Merge branch 'bpftool-improvements-kallsymfix'

Daniel Borkmann says:

====================
This work adds correlation of maps and calls into the bpftool
xlated dump in order to help debugging and introspection of
loaded BPF progs. First patch makes kallsyms work on subprogs
with bpf calls, and second implements the actual correlation.
Details and example output can be found in the 2nd patch.
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 172 insertions, 9 deletions

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 037484ceaeaf..42ee8892549c 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -401,6 +401,88 @@ static int do_show(int argc, char **argv)
 	return err;
 }
 
+#define SYM_MAX_NAME	256
+
+struct kernel_sym {
+	unsigned long address;
+	char name[SYM_MAX_NAME];
+};
+
+struct dump_data {
+	unsigned long address_call_base;
+	struct kernel_sym *sym_mapping;
+	__u32 sym_count;
+	char scratch_buff[SYM_MAX_NAME];
+};
+
+static int kernel_syms_cmp(const void *sym_a, const void *sym_b)
+{
+	return ((struct kernel_sym *)sym_a)->address -
+	       ((struct kernel_sym *)sym_b)->address;
+}
+
+static void kernel_syms_load(struct dump_data *dd)
+{
+	struct kernel_sym *sym;
+	char buff[256];
+	void *tmp, *address;
+	FILE *fp;
+
+	fp = fopen("/proc/kallsyms", "r");
+	if (!fp)
+		return;
+
+	while (!feof(fp)) {
+		if (!fgets(buff, sizeof(buff), fp))
+			break;
+		tmp = realloc(dd->sym_mapping,
+			      (dd->sym_count + 1) *
+			      sizeof(*dd->sym_mapping));
+		if (!tmp) {
+out:
+			free(dd->sym_mapping);
+			dd->sym_mapping = NULL;
+			fclose(fp);
+			return;
+		}
+		dd->sym_mapping = tmp;
+		sym = &dd->sym_mapping[dd->sym_count];
+		if (sscanf(buff, "%p %*c %s", &address, sym->name) != 2)
+			continue;
+		sym->address = (unsigned long)address;
+		if (!strcmp(sym->name, "__bpf_call_base")) {
+			dd->address_call_base = sym->address;
+			/* sysctl kernel.kptr_restrict was set */
+			if (!sym->address)
+				goto out;
+		}
+		if (sym->address)
+			dd->sym_count++;
+	}
+
+	fclose(fp);
+
+	qsort(dd->sym_mapping, dd->sym_count,
+	      sizeof(*dd->sym_mapping), kernel_syms_cmp);
+}
+
+static void kernel_syms_destroy(struct dump_data *dd)
+{
+	free(dd->sym_mapping);
+}
+
+static struct kernel_sym *kernel_syms_search(struct dump_data *dd,
+					     unsigned long key)
+{
+	struct kernel_sym sym = {
+		.address = key,
+	};
+
+	return dd->sym_mapping ?
+	       bsearch(&sym, dd->sym_mapping, dd->sym_count,
+		       sizeof(*dd->sym_mapping), kernel_syms_cmp) : NULL;
+}
+
 static void print_insn(struct bpf_verifier_env *env, const char *fmt, ...)
 {
 	va_list args;
@@ -410,8 +492,71 @@ static void print_insn(struct bpf_verifier_env *env, const char *fmt, ...)
 	va_end(args);
 }
 
