[PATCH v7 03/10] kbuild/modpost: create symbols.klp and integrate klp-convert

Joe Lawrence
2023-03-06T14:38:34Z

For automatic resolution of livepatch relocations, a file called
symbols.klp is used. This file maps symbols within every compiled kernel
object allowing the identification of symbols whose name is unique, thus
relocation can be automatically inferred, or providing information that
helps developers when code annotation is required for solving the
matter.

Add support for creating symbols.klp in the main Makefile. First, ensure
that built-in is compiled when CONFIG_LIVEPATCH is enabled (as required
to achieve a complete symbols.klp file). Define the command to build
symbols.klp (filechk_klp_map) and hook it in the modules rule. Save the
list of livepatch modules in $(MODULES_LIVEPATCH).

As it is undesirable to have symbols from livepatch objects inside
symbols.klp, filechk_klp_map filters out modules.livepatch from
modules.order: `sort $(MODORDER) $(MODULES_LIVEPATCH) | uniq -u`.

The "clean" Makefile target may remove the modules.livepatch file,
however, symbols.klp may be needed for building external modules, so
defer its cleanup to the "mrproper" target.

Finally, update the modpost program so that it does not warn about
unresolved symbols resolved by klp-convert.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Joao Moreira <jmoreira@suse.de>
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
---
.gitignore | 2 ++
Documentation/dontdiff | 1 +
Makefile | 16 +++++++++++-----
scripts/Makefile.modfinal | 33 +++++++++++++++++++++++++++++++++
scripts/Makefile.modpost | 5 +++++
scripts/mod/modpost.c | 28 ++++++++++++++++++++++++++--
scripts/mod/modpost.h | 1 +
7 files changed, 79 insertions(+), 7 deletions(-)

diff --git a/.gitignore b/.gitignore
index 20dce5c3b9e0..fc9b2f13b049 100644
--- a/.gitignore
+++ b/.gitignore
@@ -53,6 +53,7 @@
*.xz
*.zst
Module.symvers
+modules.livepatch
modules.order

#
@@ -66,6 +67,7 @@ modules.order
/vmlinux.symvers
/vmlinux-gdb.py
/vmlinuz
+/symbols.klp
/System.map
/Module.markers
/modules.builtin
diff --git a/Documentation/dontdiff b/Documentation/dontdiff
index 352ff53a2306..23c2a89fb791 100644
--- a/Documentation/dontdiff
+++ b/Documentation/dontdiff
@@ -76,6 +76,7 @@ Module.markers
Module.symvers
PENDING
SCCS
+symbols.klp
System.map*
TAGS
aconf
diff --git a/Makefile b/Makefile
index 3f6628780eb2..dd5d6c258906 100644
--- a/Makefile
+++ b/Makefile
@@ -730,8 +730,13 @@ KBUILD_MODULES :=
KBUILD_BUILTIN := 1

# If we have only "make modules", don't compile built-in objects.
+# When we're building livepatch modules, we need to consider the
+# built-in objects during the descend as well, as built-in objects may
+# hold symbols which are referenced from livepatches and are required by
+# klp-convert post-processing tool for resolving these cases.
+
ifeq ($(MAKECMDGOALS),modules)
- KBUILD_BUILTIN :=
+ KBUILD_BUILTIN := $(if $(CONFIG_LIVEPATCH),1)
endif

# If we have "make <whatever> modules", compile modules
@@ -1183,6 +1188,7 @@ PHONY += prepare0
export extmod_prefix = $(if $(KBUILD_EXTMOD),$(KBUILD_EXTMOD)/)
export MODORDER := $(extmod_prefix)modules.order
export MODULES_NSDEPS := $(extmod_prefix)modules.nsdeps
+export MODULES_LIVEPATCH := $(extmod-prefix)modules.livepatch

ifeq ($(KBUILD_EXTMOD),)

@@ -1543,8 +1549,8 @@ endif
#

# *.ko are usually independent of vmlinux, but CONFIG_DEBUG_INFOBTF_MODULES
-# is an exception.
-ifdef CONFIG_DEBUG_INFO_BTF_MODULES
+# and CONFIG_LIVEPATCH are exceptions.
+ifneq ($(or $(CONFIG_DEBUG_INFO_BTF_MODULES),$(CONFIG_LIVEPATCH)),)
KBUILD_BUILTIN := 1
modules: vmlinux
endif
@@ -1602,14 +1608,14 @@ endif # CONFIG_MODULES
CLEAN_FILES += include/ksym vmlinux.symvers modules-only.symvers \
modules.builtin modules.builtin.modinfo modules.nsdeps \
compile_commands.json .thinlto-cache rust/test rust/doc \
- .vmlinux.objs .vmlinux.export.c
+ modules.livepatch .vmlinux.objs .vmlinux.export.c

# Directories & files removed with 'make mrproper'
MRPROPER_FILES += include/config include/generated \
arch/$(SRCARCH)/include/generated .objdiff \
debian snap tar-install \
.config .config.old .version \
- Module.symvers \
+ Module.symvers symbols.klp \
certs/signing_key.pem \
certs/x509.genkey \
vmlinux-gdb.py \
diff --git a/scripts/Makefile.modfinal b/scripts/Makefile.modfinal
index a30d5b08eee9..a8901e4e98c5 100644
--- a/scripts/Makefile.modfinal
+++ b/scripts/Makefile.modfinal
@@ -14,6 +14,7 @@ include $(srctree)/scripts/Makefile.lib

# find all modules listed in modules.order
modules := $(call read-file, $(MODORDER))
+modules-klp := $(call read-file, $(MODULES_LIVEPATCH))

