gendwarfksyms: Add symbol versioning

Add a basic CRC32 implementation adapted from genksyms, and produce
matching output from symtypes strings in type_map.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

Author: samitolvanen

scripts/gendwarfksyms/Makefile

@@ -2,6 +2,7 @@ hostprogs-always-y += gendwarfksyms
 
 gendwarfksyms-objs += gendwarfksyms.o
 gendwarfksyms-objs += cache.o
+gendwarfksyms-objs += crc32.o
 gendwarfksyms-objs += die.o
 gendwarfksyms-objs += dwarf.o
 gendwarfksyms-objs += symbols.o

scripts/gendwarfksyms/crc32.c

@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Based on scripts/genksyms/genksyms.c, which has the following
+ * notice:
+ *
+ * Generate kernel symbol version hashes.
+ * Copyright 1996, 1997 Linux International.
+ *
+ * New implementation contributed by Richard Henderson <rth@tamu.edu>
+ * Based on original work by Bjorn Ekwall <bj0rn@blox.se>
+ *
+ * This file was part of the Linux modutils 2.4.22: moved back into the
+ * kernel sources by Rusty Russell/Kai Germaschewski.
+ */
+
+const unsigned int crctab32[] = {
+	0x00000000U, 0x77073096U, 0xee0e612cU, 0x990951baU, 0x076dc419U,
+	0x706af48fU, 0xe963a535U, 0x9e6495a3U, 0x0edb8832U, 0x79dcb8a4U,
+	0xe0d5e91eU, 0x97d2d988U, 0x09b64c2bU, 0x7eb17cbdU, 0xe7b82d07U,
+	0x90bf1d91U, 0x1db71064U, 0x6ab020f2U, 0xf3b97148U, 0x84be41deU,
+	0x1adad47dU, 0x6ddde4ebU, 0xf4d4b551U, 0x83d385c7U, 0x136c9856U,
+	0x646ba8c0U, 0xfd62f97aU, 0x8a65c9ecU, 0x14015c4fU, 0x63066cd9U,
+	0xfa0f3d63U, 0x8d080df5U, 0x3b6e20c8U, 0x4c69105eU, 0xd56041e4U,
+	0xa2677172U, 0x3c03e4d1U, 0x4b04d447U, 0xd20d85fdU, 0xa50ab56bU,
+	0x35b5a8faU, 0x42b2986cU, 0xdbbbc9d6U, 0xacbcf940U, 0x32d86ce3U,
+	0x45df5c75U, 0xdcd60dcfU, 0xabd13d59U, 0x26d930acU, 0x51de003aU,
+	0xc8d75180U, 0xbfd06116U, 0x21b4f4b5U, 0x56b3c423U, 0xcfba9599U,
+	0xb8bda50fU, 0x2802b89eU, 0x5f058808U, 0xc60cd9b2U, 0xb10be924U,
+	0x2f6f7c87U, 0x58684c11U, 0xc1611dabU, 0xb6662d3dU, 0x76dc4190U,
+	0x01db7106U, 0x98d220bcU, 0xefd5102aU, 0x71b18589U, 0x06b6b51fU,
+	0x9fbfe4a5U, 0xe8b8d433U, 0x7807c9a2U, 0x0f00f934U, 0x9609a88eU,
+	0xe10e9818U, 0x7f6a0dbbU, 0x086d3d2dU, 0x91646c97U, 0xe6635c01U,
+	0x6b6b51f4U, 0x1c6c6162U, 0x856530d8U, 0xf262004eU, 0x6c0695edU,
+	0x1b01a57bU, 0x8208f4c1U, 0xf50fc457U, 0x65b0d9c6U, 0x12b7e950U,
