[PATCH v5 16/21] kbuild: generate KSYMTAB entries by modpost

Masahiro Yamada
2023-05-14T15:29:28Z

Commit 7b4537199a4a ("kbuild: link symbol CRCs at final link, removing
CONFIG_MODULE_REL_CRCS") made modpost output CRCs in the same way
whether the EXPORT_SYMBOL() is placed in *.c or *.S.

This commit applies a similar approach to the entire data structure of
EXPORT_SYMBOL() for further cleanups. The EXPORT_SYMBOL() compilation
is split into two stages.

When a source file is compiled, EXPORT_SYMBOL() is converted into a
dummy symbol in the .export_symbol section.

For example,

EXPORT_SYMBOL(foo);
EXPORT_SYMBOL_NS_GPL(bar, BAR_NAMESPACE);

will be encoded into the following assembly code:

.section ".export_symbol","a"
__export_symbol__foo:
.asciz ""
.balign 8
.quad foo
.previous

.section ".export_symbol","a"
__export_symbol_gpl_bar:
.asciz "BAR_NAMESPACE"
.balign 8
.quad bar
.previous

They are just markers to tell modpost the name, license, and namespace
of the symbols. They will be dropped from the final vmlinux and modules
because the *(.export_symbol) will go into /DISCARD/ in the linker script.

Then, modpost extracts all the information about EXPORT_SYMBOL() from the
.export_symbol section, and generates C code:

KSYMTAB_FUNC(foo, "", "");
KSYMTAB_FUNC(bar, "_gpl", "BAR_NAMESPACE");

KSYMTAB_FUNC() (or KSYMTAB_DATA() if it is data) is expanded to struct
kernel_symbol that will be linked to the vmlinux or a module.

With this change, EXPORT_SYMBOL() works in the same way for *.c and *.S
files, providing the following benefits.

[1] Deprecate EXPORT_DATA_SYMBOL()

In the old days, EXPORT_SYMBOL() was only available in C files. To export
a symbol in *.S, EXPORT_SYMBOL() was placed in a separate *.c file.
arch/arm/kernel/armksyms.c is one example written in the classic manner.

Commit 22823ab419d8 ("EXPORT_SYMBOL() for asm") removed this limitation.
Since then, EXPORT_SYMBOL() can be placed close to the symbol definition
in *.S files. It was a nice improvement.

However, as that commit mentioned, you need to use EXPORT_DATA_SYMBOL()
for data objects on some architectures.

In the new approach, modpost checks symbol's type (STT_FUNC or not),
and outputs KSYMTAB_FUNC() or KSYMTAB_DATA() accordingly.

There are only two users of EXPORT_DATA_SYMBOL:

EXPORT_DATA_SYMBOL_GPL(empty_zero_page) (arch/ia64/kernel/head.S)
EXPORT_DATA_SYMBOL(ia64_ivt) (arch/ia64/kernel/ivt.S)

They are transformed as follows and output into .vmlinux.export.c

KSYMTAB_DATA(empty_zero_page, "_gpl", "");
KSYMTAB_DATA(ia64_ivt, "", "");

The other EXPORT_SYMBOL users in ia64 assembly are output as
KSYMTAB_FUNC().

EXPORT_DATA_SYMBOL() is now deprecated.

[2] merge <linux/export.h> and <asm-generic/export.h>

There are two similar header implementations:

include/linux/export.h for .c files
include/asm-generic/export.h for .S files

Ideally, the functionality should be consistent between them, but they
tend to diverge.

Commit 8651ec01daed ("module: add support for symbol namespaces.") did
not support the namespace for *.S files.

This commit shifts the essential implementation part to C, which supports
EXPORT_SYMBOL_NS() for *.S files.

<asm/export.h> and <asm-generic/export.h> will remain as a wrapper of
<linux/export.h> for a while.

They will be removed after #include <asm/export.h> directives are all
replaced with #include <linux/export.h>.

