As a part of my quest to get allyesconfig working on UML, I found a new
build error, with CONFIG_DEBUG_INFO_BTF=y:
scripts/link-vmlinux.sh: line 106: 17463 Segmentation fault LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1}
objcopy: --change-section-vma .BTF=0x0000000000000000 never used
objcopy: --change-section-lma .BTF=0x0000000000000000 never used
objcopy: error: the input file '.btf.vmlinux.bin' is empty
Failed to generate BTF for vmlinux
Try to disable CONFIG_DEBUG_INFO_BTF
make: *** [Makefile:1078: vmlinux] Error 1
The most interesting bit seems to be the:
objcopy: error: the input file '.btf.vmlinux.bin' is empty
Thinking about it, I am not sure if it makes sense for UML to produce
BTF type information, so I proposed a fix here that:
1. Adds the ability for architectures to turn BTF support off.
2. Turns BTF support off for UML.
I am also totally fine with just saying that DEBUG_INFO_BTF
depends on !UML, but I figured people would prefer this approach more.
Brendan Higgins (2):
kbuild: add arch specific dependency for BTF support
arch: um: turn BTF_TYPEINFO support off
arch/um/Kconfig | 1 +
lib/Kconfig.debug | 5 ++++-
2 files changed, 5 insertions(+), 1 deletion(-)
--
2.25.0.341.g760bfbb309-goog
Currently CONFIG_DEBUG_INFO_BTF=y doesn't work on UML:
scripts/link-vmlinux.sh: line 106: 17463 Segmentation fault LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1}
objcopy: --change-section-vma .BTF=0x0000000000000000 never used
objcopy: --change-section-lma .BTF=0x0000000000000000 never used
objcopy: error: the input file '.btf.vmlinux.bin' is empty
Failed to generate BTF for vmlinux
Try to disable CONFIG_DEBUG_INFO_BTF
make: *** [Makefile:1078: vmlinux] Error 1
So turn off ARCH_HAS_BTF_TYPEINFO support off for the UM architecture.
Signed-off-by: Brendan Higgins <[email protected]>
---
arch/um/Kconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 0917f8443c285..53e13d8b210e0 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -6,6 +6,7 @@ config UML
bool
default y
select ARCH_HAS_KCOV
+ select ARCH_NO_BTF_TYPEINFO
select ARCH_NO_PREEMPT
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_SECCOMP_FILTER
--
2.25.0.341.g760bfbb309-goog
Some archs (like UM) do not build with CONFIG_DEBUG_INFO_BTF=y, so add
an options for archs to select to opt-in or out of BTF typeinfo support.
Signed-off-by: Brendan Higgins <[email protected]>
---
lib/Kconfig.debug | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index e4676b992eae9..f5bcb391f1b7d 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -238,9 +238,12 @@ config DEBUG_INFO_DWARF4
But it significantly improves the success of resolving
variables in gdb on optimized code.
+config ARCH_NO_BTF_TYPEINFO
+ bool
+
config DEBUG_INFO_BTF
bool "Generate BTF typeinfo"
- depends on DEBUG_INFO
+ depends on DEBUG_INFO && !ARCH_NO_BTF_TYPEINFO
help
Generate deduplicated BTF type information from DWARF debug info.
Turning this on expects presence of pahole tool, which will convert
--
2.25.0.341.g760bfbb309-goog
Hi.
On Tue, Jan 28, 2020 at 4:36 AM Brendan Higgins
<[email protected]> wrote:
>
> Some archs (like UM) do not build with CONFIG_DEBUG_INFO_BTF=y, so add
> an options for archs to select to opt-in or out of BTF typeinfo support.
Could you use a different subject prefix (e.g. "btf:") ?
This is unrelated to kbuild.
Thanks.
> Signed-off-by: Brendan Higgins <[email protected]>
> ---
> lib/Kconfig.debug | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index e4676b992eae9..f5bcb391f1b7d 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -238,9 +238,12 @@ config DEBUG_INFO_DWARF4
> But it significantly improves the success of resolving
> variables in gdb on optimized code.
