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Message-ID: <CAK7LNAS=8uU-FUpVqh-z-=7LOfXxYcDQExKLvB+6qe8Fdq_51Q@mail.gmail.com>
Date: Thu, 29 Aug 2024 03:16:21 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Luis Chamberlain <mcgrof@...nel.org>, Miguel Ojeda <ojeda@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Matthew Maurer <mmaurer@...gle.com>,
Alex Gaynor <alex.gaynor@...il.com>, Wedson Almeida Filho <wedsonaf@...il.com>, Gary Guo <gary@...yguo.net>,
Petr Pavlu <petr.pavlu@...e.com>, Neal Gompa <neal@...pa.dev>, Hector Martin <marcan@...can.st>,
Janne Grunau <j@...nau.net>, Asahi Linux <asahi@...ts.linux.dev>, linux-kbuild@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org,
rust-for-linux@...r.kernel.org
Subject: Re: [PATCH v2 02/19] gendwarfksyms: Add symbol list handling
On Fri, Aug 16, 2024 at 2:39 AM Sami Tolvanen <samitolvanen@...gle.com> wrote:
>
> Add support for passing a list of exported symbols to gendwarfksyms
> via stdin and filter out non-exported symbols from the output.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> ---
> scripts/gendwarfksyms/Makefile | 1 +
> scripts/gendwarfksyms/dwarf.c | 53 ++++++++++++++-
> scripts/gendwarfksyms/gendwarfksyms.c | 4 +-
> scripts/gendwarfksyms/gendwarfksyms.h | 21 ++++++
> scripts/gendwarfksyms/symbols.c | 96 +++++++++++++++++++++++++++
> 5 files changed, 171 insertions(+), 4 deletions(-)
> create mode 100644 scripts/gendwarfksyms/symbols.c
>
> diff --git a/scripts/gendwarfksyms/Makefile b/scripts/gendwarfksyms/Makefile
> index c1389c161f9c..623f8fc975ea 100644
> --- a/scripts/gendwarfksyms/Makefile
> +++ b/scripts/gendwarfksyms/Makefile
> @@ -2,6 +2,7 @@ hostprogs-always-y += gendwarfksyms
>
> gendwarfksyms-objs += gendwarfksyms.o
> gendwarfksyms-objs += dwarf.o
> +gendwarfksyms-objs += symbols.o
>
> HOST_EXTRACFLAGS := -I $(srctree)/tools/include
> HOSTLDLIBS_gendwarfksyms := -ldw -lelf
> diff --git a/scripts/gendwarfksyms/dwarf.c b/scripts/gendwarfksyms/dwarf.c
> index 65a29d0bd8f4..71cfab0553da 100644
> --- a/scripts/gendwarfksyms/dwarf.c
> +++ b/scripts/gendwarfksyms/dwarf.c
> @@ -5,6 +5,48 @@
>
> #include "gendwarfksyms.h"
>
> +static bool get_ref_die_attr(Dwarf_Die *die, unsigned int id, Dwarf_Die *value)
> +{
> + Dwarf_Attribute da;
> +
> + /* dwarf_formref_die returns a pointer instead of an error value. */
> + return dwarf_attr(die, id, &da) && dwarf_formref_die(&da, value);
> +}
> +
> +static const char *get_name(Dwarf_Die *die)
> +{
> + Dwarf_Attribute attr;
> +
> + /* rustc uses DW_AT_linkage_name for exported symbols */
> + if (dwarf_attr(die, DW_AT_linkage_name, &attr) ||
> + dwarf_attr(die, DW_AT_name, &attr)) {
> + return dwarf_formstring(&attr);
> + }
> +
> + return NULL;
> +}
> +
> +static bool is_export_symbol(struct state *state, Dwarf_Die *die)
> +{
> + Dwarf_Die *source = die;
> + Dwarf_Die origin;
> +
> + state->sym = NULL;
> +
> + /* If the DIE has an abstract origin, use it for type information. */
> + if (get_ref_die_attr(die, DW_AT_abstract_origin, &origin))
> + source = &origin;
> +
> + state->sym = symbol_get(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->die = *source;
> + return !!state->sym;
> +}
> +
> /*
> * Type string processing
> */
> @@ -40,7 +82,7 @@ int process_die_container(struct state *state, Dwarf_Die *die,
> }
>
> /*
> - * Symbol processing
> + * Exported symbol processing
> */
> static int process_subprogram(struct state *state, Dwarf_Die *die)
> {
> @@ -67,10 +109,15 @@ static int process_exported_symbols(struct state *state, Dwarf_Die *die)
> /* Possible exported symbols */
> case DW_TAG_subprogram:
> case DW_TAG_variable:
> + if (!is_export_symbol(state, die))
> + return 0;
> +
> + debug("%s", state->sym->name);
> +
> if (tag == DW_TAG_subprogram)
> - check(process_subprogram(state, die));
> + check(process_subprogram(state, &state->die));
> else
> - check(process_variable(state, die));
> + check(process_variable(state, &state->die));
>
> return 0;
> default:
> diff --git a/scripts/gendwarfksyms/gendwarfksyms.c b/scripts/gendwarfksyms/gendwarfksyms.c
> index 27f2d6423c45..d209b237766b 100644
> --- a/scripts/gendwarfksyms/gendwarfksyms.c
> +++ b/scripts/gendwarfksyms/gendwarfksyms.c
> @@ -27,7 +27,7 @@ static const struct {
>
> static int usage(void)
> {
> - error("usage: gendwarfksyms [options] elf-object-file ...");
> + error("usage: gendwarfksyms [options] elf-object-file ... < symbol-list");
> return -1;
> }
>
> @@ -105,6 +105,8 @@ int main(int argc, const char **argv)
> if (parse_options(argc, argv) < 0)
> return usage();
>
> + check(symbol_read_exports(stdin));
symbol_read_exports() is only called from main().