[3] Implement CONFIG_TRIM_UNUSED_KSYMS in one-pass algorithm (by a later commit)

When CONFIG_TRIM_UNUSED_KSYMS is enabled, Kbuild recursively traverses
the directory tree to determine which EXPORT_SYMBOL to trim. If an
EXPORT_SYMBOL turns out to be unused by anyone, Kbuild begins the
second traverse, where some source files are recompiled with their
EXPORT_SYMBOL() tuned into a no-op.

We can do this better now; modpost can selectively emit KSYMTAB entries
that are really used by modules.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

Changes in v5:
- Fix build error on ARM

Changes in v4:
- Version 3 did not work if a same name symbol exists in a different compilation unit
Fix it.

Changes in v3:
- Move struct kernel_symbol to kernel/module/internal.h

Changes in v2:
- Use KSYMTAB_FUNC and KSYMTAB_DATA for functions and data, respectively
This distinction is needed for ia64.

arch/ia64/include/asm/Kbuild | 1 +
arch/ia64/include/asm/export.h | 3 -
include/asm-generic/export.h | 84 ++-----------------------
include/asm-generic/vmlinux.lds.h | 1 +
include/linux/export-internal.h | 49 +++++++++++++++
include/linux/export.h | 98 +++++++++++------------------
include/linux/pm.h | 8 +--
kernel/module/internal.h | 12 ++++
scripts/Makefile.build | 8 +--
scripts/check-local-export | 4 +-
scripts/mod/modpost.c | 101 ++++++++++++++++++++----------
scripts/mod/modpost.h | 1 +
12 files changed, 182 insertions(+), 188 deletions(-)
delete mode 100644 arch/ia64/include/asm/export.h

diff --git a/arch/ia64/include/asm/Kbuild b/arch/ia64/include/asm/Kbuild
index aefae2efde9f..33733245f42b 100644
--- a/arch/ia64/include/asm/Kbuild
+++ b/arch/ia64/include/asm/Kbuild
@@ -1,6 +1,7 @@
# SPDX-License-Identifier: GPL-2.0
generated-y += syscall_table.h
generic-y += agp.h
+generic-y += export.h
generic-y += kvm_para.h
generic-y += mcs_spinlock.h
generic-y += vtime.h
diff --git a/arch/ia64/include/asm/export.h b/arch/ia64/include/asm/export.h
deleted file mode 100644
index ad18c6583252..000000000000
--- a/arch/ia64/include/asm/export.h
+++ /dev/null
@@ -1,3 +0,0 @@
-/* EXPORT_DATA_SYMBOL != EXPORT_SYMBOL here */
-#define KSYM_FUNC(name) @fptr(name)
-#include <asm-generic/export.h>
diff --git a/include/asm-generic/export.h b/include/asm-generic/export.h
index 5e4b1f2369d2..0ae9f38a904c 100644
--- a/include/asm-generic/export.h
+++ b/include/asm-generic/export.h
@@ -3,86 +3,12 @@
#define __ASM_GENERIC_EXPORT_H

/*
- * This comment block is used by fixdep. Please do not remove.
- *
- * When CONFIG_MODVERSIONS is changed from n to y, all source files having
- * EXPORT_SYMBOL variants must be re-compiled because genksyms is run as a
- * side effect of the *.o build rule.
+ * <asm/export.h> and <asm-generic/export.h> are deprecated.
+ * Please include <linux/export.h> directly.
*/
+#include <linux/export.h>

