[CC: Sam Ravnborg as originally intended]
Alan Jenkins wrote:
> modpost of vmlinux.o now extracts the ksymtab sections and outputs
> sorted versions of them as .tmp_exports.c. These sorted sections
> are linked into vmlinux and the original unsorted sections are
> discarded.
>
> This will allow modules to be loaded faster, resolving symbols using
> binary search, without any increase in the memory needed for the
> symbol tables.
>
> This does not affect the building of modules, so hopefully it won't
> affect compile times too much.
>
> Signed-off-by: Alan Jenkins <alan-jenkins@xxxxxxxxxxxxxx>
> ---
> Makefile | 20 ++++++++---
> include/asm-generic/vmlinux.lds.h | 40 ++++++++++++++++------
> include/linux/mod_export.h | 19 ++++++++--
> scripts/Makefile.modpost | 2 +-
> scripts/mod/modpost.c | 66 ++++++++++++++++++++++++++++++++++++-
> 5 files changed, 124 insertions(+), 23 deletions(-)
>
> diff --git a/Makefile b/Makefile
> index 60de4ef..bb35b4d 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -674,6 +674,8 @@ libs-y := $(libs-y1) $(libs-y2)
> # +--< $(vmlinux-main)
> # | +--< driver/built-in.o mm/built-in.o + more
> # |
> +# +-< .tmp_exports.o (see comments regarding modpost of vmlinux.o)
> +# |
> # +-< kallsyms.o (see description in CONFIG_KALLSYMS section)
> #
> # vmlinux version (uname -v) cannot be updated during normal
> @@ -737,7 +739,6 @@ define rule_vmlinux__
> $(verify_kallsyms)
> endef
>
> -
> ifdef CONFIG_KALLSYMS
> # Generate section listing all symbols and add it into vmlinux $(kallsyms.o)
> # It's a three stage process:
> @@ -797,13 +798,13 @@ quiet_cmd_kallsyms = KSYM $@
> $(call cmd,kallsyms)
>
> # .tmp_vmlinux1 must be complete except kallsyms, so update vmlinux version
> -.tmp_vmlinux1: $(vmlinux-lds) $(vmlinux-all) FORCE
> +.tmp_vmlinux1: $(vmlinux-lds) $(vmlinux-all) .tmp_exports.o FORCE
> $(call if_changed_rule,ksym_ld)
>
> -.tmp_vmlinux2: $(vmlinux-lds) $(vmlinux-all) .tmp_kallsyms1.o FORCE
> +.tmp_vmlinux2: $(vmlinux-lds) $(vmlinux-all) .tmp_exports.o .tmp_kallsyms1.o FORCE
> $(call if_changed,vmlinux__)
>
> -.tmp_vmlinux3: $(vmlinux-lds) $(vmlinux-all) .tmp_kallsyms2.o FORCE
> +.tmp_vmlinux3: $(vmlinux-lds) $(vmlinux-all) .tmp_exports.o .tmp_kallsyms2.o FORCE
> $(call if_changed,vmlinux__)
>
> # Needs to visit scripts/ before $(KALLSYMS) can be used.
> @@ -835,7 +836,7 @@ define rule_vmlinux-modpost
> endef
>
> # vmlinux image - including updated kernel symbols
> -vmlinux: $(vmlinux-lds) $(vmlinux-init) $(vmlinux-main) vmlinux.o $(kallsyms.o) FORCE
> +vmlinux: $(vmlinux-lds) $(vmlinux-init) $(vmlinux-main) vmlinux.o .tmp_exports.o $(kallsyms.o) FORCE
> ifdef CONFIG_HEADERS_CHECK
> $(Q)$(MAKE) -f $(srctree)/Makefile headers_check
> endif
> @@ -858,6 +859,12 @@ modpost-init := $(filter-out init/built-in.o, $(vmlinux-init))
> vmlinux.o: $(modpost-init) $(vmlinux-main) FORCE
> $(call if_changed_rule,vmlinux-modpost)
>
> +# The modpost of vmlinux.o above creates .tmp_exports.c, a list of exported
> +# symbols sorted by name. This list is linked into vmlinux to replace the
> +# original unsorted exports. It allows symbols to be resolved efficiently
> +# when loading modules.
