Re: [PATCH v2 13/19] gendwarfksyms: Add symtypes output
From: Petr Pavlu
Date: Tue Sep 10 2024 - 10:59:07 EST
On 8/15/24 19:39, Sami Tolvanen wrote:
> Add support for producing genksyms-style symtypes files. Process
> die_map to find the longest expansions for each type, and use symtypes
> references in type definitions. The basic file format is similar to
> genksyms, with two notable exceptions:
>
> 1. Type names with spaces (common with Rust) in references are
> wrapped in single quotes. E.g.:
>
> s#'core::result::Result<u8, core::num::error::ParseIntError>'
>
> 2. The actual type definition is the simple parsed DWARF format we
> output with --dump-dies, not the preprocessed C-style format
> genksyms produces.
Thank you for adding this output to the tool.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
> ---
> scripts/gendwarfksyms/Makefile | 1 +
> scripts/gendwarfksyms/die.c | 13 +
> scripts/gendwarfksyms/dwarf.c | 14 +-
> scripts/gendwarfksyms/gendwarfksyms.c | 28 +-
> scripts/gendwarfksyms/gendwarfksyms.h | 21 +-
> scripts/gendwarfksyms/symbols.c | 11 +-
> scripts/gendwarfksyms/types.c | 439 ++++++++++++++++++++++++++
> 7 files changed, 517 insertions(+), 10 deletions(-)
> create mode 100644 scripts/gendwarfksyms/types.c
>
> diff --git a/scripts/gendwarfksyms/Makefile b/scripts/gendwarfksyms/Makefile
> index 681b42441840..4866a2fd0e46 100644
> --- a/scripts/gendwarfksyms/Makefile
> +++ b/scripts/gendwarfksyms/Makefile
> @@ -5,6 +5,7 @@ gendwarfksyms-objs += cache.o
> gendwarfksyms-objs += die.o
> gendwarfksyms-objs += dwarf.o
> gendwarfksyms-objs += symbols.o
> +gendwarfksyms-objs += types.o
>
> HOST_EXTRACFLAGS := -I $(srctree)/tools/include
> HOSTLDLIBS_gendwarfksyms := -ldw -lelf
> diff --git a/scripts/gendwarfksyms/die.c b/scripts/gendwarfksyms/die.c
> index fdd52df88fdd..e40f04b70f7f 100644
> --- a/scripts/gendwarfksyms/die.c
> +++ b/scripts/gendwarfksyms/die.c
> @@ -85,6 +85,19 @@ static void reset_die(struct die *cd)
> cd->list = NULL;
> }
>
> +int die_map_for_each(die_map_callback_t func, void *arg)
> +{
> + struct die *cd;
> + struct hlist_node *tmp;
> + int i;
> +
> + hash_for_each_safe(die_map, i, tmp, cd, hash) {
> + check(func(cd, arg));
> + }
> +
> + return 0;
> +}
> +
> void die_map_free(void)
> {
> struct hlist_node *tmp;
> diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
> index 9bca21a71639..62241cc97a76 100644
> --- a/scripts/gendwarfksyms/dwarf.c
> +++ b/scripts/gendwarfksyms/dwarf.c
> @@ -60,11 +60,11 @@ static bool is_export_symbol(struct state *state, Dwarf_Die *die)
> if (get_ref_die_attr(die, DW_AT_abstract_origin, &origin))
> source = &origin;
>
> - state->sym = symbol_get(get_name(die));
> + state->sym = symbol_get_unprocessed(get_name(die));
>
> /* Look up using the origin name if there are no matches. */
> if (!state->sym && source != die)
> - state->sym = symbol_get(get_name(source));
> + state->sym = symbol_get_unprocessed(get_name(source));
>
> state->die = *source;
> return !!state->sym;
> @@ -384,6 +384,7 @@ static int process_subroutine_type(struct state *state, struct die *cache,
> return check(__process_subroutine_type(state, cache, die,
> "subroutine_type"));
> }
> +
> static int process_variant_type(struct state *state, struct die *cache,
> Dwarf_Die *die)