-#ifndef KSYM_FUNC
-#define KSYM_FUNC(x) x
-#endif
-#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
-#define KSYM_ALIGN 4
-#elif defined(CONFIG_64BIT)
-#define KSYM_ALIGN 8
-#else
-#define KSYM_ALIGN 4
-#endif
-
-.macro __put, val, name
-#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
- .long \val - ., \name - ., 0
-#elif defined(CONFIG_64BIT)
- .quad \val, \name, 0
-#else
- .long \val, \name, 0
-#endif
-.endm
-
-/*
- * note on .section use: we specify progbits since usage of the "M" (SHF_MERGE)
- * section flag requires it. Use '%progbits' instead of '@progbits' since the
- * former apparently works on all arches according to the binutils source.
- */
-
-.macro ___EXPORT_SYMBOL name,val,sec
-#if defined(CONFIG_MODULES) && !defined(__DISABLE_EXPORTS)
- .section ___ksymtab\sec+\name,"a"
- .balign KSYM_ALIGN
-__ksymtab_\name:
- __put \val, __kstrtab_\name
- .previous
- .section __ksymtab_strings,"aMS",%progbits,1
-__kstrtab_\name:
- .asciz "\name"
- .previous
-#endif
-.endm
-
-#if defined(CONFIG_TRIM_UNUSED_KSYMS)
-
-#include <linux/kconfig.h>
-#include <generated/autoksyms.h>
-
-.macro __ksym_marker sym
- .section ".discard.ksym","a"
-__ksym_marker_\sym:
- .previous
-.endm
-
-#define __EXPORT_SYMBOL(sym, val, sec) \
- __ksym_marker sym; \
- __cond_export_sym(sym, val, sec, __is_defined(__KSYM_##sym))
-#define __cond_export_sym(sym, val, sec, conf) \
- ___cond_export_sym(sym, val, sec, conf)
-#define ___cond_export_sym(sym, val, sec, enabled) \
- __cond_export_sym_##enabled(sym, val, sec)
-#define __cond_export_sym_1(sym, val, sec) ___EXPORT_SYMBOL sym, val, sec
-#define __cond_export_sym_0(sym, val, sec) /* nothing */
-
-#else
-#define __EXPORT_SYMBOL(sym, val, sec) ___EXPORT_SYMBOL sym, val, sec
-#endif
-
-#define EXPORT_SYMBOL(name) \
- __EXPORT_SYMBOL(name, KSYM_FUNC(name),)
-#define EXPORT_SYMBOL_GPL(name) \
- __EXPORT_SYMBOL(name, KSYM_FUNC(name), _gpl)
-#define EXPORT_DATA_SYMBOL(name) \
- __EXPORT_SYMBOL(name, name,)
-#define EXPORT_DATA_SYMBOL_GPL(name) \
- __EXPORT_SYMBOL(name, name,_gpl)
+#define EXPORT_DATA_SYMBOL(name) EXPORT_SYMBOL(name)
+#define EXPORT_DATA_SYMBOL_GPL(name) EXPORT_SYMBOL_GPL(name)

#endif
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index d1f57e4868ed..e65d55e8819c 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -1006,6 +1006,7 @@
PATCHABLE_DISCARDS \
*(.discard) \
*(.discard.*) \
+ *(.export_symbol) \
*(.modinfo) \
/* ld.bfd warns about .gnu.version* even when not emitted */ \
*(.gnu.version*) \
diff --git a/include/linux/export-internal.h b/include/linux/export-internal.h
index fe7e6ba918f1..1c849db953a5 100644
--- a/include/linux/export-internal.h
+++ b/include/linux/export-internal.h
@@ -10,6 +10,55 @@
#include <linux/compiler.h>
#include <linux/types.h>

