diff mbox series

[RFC,bpf-next,3/3] selftests/bpf: Mark uprobe trigger functions with nocf_check attribute

Message ID 20240318093139.293497-4-jolsa@kernel.org (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series uprobe: uretprobe speed up | expand

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Commit Message

Jiri Olsa March 18, 2024, 9:31 a.m. UTC 
Some distros seem to enable the -fcf-protection=branch by default,
which breaks our setup on first instruction of uprobe trigger
functions and place there endbr64 instruction.

Marking them with nocf_check attribute to skip that.

Adding -Wno-attributes for bench objects, becase nocf_check can
be used only when -fcf-protection=branch is enabled, otherwise
we get a warning and break compilation.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
 tools/include/linux/compiler.h                     | 4 ++++
 tools/testing/selftests/bpf/Makefile               | 2 +-
 tools/testing/selftests/bpf/benchs/bench_trigger.c | 6 +++---
 3 files changed, 8 insertions(+), 4 deletions(-)

Comments

Andrii Nakryiko March 19, 2024, 1:22 a.m. UTC | #1 
On Mon, Mar 18, 2024 at 2:32 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> Some distros seem to enable the -fcf-protection=branch by default,
> which breaks our setup on first instruction of uprobe trigger
> functions and place there endbr64 instruction.
>
> Marking them with nocf_check attribute to skip that.
>
> Adding -Wno-attributes for bench objects, becase nocf_check can
> be used only when -fcf-protection=branch is enabled, otherwise
> we get a warning and break compilation.
>
> Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> ---
>  tools/include/linux/compiler.h                     | 4 ++++
>  tools/testing/selftests/bpf/Makefile               | 2 +-
>  tools/testing/selftests/bpf/benchs/bench_trigger.c | 6 +++---
>  3 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
> index 7b65566f3e42..14038ce04ca4 100644
> --- a/tools/include/linux/compiler.h
> +++ b/tools/include/linux/compiler.h
> @@ -58,6 +58,10 @@
>  #define noinline
>  #endif
>
> +#ifndef __nocfcheck
> +#define __nocfcheck __attribute__((nocf_check))
> +#endif

Let's preserve spelling of the attribut, __nocf_check ?

BTW, just FYI, seems like kernel is defining it as:

#define __noendbr    __attribute__((nocf_check))

Thought somewhere deep in x86-specific code, so probably not a good
idea to use it here?

> +
>  /* Are two types/vars the same type (ignoring qualifiers)? */
>  #ifndef __same_type
>  # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index e425a946276b..506d3d592093 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -726,7 +726,7 @@ $(OUTPUT)/test_cpp: test_cpp.cpp $(OUTPUT)/test_core_extern.skel.h $(BPFOBJ)
>  # Benchmark runner
>  $(OUTPUT)/bench_%.o: benchs/bench_%.c bench.h $(BPFOBJ)
>         $(call msg,CC,,$@)
> -       $(Q)$(CC) $(CFLAGS) -O2 -c $(filter %.c,$^) $(LDLIBS) -o $@
> +       $(Q)$(CC) $(CFLAGS) -O2 -Wno-attributes -c $(filter %.c,$^) $(LDLIBS) -o $@

let's better use `#pragma warning disable` in relevant .c files,
instead of this global flag?

>  $(OUTPUT)/bench_rename.o: $(OUTPUT)/test_overhead.skel.h
>  $(OUTPUT)/bench_trigger.o: $(OUTPUT)/trigger_bench.skel.h
>  $(OUTPUT)/bench_ringbufs.o: $(OUTPUT)/ringbuf_bench.skel.h \