> {
> @@ -695,14 +696,16 @@ static int process_type(struct state *state, struct die *parent, Dwarf_Die *die)
> static int process_subprogram(struct state *state, Dwarf_Die *die)
> {
> check(__process_subroutine_type(state, NULL, die, "subprogram"));
> - return check(process(state, NULL, ";\n"));
> + state->sym->state = MAPPED;
> + return 0;
> }
>
> static int process_variable(struct state *state, Dwarf_Die *die)
> {
> check(process(state, NULL, "variable "));
> check(process_type_attr(state, NULL, die));
> - return check(process(state, NULL, ";\n"));
> + state->sym->state = MAPPED;
> + return 0;
> }
>
> static int process_symbol_ptr(struct state *state, Dwarf_Die *die)
> @@ -757,6 +760,9 @@ 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:
> diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
> index 1349e592783b..6a219a54c342 100644
> --- a/scripts/gendwarfksyms/gendwarfksyms.c
> +++ b/scripts/gendwarfksyms/gendwarfksyms.c
> @@ -20,6 +20,11 @@ bool debug;
> bool dump_dies;
> /* Print out inline debugging information about die_map changes */
> bool dump_die_map;
> +/* Print out type_map contents */
> +bool dump_types;
> +/* Produce a symtypes file */
> +bool symtypes;
> +static const char *symtypes_file;
>
> static const struct {
> const char *arg;
> @@ -29,6 +34,8 @@ static const struct {
> { "--debug", &debug, NULL },
> { "--dump-dies", &dump_dies, NULL },
> { "--dump-die-map", &dump_die_map, NULL },
> + { "--dump-types", &dump_types, NULL },
> + { "--symtypes", &symtypes, &symtypes_file },
> };
>
> static int usage(void)
> @@ -79,6 +86,7 @@ static int process_modules(Dwfl_Module *mod, void **userdata, const char *name,
> Dwarf_Die cudie;
> Dwarf_CU *cu = NULL;
> Dwarf *dbg;
> + FILE *symfile = arg;
> int res;
>
> debug("%s", name);
> @@ -100,6 +108,10 @@ static int process_modules(Dwfl_Module *mod, void **userdata, const char *name,
> check(process_module(mod, dbg, &cudie));
> } while (cu);
>
> + /*
> + * Use die_map to expand type strings and write them to `symfile`.
> + */
> + check(generate_symtypes(symfile));
> die_map_free();
>
> return DWARF_CB_OK;
> @@ -112,6 +124,7 @@ static const Dwfl_Callbacks callbacks = {
>
> int main(int argc, const char **argv)
> {
> + FILE *symfile = NULL;
> unsigned int n;
>
> if (parse_options(argc, argv) < 0)
> @@ -122,6 +135,16 @@ int main(int argc, const char **argv)
>
> check(symbol_read_exports(stdin));
>
> + if (symtypes_file) {
> + symfile = fopen(symtypes_file, "w+");
The file is sufficient to open only for writing.
> +
> + if (!symfile) {
> + error("fopen failed for '%s': %s", symtypes_file,
> + strerror(errno));
> + return -1;
> + }
> + }
> +
> for (n = 0; n < object_count; n++) {
> Dwfl *dwfl;
> int fd;
> @@ -151,7 +174,7 @@ int main(int argc, const char **argv)
>
> dwfl_report_end(dwfl, NULL, NULL);
>
> - if (dwfl_getmodules(dwfl, &process_modules, NULL, 0)) {
> + if (dwfl_getmodules(dwfl, &process_modules, symfile, 0)) {
> error("dwfl_getmodules failed for '%s'",
> object_files[n]);
> return -1;
> @@ -161,5 +184,8 @@ int main(int argc, const char **argv)
> close(fd);
> }
>
> + if (symfile)
> + fclose(symfile);
> +
> return 0;
> }
The fclose() call should be wrapped in check() to catch a situation when
flushing the stream potentially failed.
> diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
> index 7cd907e3d5e3..6edbd6478e0f 100644
> --- a/scripts/gendwarfksyms/gendwarfksyms.h
> +++ b/scripts/gendwarfksyms/gendwarfksyms.h
> @@ -22,6 +22,8 @@
> extern bool debug;
> extern bool dump_dies;
> extern bool dump_die_map;
> +extern bool dump_types;
> +extern bool symtypes;
>
> #define MAX_INPUT_FILES 128
>
> @@ -89,6 +91,12 @@ extern bool dump_die_map;
> #define SYMBOL_PTR_PREFIX "__gendwarfksyms_ptr_"
> #define SYMBOL_PTR_PREFIX_LEN (sizeof(SYMBOL_PTR_PREFIX) - 1)
>
> +/* See dwarf.c:is_declaration */
> +#define SYMBOL_DECLONLY_PREFIX "__gendwarfksyms_declonly_"
> +#define SYMBOL_DECLONLY_PREFIX_LEN (sizeof(SYMBOL_DECLONLY_PREFIX) - 1)
Nit: These defines should go into the patch 15/19 "gendwarfksyms: Add
support for declaration-only data structures".
> +
> +enum symbol_state { UNPROCESSED, MAPPED };
> +
> struct symbol_addr {
> uint32_t section;
> Elf64_Addr address;
> @@ -109,12 +117,14 @@ struct symbol {
> struct symbol_addr addr;
> struct hlist_node addr_hash;
> struct hlist_node name_hash;
> + enum symbol_state state;
> + uintptr_t die_addr;
> };
>
> 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(const char *name);
> +extern struct symbol *symbol_get_unprocessed(const char *name);
>
> /*
> * die.c
> @@ -157,12 +167,15 @@ struct die {
> struct hlist_node hash;
> };
>
> +typedef int (*die_map_callback_t)(struct die *, void *arg);
> +
> extern int __die_map_get(uintptr_t addr, enum die_state state,
> struct die **res);
> extern int die_map_get(Dwarf_Die *die, enum die_state state, struct die **res);
> extern int die_map_add_string(struct die *pd, const char *str);
> extern int die_map_add_linebreak(struct die *pd, int linebreak);
> extern int die_map_add_die(struct die *pd, struct die *child);
> +extern int die_map_for_each(die_map_callback_t func, void *arg);
> extern void die_map_free(void);
>
> /*
> @@ -222,4 +235,10 @@ extern int process_die_container(struct state *state, struct die *cache,
>
> extern int process_module(Dwfl_Module *mod, Dwarf *dbg, Dwarf_Die *cudie);
>
> +/*
> + * types.c
> + */
> +
> +extern int generate_symtypes(FILE *file);
> +
> #endif /* __GENDWARFKSYMS_H */
> diff --git a/scripts/gendwarfksyms/symbols.c b/scripts/gendwarfksyms/symbols.c
> index d6d016458ae1..8cc04e6295a7 100644
> --- a/scripts/gendwarfksyms/symbols.c
> +++ b/scripts/gendwarfksyms/symbols.c
> @@ -117,6 +117,7 @@ int symbol_read_exports(FILE *file)
>
> sym->name = name;
> sym->addr.section = SHN_UNDEF;
> + sym->state = UNPROCESSED;
> name = NULL;
>
> hash_add(symbol_names, &sym->name_hash, name_hash(sym->name));
> @@ -132,19 +133,21 @@ int symbol_read_exports(FILE *file)
> return 0;
> }
>
> -static int get_symbol(struct symbol *sym, void *arg)
> +static int get_unprocessed(struct symbol *sym, void *arg)
> {
> struct symbol **res = arg;
>
> - *res = sym;
> + if (sym->state == UNPROCESSED)
> + *res = sym;
> +
> return 0;
> }
>
> -struct symbol *symbol_get(const char *name)
> +struct symbol *symbol_get_unprocessed(const char *name)
> {
> struct symbol *sym = NULL;
>
> - for_each(name, false, get_symbol, &sym);
> + for_each(name, false, get_unprocessed, &sym);
> return sym;
> }
>
> diff --git a/scripts/gendwarfksyms/types.c b/scripts/gendwarfksyms/types.c
> new file mode 100644
> index 000000000000..7b9997d8322d
> --- /dev/null
> +++ b/scripts/gendwarfksyms/types.c
> @@ -0,0 +1,439 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2024 Google LLC
> + */
> +
> +#include "gendwarfksyms.h"
> +#include "crc32.h"
> +
> +static struct expansion_cache expansion_cache;
> +
> +/*
> + * A simple linked list of shared or owned strings to avoid copying strings
> + * around when not necessary.
