On Wed, Sep 29, 2021 at 11:30 PM Kumar Kartikeya Dwivedi
<memxor@xxxxxxxxx> wrote:
>
> This adds selftests that tests the success and failure path for modules
> kfuncs (in presence of invalid kfunc calls) for both libbpf and
> gen_loader. It also adds a prog_test kfunc_btf_id_list so that we can
> add module BTF ID set from bpf_testmod.
>
> This also introduces a couple of test cases to verifier selftests for
> validating whether we get an error or not depending on if invalid kfunc
> call remains after elimination of unreachable instructions.
>
> Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
> ---
> include/linux/btf.h | 2 +
> kernel/bpf/btf.c | 2 +
> net/bpf/test_run.c | 5 +-
> tools/testing/selftests/bpf/Makefile | 8 ++--
> .../selftests/bpf/bpf_testmod/bpf_testmod.c | 23 +++++++++-
> .../selftests/bpf/prog_tests/ksyms_module.c | 29 ++++++------
> .../bpf/prog_tests/ksyms_module_libbpf.c | 28 +++++++++++
> .../selftests/bpf/progs/test_ksyms_module.c | 46 ++++++++++++++-----
> tools/testing/selftests/bpf/verifier/calls.c | 23 ++++++++++
> 9 files changed, 135 insertions(+), 31 deletions(-)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/ksyms_module_libbpf.c
>
[...]
> @@ -243,7 +244,9 @@ BTF_SET_END(test_sk_kfunc_ids)
>
> bool bpf_prog_test_check_kfunc_call(u32 kfunc_id, struct module *owner)
> {
> - return btf_id_set_contains(&test_sk_kfunc_ids, kfunc_id);
> + if (btf_id_set_contains(&test_sk_kfunc_ids, kfunc_id))
> + return true;
> + return __bpf_prog_test_check_kfunc_call(kfunc_id, owner);
> }
>
> static void *bpf_test_init(const union bpf_attr *kattr, u32 size,
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index e1ce73be7a5b..df461699932d 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -174,6 +174,7 @@ $(OUTPUT)/bpf_testmod.ko: $(VMLINUX_BTF) $(wildcard bpf_testmod/Makefile bpf_tes
> $(Q)$(RM) bpf_testmod/bpf_testmod.ko # force re-compilation
> $(Q)$(MAKE) $(submake_extras) -C bpf_testmod
> $(Q)cp bpf_testmod/bpf_testmod.ko $@
> + $(Q)$(RESOLVE_BTFIDS) -b $(VMLINUX_BTF) bpf_testmod.ko
This should be done by kernel Makefiles, which are used to build
bpf_testmod.ko. If this is not happening, something is wrong and let's
try to figure out what.
>
> $(OUTPUT)/test_stub.o: test_stub.c $(BPFOBJ)
> $(call msg,CC,,$@)
> @@ -315,8 +316,9 @@ LINKED_SKELS := test_static_linked.skel.h linked_funcs.skel.h \
> linked_vars.skel.h linked_maps.skel.h
>
> LSKELS := kfunc_call_test.c fentry_test.c fexit_test.c fexit_sleep.c \
> - test_ksyms_module.c test_ringbuf.c atomics.c trace_printk.c \
> - trace_vprintk.c
> + test_ringbuf.c atomics.c trace_printk.c trace_vprintk.c
> +# Generate both light skeleton and libbpf skeleton for these
> +LSKELS_EXTRA := test_ksyms_module.c
> SKEL_BLACKLIST += $$(LSKELS)
>
[...]
> +#define X_0(x)
> +#define X_1(x) x X_0(x)
> +#define X_2(x) x X_1(x)
> +#define X_3(x) x X_2(x)
> +#define X_4(x) x X_3(x)
> +#define X_5(x) x X_4(x)
> +#define X_6(x) x X_5(x)
> +#define X_7(x) x X_6(x)
> +#define X_8(x) x X_7(x)
> +#define X_9(x) x X_8(x)
> +#define X_10(x) x X_9(x)
> +#define REPEAT_256(Y) X_2(X_10(X_10(Y))) X_5(X_10(Y)) X_6(Y)
this is impressive, I can even sort of read it :)
> +
> extern const int bpf_testmod_ksym_percpu __ksym;
> +extern void bpf_testmod_test_mod_kfunc(int i) __ksym;
> +extern void bpf_testmod_invalid_mod_kfunc(void) __ksym __weak;
>
> -int out_mod_ksym_global = 0;
> -bool triggered = false;
> +int out_bpf_testmod_ksym = 0;
> +const volatile int x = 0;
>
> -SEC("raw_tp/sys_enter")
> -int handler(const void *ctx)
> +SEC("tc")
Did you switch to tc because kfuncs are not allowed from raw_tp
programs? Or is there some other reason?
> +int load(struct __sk_buff *skb)
> {
> - int *val;
> - __u32 cpu;
> -
> - val = (int *)bpf_this_cpu_ptr(&bpf_testmod_ksym_percpu);
> - out_mod_ksym_global = *val;
> - triggered = true;
> + /* This will be kept by clang, but removed by verifier. Since it is
> + * marked as __weak, libbpf and gen_loader don't error out if BTF ID
> + * is not found for it, instead imm and off is set to 0 for it.
> + */
> + if (x)
> + bpf_testmod_invalid_mod_kfunc();
> + bpf_testmod_test_mod_kfunc(42);
> + out_bpf_testmod_ksym = *(int *)bpf_this_cpu_ptr(&bpf_testmod_ksym_percpu);
> + return 0;
> +}
>
[...]