> +.tmp_exports.c: vmlinux.o
> +
> # The actual objects are generated when descending,
> # make sure no implicit rule kicks in
> $(sort $(vmlinux-init) $(vmlinux-main)) $(vmlinux-lds): $(vmlinux-dirs) ;
> @@ -1190,7 +1197,8 @@ endif # CONFIG_MODULES
> # Directories & files removed with 'make clean'
> CLEAN_DIRS += $(MODVERDIR)
> CLEAN_FILES += vmlinux System.map \
> - .tmp_kallsyms* .tmp_version .tmp_vmlinux* .tmp_System.map
> + .tmp_kallsyms* .tmp_version .tmp_vmlinux* .tmp_System.map \
> + .tmp_exports*
>
> # Directories & files removed with 'make mrproper'
> MRPROPER_DIRS += include/config include2 usr/include include/generated
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 6ad76bf..16c3e01 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -253,79 +253,97 @@
> \
> TRACEDATA \
> \
> + /* \
> + * Kernel symbol table: discard the original unsorted tables \
> + * in favour of the sorted versions. \
> + */ \
> + /DISCARD/ : { \
> + *(__ksymtab) \
> + *(__ksymtab_gpl) \
> + *(__ksymtab_unused) \
> + *(__ksymtab_unused_gpl) \
> + *(__ksymtab_gpl_future) \
> + *(__kcrctab) \
> + *(__kcrctab_gpl) \
> + *(__kcrctab_unused) \
> + *(__kcrctab_unused_gpl) \
> + *(__kcrctab_gpl_future) \
> + *(__ksymtab_strings) \
> + } \
> + \
> /* Kernel symbol table: Normal symbols */ \
> __ksymtab : AT(ADDR(__ksymtab) - LOAD_OFFSET) { \
> VMLINUX_SYMBOL(__start___ksymtab) = .; \
> - *(__ksymtab) \
> + *(__ksymtab_sorted) \
> VMLINUX_SYMBOL(__stop___ksymtab) = .; \
> } \
> \
> /* Kernel symbol table: GPL-only symbols */ \
> __ksymtab_gpl : AT(ADDR(__ksymtab_gpl) - LOAD_OFFSET) { \
> VMLINUX_SYMBOL(__start___ksymtab_gpl) = .; \
> - *(__ksymtab_gpl) \
> + *(__ksymtab_gpl_sorted) \
> VMLINUX_SYMBOL(__stop___ksymtab_gpl) = .; \
> } \
> \
> /* Kernel symbol table: Normal unused symbols */ \
> __ksymtab_unused : AT(ADDR(__ksymtab_unused) - LOAD_OFFSET) { \
> VMLINUX_SYMBOL(__start___ksymtab_unused) = .; \
> - *(__ksymtab_unused) \
> + *(__ksymtab_unused_sorted) \
> VMLINUX_SYMBOL(__stop___ksymtab_unused) = .; \
> } \
> \
> /* Kernel symbol table: GPL-only unused symbols */ \
> __ksymtab_unused_gpl : AT(ADDR(__ksymtab_unused_gpl) - LOAD_OFFSET) { \
> VMLINUX_SYMBOL(__start___ksymtab_unused_gpl) = .; \
> - *(__ksymtab_unused_gpl) \
> + *(__ksymtab_unused_gpl_sorted) \
> VMLINUX_SYMBOL(__stop___ksymtab_unused_gpl) = .; \
> } \
> \
> /* Kernel symbol table: GPL-future-only symbols */ \
> __ksymtab_gpl_future : AT(ADDR(__ksymtab_gpl_future) - LOAD_OFFSET) { \
> VMLINUX_SYMBOL(__start___ksymtab_gpl_future) = .; \
> - *(__ksymtab_gpl_future) \
> + *(__ksymtab_gpl_future_sorted) \
> VMLINUX_SYMBOL(__stop___ksymtab_gpl_future) = .; \
> } \
> \
> /* Kernel symbol table: Normal symbols */ \
> __kcrctab : AT(ADDR(__kcrctab) - LOAD_OFFSET) { \
> VMLINUX_SYMBOL(__start___kcrctab) = .; \
> - *(__kcrctab) \
> + *(__kcrctab_sorted) \
> VMLINUX_SYMBOL(__stop___kcrctab) = .; \
> } \
> \
> /* Kernel symbol table: GPL-only symbols */ \
> __kcrctab_gpl : AT(ADDR(__kcrctab_gpl) - LOAD_OFFSET) { \
> VMLINUX_SYMBOL(__start___kcrctab_gpl) = .; \
> - *(__kcrctab_gpl) \
> + *(__kcrctab_gpl_sorted) \
> VMLINUX_SYMBOL(__stop___kcrctab_gpl) = .; \
> } \
> \
> /* Kernel symbol table: Normal unused symbols */ \
> __kcrctab_unused : AT(ADDR(__kcrctab_unused) - LOAD_OFFSET) { \
> VMLINUX_SYMBOL(__start___kcrctab_unused) = .; \
