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Date: Mon, 25 Apr 2022 04:08:07 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: linux-kbuild@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
Masahiro Yamada <masahiroy@...nel.org>,
Michal Marek <michal.lkml@...kovi.net>,
Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
llvm@...ts.linux.dev
Subject: [PATCH 23/27] modpost: retrieve symbol versions by parsing *.cmd files
Currently, CONFIG_MODVERSIONS needs extra link to embed the symbol
versions into objects. Then, modpost parses the ELF objects to retrieve
the version CRCs.
See the current build flow below.
Current implementation
======================
embed CRC |---------| |------------|
$(CC) $(LD) | | | final link |
*.c ------> *.o --------> *.o -->| modpost |-- *.o ------>| for |
/ | | | vmlinux |
genksyms / | |-- *.mod.c -->| or module |
*.c ------> *.symversions |---------| |------------|
Genksyms outputs the calculated CRCs in the form of linker script
(*.symversions), which is used by $(LD) to update the object.
If CONFIG_LTO_CLANG=y, the build process becomes much more complex.
Embedding the CRCs is postponed until the LLVM bitcode is converted
into ELF, creating another intermediate *.prelink.o.
However, this complexity is unneeded in the first place. There is no
reason why we must embed version CRCs in objects so early.
There is final link stage for vmlinux (scripts/link-vmlinux.sh) and
modules (scripts/Makefile.modfinal). We can embed CRCs at the very
last moment.
See the following figure, which explains what I want to do.
New implementation
==================
$(CC) |---------| |------------|
*.c ------> *.o --->| |-- *.o ------------>| final link |
| modpost |-- *.mod.c -------->| for |
genksyms | |-- *.symver.lds --->| vmlinux |
*.c ------> *.cmd -->| | | or module |
|---------| |------------|
We can pass the symbol versions to modpost as separate text data.
(The previous commit output the versions in *.cmd files.)
This commit changes modpost to retrieve CRCs from *.cmd files instead
of from ELF objects.
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---
scripts/mod/modpost.c | 177 ++++++++++++++++++++++++++++++++----------
1 file changed, 136 insertions(+), 41 deletions(-)
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index fb50927cd241..43ab4f000ae3 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -246,6 +246,9 @@ static inline unsigned int tdb_hash(const char *name)
/* hash table of all exported symbols */
HASHTABLE_DECLARE(exported_symbols, 8192);
+/* hash table of CRCs */
+HASHTABLE_DECLARE(crc_symbols, 1024);
+
/**
* Allocate a new symbols for use in the hash of exported symbols or
* the list of unresolved symbols per module
@@ -420,7 +423,27 @@ static void sym_add_exported(const char *name, struct module *mod,
s->module->is_vmlinux ? "" : ".ko");
}
- s = alloc_symbol(name);
+ s = NULL;
+
+ if (modversions) {
+ struct hlist_node *n;
+
+ hash_for_matched_symbol_safe(s, n, crc_symbols, name) {
+ if (s->module == mod)
+ hash_del_symbol(s);
+ break;
+ }
+
+ if (!s)
+ warn("EXPORT symbol \"%s\" [%s%s] version generation failed, symbol will not be versioned.\n"
+ "Is \"%s\" prototyped in <asm/asm-prototypes.h>?\n",
+ name, mod->name, mod->is_vmlinux ? "" : ".ko",
+ name);
+ }
+
+ if (!s)
+ s = alloc_symbol(name);
+
s->module = mod;
s->is_static = !mod->from_dump;
s->export = export;
@@ -428,19 +451,116 @@ static void sym_add_exported(const char *name, struct module *mod,
hash_add_symbol(s, exported_symbols);
}
-static void sym_set_crc(const char *name, unsigned int crc)
+static void sym_add_crc(const char *name, unsigned int crc, struct module *mod)
{
- struct symbol *s = find_symbol(name);
+ struct symbol *sym;
- /*
- * Ignore stand-alone __crc_*, which might be auto-generated symbols
- * such as __*_veneer in ARM ELF.