+	0x8bbeb8eaU, 0xfcb9887cU, 0x62dd1ddfU, 0x15da2d49U, 0x8cd37cf3U,
+	0xfbd44c65U, 0x4db26158U, 0x3ab551ceU, 0xa3bc0074U, 0xd4bb30e2U,
+	0x4adfa541U, 0x3dd895d7U, 0xa4d1c46dU, 0xd3d6f4fbU, 0x4369e96aU,
+	0x346ed9fcU, 0xad678846U, 0xda60b8d0U, 0x44042d73U, 0x33031de5U,
+	0xaa0a4c5fU, 0xdd0d7cc9U, 0x5005713cU, 0x270241aaU, 0xbe0b1010U,
+	0xc90c2086U, 0x5768b525U, 0x206f85b3U, 0xb966d409U, 0xce61e49fU,
+	0x5edef90eU, 0x29d9c998U, 0xb0d09822U, 0xc7d7a8b4U, 0x59b33d17U,
+	0x2eb40d81U, 0xb7bd5c3bU, 0xc0ba6cadU, 0xedb88320U, 0x9abfb3b6U,
+	0x03b6e20cU, 0x74b1d29aU, 0xead54739U, 0x9dd277afU, 0x04db2615U,
+	0x73dc1683U, 0xe3630b12U, 0x94643b84U, 0x0d6d6a3eU, 0x7a6a5aa8U,
+	0xe40ecf0bU, 0x9309ff9dU, 0x0a00ae27U, 0x7d079eb1U, 0xf00f9344U,
+	0x8708a3d2U, 0x1e01f268U, 0x6906c2feU, 0xf762575dU, 0x806567cbU,
+	0x196c3671U, 0x6e6b06e7U, 0xfed41b76U, 0x89d32be0U, 0x10da7a5aU,
+	0x67dd4accU, 0xf9b9df6fU, 0x8ebeeff9U, 0x17b7be43U, 0x60b08ed5U,
+	0xd6d6a3e8U, 0xa1d1937eU, 0x38d8c2c4U, 0x4fdff252U, 0xd1bb67f1U,
+	0xa6bc5767U, 0x3fb506ddU, 0x48b2364bU, 0xd80d2bdaU, 0xaf0a1b4cU,
+	0x36034af6U, 0x41047a60U, 0xdf60efc3U, 0xa867df55U, 0x316e8eefU,
+	0x4669be79U, 0xcb61b38cU, 0xbc66831aU, 0x256fd2a0U, 0x5268e236U,
+	0xcc0c7795U, 0xbb0b4703U, 0x220216b9U, 0x5505262fU, 0xc5ba3bbeU,
+	0xb2bd0b28U, 0x2bb45a92U, 0x5cb36a04U, 0xc2d7ffa7U, 0xb5d0cf31U,
+	0x2cd99e8bU, 0x5bdeae1dU, 0x9b64c2b0U, 0xec63f226U, 0x756aa39cU,
+	0x026d930aU, 0x9c0906a9U, 0xeb0e363fU, 0x72076785U, 0x05005713U,
+	0x95bf4a82U, 0xe2b87a14U, 0x7bb12baeU, 0x0cb61b38U, 0x92d28e9bU,
+	0xe5d5be0dU, 0x7cdcefb7U, 0x0bdbdf21U, 0x86d3d2d4U, 0xf1d4e242U,
+	0x68ddb3f8U, 0x1fda836eU, 0x81be16cdU, 0xf6b9265bU, 0x6fb077e1U,
+	0x18b74777U, 0x88085ae6U, 0xff0f6a70U, 0x66063bcaU, 0x11010b5cU,
+	0x8f659effU, 0xf862ae69U, 0x616bffd3U, 0x166ccf45U, 0xa00ae278U,
+	0xd70dd2eeU, 0x4e048354U, 0x3903b3c2U, 0xa7672661U, 0xd06016f7U,
+	0x4969474dU, 0x3e6e77dbU, 0xaed16a4aU, 0xd9d65adcU, 0x40df0b66U,
+	0x37d83bf0U, 0xa9bcae53U, 0xdebb9ec5U, 0x47b2cf7fU, 0x30b5ffe9U,
+	0xbdbdf21cU, 0xcabac28aU, 0x53b39330U, 0x24b4a3a6U, 0xbad03605U,
+	0xcdd70693U, 0x54de5729U, 0x23d967bfU, 0xb3667a2eU, 0xc4614ab8U,
+	0x5d681b02U, 0x2a6f2b94U, 0xb40bbe37U, 0xc30c8ea1U, 0x5a05df1bU,
+	0x2d02ef8dU
+};

