2023-03-24 20:05 UTC-0700 ~ Stanislav Fomichev <sdf@xxxxxxxxxx>
> On 03/24, Quentin Monnet wrote:
>> We support dumping the control flow graph of loaded programs to the DOT
>> format with bpftool, but so far this feature wouldn't display the source
>> code lines available through BTF along with the eBPF bytecode. Let's add
>> support for these annotations, to make it easier to read the graph.
>
>> In prog.c, we move the call to dump_xlated_cfg() in order to pass and
>> use the full struct dump_data, instead of creating a minimal one in
>> draw_bb_node().
>
>> We pass the pointer to this struct down to dump_xlated_for_graph() in
>> xlated_dumper.c, where most of the logics is added. We deal with BTF
>> mostly like we do for plain or JSON output, except that we cannot use a
>> "nr_skip" value to skip a given number of linfo records (we don't
>> process the BPF instructions linearly, and apart from the root of the
>> graph we don't know how many records we should skip, so we just store
>> the last linfo and make sure the new one we find is different before
>> printing it).
>
>> When printing the source instructions to the label of a DOT graph node,
>> there are a few subtleties to address. We want some special newline
>> markers, and there are some characters that we must escape. To deal with
>> them, we introduce a new dedicated function btf_dump_linfo_dotlabel() in
>> btf_dumper.c. We'll reuse this function in a later commit to format the
>> filepath, line, and column references as well.
>
>> Signed-off-by: Quentin Monnet <quentin@xxxxxxxxxxxxx>
>> ---
>> tools/bpf/bpftool/btf_dumper.c | 34 +++++++++++++++++++++++++++++++
>> tools/bpf/bpftool/cfg.c | 23 +++++++++------------
>> tools/bpf/bpftool/cfg.h | 4 +++-
>> tools/bpf/bpftool/main.h | 2 ++
>> tools/bpf/bpftool/prog.c | 17 +++++++---------
>> tools/bpf/bpftool/xlated_dumper.c | 32 ++++++++++++++++++++++++++++-
>> 6 files changed, 87 insertions(+), 25 deletions(-)
>
>> diff --git a/tools/bpf/bpftool/btf_dumper.c
>> b/tools/bpf/bpftool/btf_dumper.c
>> index e7f6ec3a8f35..504d7c75cc27 100644
>> --- a/tools/bpf/bpftool/btf_dumper.c
>> +++ b/tools/bpf/bpftool/btf_dumper.c
>> @@ -821,3 +821,37 @@ void btf_dump_linfo_json(const struct btf *btf,
>> BPF_LINE_INFO_LINE_COL(linfo->line_col));
>> }
>> }
>> +
>> +static void dotlabel_puts(const char *s)
>> +{
>> + FILE *stream = stdout;
>> +
>> + for (; *s; ++s) {
>> + switch (*s) {
>> + case '\\':
>> + case '"':
>> + case '{':
>> + case '}':
>> + case '>':
>> + case '|':
>> + fputc('\\', stream);
>> + __fallthrough;
>> + default:
>> + fputc(*s, stream);
>> + }
>
> nit: optionally, if you're going to respin, maybe do putchar instead
> of fputc + stdout? (not sure why you're doing fputs)
Right, no particular reason, I'll switch to putchar() and respin.
Thanks for the review!
Quentin