__modfinal: $(modules:%.o=%.ko)
@:
@@ -65,6 +66,38 @@ endif

targets += $(modules:%.o=%.ko) $(modules:%.o=%.mod.o)

+# Livepatch
+# ---------------------------------------------------------------------------
+
+%.tmp.ko: %.o %.mod.o symbols.klp FORCE
+ +$(call if_changed,ld_ko_o)
+
+quiet_cmd_klp_convert = KLP $@
+ cmd_klp_convert = scripts/livepatch/klp-convert symbols.klp $< $@
+
+$(modules-klp:%.o=%.ko): %.ko: %.tmp.ko FORCE
+ $(call if_changed,klp_convert)
+
+targets += $(modules-klp:.ko=.tmp.ko)
+
+ifeq ($(KBUILD_EXTMOD),)
+filechk_klp_map = \
+ echo "klp-convert-symbol-data.0.1"; \
+ echo "*vmlinux"; \
+ $(NM) -f posix vmlinux | cut -d\ -f1; \
+ sort $(MODORDER) $(MODULES_LIVEPATCH) | \
+ uniq -u | \
+ sed 's/\.o$$//' | \
+ while read o; \
+ do \
+ echo "*$$(basename $$o)"; \
+ $(NM) -f posix $$o.o | cut -d\ -f1; \
+ done
+
+symbols.klp: FORCE
+ $(call filechk,klp_map)
+endif
+
# Add FORCE to the prequisites of a target to force it to be always rebuilt.
# ---------------------------------------------------------------------------

diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 43343e13c542..02f1354d4cff 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -47,6 +47,7 @@ modpost-args = \
$(if $(KBUILD_MODPOST_WARN),-w) \
$(if $(KBUILD_NSDEPS),-d $(MODULES_NSDEPS)) \
$(if $(CONFIG_MODULE_ALLOW_MISSING_NAMESPACE_IMPORTS)$(KBUILD_NSDEPS),-N) \
+ $(if $(CONFIG_LIVEPATCH),-l $(MODULES_LIVEPATCH)) \
-o $@

modpost-deps := $(MODPOST)
@@ -138,6 +139,10 @@ $(output-symdump): $(modpost-deps) FORCE
$(call if_changed,modpost)

__modpost: $(output-symdump)
+ifndef CONFIG_LIVEPATCH
+ $(Q)rm -f $(MODULES_LIVEPATCH)
+ $(Q)touch $(MODULES_LIVEPATCH)
+endif
PHONY += FORCE
FORCE:

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index efff8078e395..0a8f0ce75761 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1831,6 +1831,10 @@ static void read_symbols(const char *modname)
handle_moddevtable(mod, &info, sym, symname);
}

+ /* Livepatch modules have unresolved symbols resolved by klp-convert */
+ if (get_modinfo(&info, "livepatch"))
+ mod->is_livepatch = true;
+
for (sym = info.symtab_start; sym < info.symtab_stop; sym++) {
symname = remove_dot(info.strtab + sym->st_name);

@@ -1919,7 +1923,7 @@ static void check_exports(struct module *mod)
const char *basename;
exp = find_symbol(s->name);
if (!exp) {
- if (!s->weak && nr_unresolved++ < MAX_UNRESOLVED_REPORTS)
+ if (!s->weak && !mod->is_livepatch && nr_unresolved++ < MAX_UNRESOLVED_REPORTS)
modpost_log(warn_unresolved ? LOG_WARN : LOG_ERROR,
"\"%s\" [%s.ko] undefined!\n",
s->name, mod->name);
@@ -2320,6 +2324,20 @@ static void write_namespace_deps_files(const char *fname)
free(ns_deps_buf.p);
}

+static void write_livepatch_modules(const char *fname)
+{
+ struct buffer buf = { };
+ struct module *mod;
+
+ list_for_each_entry(mod, &modules, list) {
+ if (mod->is_livepatch)
+ buf_printf(&buf, "%s.o\n", mod->name);
+ }
+
+ write_if_changed(&buf, fname);
+ free(buf.p);
+}
+
struct dump_list {
struct list_head list;
const char *file;
@@ -2330,11 +2348,12 @@ int main(int argc, char **argv)
struct module *mod;
char *missing_namespace_deps = NULL;
char *dump_write = NULL, *files_source = NULL;
+ char *livepatch_modules = NULL;
int opt;
LIST_HEAD(dump_lists);
struct dump_list *dl, *dl2;

- while ((opt = getopt(argc, argv, "ei:mnT:o:awENd:")) != -1) {
+ while ((opt = getopt(argc, argv, "ei:l:mnT:o:awENd:")) != -1) {
switch (opt) {
case 'e':
external_module = true;
@@ -2344,6 +2363,9 @@ int main(int argc, char **argv)
dl->file = optarg;
list_add_tail(&dl->list, &dump_lists);
break;
+ case 'l':
+ livepatch_modules = optarg;
+ break;
case 'm':
modversions = true;
break;
@@ -2403,6 +2425,8 @@ int main(int argc, char **argv)

if (dump_write)
write_dump(dump_write);
+ if (livepatch_modules)
+ write_livepatch_modules(livepatch_modules);
if (sec_mismatch_count && !sec_mismatch_warn_only)
error("Section mismatches detected.\n"
"Set CONFIG_SECTION_MISMATCH_WARN_ONLY=y to allow them.\n");
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 1178f40a73f3..9be9bf6fb7da 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -119,6 +119,7 @@ struct module {
bool is_gpl_compatible;
bool from_dump; /* true if module was loaded from *.symvers */
bool is_vmlinux;
+ bool is_livepatch;
bool seen;
bool has_init;
bool has_cleanup;
--
2.39.2