scripts/gendwarfksyms/crc32.h

@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Based on scripts/genksyms/genksyms.c, which has the following
+ * notice:
+ *
+ * Generate kernel symbol version hashes.
+ * Copyright 1996, 1997 Linux International.
+ *
+ * New implementation contributed by Richard Henderson <rth@tamu.edu>
+ * Based on original work by Bjorn Ekwall <bj0rn@blox.se>
+ *
+ * This file was part of the Linux modutils 2.4.22: moved back into the
+ * kernel sources by Rusty Russell/Kai Germaschewski.
+ */
+
+#ifndef __CRC32_H
+#define __CRC32_H
+
+extern const unsigned int crctab32[];
+
+static inline unsigned long partial_crc32_one(unsigned char c,
+					      unsigned long crc)
+{
+	return crctab32[(crc ^ c) & 0xff] ^ (crc >> 8);
+}
+
+static inline unsigned long partial_crc32(const char *s, unsigned long crc)
+{
+	while (*s)
+		crc = partial_crc32_one(*s++, crc);
+	return crc;
+}
+
+#endif /* __CRC32_H */

scripts/gendwarfksyms/dwarf.c

@@ -693,18 +693,51 @@ static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
 /*
  * Exported symbol processing
  */
+static int get_symbol_cache(struct state *state, Dwarf_Die *die,
+			    struct die **cache)
+{
+	checkp(symbol_set_die(state->sym, die));
+	check(die_map_get(die, SYMBOL, cache));
+
+	if ((*cache)->state != INCOMPLETE)
+		return 1; /* We already processed a symbol for this DIE */
+
+	(*cache)->tag = dwarf_tag(die);
+	return 0;
+}
+
 static int process_subprogram(struct state *state, Dwarf_Die *die)
 {
-	check(__process_subroutine_type(state, NULL, die, "subprogram"));
-	state->sym->state = MAPPED;
+	struct die *cache;
+
+	if (checkp(get_symbol_cache(state, die, &cache)) > 0)
+		return 0;
+
+	debug("%s", state->sym->name);
+	check(__process_subroutine_type(state, cache, die, "subprogram"));
+	cache->state = SYMBOL;
+
+	if (dump_dies)
+		fputs("\n", stderr);
+
 	return 0;
 }
 
 static int process_variable(struct state *state, Dwarf_Die *die)
 {
-	check(process(state, NULL, "variable "));
-	check(process_type_attr(state, NULL, die));
-	state->sym->state = MAPPED;
+	struct die *cache;
+
+	if (checkp(get_symbol_cache(state, die, &cache)) > 0)
+		return 0;
+
+	debug("%s", state->sym->name);
+	check(process(state, cache, "variable "));
+	check(process_type_attr(state, cache, die));
+	cache->state = SYMBOL;
+
+	if (dump_dies)
+		fputs("\n", stderr);
+
 	return 0;
 }
 
@@ -750,7 +783,6 @@ static int process_exported_symbols(struct state *state, struct die *cache,
 		if (!is_export_symbol(state, die))
 			return 0;
 
-		debug("%s", state->sym->name);
 		state_init(state);
 
 		if (is_symbol_ptr(get_name(&state->die)))
@@ -760,9 +792,6 @@ static int process_exported_symbols(struct state *state, struct die *cache,
 		else
 			check(process_variable(state, &state->die));
 
-		if (dump_dies)
-			fputs("\n", stderr);
-
 		cache_clear_expanded(&state->expansion_cache);
 		return 0;
 	default:

scripts/gendwarfksyms/gendwarfksyms.c

@@ -22,6 +22,8 @@ bool dump_dies;
 bool dump_die_map;
 /* Print out type_map contents */
 bool dump_types;
+/* Print out expanded type strings used for version calculations */
+bool dump_versions;
 /* Produce a symtypes file */
 bool symtypes;
 static const char *symtypes_file;
@@ -35,6 +37,7 @@ static const struct {
 	{ "--dump-dies", &dump_dies, NULL },
 	{ "--dump-die-map", &dump_die_map, NULL },
 	{ "--dump-types", &dump_types, NULL },
+	{ "--dump-versions", &dump_versions, NULL },
 	{ "--symtypes", &symtypes, &symtypes_file },
 };
 
@@ -109,9 +112,10 @@ static int process_modules(Dwfl_Module *mod, void **userdata, const char *name,
 	} while (cu);
 
 	/*
-	 * Use die_map to expand type strings and write them to `symfile`.
+	 * Use die_map to expand type strings, write them to `symfile`, and
+	 * calculate symbol versions.
 	 */
-	check(generate_symtypes(symfile));
+	check(generate_symtypes_and_versions(symfile));
 	die_map_free();
 
 	return DWARF_CB_OK;
@@ -187,5 +191,7 @@ int main(int argc, const char **argv)
 	if (symfile)
 		fclose(symfile);
 
+	symbol_print_versions();
+
 	return 0;
 }

scripts/gendwarfksyms/gendwarfksyms.h

@@ -23,6 +23,7 @@ extern bool debug;
 extern bool dump_dies;
 extern bool dump_die_map;
 extern bool dump_types;
+extern bool dump_versions;
 extern bool symtypes;
 
 #define MAX_INPUT_FILES 128
@@ -95,7 +96,7 @@ extern bool symtypes;
 #define SYMBOL_DECLONLY_PREFIX "__gendwarfksyms_declonly_"
 #define SYMBOL_DECLONLY_PREFIX_LEN (sizeof(SYMBOL_DECLONLY_PREFIX) - 1)
 
