[PATCH 5.4 078/110] libbpf: Fix BTF-defined maps __type macro handling of arrays

Greg Kroah-Hartman
2020-01-30T18:45:06Z

From: Andrii Nakryiko <andriin@fb.com>

[ Upstream commit a53ba15d81995868651dd28a85d8045aef3d4e20 ]

Due to a quirky C syntax of declaring pointers to array or function
prototype, existing __type() macro doesn't work with map key/value types
that are array or function prototype. One has to create a typedef first
and use it to specify key/value type for a BPF map. By using typeof(),
pointer to type is now handled uniformly for all kinds of types. Convert
one of self-tests as a demonstration.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20191004040211.2434033-1-andriin@fb.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/testing/selftests/bpf/bpf_helpers.h | 2 +-
tools/testing/selftests/bpf/progs/test_get_stack_rawtp.c | 3 +--
2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/bpf/bpf_helpers.h b/tools/testing/selftests/bpf/bpf_helpers.h
index 54a50699bbfda..9f77cbaac01c1 100644
--- a/tools/testing/selftests/bpf/bpf_helpers.h
+++ b/tools/testing/selftests/bpf/bpf_helpers.h
@@ -3,7 +3,7 @@
#define __BPF_HELPERS__

#define __uint(name, val) int (*name)[val]
-#define __type(name, val) val *name
+#define __type(name, val) typeof(val) *name

/* helper macro to print out debug messages */
#define bpf_printk(fmt, ...) \
diff --git a/tools/testing/selftests/bpf/progs/test_get_stack_rawtp.c b/tools/testing/selftests/bpf/progs/test_get_stack_rawtp.c
index f8ffa3f3d44bb..6cc4479ac9df6 100644
--- a/tools/testing/selftests/bpf/progs/test_get_stack_rawtp.c
+++ b/tools/testing/selftests/bpf/progs/test_get_stack_rawtp.c
@@ -47,12 +47,11 @@ struct {
* issue and avoid complicated C programming massaging.
* This is an acceptable workaround since there is one entry here.
*/
-typedef __u64 raw_stack_trace_t[2 * MAX_STACK_RAWTP];
struct {
__uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
__uint(max_entries, 1);
__type(key, __u32);
- __type(value, raw_stack_trace_t);
+ __type(value, __u64[2 * MAX_STACK_RAWTP]);
} rawdata_map SEC(".maps");

SEC("raw_tracepoint/sys_enter")
--
2.20.1