+#if defined(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)
+/*
+ * relative reference: this reduces the size by half on 64-bit architectures,
+ * and eliminates the need for absolute relocations that require runtime
+ * processing on relocatable kernels.
+ */
+#define __KSYM_REF(sym) ".long " #sym "- ."
+#elif defined(CONFIG_64BIT)
+#define __KSYM_REF(sym) ".quad " #sym
+#else
+#define __KSYM_REF(sym) ".long " #sym
+#endif
+
+/*
+ * For every exported symbol, do the following:
+ *
+ * - Put the name of the symbol and namespace (empty string "" for none) in
+ * __ksymtab_strings.
+ * - Place a struct kernel_symbol entry in the __ksymtab section.
+ *
+ * Note on .section use: we specify progbits since usage of the "M" (SHF_MERGE)
+ * section flag requires it. Use '%progbits' instead of '@progbits' since the
+ * former apparently works on all arches according to the binutils source.
+ */
+#define __KSYMTAB(name, sym, sec, ns) \
+ asm(" .section \"__ksymtab_strings\",\"aMS\",%progbits,1" "\n" \
+ "__kstrtab_" #name ":" "\n" \
+ " .asciz \"" #name "\"" "\n" \
+ "__kstrtabns_" #name ":" "\n" \
+ " .asciz \"" ns "\"" "\n" \
+ " .previous" "\n" \
+ " .section \"___ksymtab" sec "+" #name "\", \"a\"" "\n" \
+ " .balign 4" "\n" \
+ "__ksymtab_" #name ":" "\n" \
+ __KSYM_REF(sym) "\n" \
+ __KSYM_REF(__kstrtab_ ##name) "\n" \
+ __KSYM_REF(__kstrtabns_ ##name) "\n" \
+ " .previous" "\n" \
+ )
+
+#ifdef CONFIG_IA64
+#define KSYM_FUNC(name) @fptr(name)
+#else
+#define KSYM_FUNC(name) name
+#endif
+
+#define KSYMTAB_FUNC(name, sec, ns) __KSYMTAB(name, KSYM_FUNC(name), sec, ns)
+#define KSYMTAB_DATA(name, sec, ns) __KSYMTAB(name, name, sec, ns)
+
#define SYMBOL_CRC(sym, crc, sec) \
asm(".section \"___kcrctab" sec "+" #sym "\",\"a\"" "\n" \
"__crc_" #sym ":" "\n" \
diff --git a/include/linux/export.h b/include/linux/export.h
index 3f31ced0d977..32461a01608c 100644
--- a/include/linux/export.h
+++ b/include/linux/export.h
@@ -2,6 +2,7 @@
#ifndef _LINUX_EXPORT_H
#define _LINUX_EXPORT_H

+#include <linux/compiler.h>
#include <linux/stringify.h>

/*
@@ -28,72 +29,35 @@ extern struct module __this_module;
#else
#define THIS_MODULE ((struct module *)0)
#endif
+#endif /* __ASSEMBLY__ */

-#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
-#include <linux/compiler.h>
-/*
- * Emit the ksymtab entry as a pair of relative references: this reduces
- * the size by half on 64-bit architectures, and eliminates the need for
- * absolute relocations that require runtime processing on relocatable
- * kernels.
- */
-#define __KSYMTAB_ENTRY(sym, sec) \
- __ADDRESSABLE(sym) \
- asm(" .section \"___ksymtab" sec "+" #sym "\", \"a\" \n" \
- " .balign 4 \n" \
- "__ksymtab_" #sym ": \n" \
- " .long " #sym "- . \n" \
- " .long __kstrtab_" #sym "- . \n" \
- " .long __kstrtabns_" #sym "- . \n" \
- " .previous \n")
-
-struct kernel_symbol {
- int value_offset;
- int name_offset;
- int namespace_offset;
-};
+#ifdef CONFIG_64BIT
+#define __EXPORT_SYMBOL_REF(sym) .balign 8; .quad sym
#else
-#define __KSYMTAB_ENTRY(sym, sec) \
- static const struct kernel_symbol __ksymtab_##sym \
- __attribute__((section("___ksymtab" sec "+" #sym), used)) \
- __aligned(sizeof(void *)) \
- = { (unsigned long)&sym, __kstrtab_##sym, __kstrtabns_##sym }
-
-struct kernel_symbol {
- unsigned long value;
- const char *name;
- const char *namespace;
-};
+#define __EXPORT_SYMBOL_REF(sym) .balign 4; .long sym
#endif

+#define ____EXPORT_SYMBOL(sym, license, ns) \
+ .section ".export_symbol","a" ; \
+ __export_symbol_##license##_##sym: ; \
+ .asciz ns ; \
+ __EXPORT_SYMBOL_REF(sym) ; \
+ .previous
+
#ifdef __GENKSYMS__

