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tracing: Allow BPF programs to call bpf_trace_printk()

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Debugging of BPF programs needs some form of printk from the
program, so let programs call limited trace_printk() with %d %u
%x %p modifiers only.

Similar to kernel modules, during program load verifier checks
whether program is calling bpf_trace_printk() and if so, kernel
allocates trace_printk buffers and emits big 'this is debug
only' banner.

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1427312966-8434-6-git-send-email-ast@plumgrid.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Alexei Starovoitov
2015-03-25 12:49:22 -07:00
committed by Ingo Molnar
parent d9847d310a
commit 9c959c863f
2 changed files with 79 additions and 0 deletions
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include/uapi/linux/bpf.h
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@@ -166,6 +166,7 @@ enum bpf_func_id {
BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */
BPF_FUNC_probe_read, /* int bpf_probe_read(void *dst, int size, void *src) */
BPF_FUNC_ktime_get_ns, /* u64 bpf_ktime_get_ns(void) */
BPF_FUNC_trace_printk, /* int bpf_trace_printk(const char *fmt, int fmt_size, ...) */
__BPF_FUNC_MAX_ID,
};