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[PATCH v2 4/4] perf build: Filter out BTF sources without a .BTF section

Ian Rogers posted 4 patches 2 years, 8 months ago
There is a newer version of this series
[PATCH v2 4/4] perf build: Filter out BTF sources without a .BTF section
Posted by Ian Rogers 2 years, 8 months ago 
If generating vmlinux.h, make the code to generate it more tolerant by
filtering out paths to kernels that lack a .BTF section.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/Makefile.perf | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index f1840af195c0..c3bb27a912b0 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -193,6 +193,7 @@ FLEX    ?= flex
 BISON   ?= bison
 STRIP   = strip
 AWK     = awk
+READELF ?= readelf
 
 # include Makefile.config by default and rule out
 # non-config cases
@@ -1080,12 +1081,28 @@ $(BPFTOOL): | $(SKEL_TMP_OUT)
 	$(Q)CFLAGS= $(MAKE) -C ../bpf/bpftool \
 		OUTPUT=$(SKEL_TMP_OUT)/ bootstrap
 
-VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux)				\
+# Paths to search for a kernel to generate vmlinux.h from.
+VMLINUX_BTF_ELF_PATHS ?= $(if $(O),$(O)/vmlinux)			\
 		     $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)	\
 		     ../../vmlinux					\
-		     /sys/kernel/btf/vmlinux				\
 		     /boot/vmlinux-$(shell uname -r)
-VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
+
+# Paths to BTF information.
+VMLINUX_BTF_BTF_PATHS ?= /sys/kernel/btf/vmlinux
+
+# Filter out kernels that don't exist or without a BTF section.
+VMLINUX_BTF_ELF_ABSPATHS ?= $(abspath $(wildcard $(VMLINUX_BTF_ELF_PATHS)))
+VMLINUX_BTF_PATHS ?= $(shell for file in $(VMLINUX_BTF_ELF_ABSPATHS); \
+			do \
+				if [ -f $$file ] && ($(READELF) -t "$$file" | grep .BTF); \
+				then \
+					echo "$$file"; \
+				fi; \
+			done) \
+			$(wildcard $(VMLINUX_BTF_BTF_PATHS))
+
+# Select the first as the source of vmlinux.h.
+VMLINUX_BTF ?= $(firstword $(VMLINUX_BTF_PATHS))
 
 $(SKEL_OUT)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
 ifeq ($(VMLINUX_H),)
-- 
2.41.0.rc0.172.g3f132b7071-goog
Re: [PATCH v2 4/4] perf build: Filter out BTF sources without a .BTF section
Posted by Namhyung Kim 2 years, 8 months ago 
Hi Ian,

On Mon, Jun 5, 2023 at 1:28 PM Ian Rogers <irogers@google.com> wrote:
>
> If generating vmlinux.h, make the code to generate it more tolerant by
> filtering out paths to kernels that lack a .BTF section.
>
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/Makefile.perf | 23 ++++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index f1840af195c0..c3bb27a912b0 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -193,6 +193,7 @@ FLEX    ?= flex
>  BISON   ?= bison
>  STRIP   = strip
>  AWK     = awk
> +READELF ?= readelf
>
>  # include Makefile.config by default and rule out
>  # non-config cases
> @@ -1080,12 +1081,28 @@ $(BPFTOOL): | $(SKEL_TMP_OUT)
>         $(Q)CFLAGS= $(MAKE) -C ../bpf/bpftool \
>                 OUTPUT=$(SKEL_TMP_OUT)/ bootstrap
>
> -VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux)                           \
> +# Paths to search for a kernel to generate vmlinux.h from.
> +VMLINUX_BTF_ELF_PATHS ?= $(if $(O),$(O)/vmlinux)                       \
>                      $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)    \
>                      ../../vmlinux                                      \
> -                    /sys/kernel/btf/vmlinux                            \
>                      /boot/vmlinux-$(shell uname -r)
> -VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
> +
> +# Paths to BTF information.
> +VMLINUX_BTF_BTF_PATHS ?= /sys/kernel/btf/vmlinux
> +
> +# Filter out kernels that don't exist or without a BTF section.
> +VMLINUX_BTF_ELF_ABSPATHS ?= $(abspath $(wildcard $(VMLINUX_BTF_ELF_PATHS)))
> +VMLINUX_BTF_PATHS ?= $(shell for file in $(VMLINUX_BTF_ELF_ABSPATHS); \
> +                       do \
> +                               if [ -f $$file ] && ($(READELF) -t "$$file" | grep .BTF); \

Wouldn't it be `readelf -S` instead?  Also I think grep needs -q to
suppress output.