-static void dump_xlated_plain(void *buf, unsigned int len, bool opcodes)
+static const char *print_call_pcrel(struct dump_data *dd,
+				    struct kernel_sym *sym,
+				    unsigned long address,
+				    const struct bpf_insn *insn)
 {
+	if (sym)
+		snprintf(dd->scratch_buff, sizeof(dd->scratch_buff),
+			 "%+d#%s", insn->off, sym->name);
+	else
+		snprintf(dd->scratch_buff, sizeof(dd->scratch_buff),
+			 "%+d#0x%lx", insn->off, address);
+	return dd->scratch_buff;
+}
+
+static const char *print_call_helper(struct dump_data *dd,
+				     struct kernel_sym *sym,
+				     unsigned long address)
+{
+	if (sym)
+		snprintf(dd->scratch_buff, sizeof(dd->scratch_buff),
+			 "%s", sym->name);
+	else
+		snprintf(dd->scratch_buff, sizeof(dd->scratch_buff),
+			 "0x%lx", address);
+	return dd->scratch_buff;
+}
+
+static const char *print_call(void *private_data,
+			      const struct bpf_insn *insn)
+{
+	struct dump_data *dd = private_data;
+	unsigned long address = dd->address_call_base + insn->imm;
+	struct kernel_sym *sym;
+
+	sym = kernel_syms_search(dd, address);
+	if (insn->src_reg == BPF_PSEUDO_CALL)
+		return print_call_pcrel(dd, sym, address, insn);
+	else
+		return print_call_helper(dd, sym, address);
+}
+
+static const char *print_imm(void *private_data,
+			     const struct bpf_insn *insn,
+			     __u64 full_imm)
+{
+	struct dump_data *dd = private_data;
+
+	if (insn->src_reg == BPF_PSEUDO_MAP_FD)
+		snprintf(dd->scratch_buff, sizeof(dd->scratch_buff),
+			 "map[id:%u]", insn->imm);
+	else
+		snprintf(dd->scratch_buff, sizeof(dd->scratch_buff),
+			 "0x%llx", (unsigned long long)full_imm);
+	return dd->scratch_buff;
+}
+
+static void dump_xlated_plain(struct dump_data *dd, void *buf,
+			      unsigned int len, bool opcodes)
+{
+	const struct bpf_insn_cbs cbs = {
+		.cb_print	= print_insn,
+		.cb_call	= print_call,
+		.cb_imm		= print_imm,
+		.private_data	= dd,
+	};
 	struct bpf_insn *insn = buf;
 	bool double_insn = false;
 	unsigned int i;
@@ -425,7 +570,7 @@ static void dump_xlated_plain(void *buf, unsigned int len, bool opcodes)
 		double_insn = insn[i].code == (BPF_LD | BPF_IMM | BPF_DW);
 
 		printf("% 4d: ", i);
-		print_bpf_insn(print_insn, NULL, insn + i, true);
+		print_bpf_insn(&cbs, NULL, insn + i, true);
 
 		if (opcodes) {
 			printf("       ");
@@ -454,8 +599,15 @@ static void print_insn_json(struct bpf_verifier_env *env, const char *fmt, ...)
 	va_end(args);
 }
 
-static void dump_xlated_json(void *buf, unsigned int len, bool opcodes)
+static void dump_xlated_json(struct dump_data *dd, void *buf,
+			     unsigned int len, bool opcodes)
 {
+	const struct bpf_insn_cbs cbs = {
+		.cb_print	= print_insn_json,
+		.cb_call	= print_call,
+		.cb_imm		= print_imm,
+		.private_data	= dd,
+	};
 	struct bpf_insn *insn = buf;
 	bool double_insn = false;
 	unsigned int i;
@@ -470,7 +622,7 @@ static void dump_xlated_json(void *buf, unsigned int len, bool opcodes)
 
 		jsonw_start_object(json_wtr);
 		jsonw_name(json_wtr, "disasm");
-		print_bpf_insn(print_insn_json, NULL, insn + i, true);
+		print_bpf_insn(&cbs, NULL, insn + i, true);
 
 		if (opcodes) {
 			jsonw_name(json_wtr, "opcodes");
@@ -505,6 +657,7 @@ static void dump_xlated_json(void *buf, unsigned int len, bool opcodes)
 static int do_dump(int argc, char **argv)
 {
 	struct bpf_prog_info info = {};
+	struct dump_data dd = {};
 	__u32 len = sizeof(info);
 	unsigned int buf_size;
 	char *filepath = NULL;
@@ -592,6 +745,14 @@ static int do_dump(int argc, char **argv)
 		goto err_free;
 	}
 
+	if ((member_len == &info.jited_prog_len &&
+	     info.jited_prog_insns == 0) ||
+	    (member_len == &info.xlated_prog_len &&
+	     info.xlated_prog_insns == 0)) {
+		p_err("error retrieving insn dump: kernel.kptr_restrict set?");
+		goto err_free;
+	}
+
 	if (filepath) {
 		fd = open(filepath, O_WRONLY | O_CREAT | O_TRUNC, 0600);
 		if (fd < 0) {
@@ -608,17 +769,19 @@ static int do_dump(int argc, char **argv)
 			goto err_free;
 		}
 	} else {
-		if (member_len == &info.jited_prog_len)
+		if (member_len == &info.jited_prog_len) {
 			disasm_print_insn(buf, *member_len, opcodes);
-		else
+		} else {
+			kernel_syms_load(&dd);
 			if (json_output)
-				dump_xlated_json(buf, *member_len, opcodes);
+				dump_xlated_json(&dd, buf, *member_len, opcodes);
 			else
-				dump_xlated_plain(buf, *member_len, opcodes);
+				dump_xlated_plain(&dd, buf, *member_len, opcodes);
+			kernel_syms_destroy(&dd);
+		}
 	}
 
 	free(buf);
-
 	return 0;
 
 err_free: