On Mon, Oct 11, 2021 at 3:57 PM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
>
> On 10/8/21 2:03 AM, andrii.nakryiko@xxxxxxxxx wrote:
> > From: Andrii Nakryiko <andrii@xxxxxxxxxx>
> >
> > Enhance existing selftests to demonstrate the use of custom
> > .data/.rodata sections.
> >
> > Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
>
> Just a thought, but wouldn't the actual demo / use case be better to show that we can
> now have a __read_mostly attribute which implies SEC(".data.read_mostly") section?
>
> Would be nice to add a ...
>
> #define __read_mostly SEC(".data.read_mostly")
>
> ... into tools/lib/bpf/bpf_helpers.h along with the series for use out of BPF programs
> as I think this should be a rather common use case. Thoughts?
But what's so special about the ".data.read_mostly" ELF section for
BPF programs? It's just another data section with no extra semantics.
So unclear why we need to have a dedicated #define for that?..
>
> > ---
> > .../selftests/bpf/prog_tests/skeleton.c | 25 +++++++++++++++++++
> > .../selftests/bpf/progs/test_skeleton.c | 10 ++++++++
> > 2 files changed, 35 insertions(+)
> [...]
> > diff --git a/tools/testing/selftests/bpf/progs/test_skeleton.c b/tools/testing/selftests/bpf/progs/test_skeleton.c
> > index 441fa1c552c8..47a7e76866c4 100644
> > --- a/tools/testing/selftests/bpf/progs/test_skeleton.c
> > +++ b/tools/testing/selftests/bpf/progs/test_skeleton.c
> > @@ -40,9 +40,16 @@ int kern_ver = 0;
> >
> > struct s out5 = {};
> >
> > +const volatile int in_dynarr_sz SEC(".rodata.dyn");
> > +const volatile int in_dynarr[4] SEC(".rodata.dyn") = { -1, -2, -3, -4 };
> > +
> > +int out_dynarr[4] SEC(".data.dyn") = { 1, 2, 3, 4 };
> > +
> > SEC("raw_tp/sys_enter")
> > int handler(const void *ctx)
> > {
> > + int i;
> > +
> > out1 = in1;
> > out2 = in2;
> > out3 = in3;
> > @@ -53,6 +60,9 @@ int handler(const void *ctx)
> > bpf_syscall = CONFIG_BPF_SYSCALL;
> > kern_ver = LINUX_KERNEL_VERSION;
> >
> > + for (i = 0; i < in_dynarr_sz; i++)
> > + out_dynarr[i] = in_dynarr[i];
> > +
> > return 0;
> > }
> >
> >
>
