bpftool: Support inline annotations when dumping the CFG of a program

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@isovalent.com>
Link: https://lore.kernel.org/r/20230405132120.59886-4-quentin@isovalent.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c
index e7f6ec3a8f357a22f54145a8b7e985ab6fc7d008..583aa843df92f39d1122a9fb05274a07bbd4df48 100644 (file)
--- 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)
+{
+       for (; *s; ++s) {
+               switch (*s) {
+               case '\\':
+               case '"':
+               case '{':
+               case '}':
+               case '<':
+               case '>':
+               case '|':
+               case ' ':
+                       putchar('\\');
+                       __fallthrough;
+               default:
+                       putchar(*s);
+               }
+       }
+}
+
+void btf_dump_linfo_dotlabel(const struct btf *btf,
+                            const struct bpf_line_info *linfo)
+{
+       const char *line = btf__name_by_offset(btf, linfo->line_off);
+
+       if (!line || !strlen(line))
+               return;
+       line = ltrim(line);
+
+       printf("; ");
+       dotlabel_puts(line);
+       printf("\\l\\\n");
+}

diff --git a/tools/bpf/bpftool/cfg.c b/tools/bpf/bpftool/cfg.c
index 1951219a9af70a8a8dcd4e225ef40d75faa7fcb7..9fdc1f0cdd6e65f315c23bf2e645b513e5a2289b 100644 (file)
--- a/tools/bpf/bpftool/cfg.c
+++ b/tools/bpf/bpftool/cfg.c
@@ -380,7 +380,8 @@ static void cfg_destroy(struct cfg *cfg)
        }
 }
 
-static void draw_bb_node(struct func_node *func, struct bb_node *bb)
+static void
+draw_bb_node(struct func_node *func, struct bb_node *bb, struct dump_data *dd)
 {
        const char *shape;
 
@@ -398,13 +399,9 @@ static void draw_bb_node(struct func_node *func, struct bb_node *bb)
                printf("EXIT");
        } else {
                unsigned int start_idx;
-               struct dump_data dd = {};
-
-               printf("{");
-               kernel_syms_load(&dd);
+               printf("{\\\n");
                start_idx = bb->head - func->start;
-               dump_xlated_for_graph(&dd, bb->head, bb->tail, start_idx);
-               kernel_syms_destroy(&dd);
+               dump_xlated_for_graph(dd, bb->head, bb->tail, start_idx);
                printf("}");
        }
 
@@ -430,12 +427,12 @@ static void draw_bb_succ_edges(struct func_node *func, struct bb_node *bb)
        }
 }
 
-static void func_output_bb_def(struct func_node *func)
+static void func_output_bb_def(struct func_node *func, struct dump_data *dd)
 {
        struct bb_node *bb;
 
        list_for_each_entry(bb, &func->bbs, l) {
-               draw_bb_node(func, bb);
+               draw_bb_node(func, bb, dd);
        }
 }
 
@@ -455,7 +452,7 @@ static void func_output_edges(struct func_node *func)
               func_idx, ENTRY_BLOCK_INDEX, func_idx, EXIT_BLOCK_INDEX);
 }
 
-static void cfg_dump(struct cfg *cfg)
+static void cfg_dump(struct cfg *cfg, struct dump_data *dd)
 {
        struct func_node *func;
 
@@ -463,14 +460,14 @@ static void cfg_dump(struct cfg *cfg)
        list_for_each_entry(func, &cfg->funcs, l) {
                printf("subgraph \"cluster_%d\" {\n\tstyle=\"dashed\";\n\tcolor=\"black\";\n\tlabel=\"func_%d ()\";\n",
                       func->idx, func->idx);
-               func_output_bb_def(func);
+               func_output_bb_def(func, dd);
                func_output_edges(func);
                printf("}\n");
        }
        printf("}\n");
 }
 
-void dump_xlated_cfg(void *buf, unsigned int len)
+void dump_xlated_cfg(struct dump_data *dd, void *buf, unsigned int len)
 {
        struct bpf_insn *insn = buf;
        struct cfg cfg;
@@ -479,7 +476,7 @@ void dump_xlated_cfg(void *buf, unsigned int len)
        if (cfg_build(&cfg, insn, len))
                return;
 
-       cfg_dump(&cfg);
+       cfg_dump(&cfg, dd);
 
        cfg_destroy(&cfg);
 }

diff --git a/tools/bpf/bpftool/cfg.h b/tools/bpf/bpftool/cfg.h
index e144257ea6d20de14ed5a4bde9de53d8da5c1d31..909d17e6d4c2a1054e4208d068e631420fae8c06 100644 (file)
--- a/tools/bpf/bpftool/cfg.h
+++ b/tools/bpf/bpftool/cfg.h
@@ -4,6 +4,8 @@
 #ifndef __BPF_TOOL_CFG_H
 #define __BPF_TOOL_CFG_H
 