[...]
Jiri Olsa March 19, 2024, 11:11 a.m. UTC | #2 
On Mon, Mar 18, 2024 at 06:22:02PM -0700, Andrii Nakryiko wrote:
> On Mon, Mar 18, 2024 at 2:32 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > Some distros seem to enable the -fcf-protection=branch by default,
> > which breaks our setup on first instruction of uprobe trigger
> > functions and place there endbr64 instruction.
> >
> > Marking them with nocf_check attribute to skip that.
> >
> > Adding -Wno-attributes for bench objects, becase nocf_check can
> > be used only when -fcf-protection=branch is enabled, otherwise
> > we get a warning and break compilation.
> >
> > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > ---
> >  tools/include/linux/compiler.h                     | 4 ++++
> >  tools/testing/selftests/bpf/Makefile               | 2 +-
> >  tools/testing/selftests/bpf/benchs/bench_trigger.c | 6 +++---
> >  3 files changed, 8 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
> > index 7b65566f3e42..14038ce04ca4 100644
> > --- a/tools/include/linux/compiler.h
> > +++ b/tools/include/linux/compiler.h
> > @@ -58,6 +58,10 @@
> >  #define noinline
> >  #endif
> >
> > +#ifndef __nocfcheck
> > +#define __nocfcheck __attribute__((nocf_check))
> > +#endif
> 
> Let's preserve spelling of the attribut, __nocf_check ?
> 
> BTW, just FYI, seems like kernel is defining it as:
> 
> #define __noendbr    __attribute__((nocf_check))
> 
> Thought somewhere deep in x86-specific code, so probably not a good
> idea to use it here?

ugh, I missed it.. better to use __noendbr

> 
> > +
> >  /* Are two types/vars the same type (ignoring qualifiers)? */
> >  #ifndef __same_type
> >  # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
> > diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> > index e425a946276b..506d3d592093 100644
> > --- a/tools/testing/selftests/bpf/Makefile
> > +++ b/tools/testing/selftests/bpf/Makefile
> > @@ -726,7 +726,7 @@ $(OUTPUT)/test_cpp: test_cpp.cpp $(OUTPUT)/test_core_extern.skel.h $(BPFOBJ)
> >  # Benchmark runner
> >  $(OUTPUT)/bench_%.o: benchs/bench_%.c bench.h $(BPFOBJ)
> >         $(call msg,CC,,$@)
> > -       $(Q)$(CC) $(CFLAGS) -O2 -c $(filter %.c,$^) $(LDLIBS) -o $@
> > +       $(Q)$(CC) $(CFLAGS) -O2 -Wno-attributes -c $(filter %.c,$^) $(LDLIBS) -o $@
> 
> let's better use `#pragma warning disable` in relevant .c files,
> instead of this global flag?

ok, will try that

thanks,
jirka
Jiri Olsa March 22, 2024, 1:40 p.m. UTC | #3 
On Tue, Mar 19, 2024 at 12:11:06PM +0100, Jiri Olsa wrote:
> On Mon, Mar 18, 2024 at 06:22:02PM -0700, Andrii Nakryiko wrote:
> > On Mon, Mar 18, 2024 at 2:32 AM Jiri Olsa <jolsa@kernel.org> wrote:
> > >
> > > Some distros seem to enable the -fcf-protection=branch by default,
> > > which breaks our setup on first instruction of uprobe trigger
> > > functions and place there endbr64 instruction.
> > >
> > > Marking them with nocf_check attribute to skip that.
> > >
> > > Adding -Wno-attributes for bench objects, becase nocf_check can
> > > be used only when -fcf-protection=branch is enabled, otherwise
> > > we get a warning and break compilation.
> > >
> > > Signed-off-by: Jiri Olsa <jolsa@kernel.org>
> > > ---
> > >  tools/include/linux/compiler.h                     | 4 ++++
> > >  tools/testing/selftests/bpf/Makefile               | 2 +-
> > >  tools/testing/selftests/bpf/benchs/bench_trigger.c | 6 +++---
> > >  3 files changed, 8 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
> > > index 7b65566f3e42..14038ce04ca4 100644
> > > --- a/tools/include/linux/compiler.h
> > > +++ b/tools/include/linux/compiler.h
> > > @@ -58,6 +58,10 @@
> > >  #define noinline
> > >  #endif
> > >
> > > +#ifndef __nocfcheck
> > > +#define __nocfcheck __attribute__((nocf_check))
> > > +#endif
> > 
> > Let's preserve spelling of the attribut, __nocf_check ?
> > 
> > BTW, just FYI, seems like kernel is defining it as:
> > 
> > #define __noendbr    __attribute__((nocf_check))
> > 
> > Thought somewhere deep in x86-specific code, so probably not a good
> > idea to use it here?
> 
> ugh, I missed it.. better to use __noendbr

