From 9fd496848b1c4cd04fee5f152bb7bcec11e1b901 Mon Sep 17 00:00:00 2001 From: Quentin Monnet Date: Wed, 5 Apr 2023 14:21:16 +0100 Subject: 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 Link: https://lore.kernel.org/r/20230405132120.59886-4-quentin@isovalent.com Signed-off-by: Alexei Starovoitov --- tools/bpf/bpftool/btf_dumper.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) (limited to 'tools/bpf/bpftool/btf_dumper.c') diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c index e7f6ec3a8f35..583aa843df92 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) +{ + 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"); +} -- cgit From 7483a7a70a12d7c00c9f80574d533b01689d39a7 Mon Sep 17 00:00:00 2001 From: Quentin Monnet Date: Wed, 5 Apr 2023 14:21:19 +0100 Subject: bpftool: Support printing opcodes and source file references in CFG Add support for displaying opcodes or/and file references (filepath, line and column numbers) when dumping the control flow graphs of loaded BPF programs with bpftool. The filepaths in the records are absolute. To avoid blocks on the graph to get too wide, we truncate them when they get too long (but we always keep the entire file name). In the unlikely case where the resulting file name is ambiguous, it remains possible to get the full path with a regular dump (no CFG). Signed-off-by: Quentin Monnet Link: https://lore.kernel.org/r/20230405132120.59886-7-quentin@isovalent.com Signed-off-by: Alexei Starovoitov --- tools/bpf/bpftool/btf_dumper.c | 51 ++++++++++++++++++++++++++++++++++++++- tools/bpf/bpftool/cfg.c | 22 +++++++++++------ tools/bpf/bpftool/cfg.h | 3 ++- tools/bpf/bpftool/main.h | 2 +- tools/bpf/bpftool/prog.c | 2 +- tools/bpf/bpftool/xlated_dumper.c | 15 ++++++++++-- tools/bpf/bpftool/xlated_dumper.h | 3 ++- 7 files changed, 83 insertions(+), 15 deletions(-) (limited to 'tools/bpf/bpftool/btf_dumper.c') diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c index 583aa843df92..6c5e0e82da22 100644 --- a/tools/bpf/bpftool/btf_dumper.c +++ b/tools/bpf/bpftool/btf_dumper.c @@ -842,8 +842,37 @@ static void dotlabel_puts(const char *s) } } +static const char *shorten_path(const char *path) +{ + const unsigned int MAX_PATH_LEN = 32; + size_t len = strlen(path); + const char *shortpath; + + if (len <= MAX_PATH_LEN) + return path; + + /* Search for last '/' under the MAX_PATH_LEN limit */ + shortpath = strchr(path + len - MAX_PATH_LEN, '/'); + if (shortpath) { + if (shortpath < path + strlen("...")) + /* We removed a very short prefix, e.g. "/w", and we'll + * make the path longer by prefixing with the ellipsis. + * Not worth it, keep initial path. + */ + return path; + return shortpath; + } + + /* File base name length is > MAX_PATH_LEN, search for last '/' */ + shortpath = strrchr(path, '/'); + if (shortpath) + return shortpath; + + return path; +} + void btf_dump_linfo_dotlabel(const struct btf *btf, - const struct bpf_line_info *linfo) + const struct bpf_line_info *linfo, bool linum) { const char *line = btf__name_by_offset(btf, linfo->line_off); @@ -851,6 +880,26 @@ void btf_dump_linfo_dotlabel(const struct btf *btf, return; line = ltrim(line); + if (linum) { + const char *file = btf__name_by_offset(btf, linfo->file_name_off); + const char *shortfile; + + /* More forgiving on file because linum option is + * expected to provide more info than the already + * available src line. + */ + if (!file) + shortfile = ""; + else + shortfile = shorten_path(file); + + printf("; [%s", shortfile > file ? "..." : ""); + dotlabel_puts(shortfile); + printf(" line:%u col:%u]\\l\\\n", + BPF_LINE_INFO_LINE_NUM(linfo->line_col), + BPF_LINE_INFO_LINE_COL(linfo->line_col)); + } + printf("; "); dotlabel_puts(line); printf("\\l\\\n"); diff --git a/tools/bpf/bpftool/cfg.c b/tools/bpf/bpftool/cfg.c index 9fdc1f0cdd6e..eec437cca2ea 100644 --- a/tools/bpf/bpftool/cfg.c +++ b/tools/bpf/bpftool/cfg.c @@ -381,7 +381,8 @@ static void cfg_destroy(struct cfg *cfg) } static void -draw_bb_node(struct func_node *func, struct bb_node *bb, struct dump_data *dd) +draw_bb_node(struct func_node *func, struct bb_node *bb, struct dump_data *dd, + bool opcodes, bool linum) { const char *shape; @@ -401,7 +402,8 @@ draw_bb_node(struct func_node *func, struct bb_node *bb, struct dump_data *dd) unsigned int start_idx; printf("{\\\n"); start_idx = bb->head - func->start; - dump_xlated_for_graph(dd, bb->head, bb->tail, start_idx); + dump_xlated_for_graph(dd, bb->head, bb->tail, start_idx, + opcodes, linum); printf("}"); } @@ -427,12 +429,14 @@ static void draw_bb_succ_edges(struct func_node *func, struct bb_node *bb) } } -static void func_output_bb_def(struct func_node *func, struct dump_data *dd) +static void +func_output_bb_def(struct func_node *func, struct dump_data *dd, + bool opcodes, bool linum) { struct bb_node *bb; list_for_each_entry(bb, &func->bbs, l) { - draw_bb_node(func, bb, dd); + draw_bb_node(func, bb, dd, opcodes, linum); } } @@ -452,7 +456,8 @@ 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, struct dump_data *dd) +static void +cfg_dump(struct cfg *cfg, struct dump_data *dd, bool opcodes, bool linum) { struct func_node *func; @@ -460,14 +465,15 @@ static void cfg_dump(struct cfg *cfg, struct dump_data *dd) 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, dd); + func_output_bb_def(func, dd, opcodes, linum); func_output_edges(func); printf("}\n"); } printf("}\n"); } -void dump_xlated_cfg(struct dump_data *dd, void *buf, unsigned int len) +void dump_xlated_cfg(struct dump_data *dd, void *buf, unsigned int len, + bool opcodes, bool linum) { struct bpf_insn *insn = buf; struct cfg cfg; @@ -476,7 +482,7 @@ void dump_xlated_cfg(struct dump_data *dd, void *buf, unsigned int len) if (cfg_build(&cfg, insn, len)) return; - cfg_dump(&cfg, dd); + cfg_dump(&cfg, dd, opcodes, linum); cfg_destroy(&cfg); } diff --git a/tools/bpf/bpftool/cfg.h b/tools/bpf/bpftool/cfg.h index 909d17e6d4c2..b3793f4e1783 100644 --- a/tools/bpf/bpftool/cfg.h +++ b/tools/bpf/bpftool/cfg.h @@ -6,6 +6,7 @@ #include "xlated_dumper.h" -void dump_xlated_cfg(struct dump_data *dd, void *buf, unsigned int len); +void dump_xlated_cfg(struct dump_data *dd, void *buf, unsigned int len, + bool opcodes, bool linum); #endif /* __BPF_TOOL_CFG_H */ diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h index e9ee514b22d4..00d11ca6d3f2 100644 --- a/tools/bpf/bpftool/main.h +++ b/tools/bpf/bpftool/main.h @@ -230,7 +230,7 @@ void btf_dump_linfo_plain(const struct btf *btf, 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); + const struct bpf_line_info *linfo, bool linum); struct nlattr; struct ifinfomsg; diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c index 092525a6933a..430f72306409 100644 --- a/tools/bpf/bpftool/prog.c +++ b/tools/bpf/bpftool/prog.c @@ -852,7 +852,7 @@ prog_dump(struct bpf_prog_info *info, enum dump_mode mode, if (json_output) dump_xlated_json(&dd, buf, member_len, opcodes, linum); else if (visual) - dump_xlated_cfg(&dd, buf, member_len); + dump_xlated_cfg(&dd, buf, member_len, opcodes, linum); else 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 2ee83561b945..da608e10c843 100644 --- a/tools/bpf/bpftool/xlated_dumper.c +++ b/tools/bpf/bpftool/xlated_dumper.c @@ -361,7 +361,8 @@ void dump_xlated_plain(struct dump_data *dd, void *buf, unsigned int len, } void dump_xlated_for_graph(struct dump_data *dd, void *buf_start, void *buf_end, - unsigned int start_idx) + unsigned int start_idx, + bool opcodes, bool linum) { const struct bpf_insn_cbs cbs = { .cb_print = print_insn_for_graph, @@ -405,7 +406,7 @@ void dump_xlated_for_graph(struct dump_data *dd, void *buf_start, void *buf_end, linfo = bpf_prog_linfo__lfind(prog_linfo, insn_off, 0); if (linfo && linfo != last_linfo) { - btf_dump_linfo_dotlabel(btf, linfo); + btf_dump_linfo_dotlabel(btf, linfo, linum); last_linfo = linfo; } } @@ -413,6 +414,16 @@ void dump_xlated_for_graph(struct dump_data *dd, void *buf_start, void *buf_end, printf("%d: ", insn_off); print_bpf_insn(&cbs, cur, true); + if (opcodes) { + printf("\\ \\ \\ \\ "); + fprint_hex(stdout, cur, 8, " "); + if (double_insn && cur <= insn_end - 1) { + printf(" "); + fprint_hex(stdout, cur + 1, 8, " "); + } + printf("\\l\\\n"); + } + if (cur != insn_end) printf("| "); } diff --git a/tools/bpf/bpftool/xlated_dumper.h b/tools/bpf/bpftool/xlated_dumper.h index 54847e174273..9a946377b0e6 100644 --- a/tools/bpf/bpftool/xlated_dumper.h +++ b/tools/bpf/bpftool/xlated_dumper.h @@ -34,6 +34,7 @@ void dump_xlated_json(struct dump_data *dd, void *buf, unsigned int len, void dump_xlated_plain(struct dump_data *dd, void *buf, unsigned int len, bool opcodes, bool linum); void dump_xlated_for_graph(struct dump_data *dd, void *buf, void *buf_end, - unsigned int start_index); + unsigned int start_index, + bool opcodes, bool linum); #endif -- cgit From 4b7ef71ac977899cf7bdb09d66052926c7d249ff Mon Sep 17 00:00:00 2001 From: Quentin Monnet Date: Thu, 20 Apr 2023 01:33:33 +0100 Subject: bpftool: Replace "__fallthrough" by a comment to address merge conflict The recent support for inline annotations in control flow graphs generated by bpftool introduced the usage of the "__fallthrough" macro in a switch/case block in btf_dumper.c. This change went through the bpf-next tree, but resulted in a merge conflict in linux-next, because this macro has been renamed "fallthrough" (no underscores) in the meantime. To address the conflict, we temporarily switch to a simple comment instead of a macro. Related: commit f7a858bffcdd ("tools: Rename __fallthrough to fallthrough") Fixes: 9fd496848b1c ("bpftool: Support inline annotations when dumping the CFG of a program") Reported-by: Sven Schnelle Reported-by: Thomas Richter Suggested-by: Daniel Borkmann Signed-off-by: Quentin Monnet Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/all/yt9dttxlwal7.fsf@linux.ibm.com/ Link: https://lore.kernel.org/bpf/20230412123636.2358949-1-tmricht@linux.ibm.com/ Link: https://lore.kernel.org/bpf/20230420003333.90901-1-quentin@isovalent.com --- tools/bpf/bpftool/btf_dumper.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'tools/bpf/bpftool/btf_dumper.c') diff --git a/tools/bpf/bpftool/btf_dumper.c b/tools/bpf/bpftool/btf_dumper.c index 6c5e0e82da22..294de231db99 100644 --- a/tools/bpf/bpftool/btf_dumper.c +++ b/tools/bpf/bpftool/btf_dumper.c @@ -835,7 +835,7 @@ static void dotlabel_puts(const char *s) case '|': case ' ': putchar('\\'); - __fallthrough; + /* fallthrough */ default: putchar(*s); } -- cgit