Merge branch 'bpf: add a ksym BPF iterator'

Alan Maguire says:

====================

a ksym BPF iterator would be useful as it would allow more flexible
interactions with kernel symbols than are currently supported; it could
for example create more efficient map representations for lookup,
speed up symbol resolution etc.

The idea was initially discussed here [1].

Changes since v5 [2]:
- no need to add kallsym_iter to bpf_iter.h as it has existed in kernels
  for a long time so will by in vmlinux.h for older kernels too, unlike
 struct bpf_iter__ksym (Yonghong, patch 2)

Changes since v4 [3]:

- add BPF_ITER_RESCHED to improve responsiveness (Hao, patch 1)
- remove pr_warn to be consistent with other iterators (Andrii, patch 1)
- add definitions to bpf_iter.h to ensure iter tests build on older
  kernels (Andrii, patch 2)

Changes since v3 [4]:

- use late_initcall() to register iter; means we are both consistent
  with other iters and can encapsulate all iter-specific code in
  kallsyms.c in CONFIG_BPF_SYSCALL (Alexei, Yonghong, patch 1).

Changes since v2 [5]:

- set iter->show_value on initialization based on current creds
  and use it in selftest to determine if we show values
  (Yonghong, patches 1/2)
- inline iter registration into kallsyms_init (Yonghong, patch 1)

Changes since RFC [6]:

- change name of iterator (and associated structures/fields) to "ksym"
  (Andrii, patches 1, 2)
- remove dependency on CONFIG_PROC_FS; it was used for other BPF
  iterators, and I assumed it was needed because of seq ops but I
  don't think it is required on digging futher (Andrii, patch 1)

[1] https://lore.kernel.org/all/YjRPZj6Z8vuLeEZo@krava/
[2] https://lore.kernel.org/bpf/1657490998-31468-1-git-send-email-alan.maguire@oracle.com/
[3] https://lore.kernel.org/bpf/1657113391-5624-1-git-send-email-alan.maguire@oracle.com/
[4] https://lore.kernel.org/bpf/1656942916-13491-1-git-send-email-alan.maguire@oracle.com
[5] https://lore.kernel.org/bpf/1656667620-18718-1-git-send-email-alan.maguire@oracle.com/
[6] https://lore.kernel.org/all/1656089118-577-1-git-send-email-alan.maguire@oracle.com/
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
index 7ff5fa93d056..a33874b081b6 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c
@@ -27,6 +27,7 @@
 #include "bpf_iter_test_kern5.skel.h"
 #include "bpf_iter_test_kern6.skel.h"
 #include "bpf_iter_bpf_link.skel.h"
+#include "bpf_iter_ksym.skel.h"
 
 static int duration;
 
@@ -1120,6 +1121,19 @@ static void test_link_iter(void)
 	bpf_iter_bpf_link__destroy(skel);
 }
 
+static void test_ksym_iter(void)
+{
+	struct bpf_iter_ksym *skel;
+
+	skel = bpf_iter_ksym__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "bpf_iter_ksym__open_and_load"))
+		return;
+
+	do_dummy_read(skel->progs.dump_ksym);
+
+	bpf_iter_ksym__destroy(skel);
+}
+
 #define CMP_BUFFER_SIZE 1024
 static char task_vma_output[CMP_BUFFER_SIZE];
 static char proc_maps_output[CMP_BUFFER_SIZE];
@@ -1267,4 +1281,6 @@ void test_bpf_iter(void)
 		test_buf_neg_offset();
 	if (test__start_subtest("link-iter"))
 		test_link_iter();
+	if (test__start_subtest("ksym"))
+		test_ksym_iter();
 }