Re: [PATCH v3 bpf-next 4/7] libbpf: use static const fmt string in __bpf_printk
From: Dave Marchevsky <hidden>
Date: 2021-08-28 16:40:53
Also in:
bpf
On 8/28/21 1:20 AM, Dave Marchevsky wrote:
quoted hunk ↗ jump to hunk
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
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
quoted hunk ↗ jump to hunk
+#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__); \ })