> - *(__kcrctab_unused) \
> + *(__kcrctab_unused_sorted) \
> VMLINUX_SYMBOL(__stop___kcrctab_unused) = .; \
> } \
> \
> /* Kernel symbol table: GPL-only unused symbols */ \
> __kcrctab_unused_gpl : AT(ADDR(__kcrctab_unused_gpl) - LOAD_OFFSET) { \
> VMLINUX_SYMBOL(__start___kcrctab_unused_gpl) = .; \
> - *(__kcrctab_unused_gpl) \
> + *(__kcrctab_unused_gpl_sorted) \
> VMLINUX_SYMBOL(__stop___kcrctab_unused_gpl) = .; \
> } \
> \
> /* Kernel symbol table: GPL-future-only symbols */ \
> __kcrctab_gpl_future : AT(ADDR(__kcrctab_gpl_future) - LOAD_OFFSET) { \
> VMLINUX_SYMBOL(__start___kcrctab_gpl_future) = .; \
> - *(__kcrctab_gpl_future) \
> + *(__kcrctab_gpl_future_sorted) \
> VMLINUX_SYMBOL(__stop___kcrctab_gpl_future) = .; \
> } \
> \
> /* Kernel symbol table: strings */ \
> __ksymtab_strings : AT(ADDR(__ksymtab_strings) - LOAD_OFFSET) { \
> - *(__ksymtab_strings) \
> + *(__ksymtab_strings_sorted) \
> } \
> \
> /* __*init sections */ \
> diff --git a/include/linux/mod_export.h b/include/linux/mod_export.h
> index 3c51b9c..737a829 100644
> --- a/include/linux/mod_export.h
> +++ b/include/linux/mod_export.h
> @@ -31,17 +31,20 @@ struct kernel_symbol
> #endif
>
> /* For every exported symbol, place a struct in the __ksymtab section */
> -#define __EXPORT_SYMBOL(sym, sec) \
> +#define __EXPORT_SYMBOL_NAME(sym, sec, stringsec) \
> extern typeof(sym) sym; \
> __CRC_SYMBOL(sym, sec) \
> static const char __kstrtab_##sym[] \
> - __attribute__((section("__ksymtab_strings"), aligned(1))) \
> + __attribute__((section(stringsec), aligned(1))) \
> = MODULE_SYMBOL_PREFIX #sym; \
> static const struct kernel_symbol __ksymtab_##sym \
> __used \
> __attribute__((section("__ksymtab" sec), unused)) \
> = { (unsigned long)&sym, __kstrtab_##sym }
>
> +#define __EXPORT_SYMBOL(sym, sec) \
> + __EXPORT_SYMBOL_NAME(sym, sec, "__ksymtab_strings")
> +
> #define EXPORT_SYMBOL(sym) \
> __EXPORT_SYMBOL(sym, "")
>
> @@ -51,14 +54,22 @@ struct kernel_symbol
> #define EXPORT_SYMBOL_GPL_FUTURE(sym) \
> __EXPORT_SYMBOL(sym, "_gpl_future")
>
> +
> #ifdef CONFIG_UNUSED_SYMBOLS
> -#define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused")
> -#define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl")
> +#define EXPORT_UNUSED_SYMBOL(sym) __EXPORT_SYMBOL(sym, "_unused", "")
> +#define EXPORT_UNUSED_SYMBOL_GPL(sym) __EXPORT_SYMBOL(sym, "_unused_gpl", "")
> #else
> #define EXPORT_UNUSED_SYMBOL(sym)
> #define EXPORT_UNUSED_SYMBOL_GPL(sym)
> #endif
>
> +/*
> + * In vmlinux (but not modules), __ksymtab and friends are replaced by sorted
> + * versions generated by scripts/mod/modpost.c
> + */
> +#define __EXPORT_SYMBOL_SORTED(sym, sec) \
> + __EXPORT_SYMBOL_NAME(sym, sec "_sorted", "__ksymtab_strings_sorted")
> +
> #endif /* __GENKSYMS__ */
>
> #else /* !CONFIG_MODULES */
> diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
> index f4053dc..8bee8cd 100644
> --- a/scripts/Makefile.modpost
> +++ b/scripts/Makefile.modpost
> @@ -98,7 +98,7 @@ __modpost: $(modules:.ko=.o) FORCE
> $(call cmd,modpost) $(wildcard vmlinux) $(filter-out FORCE,$^)
>
> quiet_cmd_kernel-mod = MODPOST $@
> - cmd_kernel-mod = $(modpost) $@
> + cmd_kernel-mod = $(modpost) -x .tmp_exports.c $@
>
> vmlinux.o: FORCE
> @rm -fr $(kernelmarkersfile)
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index 4522948..6302ce7 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -154,6 +154,7 @@ struct symbol {