#define ___EXPORT_SYMBOL(sym, sec, ns) __GENKSYMS_EXPORT_SYMBOL(sym)

+#elif defined(__ASSEMBLY__)
+
+#define ___EXPORT_SYMBOL(sym, license, ns) \
+ ____EXPORT_SYMBOL(sym, license, ns)
+
#else

-/*
- * For every exported symbol, do the following:
- *
- * - Put the name of the symbol and namespace (empty string "" for none) in
- * __ksymtab_strings.
- * - Place a struct kernel_symbol entry in the __ksymtab section.
- *
- * note on .section use: we specify progbits since usage of the "M" (SHF_MERGE)
- * section flag requires it. Use '%progbits' instead of '@progbits' since the
- * former apparently works on all arches according to the binutils source.
- */
-#define ___EXPORT_SYMBOL(sym, sec, ns) \
- extern typeof(sym) sym; \
- extern const char __kstrtab_##sym[]; \
- extern const char __kstrtabns_##sym[]; \
- asm(" .section \"__ksymtab_strings\",\"aMS\",%progbits,1 \n" \
- "__kstrtab_" #sym ": \n" \
- " .asciz \"" #sym "\" \n" \
- "__kstrtabns_" #sym ": \n" \
- " .asciz \"" ns "\" \n" \
- " .previous \n"); \
- __KSYMTAB_ENTRY(sym, sec)
+#define ___EXPORT_SYMBOL(sym, license, ns) \
+ __ADDRESSABLE(sym) \
+ asm(__stringify(____EXPORT_SYMBOL(sym, license, ns)))

#endif

@@ -117,9 +81,21 @@ struct kernel_symbol {
* from the $(NM) output (see scripts/gen_ksymdeps.sh). These symbols are
* discarded in the final link stage.
*/
+
+#ifdef __ASSEMBLY__
+
+#define __ksym_marker(sym) \
+ .section ".discard.ksym","a" ; \
+__ksym_marker_##sym: ; \
+ .previous
+
+#else
+
#define __ksym_marker(sym) \
static int __ksym_marker_##sym[0] __section(".discard.ksym") __used

+#endif
+
#define __EXPORT_SYMBOL(sym, sec, ns) \
__ksym_marker(sym); \
__cond_export_sym(sym, sec, ns, __is_defined(__KSYM_##sym))
@@ -147,11 +123,9 @@ struct kernel_symbol {
#define _EXPORT_SYMBOL(sym, sec) __EXPORT_SYMBOL(sym, sec, "")
#endif

-#define EXPORT_SYMBOL(sym) _EXPORT_SYMBOL(sym, "")
-#define EXPORT_SYMBOL_GPL(sym) _EXPORT_SYMBOL(sym, "_gpl")
-#define EXPORT_SYMBOL_NS(sym, ns) __EXPORT_SYMBOL(sym, "", __stringify(ns))
-#define EXPORT_SYMBOL_NS_GPL(sym, ns) __EXPORT_SYMBOL(sym, "_gpl", __stringify(ns))
-
-#endif /* !__ASSEMBLY__ */
+#define EXPORT_SYMBOL(sym) _EXPORT_SYMBOL(sym,)
+#define EXPORT_SYMBOL_GPL(sym) _EXPORT_SYMBOL(sym,gpl)
+#define EXPORT_SYMBOL_NS(sym, ns) __EXPORT_SYMBOL(sym,, __stringify(ns))
+#define EXPORT_SYMBOL_NS_GPL(sym, ns) __EXPORT_SYMBOL(sym,gpl, __stringify(ns))

#endif /* _LINUX_EXPORT_H */
diff --git a/include/linux/pm.h b/include/linux/pm.h
index 035d9649eba4..aabb6bd8f89e 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -388,10 +388,10 @@ const struct dev_pm_ops name = { \
#define EXPORT_PM_FN_NS_GPL(name, ns)
#endif