-void dump_xlated_cfg(void *buf, unsigned int len);
+#include "xlated_dumper.h"
+
+void dump_xlated_cfg(struct dump_data *dd, void *buf, unsigned int len);
 
 #endif /* __BPF_TOOL_CFG_H */

diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index 0ef373cef4c76f8226f789a2ac121408291a88eb..e9ee514b22d412083ee1f42e7a105265254d41da 100644 (file)
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -229,6 +229,8 @@ void btf_dump_linfo_plain(const struct btf *btf,
                          const char *prefix, bool linum);
 void btf_dump_linfo_json(const struct btf *btf,
                         const struct bpf_line_info *linfo, bool linum);
+void btf_dump_linfo_dotlabel(const struct btf *btf,
+                            const struct bpf_line_info *linfo);
 
 struct nlattr;
 struct ifinfomsg;

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index afbe3ec342c85fafc1e9e8e20066ac194e165c6f..d855118f0d9632a3f718260a45085339a74bde47 100644 (file)
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -840,11 +840,6 @@ prog_dump(struct bpf_prog_info *info, enum dump_mode mode,
                                              false))
                                goto exit_free;
                }
-       } else if (visual) {
-               if (json_output)
-                       jsonw_null(json_wtr);
-               else
-                       dump_xlated_cfg(buf, member_len);
        } else {
                kernel_syms_load(&dd);
                dd.nr_jited_ksyms = info->nr_jited_ksyms;
@@ -854,12 +849,14 @@ prog_dump(struct bpf_prog_info *info, enum dump_mode mode,
                dd.finfo_rec_size = info->func_info_rec_size;
                dd.prog_linfo = prog_linfo;
 
-               if (json_output)
-                       dump_xlated_json(&dd, buf, member_len, opcodes,
-                                        linum);
+               if (json_output && visual)
+                       jsonw_null(json_wtr);
+               else if (json_output)
+                       dump_xlated_json(&dd, buf, member_len, opcodes, linum);
+               else if (visual)
+                       dump_xlated_cfg(&dd, buf, member_len);
                else
-                       dump_xlated_plain(&dd, buf, member_len, opcodes,
-                                         linum);
+                       dump_xlated_plain(&dd, buf, member_len, opcodes, linum);
                kernel_syms_destroy(&dd);
        }
 

diff --git a/tools/bpf/bpftool/xlated_dumper.c b/tools/bpf/bpftool/xlated_dumper.c
index 3daa05d9bbb7337cecf1303174a3627fb88a0af9..2ee83561b945beff29de361398f6753a4f70330e 100644 (file)
--- a/tools/bpf/bpftool/xlated_dumper.c
+++ b/tools/bpf/bpftool/xlated_dumper.c
@@ -369,21 +369,51 @@ void dump_xlated_for_graph(struct dump_data *dd, void *buf_start, void *buf_end,
                .cb_imm         = print_imm,
                .private_data   = dd,
        };
+       const struct bpf_prog_linfo *prog_linfo = dd->prog_linfo;
+       const struct bpf_line_info *last_linfo = NULL;
+       struct bpf_func_info *record = dd->func_info;
        struct bpf_insn *insn_start = buf_start;
        struct bpf_insn *insn_end = buf_end;
        struct bpf_insn *cur = insn_start;
+       struct btf *btf = dd->btf;
        bool double_insn = false;
+       char func_sig[1024];
 
        for (; cur <= insn_end; cur++) {
+               unsigned int insn_off;
+
                if (double_insn) {
                        double_insn = false;
                        continue;
                }
                double_insn = cur->code == (BPF_LD | BPF_IMM | BPF_DW);
 
-               printf("% 4d: ", (int)(cur - insn_start + start_idx));
+               insn_off = (unsigned int)(cur - insn_start + start_idx);
+               if (btf && record) {
+                       if (record->insn_off == insn_off) {
+                               btf_dumper_type_only(btf, record->type_id,
+                                                    func_sig,
+                                                    sizeof(func_sig));
+                               if (func_sig[0] != '\0')
+                                       printf("; %s:\\l\\\n", func_sig);
+                               record = (void *)record + dd->finfo_rec_size;
+                       }
+               }
+
+               if (prog_linfo) {
+                       const struct bpf_line_info *linfo;
+
+                       linfo = bpf_prog_linfo__lfind(prog_linfo, insn_off, 0);
+                       if (linfo && linfo != last_linfo) {
+                               btf_dump_linfo_dotlabel(btf, linfo);
+                               last_linfo = linfo;
+                       }
+               }
+
+               printf("%d: ", insn_off);
                print_bpf_insn(&cbs, cur, true);
+
                if (cur != insn_end)
-                       printf(" | ");
+                       printf("| ");
        }
 }