> +                               then \
> +                                       echo "$$file"; \
> +                               fi; \
> +                       done) \
> +                       $(wildcard $(VMLINUX_BTF_BTF_PATHS))

This changes the order of processing the sysfs file.
But I'm not sure it matters much as both /boot/vmlinux and sysfs
should refer to the running kernel.

Thanks,
Namhyung


> +
> +# Select the first as the source of vmlinux.h.
> +VMLINUX_BTF ?= $(firstword $(VMLINUX_BTF_PATHS))
>
>  $(SKEL_OUT)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
>  ifeq ($(VMLINUX_H),)
> --
> 2.41.0.rc0.172.g3f132b7071-goog
>
Re: [PATCH v2 4/4] perf build: Filter out BTF sources without a .BTF section
Posted by Ian Rogers 2 years, 8 months ago 
On Mon, Jun 5, 2023 at 4:35 PM Namhyung Kim <namhyung@kernel.org> wrote:
>
> Hi Ian,
>
> On Mon, Jun 5, 2023 at 1:28 PM Ian Rogers <irogers@google.com> wrote:
> >
> > If generating vmlinux.h, make the code to generate it more tolerant by
> > filtering out paths to kernels that lack a .BTF section.
> >
> > Signed-off-by: Ian Rogers <irogers@google.com>
> > ---
> >  tools/perf/Makefile.perf | 23 ++++++++++++++++++++---
> >  1 file changed, 20 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> > index f1840af195c0..c3bb27a912b0 100644
> > --- a/tools/perf/Makefile.perf
> > +++ b/tools/perf/Makefile.perf
> > @@ -193,6 +193,7 @@ FLEX    ?= flex
> >  BISON   ?= bison
> >  STRIP   = strip
> >  AWK     = awk
> > +READELF ?= readelf
> >
> >  # include Makefile.config by default and rule out
> >  # non-config cases
> > @@ -1080,12 +1081,28 @@ $(BPFTOOL): | $(SKEL_TMP_OUT)
> >         $(Q)CFLAGS= $(MAKE) -C ../bpf/bpftool \
> >                 OUTPUT=$(SKEL_TMP_OUT)/ bootstrap
> >
> > -VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux)                           \
> > +# Paths to search for a kernel to generate vmlinux.h from.
> > +VMLINUX_BTF_ELF_PATHS ?= $(if $(O),$(O)/vmlinux)                       \
> >                      $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)    \
> >                      ../../vmlinux                                      \
> > -                    /sys/kernel/btf/vmlinux                            \
> >                      /boot/vmlinux-$(shell uname -r)
> > -VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
> > +
> > +# Paths to BTF information.
> > +VMLINUX_BTF_BTF_PATHS ?= /sys/kernel/btf/vmlinux
> > +
> > +# Filter out kernels that don't exist or without a BTF section.
> > +VMLINUX_BTF_ELF_ABSPATHS ?= $(abspath $(wildcard $(VMLINUX_BTF_ELF_PATHS)))
> > +VMLINUX_BTF_PATHS ?= $(shell for file in $(VMLINUX_BTF_ELF_ABSPATHS); \
> > +                       do \
> > +                               if [ -f $$file ] && ($(READELF) -t "$$file" | grep .BTF); \
>
> Wouldn't it be `readelf -S` instead?  Also I think grep needs -q to
> suppress output.

Makes sense, I can change it in v3.

> > +                               then \
> > +                                       echo "$$file"; \
> > +                               fi; \
> > +                       done) \
> > +                       $(wildcard $(VMLINUX_BTF_BTF_PATHS))
>
> This changes the order of processing the sysfs file.
> But I'm not sure it matters much as both /boot/vmlinux and sysfs
> should refer to the running kernel.

Agreed. readelf fails for /sys/kernel/btf/vmlinux as it isn't an elf
file and I'm not sure it is worth worrying too much about the order
here.

Thanks,
Ian

> Thanks,
> Namhyung
>
>
> > +
> > +# Select the first as the source of vmlinux.h.
> > +VMLINUX_BTF ?= $(firstword $(VMLINUX_BTF_PATHS))
> >
> >  $(SKEL_OUT)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
> >  ifeq ($(VMLINUX_H),)
> > --
> > 2.41.0.rc0.172.g3f132b7071-goog
> >

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