clang does not do anything about -g0 for the external assembler.
You're right. Thank you for your thoughtful testing — I forgot to check
LLVM for v3. I thought maybe adding -Wa,-g0 would be enough, but it
turns out that GAS doesn't support that. If -g has been specified,
there doesn't seem to be any way to disable debug info again later in
the command line.
So we probably can't do better than v2 while LLVM_IAS=0 is supported.
The only other option I see is (untested):
asflags-y += -g0
asflags-remove-y += -Wa,-g -Wa,-gdwarf-4 -Wa,-gdwarf-5
But I don't like that option, because it means there are two completely
different ways of doing it depending on the compiler setup, and it makes
it even less likely anybody would remember to update asflags-remove-y
when DWARF 6 comes around or whatever.
> I was thinking of dropping LLVM_IAS=0 support.
> When we decide to give up -fno-integrated-as,
> we can clean up the code in various places.
>
>
> Anyway, v3 does not work in the current situation.
>
>
> V2 works for all usecases.
>
>
>
>
> --
> Best Regards
> Masahiro Yamada
On Sat, Apr 1, 2023 at 5:27 AM Alyssa Ross <[email protected]> wrote:
>
> On Sat, Apr 01, 2023 at 12:42:13AM +0900, Masahiro Yamada wrote:
> > On Fri, Mar 31, 2023 at 7:29 AM Nathan Chancellor <[email protected]> wrote:
> > >
> > > On Thu, Mar 30, 2023 at 06:22:24PM +0000, Alyssa Ross wrote:
> > > > Since 32ef9e5054ec, -Wa,-gdwarf-2 is no longer used in KBUILD_AFLAGS.
> > > > Instead, it includes -g, the appropriate -gdwarf-* flag, and also the
> > > > -Wa versions of both of those if building with Clang and GNU as. As a
> > > > result, debug info was being generated for the purgatory objects, even
> > > > though the intention was that it not be.
> > > >
> > > > Fixes: 32ef9e5054ec ("Makefile.debug: re-enable debug info for .S files")
> > > > Signed-off-by: Alyssa Ross <[email protected]>
> > > > Cc: [email protected]
> > > > Acked-by: Nick Desaulniers <[email protected]>
> > >
> > > This is definitely more future proof.
> > >
> > > Reviewed-by: Nathan Chancellor <[email protected]>
> > > Tested-by: Nathan Chancellor <[email protected]>
> >
> >
> >
> > I prefer v3 since it is cleaner, but unfortunately
> > it does not work for Clang+GAS.
> >
> >
> > With v3 applied, I still see the debug info.
> >
> >
> >
> > $ make LLVM=1 LLVM_IAS=0 arch/x86/purgatory/setup-x86_64.o
> > UPD include/config/kernel.release
> > UPD include/generated/utsrelease.h
> > CALL scripts/checksyscalls.sh
> > DESCEND objtool
> > INSTALL libsubcmd_headers
> > AS arch/x86/purgatory/setup-x86_64.o
> > $ readelf -S arch/x86/purgatory/setup-x86_64.o
> > There are 18 section headers, starting at offset 0x14d8:
> >
> > Section Headers:
> > [Nr] Name Type Address Offset
> > Size EntSize Flags Link Info Align
> > [ 0] NULL 0000000000000000 00000000
> > 0000000000000000 0000000000000000 0 0 0
> > [ 1] .text PROGBITS 0000000000000000 00000040
> > 0000000000000027 0000000000000000 AX 0 0 16
> > [ 2] .rela.text RELA 0000000000000000 000012f8
> > 0000000000000060 0000000000000018 I 15 1 8
> > [ 3] .data PROGBITS 0000000000000000 00000067
> > 0000000000000000 0000000000000000 WA 0 0 1
> > [ 4] .bss NOBITS 0000000000000000 00001000
> > 0000000000001000 0000000000000000 WA 0 0 4096
> > [ 5] .rodata PROGBITS 0000000000000000 00001000
> > 0000000000000020 0000000000000000 A 0 0 16
> > [ 6] .rela.rodata RELA 0000000000000000 00001358
> > 0000000000000018 0000000000000018 I 15 5 8
> > [ 7] .debug_line PROGBITS 0000000000000000 00001020
> > 000000000000005f 0000000000000000 0 0 1
> > [ 8] .rela.debug_line RELA 0000000000000000 00001370
> > 0000000000000018 0000000000000018 I 15 7 8
> > [ 9] .debug_info PROGBITS 0000000000000000 0000107f
> > 0000000000000027 0000000000000000 0 0 1
> > [10] .rela.debug_info RELA 0000000000000000 00001388
> > 0000000000000090 0000000000000018 I 15 9 8
> > [11] .debug_abbrev PROGBITS 0000000000000000 000010a6
> > 0000000000000014 0000000000000000 0 0 1
> > [12] .debug_aranges PROGBITS 0000000000000000 000010c0
> > 0000000000000030 0000000000000000 0 0 16
> > [13] .rela.debug_[...] RELA 0000000000000000 00001418
> > 0000000000000030 0000000000000018 I 15 12 8
> > [14] .debug_str PROGBITS 0000000000000000 000010f0
> > 0000000000000054 0000000000000001 MS 0 0 1
> > [15] .symtab SYMTAB 0000000000000000 00001148
> > 0000000000000168 0000000000000018 16 12 8
> > [16] .strtab STRTAB 0000000000000000 000012b0
> > 0000000000000041 0000000000000000 0 0 1
> > [17] .shstrtab STRTAB 0000000000000000 00001448
> > 000000000000008d 0000000000000000 0 0 1
> > Key to Flags:
> > W (write), A (alloc), X (execute), M (merge), S (strings), I (info),
> > L (link order), O (extra OS processing required), G (group), T (TLS),
> > C (compressed), x (unknown), o (OS specific), E (exclude),
> > D (mbind), l (large), p (processor specific)
> >
> >
> >
> >
> >
> >
> > With -g0 given, GCC stops passing -g -gdwarf-4 down to GAS.
> >
> >
> > Clang does not do anything about -g0 for the external assembler.
>
> You're right. Thank you for your thoughtful testing — I forgot to check
> LLVM for v3. I thought maybe adding -Wa,-g0 would be enough, but it
> turns out that GAS doesn't support that. If -g has been specified,
> there doesn't seem to be any way to disable debug info again later in
> the command line.
>
> So we probably can't do better than v2 while LLVM_IAS=0 is supported.
> The only other option I see is (untested):
>
> asflags-y += -g0
> asflags-remove-y += -Wa,-g -Wa,-gdwarf-4 -Wa,-gdwarf-5
>
> But I don't like that option, because it means there are two completely
> different ways of doing it depending on the compiler setup, and it makes
> it even less likely anybody would remember to update asflags-remove-y
> when DWARF 6 comes around or whatever.
Agree.
This is uglier than v2.
If nobody comes up with a better idea,
I will pick up v2.
--
Best Regards
Masahiro Yamada