Re: [PATCH v3 bpf-next 4/7] libbpf: use static const fmt string in __bpf_printk

The __bpf_printk convenience macro was using a 'char' fmt string holder
as it predates support for globals in libbpf. Move to more efficient
'static const char', but provide a fallback to the old way via
BPF_NO_GLOBAL_DATA so users on old kernels can still use the macro.

Signed-off-by: Dave Marchevsky <redacted>
---
 tools/lib/bpf/bpf_helpers.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index 5f087306cdfe..a1d5ec6f285c 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h

@@ -216,10 +216,16 @@ enum libbpf_tristate {
                     ___param, sizeof(___param));               \
 })

+#ifdef BPF_NO_GLOBAL_DATA
+#define BPF_PRINTK_FMT_TYPE char
+#else
+#define BPF_PRINTK_FMT_TYPE static const char
+#endif
+
 /* Helper macro to print out debug messages */
 #define __bpf_printk(fmt, ...)                         \
 ({                                                     \
-       char ____fmt[] = fmt;                           \
+       BPF_PRINTK_FMT_TYPE ____fmt[] = fmt;            \