nah, I'll keep using __nocf_check, __noendbr is bery arch
specific as you said

jirka

> 
> > 
> > > +
> > >  /* Are two types/vars the same type (ignoring qualifiers)? */
> > >  #ifndef __same_type
> > >  # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
> > > diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> > > index e425a946276b..506d3d592093 100644
> > > --- a/tools/testing/selftests/bpf/Makefile
> > > +++ b/tools/testing/selftests/bpf/Makefile
> > > @@ -726,7 +726,7 @@ $(OUTPUT)/test_cpp: test_cpp.cpp $(OUTPUT)/test_core_extern.skel.h $(BPFOBJ)
> > >  # Benchmark runner
> > >  $(OUTPUT)/bench_%.o: benchs/bench_%.c bench.h $(BPFOBJ)
> > >         $(call msg,CC,,$@)
> > > -       $(Q)$(CC) $(CFLAGS) -O2 -c $(filter %.c,$^) $(LDLIBS) -o $@
> > > +       $(Q)$(CC) $(CFLAGS) -O2 -Wno-attributes -c $(filter %.c,$^) $(LDLIBS) -o $@
> > 
> > let's better use `#pragma warning disable` in relevant .c files,
> > instead of this global flag?
> 
> ok, will try that
> 
> thanks,
> jirka
diff mbox series

Patch

diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
index 7b65566f3e42..14038ce04ca4 100644
--- a/tools/include/linux/compiler.h
+++ b/tools/include/linux/compiler.h
@@ -58,6 +58,10 @@ 
 #define noinline
 #endif
 
+#ifndef __nocfcheck
+#define __nocfcheck __attribute__((nocf_check))
+#endif
+
 /* Are two types/vars the same type (ignoring qualifiers)? */
 #ifndef __same_type
 # define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index e425a946276b..506d3d592093 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -726,7 +726,7 @@  $(OUTPUT)/test_cpp: test_cpp.cpp $(OUTPUT)/test_core_extern.skel.h $(BPFOBJ)
 # Benchmark runner
 $(OUTPUT)/bench_%.o: benchs/bench_%.c bench.h $(BPFOBJ)
 	$(call msg,CC,,$@)
-	$(Q)$(CC) $(CFLAGS) -O2 -c $(filter %.c,$^) $(LDLIBS) -o $@
+	$(Q)$(CC) $(CFLAGS) -O2 -Wno-attributes -c $(filter %.c,$^) $(LDLIBS) -o $@
 $(OUTPUT)/bench_rename.o: $(OUTPUT)/test_overhead.skel.h
 $(OUTPUT)/bench_trigger.o: $(OUTPUT)/trigger_bench.skel.h
 $(OUTPUT)/bench_ringbufs.o: $(OUTPUT)/ringbuf_bench.skel.h \
diff --git a/tools/testing/selftests/bpf/benchs/bench_trigger.c b/tools/testing/selftests/bpf/benchs/bench_trigger.c
index ace0d1011a8e..3aecc3ef74e9 100644
--- a/tools/testing/selftests/bpf/benchs/bench_trigger.c
+++ b/tools/testing/selftests/bpf/benchs/bench_trigger.c
@@ -137,7 +137,7 @@  static void trigger_fmodret_setup(void)
  * GCC doesn't generate stack setup preample for these functions due to them
  * having no input arguments and doing nothing in the body.
  */
-__weak void uprobe_target_nop(void)
+__nocfcheck __weak void uprobe_target_nop(void)
 {
 	asm volatile ("nop");
 }
@@ -146,7 +146,7 @@  __weak void opaque_noop_func(void)
 {
 }
 
-__weak int uprobe_target_push(void)
+__nocfcheck __weak int uprobe_target_push(void)
 {
 	/* overhead of function call is negligible compared to uprobe
 	 * triggering, so this shouldn't affect benchmark results much
@@ -155,7 +155,7 @@  __weak int uprobe_target_push(void)
 	return 1;
 }
 
-__weak void uprobe_target_ret(void)
+__nocfcheck __weak void uprobe_target_ret(void)
 {
 	asm volatile ("");
 }