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libbpf: Use static const fmt string in __bpf_printk

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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@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210917182911.2426606-6-davemarchevsky@fb.com
This commit is contained in:
Dave Marchevsky 2021-09-17 11:29:07 -07:00 committed by Alexei Starovoitov
parent c2758baa97
commit 6c66b0e7c9
1 changed files with 7 additions and 1 deletions
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8
tools/lib/bpf/bpf_helpers.h
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@ -216,9 +216,15 @@ enum libbpf_tristate {
___param, sizeof(___param)); \
})
#ifdef BPF_NO_GLOBAL_DATA
#define BPF_PRINTK_FMT_MOD
#else
#define BPF_PRINTK_FMT_MOD static const
#endif
#define __bpf_printk(fmt, ...) \
({ \
char ____fmt[] = fmt; \
BPF_PRINTK_FMT_MOD char ____fmt[] = fmt; \
bpf_trace_printk(____fmt, sizeof(____fmt), \
##__VA_ARGS__); \
})