-#define EXPORT_DEV_PM_OPS(name) _EXPORT_DEV_PM_OPS(name, "", "")
-#define EXPORT_GPL_DEV_PM_OPS(name) _EXPORT_DEV_PM_OPS(name, "_gpl", "")
-#define EXPORT_NS_DEV_PM_OPS(name, ns) _EXPORT_DEV_PM_OPS(name, "", #ns)
-#define EXPORT_NS_GPL_DEV_PM_OPS(name, ns) _EXPORT_DEV_PM_OPS(name, "_gpl", #ns)
+#define EXPORT_DEV_PM_OPS(name) _EXPORT_DEV_PM_OPS(name,, "")
+#define EXPORT_GPL_DEV_PM_OPS(name) _EXPORT_DEV_PM_OPS(name,gpl, "")
+#define EXPORT_NS_DEV_PM_OPS(name, ns) _EXPORT_DEV_PM_OPS(name,, #ns)
+#define EXPORT_NS_GPL_DEV_PM_OPS(name, ns) _EXPORT_DEV_PM_OPS(name,gpl, #ns)

/*
* Use this if you want to use the same suspend and resume callbacks for suspend
diff --git a/kernel/module/internal.h b/kernel/module/internal.h
index dc7b0160c480..c8b7b4dcf782 100644
--- a/kernel/module/internal.h
+++ b/kernel/module/internal.h
@@ -32,6 +32,18 @@
/* Maximum number of characters written by module_flags() */
#define MODULE_FLAGS_BUF_SIZE (TAINT_FLAGS_COUNT + 4)

+struct kernel_symbol {
+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
+ int value_offset;
+ int name_offset;
+ int namespace_offset;
+#else
+ unsigned long value;
+ const char *name;
+ const char *namespace;
+#endif
+};
+
extern struct mutex module_mutex;
extern struct list_head modules;

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 9f94fc83f086..6bf026a304e4 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -161,7 +161,7 @@ quiet_cmd_cc_o_c = CC $(quiet_modtag) $@
ifdef CONFIG_MODVERSIONS
# When module versioning is enabled the following steps are executed:
# o compile a <file>.o from <file>.c
-# o if <file>.o doesn't contain a __ksymtab version, i.e. does
+# o if <file>.o doesn't contain a __export_symbol*, i.e. does
# not export symbols, it's done.
# o otherwise, we calculate symbol versions using the good old
# genksyms on the preprocessed source and dump them into the .cmd file.
@@ -169,7 +169,7 @@ ifdef CONFIG_MODVERSIONS
# be compiled and linked to the kernel and/or modules.

gen_symversions = \
- if $(NM) $@ 2>/dev/null | grep -q __ksymtab; then \
+ if $(NM) $@ 2>/dev/null | grep -q '__export_symbol_[^_]*_'; then \
$(call cmd_gensymtypes_$(1),$(KBUILD_SYMTYPES),$(@:.o=.symtypes)) \
>> $(dot-target).cmd; \
fi
@@ -340,9 +340,7 @@ $(obj)/%.ll: $(src)/%.rs FORCE
cmd_gensymtypes_S = \
{ echo "\#include <linux/kernel.h>" ; \
echo "\#include <asm/asm-prototypes.h>" ; \
- $(CPP) $(a_flags) $< | \
- grep "\<___EXPORT_SYMBOL\>" | \
- sed 's/.*___EXPORT_SYMBOL[[:space:]]*\([a-zA-Z0-9_]*\)[[:space:]]*,.*/EXPORT_SYMBOL(\1);/' ; } | \
+ $(NM) $@ | sed -n 's/.*__export_symbol_[^_]*_\(.*\)/EXPORT_SYMBOL(\1);/p' ; } | \
$(CPP) -D__GENKSYMS__ $(c_flags) -xc - | $(genksyms)

quiet_cmd_cc_symtypes_S = SYM $(quiet_modtag) $@
diff --git a/scripts/check-local-export b/scripts/check-local-export
index f90b5a9c67b3..969a313b9299 100755
--- a/scripts/check-local-export
+++ b/scripts/check-local-export
@@ -46,9 +46,9 @@ BEGIN {
{ symbol_types[$3]=$2 }

