On 8/28/21 1:20 AM, Dave Marchevsky wrote:
> 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 <davemarchevsky@xxxxxx>
> ---
> 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
The reference_tracking prog test is failing as a result of this.
Specifically, it fails to load bpf_sk_lookup_test0 prog, which
has a bpf_printk:
47: (b4) w3 = 0
48: (18) r1 = 0x0
50: (b4) w2 = 7
51: (85) call bpf_trace_printk#6
R1 type=inv expected=fp, pkt, pkt_meta, map_key, map_value, mem, rdonly_buf, rdwr_buf
Setting BPF_NO_GLOBAL_DATA in the test results in a pass
> +#endif
> +
> /* Helper macro to print out debug messages */
> #define __bpf_printk(fmt, ...) \
> ({ \
> - char ____fmt[] = fmt; \
> + BPF_PRINTK_FMT_TYPE ____fmt[] = fmt; \
> bpf_trace_printk(____fmt, sizeof(____fmt), \
> ##__VA_ARGS__); \
> })
>