> + */
> +struct type_list {
> + const char *str;
> + void *owned;
> + struct type_list *next;
> +};
> +
> +static struct type_list *type_list_alloc(void)
> +{
> + struct type_list *list;
> +
> + list = calloc(1, sizeof(struct type_list));
> + if (!list)
> + error("calloc failed");
> +
> + return list;
> +}
> +
> +static void type_list_free(struct type_list *list)
> +{
> + struct type_list *tmp;
> +
> + while (list) {
> + if (list->owned)
> + free(list->owned);
> +
> + tmp = list;
> + list = list->next;
> + free(tmp);
> + }
> +}
> +
> +static int type_list_append(struct type_list *list, const char *s, void *owned)
> +{
> + if (!list || !s)
> + return 0;
> +
> + while (list->next)
> + list = list->next;
> +
> + if (list->str) {
> + list->next = type_list_alloc();
> +
> + if (!list->next) {
> + error("type_list_alloc failed");
> + return -1;
> + }
> +
> + list = list->next;
> + }
> +
> + list->str = s;
> + list->owned = owned;
> +
> + return strlen(list->str);
> +}
> +
> +static int type_list_write(struct type_list *list, FILE *file)
> +{
> + while (list) {
> + if (list->str)
> + checkp(fputs(list->str, file));
> + list = list->next;
> + }
> +
> + return 0;
> +}
> +
> +/*
> + * An expanded type string in symtypes format.
> + */
> +struct type_expansion {
> + char *name;
> + struct type_list *expanded;
> + struct type_list *last;
> + size_t len;
> + struct hlist_node hash;
> +};
I found the manipulation of type_expansion.expanded and
type_expansion.last somewhat strange.
The list starts already with one element in type_expansion_init(). This
is apparently to make the last pointer valid. This element is however
empty and gets only assigned on the first call to type_list_append().
Other elements are then added normally, always assigned.
Perhaps consider using a regular list implementation, similarly to what
was discussed under the patch 06/19 "gendwarfksyms: Add a cache for
processed DIEs".
> +
> +static int type_expansion_init(struct type_expansion *type, bool alloc)
> +{
> + memset(type, 0, sizeof(struct type_expansion));
> + if (alloc) {
> + type->expanded = type_list_alloc();
> + if (!type->expanded)
> + return -1;
> +
> + type->last = type->expanded;
> + }
> + return 0;
> +}
> +
> +static inline void type_expansion_free(struct type_expansion *type)
> +{
> + free(type->name);
> + type_list_free(type->expanded);
> + type_expansion_init(type, false);
> +}
> +
> +static int type_expansion_append(struct type_expansion *type, const char *s,
> + void *owned)
> +{
> + type->len += checkp(type_list_append(type->last, s, owned));
> +
> + if (type->last->next)
> + type->last = type->last->next;
> +
> + return 0;
> +}
> +
> +/*
> + * type_map -- the longest expansions for each type.