# append the exported symbol to the array
-($3 ~ /^__ksymtab_/) {
+($3 ~ /^__export_symbol_(gpl)?_.*/) {
export_symbols[i] = $3
- sub(/^__ksymtab_/, "", export_symbols[i])
+ sub(/^__export_symbol_(gpl)?_/, "", export_symbols[i])
i++
}

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 23a352f52b8f..921a61fea0b4 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -215,6 +215,7 @@ struct symbol {
unsigned int crc;
bool crc_valid;
bool weak;
+ bool is_func;
bool is_gpl_only; /* exported by EXPORT_SYMBOL_GPL */
char name[];
};
@@ -531,6 +532,8 @@ static int parse_elf(struct elf_info *info, const char *filename)
fatal("%s has NOBITS .modinfo\n", filename);
info->modinfo = (void *)hdr + sechdrs[i].sh_offset;
info->modinfo_len = sechdrs[i].sh_size;
+ } else if (!strcmp(secname, ".export_symbol")) {
+ info->export_symbol_secndx = i;
}

if (sechdrs[i].sh_type == SHT_SYMTAB) {
@@ -653,18 +656,6 @@ static void handle_symbol(struct module *mod, struct elf_info *info,
ELF_ST_BIND(sym->st_info) == STB_WEAK);
break;
default:
- /* All exported symbols */
- if (strstarts(symname, "__ksymtab_")) {
- const char *name, *secname;
-
- name = symname + strlen("__ksymtab_");
- secname = sec_name(info, get_secindex(info, sym));
-
- if (strstarts(secname, "___ksymtab_gpl+"))
- sym_add_exported(name, mod, true);
- else if (strstarts(secname, "___ksymtab+"))
- sym_add_exported(name, mod, false);
- }
if (strcmp(symname, "init_module") == 0)
mod->has_init = true;
if (strcmp(symname, "cleanup_module") == 0)
@@ -865,7 +856,6 @@ enum mismatch {
XXXEXIT_TO_SOME_EXIT,
ANY_INIT_TO_ANY_EXIT,
ANY_EXIT_TO_ANY_INIT,
- EXPORT_TO_INIT_EXIT,
EXTABLE_TO_NON_TEXT,
};

@@ -947,12 +937,6 @@ static const struct sectioncheck sectioncheck[] = {
.bad_tosec = { INIT_SECTIONS, NULL },
.mismatch = ANY_INIT_TO_ANY_EXIT,
},
-/* Do not export init/exit functions or data */
-{
- .fromsec = { "___ksymtab*", NULL },
- .bad_tosec = { INIT_SECTIONS, EXIT_SECTIONS, NULL },
- .mismatch = EXPORT_TO_INIT_EXIT,
-},
{
.fromsec = { "__ex_table", NULL },
/* If you're adding any new black-listed sections in here, consider
@@ -1215,10 +1199,6 @@ static void default_mismatch_handler(const char *modname, struct elf_info *elf,
warn("%s: section mismatch in reference: %s (section: %s) -> %s (section: %s)\n",
modname, fromsym, fromsec, tosym, tosec);
break;
- case EXPORT_TO_INIT_EXIT:
- warn("%s: EXPORT_SYMBOL used for init/exit symbol: %s (section: %s)\n",
- modname, tosym, tosec);
- break;
case EXTABLE_TO_NON_TEXT:
warn("%s(%s+0x%lx): Section mismatch in reference to the %s:%s\n",
modname, fromsec, (long)faddr, tosec, tosym);
@@ -1246,14 +1226,70 @@ static void default_mismatch_handler(const char *modname, struct elf_info *elf,
}
}