-enum symbol_state { UNPROCESSED, MAPPED };
+enum symbol_state { UNPROCESSED, MAPPED, PROCESSED };
 
 struct symbol_addr {
 	uint32_t section;
@@ -119,18 +120,25 @@ struct symbol {
 	struct hlist_node name_hash;
 	enum symbol_state state;
 	uintptr_t die_addr;
+	unsigned long crc;
 };
 
+typedef int (*symbol_callback_t)(struct symbol *, void *arg);
+
 extern bool is_symbol_ptr(const char *name);
 extern int symbol_read_exports(FILE *file);
 extern int symbol_read_symtab(int fd);
 extern struct symbol *symbol_get_unprocessed(const char *name);
+extern int symbol_set_die(struct symbol *sym, Dwarf_Die *die);
+extern int symbol_set_crc(struct symbol *sym, unsigned long crc);
+extern int symbol_for_each(symbol_callback_t func, void *arg);
+extern void symbol_print_versions(void);
 
 /*
  * die.c
  */
 
-enum die_state { INCOMPLETE, UNEXPANDED, COMPLETE, LAST = COMPLETE };
+enum die_state { INCOMPLETE, UNEXPANDED, COMPLETE, SYMBOL, LAST = SYMBOL };
 enum die_fragment_type { EMPTY, STRING, LINEBREAK, DIE };
 
 struct die_fragment {
@@ -154,6 +162,7 @@ static inline const char *die_state_name(enum die_state state)
 	CASE_CONST_TO_STR(INCOMPLETE)
 	CASE_CONST_TO_STR(UNEXPANDED)
 	CASE_CONST_TO_STR(COMPLETE)
+	CASE_CONST_TO_STR(SYMBOL)
 	}
 }
 
@@ -239,6 +248,6 @@ extern int process_module(Dwfl_Module *mod, Dwarf *dbg, Dwarf_Die *cudie);
  * types.c
  */
 
-extern int generate_symtypes(FILE *file);
+extern int generate_symtypes_and_versions(FILE *file);
 
 #endif /* __GENDWARFKSYMS_H */

scripts/gendwarfksyms/symbols.c

@@ -84,6 +84,38 @@ static int for_each(const char *name, bool name_only, symbol_callback_t func,
 	return 0;
 }
 
+static int set_crc(struct symbol *sym, void *data)
+{
+	unsigned long *crc = data;
+
+	if (sym->state == PROCESSED && sym->crc != *crc)
+		warn("overriding version for symbol %s (crc %lx vs. %lx)",
+		     sym->name, sym->crc, *crc);
+
+	sym->state = PROCESSED;
+	sym->crc = *crc;
+	return 0;
+}
+
+int symbol_set_crc(struct symbol *sym, unsigned long crc)
+{
+	if (checkp(for_each(sym->name, false, set_crc, &crc)) > 0)
+		return 0;
+	return -1;
+}
+
+static int set_die(struct symbol *sym, void *data)
+{
+	sym->die_addr = (uintptr_t)((Dwarf_Die *)data)->addr;
+	sym->state = MAPPED;
+	return 0;
+}
+
+int symbol_set_die(struct symbol *sym, Dwarf_Die *die)
+{
+	return checkp(for_each(sym->name, false, set_die, die));
+}
+
 static bool is_exported(const char *name)
 {
 	return checkp(for_each(name, true, NULL, NULL)) > 0;
@@ -151,6 +183,19 @@ struct symbol *symbol_get_unprocessed(const char *name)
 	return sym;
 }
 
+int symbol_for_each(symbol_callback_t func, void *arg)
+{
+	struct hlist_node *tmp;
+	struct symbol *sym;
+	int i;
+
+	hash_for_each_safe(symbol_names, i, tmp, sym, name_hash) {
+		check(func(sym, arg));
+	}
+
+	return 0;
+}
+
 typedef int (*elf_symbol_callback_t)(const char *name, GElf_Sym *sym,
 				     Elf32_Word xndx, void *arg);
 
@@ -264,3 +309,23 @@ int symbol_read_symtab(int fd)
 {
 	return elf_for_each_symbol(fd, process_symbol, NULL);
 }
+
+void symbol_print_versions(void)
+{
+	struct hlist_node *tmp;
+	struct symbol *sym;
+	int i;
+
+	hash_for_each_safe(symbol_names, i, tmp, sym, name_hash) {
+		if (sym->state != PROCESSED)
+			warn("no information for symbol %s", sym->name);
+
+		printf("#SYMVER %s 0x%08lx\n", sym->name, sym->crc);
+
+		free((void *)sym->name);
+		free(sym);
+	}
+
+	hash_init(symbol_addrs);
+	hash_init(symbol_names);
+}