- */
- if (!s)
+ sym = alloc_symbol(name);
+
+ sym->crc = crc;
+ sym->crc_valid = true;
+ sym->module = mod;
+
+ hash_add_symbol(sym, crc_symbols);
+}
+
+/*
+ * The CRCs are recorded in .*.cmd files in the form of:
+ * #__crc_<name>=<crc>
+ */
+static void retrieve_crcs_from_cmdfile(const char *object, struct module *mod)
+{
+ char cmd_file[PATH_MAX];
+ char *buf, *p;
+ const char *base;
+ int dirlen, ret;
+
+ base = strrchr(object, '/');
+ if (base) {
+ base++;
+ dirlen = base - object;
+ } else {
+ dirlen = 0;
+ base = object;
+ }
+
+ ret = snprintf(cmd_file, sizeof(cmd_file), "%.*s.%s.cmd",
+ dirlen, object, base);
+ if (ret >= sizeof(cmd_file)) {
+ error("%s: too long path was truncated\n", cmd_file);
return;
+ }
+
+ buf = read_text_file(cmd_file);
+ p = buf;
+
+ while ((p = strstr(p, "\n#__crc_"))) {
+ char *name;
+ size_t namelen;
+ unsigned int crc;
+ char *end;
+
+ name = p + strlen("\n#__crc_");
+
+ p = strchr(name, '=');
+ if (!p) {
+ error("invalid\n");
+ goto out;
+ }
+
+ namelen = p - name;
+
+ p++;
- s->crc = crc;
- s->crc_valid = true;
+ if (!isdigit(*p)) {
+ error("invalid\n");
+ goto out;
+ }
+
+ crc = strtol(p, &end, 0);
+ p = end;
+
+ if (*p != '\n') {
+ error("invalid\n");
+ goto out;
+ }
+
+ name[namelen] = '\0';
+ sym_add_crc(name, crc, mod);
+ }
+
+out:
+ free(buf);
+}
+
+/*
+ * The symbol versions (CRC) are recorded in the .*.cmd files.
+ * Parse them to retrieve CRCs for the current module.
+ */
+static void retrieve_crcs(struct module *mod)
+{
+ char objlist[PATH_MAX];
+ char *buf, *p, *obj;
+ int ret;
+
+ if (mod->is_vmlinux) {
+ strcpy(objlist, ".vmlinux.objs");
+ } else {
+ /* objects for a module are listed in the *.mod file. */
+ ret = snprintf(objlist, sizeof(objlist), "%s.mod", mod->name);
+ if (ret >= sizeof(objlist)) {
+ error("%s: too long path was truncated\n", objlist);
+ return;
+ }
+ }
+
+ buf = read_text_file(objlist);
+ p = buf;
+
+ while ((obj = strsep(&p, "\n")) && obj[0])
+ retrieve_crcs_from_cmdfile(obj, mod);
+
+ free(buf);
}
static void *grab_file(const char *filename, size_t *size)
@@ -663,33 +783,6 @@ static int ignore_undef_symbol(struct elf_info *info, const char *symname)
return 0;
}
-static void handle_modversion(const struct module *mod,
- const struct elf_info *info,
- const Elf_Sym *sym, const char *symname)
-{
- unsigned int crc;
-
- if (sym->st_shndx == SHN_UNDEF) {
- warn("EXPORT symbol \"%s\" [%s%s] version generation failed, symbol will not be versioned.\n"
- "Is \"%s\" prototyped in <asm/asm-prototypes.h>?\n",
- symname, mod->name, mod->is_vmlinux ? "" : ".ko",
- symname);
-
- return;
- }
-
- if (sym->st_shndx == SHN_ABS) {
- crc = sym->st_value;
- } else {
- unsigned int *crcp;
-
- /* symbol points to the CRC in the ELF object */
- crcp = sym_get_data(info, sym);
- crc = TO_NATIVE(*crcp);
- }
- sym_set_crc(symname, crc);
-}
-
static void handle_symbol(struct module *mod, struct elf_info *info,
const Elf_Sym *sym, const char *symname)
{
@@ -2019,6 +2112,10 @@ static void read_symbols(const char *modname)
if (strends(tmp, ".prelink"))
tmp[strlen(tmp) - 8] = '\0';
mod = new_module(tmp);
+
+ if (modversions)
+ retrieve_crcs(mod);
+
free(tmp);
}
@@ -2058,9 +2155,6 @@ static void read_symbols(const char *modname)
if (strstarts(symname, "__kstrtabns_"))
sym_update_namespace(symname + strlen("__kstrtabns_"),
sym_get_data(&info, sym));
- if (strstarts(symname, "__crc_"))
- handle_modversion(mod, &info, sym,
- symname + strlen("__crc_"));
}
// check for static EXPORT_SYMBOL_* functions && global vars
@@ -2451,8 +2545,9 @@ static void read_dump(const char *fname)
mod = new_module(modname);
mod->from_dump = true;
}
+
+ sym_add_crc(symname, crc, mod);
sym_add_exported(symname, mod, export_no(export));
- sym_set_crc(symname, crc);
sym_update_namespace(symname, namespace);
}
free(buf);
--
2.32.0
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