+static void check_export_symbol(struct module *mod, struct elf_info *elf,
+ Elf_Addr faddr, const char *secname,
+ Elf_Addr addr, Elf_Sym *sym)
+{
+ const char *label_name, *name, *prefix;
+ Elf_Sym *label;
+ struct symbol *s;
+ bool is_gpl;
+
+ label = find_fromsym(elf, faddr, elf->export_symbol_secndx);
+ label_name = sym_name(elf, label);
+
+ sym = find_tosym(elf, addr, sym);
+ name = sym_name(elf, sym);
+
+ if (strstarts(label_name, "__export_symbol_gpl_")) {
+ prefix = "__export_symbol_gpl_";
+ is_gpl = true;
+ } else if (strstarts(label_name, "__export_symbol__")) {
+ prefix = "__export_symbol__";
+ is_gpl = false;
+ } else {
+ error("%s: .export_symbol section contains strange symbol '%s'\n",
+ mod->name, label_name);
+ return;
+ }
+
+ if (strcmp(label_name + strlen(prefix), name)) {
+ error("%s: .export_symbol section references '%s', but it does not seem to be an export symbol\n",
+ mod->name, name);
+ return;
+ }
+
+ s = sym_add_exported(name, mod, is_gpl);
+ sym_update_namespace(name, sym_get_data(elf, label));
+
+ /*
+ * We need to be aware whether we are exporting a function or
+ * a data on some architectures.
+ */
+ s->is_func = (ELF_ST_TYPE(sym->st_info) == STT_FUNC);
+
+ if (match(secname, PATTERNS(INIT_SECTIONS)))
+ error("%s: %s: EXPORT_SYMBOL used for init symbol. Remove __init or EXPORT_SYMBOL.\n",
+ mod->name, name);
+ else if (match(secname, PATTERNS(EXIT_SECTIONS)))
+ error("%s: %s: EXPORT_SYMBOL used for exit symbol. Remove __exit or EXPORT_SYMBOL.\n",
+ mod->name, name);
+}
+
static void check_section_mismatch(struct module *mod, struct elf_info *elf,
Elf_Sym *sym,
unsigned int fsecndx, const char *fromsec,
Elf_Addr faddr, Elf_Addr taddr)
{
const char *tosec = sec_name(elf, get_secindex(elf, sym));
- const struct sectioncheck *mismatch = section_mismatch(fromsec, tosec);
+ const struct sectioncheck *mismatch;

+ if (elf->export_symbol_secndx == fsecndx) {
+ check_export_symbol(mod, elf, faddr, tosec, taddr, sym);
+ return;
+ }
+
+ mismatch = section_mismatch(fromsec, tosec);
if (!mismatch)
return;

@@ -1659,15 +1695,6 @@ static void read_symbols(const char *modname)
handle_moddevtable(mod, &info, sym, symname);
}

- for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
- symname = remove_dot(info.strtab + sym->st_name);
-
- /* Apply symbol namespaces from __kstrtabns_<symbol> entries. */
- if (strstarts(symname, "__kstrtabns_"))
- sym_update_namespace(symname + strlen("__kstrtabns_"),
- sym_get_data(&info, sym));
- }
-
check_sec_ref(mod, &info);

if (!mod->is_vmlinux) {
@@ -1851,6 +1878,14 @@ static void add_exported_symbols(struct buffer *buf, struct module *mod)
{
struct symbol *sym;

+ /* generate struct for exported symbols */
+ buf_printf(buf, "\n");
+ list_for_each_entry(sym, &mod->exported_symbols, list)
+ buf_printf(buf, "KSYMTAB_%s(%s, \"%s\", \"%s\");\n",
+ sym->is_func ? "FUNC" : "DATA", sym->name,
+ sym->is_gpl_only ? "_gpl" : "",
+ sym->namespace ?: "");
+
if (!modversions)
return;

diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 1178f40a73f3..f518fbe46541 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -137,6 +137,7 @@ struct elf_info {
Elf_Shdr *sechdrs;
Elf_Sym *symtab_start;
Elf_Sym *symtab_stop;
+ unsigned int export_symbol_secndx; /* .export_symbol section */
char *strtab;
char *modinfo;
unsigned int modinfo_len;
--
2.39.2