> };
>
> static struct symbol *symbolhash[SYMBOL_HASH_SIZE];
> +unsigned int symbolcount;
>
> /* This is based on the hash agorithm from gdbm, via tdb */
> static inline unsigned int tdb_hash(const char *name)
> @@ -191,6 +192,7 @@ static struct symbol *new_symbol(const char *name, struct module *module,
> unsigned int hash;
> struct symbol *new;
>
> + symbolcount++;
> hash = tdb_hash(name) % SYMBOL_HASH_SIZE;
> new = symbolhash[hash] = alloc_symbol(name, 0, symbolhash[hash]);
> new->module = module;
> @@ -1976,6 +1978,61 @@ static void write_dump(const char *fname)
> write_if_changed(&buf, fname);
> }
>
> +static const char *section_names[] = {
> + [export_plain] = "",
> + [export_unused] = "_unused",
> + [export_gpl] = "_gpl",
> + [export_unused_gpl] = "_unused_gpl",
> + [export_gpl_future] = "_gpl_future",
> +};
> +
> +static int compare_symbol_names(const void *a, const void *b)
> +{
> + struct symbol *const *syma = a;
> + struct symbol *const *symb = b;
> +
> + return strcmp((*syma)->name, (*symb)->name);
> +}
> +
> +/* sort exported symbols and output as */
> +static void write_exports(const char *fname)
> +{
> + struct buffer buf = { };
> + struct symbol *sym, **symbols;
> + int i, n;
> +
> + symbols = NOFAIL(malloc(sizeof (struct symbol *) * symbolcount));
> + n = 0;
> +
> + for (i = 0; i < SYMBOL_HASH_SIZE; i++) {
> + for (sym = symbolhash[i]; sym; sym = sym->next)
> + symbols[n++] = sym;
> + }
> +
> + qsort(symbols, n, sizeof(struct symbol *), compare_symbol_names);
> +
> + buf_printf(&buf, "#include <linux/mod_export.h>\n");
> + buf_printf(&buf, "\n");
> +
> + for (i = 0; i < n; i++) {
> + sym = symbols[i];
> +
> + /*
> + * We need to declare the symbol with extern linkage.
> + * Don't worry about the type. The linker won't care, and the
> + * compiler won't complain unless we include a conflicting
> + * declaration.
> + */
> + buf_printf(&buf, "extern void *%s;\n", sym->name);
> +
> + buf_printf(&buf, "__EXPORT_SYMBOL_SORTED(%s, \"%s\");\n",
> + sym->name,
> + section_names[sym->export]);
> + }
> +
> + write_if_changed(&buf, fname);
> +}
> +
> static void add_marker(struct module *mod, const char *name, const char *fmt)
> {
> char *line = NULL;
> @@ -2077,6 +2134,7 @@ int main(int argc, char **argv)
> struct buffer buf = { };
> char *kernel_read = NULL, *module_read = NULL;
> char *dump_write = NULL;
> + char *exports_write = NULL;
> char *markers_read = NULL;
> char *markers_write = NULL;
> int opt;
> @@ -2084,7 +2142,7 @@ int main(int argc, char **argv)
> struct ext_sym_list *extsym_iter;
> struct ext_sym_list *extsym_start = NULL;
>
> - while ((opt = getopt(argc, argv, "i:I:e:cmsSo:awM:K:")) != -1) {
> + while ((opt = getopt(argc, argv, "i:I:e:cmsSo:awM:K:x:")) != -1) {
> switch (opt) {
> case 'i':
> kernel_read = optarg;
> @@ -2122,6 +2180,9 @@ int main(int argc, char **argv)
> case 'w':
> warn_unresolved = 1;
> break;
> + case 'x':
> + exports_write = optarg;
> + break;
> case 'M':
> markers_write = optarg;
> break;
> @@ -2182,6 +2243,9 @@ int main(int argc, char **argv)
> "'make CONFIG_DEBUG_SECTION_MISMATCH=y'\n",
> sec_mismatch_count);
>
> + if (exports_write)
> + write_exports(exports_write);
> +
> if (markers_read)
> read_markers(markers_read);
>
>
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