>
> +config ARCH_NO_BTF_TYPEINFO
> + bool
> +
> config DEBUG_INFO_BTF
> bool "Generate BTF typeinfo"
> - depends on DEBUG_INFO
> + depends on DEBUG_INFO && !ARCH_NO_BTF_TYPEINFO
> help
> Generate deduplicated BTF type information from DWARF debug info.
> Turning this on expects presence of pahole tool, which will convert
> --
> 2.25.0.341.g760bfbb309-goog
>
--
Best Regards
Masahiro Yamada
On Mon, Jan 27, 2020 at 7:28 PM Masahiro Yamada <[email protected]> wrote:
>
> Hi.
>
> On Tue, Jan 28, 2020 at 4:36 AM Brendan Higgins
> <[email protected]> wrote:
> >
> > Some archs (like UM) do not build with CONFIG_DEBUG_INFO_BTF=y, so add
> > an options for archs to select to opt-in or out of BTF typeinfo support.
>
>
> Could you use a different subject prefix (e.g. "btf:") ?
>
> This is unrelated to kbuild.
Sure. My apologies, I just used the kbuild subject prefix because
that's what the previous commit that touched BTF used. Will fix in
next revision.
Thanks!
> > Signed-off-by: Brendan Higgins <[email protected]>
> > ---
> > lib/Kconfig.debug | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index e4676b992eae9..f5bcb391f1b7d 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -238,9 +238,12 @@ config DEBUG_INFO_DWARF4
> > But it significantly improves the success of resolving
> > variables in gdb on optimized code.
> >
> > +config ARCH_NO_BTF_TYPEINFO
> > + bool
> > +
> > config DEBUG_INFO_BTF
> > bool "Generate BTF typeinfo"
> > - depends on DEBUG_INFO
> > + depends on DEBUG_INFO && !ARCH_NO_BTF_TYPEINFO
> > help
> > Generate deduplicated BTF type information from DWARF debug info.
> > Turning this on expects presence of pahole tool, which will convert
> > --
> > 2.25.0.341.g760bfbb309-goog
> >
>
>
> --
> Best Regards
> Masahiro Yamada
On 27/01/2020 19:35, Brendan Higgins wrote:
> Currently CONFIG_DEBUG_INFO_BTF=y doesn't work on UML:
>
> scripts/link-vmlinux.sh: line 106: 17463 Segmentation fault LLVM_OBJCOPY=${OBJCOPY} ${PAHOLE} -J ${1}
> objcopy: --change-section-vma .BTF=0x0000000000000000 never used
> objcopy: --change-section-lma .BTF=0x0000000000000000 never used
> objcopy: error: the input file '.btf.vmlinux.bin' is empty
> Failed to generate BTF for vmlinux
> Try to disable CONFIG_DEBUG_INFO_BTF
> make: *** [Makefile:1078: vmlinux] Error 1
>
> So turn off ARCH_HAS_BTF_TYPEINFO support off for the UM architecture.
>
> Signed-off-by: Brendan Higgins <[email protected]>
> ---
> arch/um/Kconfig | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/um/Kconfig b/arch/um/Kconfig
> index 0917f8443c285..53e13d8b210e0 100644
> --- a/arch/um/Kconfig
> +++ b/arch/um/Kconfig
> @@ -6,6 +6,7 @@ config UML
> bool
> default y
> select ARCH_HAS_KCOV
> + select ARCH_NO_BTF_TYPEINFO
> select ARCH_NO_PREEMPT
> select HAVE_ARCH_AUDITSYSCALL
> select HAVE_ARCH_SECCOMP_FILTER
>
Acked-by: Anton Ivanov <[email protected]>
--
Anton R. Ivanov
Cambridgegreys Limited. Registered in England. Company Number 10273661
https://www.cambridgegreys.com/