Do you need to make symbol_read_exports() return
the error code all the way back to the main()
function?
Personally, I'd like to make the program bail out as early as
possible if there is no point in continuing running.
See also this patchset.
https://lore.kernel.org/linux-kbuild/20240812124858.2107328-1-masahiroy@kernel.org/T/#m5c0f795b57588a2c313cd2cc6e24ac95169fd225
> +
> for (n = 0; n < object_count; n++) {
> Dwfl *dwfl;
> int fd;
> diff --git a/scripts/gendwarfksyms/gendwarfksyms.h b/scripts/gendwarfksyms/gendwarfksyms.h
> index 5ab7ce7d4efb..03f3e408a839 100644
> --- a/scripts/gendwarfksyms/gendwarfksyms.h
> +++ b/scripts/gendwarfksyms/gendwarfksyms.h
> @@ -7,9 +7,11 @@
> #include <elfutils/libdw.h>
> #include <elfutils/libdwfl.h>
> #include <linux/hashtable.h>
> +#include <linux/jhash.h>
> #include <inttypes.h>
> #include <stdlib.h>
> #include <stdio.h>
> +#include <string.h>
>
> #ifndef __GENDWARFKSYMS_H
> #define __GENDWARFKSYMS_H
> @@ -56,6 +58,23 @@ extern bool debug;
> /* Error == negative values */
> #define checkp(expr) __check(expr, __res < 0, __res)
>
> +/*
> + * symbols.c
> + */
> +
> +static inline u32 name_hash(const char *name)
> +{
> + return jhash(name, strlen(name), 0);
> +}
> +
> +struct symbol {
> + const char *name;
> + struct hlist_node name_hash;
> +};
> +
> +extern int symbol_read_exports(FILE *file);
> +extern struct symbol *symbol_get(const char *name);
> +
> /*
> * dwarf.c
> */
> @@ -63,6 +82,8 @@ extern bool debug;
> struct state {
> Dwfl_Module *mod;
> Dwarf *dbg;
> + struct symbol *sym;
> + Dwarf_Die die;
> };
>
> typedef int (*die_callback_t)(struct state *state, Dwarf_Die *die);
> diff --git a/scripts/gendwarfksyms/symbols.c b/scripts/gendwarfksyms/symbols.c
> new file mode 100644
> index 000000000000..673ad9cf9e77
> --- /dev/null
> +++ b/scripts/gendwarfksyms/symbols.c
> @@ -0,0 +1,96 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2024 Google LLC
> + */
> +
> +#include "gendwarfksyms.h"
> +
> +#define SYMBOL_HASH_BITS 15
> +static DEFINE_HASHTABLE(symbol_names, SYMBOL_HASH_BITS);
> +
> +typedef int (*symbol_callback_t)(struct symbol *, void *arg);
> +
> +static int for_each(const char *name, symbol_callback_t func, void *data)
> +{
> + struct hlist_node *tmp;
> + struct symbol *match;
> +
> + if (!name || !*name)
> + return 0;
> +
> + hash_for_each_possible_safe(symbol_names, match, tmp, name_hash,
> + name_hash(name)) {
> + if (strcmp(match->name, name))
> + continue;
> +
> + if (func)
> + check(func(match, data));
> +
> + return 1;
> + }
> +
> + return 0;
> +}
> +
> +static bool is_exported(const char *name)
> +{
> + return checkp(for_each(name, NULL, NULL)) > 0;
> +}
> +
> +int symbol_read_exports(FILE *file)
> +{
> + struct symbol *sym;
> + char *line = NULL;
> + char *name = NULL;
> + size_t size = 0;
> + int nsym = 0;
> +
> + while (getline(&line, &size, file) > 0) {
> + if (sscanf(line, "%ms\n", &name) != 1) {
> + error("malformed input line: %s", line);
> + return -1;
> + }
> +
> + free(line);
> + line = NULL;
> +
> + if (is_exported(name))
> + continue; /* Ignore duplicates */
> +
> + sym = malloc(sizeof(struct symbol));
> + if (!sym) {
> + error("malloc failed");
> + return -1;
> + }
> +
> + sym->name = name;
> + name = NULL;
Is this necessary?
> +
> + hash_add(symbol_names, &sym->name_hash, name_hash(sym->name));
> + ++nsym;
> +
> + debug("%s", sym->name);
> + }
> +
> + if (line)
> + free(line);
> +
> + debug("%d exported symbols", nsym);
> + return 0;
> +}
> +
> +static int get_symbol(struct symbol *sym, void *arg)
> +{
> + struct symbol **res = arg;
> +
> + *res = sym;
> + return 0;
> +}
> +
> +struct symbol *symbol_get(const char *name)
> +{
> + struct symbol *sym = NULL;
> +
> + for_each(name, get_symbol, &sym);
> + return sym;
> +}
> --
> 2.46.0.184.g6999bdac58-goog
>
--
Best Regards
Masahiro Yamada
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