objtool: Add a statistics mode

Have it print a few numbers which can be used to size the hashtables.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20200324160924.321381240@infradead.org

tools/objtool/builtin-check.c

@@ -17,7 +17,7 @@
 #include "builtin.h"
 #include "check.h"
 
-bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess;
+bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats;
 
 static const char * const check_usage[] = {
 	"objtool check [<options>] file.o",
@@ -31,6 +31,7 @@ const struct option check_options[] = {
 	OPT_BOOLEAN('m', "module", &module, "Indicates the object will be part of a kernel module"),
 	OPT_BOOLEAN('b', "backtrace", &backtrace, "unwind on error"),
 	OPT_BOOLEAN('a', "uaccess", &uaccess, "enable uaccess checking"),
+	OPT_BOOLEAN('s', "stats", &stats, "print statistics"),
 	OPT_END(),
 };
 

tools/objtool/builtin.h

@@ -8,7 +8,7 @@
 #include <subcmd/parse-options.h>
 
 extern const struct option check_options[];
-extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess;
+extern bool no_fp, no_unreachable, retpoline, module, backtrace, uaccess, stats;
 
 extern int cmd_check(int argc, const char **argv);
 extern int cmd_orc(int argc, const char **argv);

tools/objtool/check.c

@@ -239,6 +239,7 @@ static int decode_instructions(struct objtool_file *file)
 	struct symbol *func;
 	unsigned long offset;
 	struct instruction *insn;
+	unsigned long nr_insns = 0;
 	int ret;
 
 	for_each_sec(file, sec) {
@@ -274,6 +275,7 @@ static int decode_instructions(struct objtool_file *file)
 
 			hash_add(file->insn_hash, &insn->hash, insn->offset);
 			list_add_tail(&insn->list, &file->insn_list);
+			nr_insns++;
 		}
 
 		list_for_each_entry(func, &sec->symbol_list, list) {
@@ -291,6 +293,9 @@ static int decode_instructions(struct objtool_file *file)
 		}
 	}
 
+	if (stats)
+		printf("nr_insns: %lu\n", nr_insns);
+
 	return 0;
 
 err:

tools/objtool/elf.c

@@ -15,6 +15,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <errno.h>
+#include "builtin.h"
 
 #include "elf.h"
 #include "warn.h"
@@ -202,6 +203,9 @@ static int read_sections(struct elf *elf)
 		sec->len = sec->sh.sh_size;
 	}
 
+	if (stats)
+		printf("nr_sections: %lu\n", (unsigned long)sections_nr);
+
 	/* sanity check, one more call to elf_nextscn() should return NULL */
 	if (elf_nextscn(elf->elf, s)) {
 		WARN("section entry mismatch");
@@ -299,6 +303,9 @@ static int read_symbols(struct elf *elf)
 		hash_add(elf->symbol_hash, &sym->hash, sym->idx);
 	}
 
+	if (stats)
+		printf("nr_symbols: %lu\n", (unsigned long)symbols_nr);
+
 	/* Create parent/child links for any cold subfunctions */
 	list_for_each_entry(sec, &elf->sections, list) {
 		list_for_each_entry(sym, &sec->symbol_list, list) {
@@ -360,6 +367,7 @@ static int read_relas(struct elf *elf)
 	struct rela *rela;
 	int i;
 	unsigned int symndx;
+	unsigned long nr_rela, max_rela = 0, tot_rela = 0;
 
 	list_for_each_entry(sec, &elf->sections, list) {
 		if (sec->sh.sh_type != SHT_RELA)
@@ -374,6 +382,7 @@ static int read_relas(struct elf *elf)
 
 		sec->base->rela = sec;
 
+		nr_rela = 0;
 		for (i = 0; i < sec->sh.sh_size / sec->sh.sh_entsize; i++) {
 			rela = malloc(sizeof(*rela));
 			if (!rela) {
@@ -401,8 +410,15 @@ static int read_relas(struct elf *elf)
 
 			list_add_tail(&rela->list, &sec->rela_list);
 			hash_add(sec->rela_hash, &rela->hash, rela->offset);
-
+			nr_rela++;
 		}
+		max_rela = max(max_rela, nr_rela);
+		tot_rela += nr_rela;
+	}
+
+	if (stats) {
+		printf("max_rela: %lu\n", max_rela);
+		printf("tot_rela: %lu\n", tot_rela);
 	}
 
 	return 0;