> + *
> + * const char *name -> struct type_expansion *
> + */
> +#define TYPE_HASH_BITS 16
> +static DEFINE_HASHTABLE(type_map, TYPE_HASH_BITS);
> +
> +static int type_map_get(const char *name, struct type_expansion **res)
> +{
> + struct type_expansion *e;
> +
> + hash_for_each_possible(type_map, e, hash, name_hash(name)) {
> + if (!strcmp(name, e->name)) {
> + *res = e;
> + return 0;
> + }
> + }
> +
> + return -1;
> +}
> +
> +static int type_map_add(const char *name, struct type_expansion *type)
> +{
> + struct type_expansion *e;
> +
> + if (type_map_get(name, &e)) {
> + e = malloc(sizeof(struct type_expansion));
> + if (!e) {
> + error("malloc failed");
> + return -1;
> + }
> +
> + type_expansion_init(e, false);
> +
> + e->name = strdup(name);
> + if (!e->name) {
> + error("strdup failed");
> + return -1;
> + }
> +
> + hash_add(type_map, &e->hash, name_hash(e->name));
> +
> + if (dump_types)
> + debug("adding %s", e->name);
> + } else {
> + /* Use the longest available expansion */
> + if (type->len <= e->len)
> + return 0;
> +
> + type_list_free(e->expanded);
> +
> + if (dump_types)
> + debug("replacing %s", e->name);
> + }
> +
> + /* Take ownership of type->expanded */
> + e->expanded = type->expanded;
> + e->last = type->last;
> + e->len = type->len;
> + type->expanded = NULL;
> + type->last = NULL;
> + type->len = 0;
> +
> + if (dump_types) {
> + fputs(e->name, stderr);
> + fputs(" ", stderr);
> + type_list_write(e->expanded, stderr);
> + fputs("\n", stderr);
> + }
> +
> + return 0;
> +}
> +
> +static int type_map_write(FILE *file)
> +{
> + struct type_expansion *e;
> + struct hlist_node *tmp;
> + int i;
> +
> + if (!file)
> + return 0;
> +
> + hash_for_each_safe(type_map, i, tmp, e, hash) {
> + checkp(fputs(e->name, file));
> + checkp(fputs(" ", file));
> + type_list_write(e->expanded, file);
> + checkp(fputs("\n", file));
> + }
> +
> + return 0;
> +}
> +
> +static void type_map_free(void)
> +{
> + struct type_expansion *e;
> + struct hlist_node *tmp;
> + int i;
> +
> + hash_for_each_safe(type_map, i, tmp, e, hash) {
> + type_expansion_free(e);
> + free(e);
> + }
> +
> + hash_init(type_map);
> +}
> +
> +/*
> + * Type reference format: <prefix>#<name>, where prefix:
> + * s -> structure
> + * u -> union
> + * e -> enum
> + * t -> typedef
> + *
> + * Names with spaces are additionally wrapped in single quotes.
> + */
> +static inline bool is_type_prefix(const char *s)
> +{
> + return (s[0] == 's' || s[0] == 'u' || s[0] == 'e' || s[0] == 't') &&
> + s[1] == '#';
> +}
> +
> +static char get_type_prefix(int tag)
> +{
> + switch (tag) {
> + case DW_TAG_class_type:
> + case DW_TAG_structure_type:
> + return 's';
> + case DW_TAG_union_type:
> + return 'u';
> + case DW_TAG_enumeration_type:
> + return 'e';
> + case DW_TAG_typedef_type:
> + return 't';
> + default:
> + return 0;
> + }
> +}
> +
> +static char *get_type_name(struct die *cache)
> +{
> + const char *format;
> + char prefix;
> + char *name;
> + size_t len;
> +
> + if (cache->state == INCOMPLETE) {
> + warn("found incomplete cache entry: %p", cache);
> + return NULL;
> + }
> + if (!cache->fqn)
> + return NULL;
> +
> + prefix = get_type_prefix(cache->tag);
> + if (!prefix)
> + return NULL;
> +
> + /* <prefix>#<type_name>\0 */
> + len = 2 + strlen(cache->fqn) + 1;
> +
> + /* Wrap names with spaces in single quotes */
> + if (strstr(cache->fqn, " ")) {
> + format = "%c#'%s'";
> + len += 2;
> + } else {
> + format = "%c#%s";
> + }
> +
> + name = malloc(len);
> + if (!name) {
> + error("malloc failed");
> + return NULL;
> + }
> +
> + if (snprintf(name, len, format, prefix, cache->fqn) >= len) {
> + error("snprintf failed for '%s' (length %zu)", cache->fqn,
> + len);
> + free(name);
> + return NULL;
> + }
This could be quite simplified:
const char *quote = strstr(cache->fqn, " ") != NULL ? "'" : "";
if (asprintf(&name, "%c#%s%s%s", prefix, quote, cache->fqn, quote) < 0)
[...]
> +
> + return name;
> +}
> +
> +static int __type_expand(struct die *cache, struct type_expansion *type,
> + bool recursive);
> +
> +static int type_expand_child(struct die *cache, struct type_expansion *type,
> + bool recursive)
> +{
> + struct type_expansion child;
> + char *name;
> +
> + name = get_type_name(cache);
> + if (!name)
> + return check(__type_expand(cache, type, recursive));
> +
> + if (recursive && !__cache_was_expanded(&expansion_cache, cache->addr)) {
> + check(__cache_mark_expanded(&expansion_cache, cache->addr));
> + check(type_expansion_init(&child, true));
> + check(__type_expand(cache, &child, true));
> + check(type_map_add(name, &child));
> + type_expansion_free(&child);
> + }
> +
> + check(type_expansion_append(type, name, name));
> + return 0;
> +}
> +
> +static int __type_expand(struct die *cache, struct type_expansion *type,
> + bool recursive)
> +{
> + struct die_fragment *df = cache->list;
> + struct die *child;
> +
> + while (df) {
> + switch (df->type) {
> + case STRING:
> + check(type_expansion_append(type, df->data.str, NULL));
> + break;
> + case DIE:
> + /* Use a complete die_map expansion if available */
> + if (__die_map_get(df->data.addr, COMPLETE, &child) &&
> + __die_map_get(df->data.addr, UNEXPANDED, &child)) {
> + error("unknown child: %" PRIxPTR,
> + df->data.addr);
> + return -1;
> + }
> +
> + check(type_expand_child(child, type, recursive));
> + break;
> + case LINEBREAK:
> + /*
> + * Keep whitespace in the symtypes format, but avoid
> + * repeated spaces.
> + */
> + if (!df->next || df->next->type != LINEBREAK)
> + check(type_expansion_append(type, " ", NULL));
> + break;
> + default:
> + error("empty die_fragment in %p", cache);
> + return -1;
> + }
> +
> + df = df->next;
> + }
> +
> + return 0;
> +}
> +
> +static int type_expand(struct die *cache, struct type_expansion *type,
> + bool recursive)
> +{
> + check(type_expansion_init(type, true));
> + check(__type_expand(cache, type, recursive));
> + cache_clear_expanded(&expansion_cache);
> + return 0;
> +}
> +
> +static int expand_type(struct die *cache, void *arg)
> +{
> + struct type_expansion type;
> + char *name;
> +
> + /*
> + * Skip unexpanded die_map entries if there's a complete
> + * expansion available for this DIE.
> + */
> + if (cache->state == UNEXPANDED)
> + __die_map_get(cache->addr, COMPLETE, &cache);
> +
> + if (cache->mapped)
> + return 0;
> +
> + cache->mapped = true;
> +
> + name = get_type_name(cache);
> + if (!name)
> + return 0;
> +
> + debug("%s", name);
> + check(type_expand(cache, &type, true));
> + check(type_map_add(name, &type));
> +
> + type_expansion_free(&type);
> + free(name);
> +
> + return 0;
> +}
> +
> +int generate_symtypes(FILE *file)
> +{
> + hash_init(expansion_cache.cache);
> +
> + /*
> + * die_map processing:
> + *
> + * 1. die_map contains all types referenced in exported symbol
> + * signatures, but can contain duplicates just like the original
> + * DWARF, and some references may not be fully expanded depending
> + * on how far we processed the DIE tree for that specific symbol.
> + *
> + * For each die_map entry, find the longest available expansion,
> + * and add it to type_map.
> + */
> + check(die_map_for_each(expand_type, NULL));
> +
> + /*
> + * 2. If a symtypes file is requested, write type_map contents to
> + * the file.
> + */
> + check(type_map_write(file));
> + type_map_free();
> +
> + return 0;
> +}
--
Thanks,
Petr