From a8ff29f0ca1d63a215ef445102662850a912d127 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Tue, 27 Jan 2026 17:12:05 -0800 Subject: livepatch/klp-build: Require Clang assembler >= 20 Some special sections specify their ELF section entsize, for example: .pushsection section, "M", @progbits, 8 The entsize (8 in this example) is needed by objtool klp-diff for extracting individual entries. Clang assembler versions older than 20 silently ignore the above construct and set entsize to 0, resulting in the following error: .discard.annotate_data: missing special section entsize or annotations Add a klp-build check to prevent the use of Clang assembler versions prior to 20. Fixes: 24ebfcd65a87 ("livepatch/klp-build: Introduce klp-build script for generating livepatch modules") Reported-by: Song Liu Acked-by: Song Liu Link: https://patch.msgid.link/957fd52e375d0e2cfa3ac729160da995084a7f5e.1769562556.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf --- scripts/livepatch/klp-build | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'scripts') diff --git a/scripts/livepatch/klp-build b/scripts/livepatch/klp-build index a73515a82272..809e198a561d 100755 --- a/scripts/livepatch/klp-build +++ b/scripts/livepatch/klp-build @@ -249,6 +249,10 @@ validate_config() { [[ -v CONFIG_GCC_PLUGIN_RANDSTRUCT ]] && \ die "kernel option 'CONFIG_GCC_PLUGIN_RANDSTRUCT' not supported" + [[ -v CONFIG_AS_IS_LLVM ]] && \ + [[ "$CONFIG_AS_VERSION" -lt 200000 ]] && \ + die "Clang assembler version < 20 not supported" + return 0 } -- cgit v1.2.3 From ab10815472fcbc2c772dc21a979460b7f74f0145 Mon Sep 17 00:00:00 2001 From: Petr Pavlu Date: Fri, 23 Jan 2026 11:26:56 +0100 Subject: livepatch: Fix having __klp_objects relics in non-livepatch modules The linker script scripts/module.lds.S specifies that all input __klp_objects sections should be consolidated into an output section of the same name, and start/stop symbols should be created to enable scripts/livepatch/init.c to locate this data. This start/stop pattern is not ideal for modules because the symbols are created even if no __klp_objects input sections are present. Consequently, a dummy __klp_objects section also appears in the resulting module. This unnecessarily pollutes non-livepatch modules. Instead, since modules are relocatable files, the usual method for locating consolidated data in a module is to read its section table. This approach avoids the aforementioned problem. The klp_modinfo already stores a copy of the entire section table with the final addresses. Introduce a helper function that scripts/livepatch/init.c can call to obtain the location of the __klp_objects section from this data. Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing object files") Signed-off-by: Petr Pavlu Acked-by: Joe Lawrence Acked-by: Miroslav Benes Reviewed-by: Aaron Tomlin Link: https://patch.msgid.link/20260123102825.3521961-2-petr.pavlu@suse.com Signed-off-by: Josh Poimboeuf --- scripts/livepatch/init.c | 20 +++++++++----------- scripts/module.lds.S | 7 +------ 2 files changed, 10 insertions(+), 17 deletions(-) (limited to 'scripts') diff --git a/scripts/livepatch/init.c b/scripts/livepatch/init.c index 2274d8f5a482..9e315fc857bd 100644 --- a/scripts/livepatch/init.c +++ b/scripts/livepatch/init.c @@ -9,19 +9,19 @@ #include #include -extern struct klp_object_ext __start_klp_objects[]; -extern struct klp_object_ext __stop_klp_objects[]; - static struct klp_patch *patch; static int __init livepatch_mod_init(void) { + struct klp_object_ext *obj_exts; + size_t obj_exts_sec_size; struct klp_object *objs; unsigned int nr_objs; int ret; - nr_objs = __stop_klp_objects - __start_klp_objects; - + obj_exts = klp_find_section_by_name(THIS_MODULE, "__klp_objects", + &obj_exts_sec_size); + nr_objs = obj_exts_sec_size / sizeof(*obj_exts); if (!nr_objs) { pr_err("nothing to patch!\n"); ret = -EINVAL; @@ -41,7 +41,7 @@ static int __init livepatch_mod_init(void) } for (int i = 0; i < nr_objs; i++) { - struct klp_object_ext *obj_ext = __start_klp_objects + i; + struct klp_object_ext *obj_ext = obj_exts + i; struct klp_func_ext *funcs_ext = obj_ext->funcs; unsigned int nr_funcs = obj_ext->nr_funcs; struct klp_func *funcs = objs[i].funcs; @@ -90,12 +90,10 @@ err: static void __exit livepatch_mod_exit(void) { - unsigned int nr_objs; - - nr_objs = __stop_klp_objects - __start_klp_objects; + struct klp_object *obj; - for (int i = 0; i < nr_objs; i++) - kfree(patch->objs[i].funcs); + klp_for_each_object_static(patch, obj) + kfree(obj->funcs); kfree(patch->objs); kfree(patch); diff --git a/scripts/module.lds.S b/scripts/module.lds.S index 3037d5e5527c..383d19beffb4 100644 --- a/scripts/module.lds.S +++ b/scripts/module.lds.S @@ -35,12 +35,7 @@ SECTIONS { __patchable_function_entries : { *(__patchable_function_entries) } __klp_funcs 0: ALIGN(8) { KEEP(*(__klp_funcs)) } - - __klp_objects 0: ALIGN(8) { - __start_klp_objects = .; - KEEP(*(__klp_objects)) - __stop_klp_objects = .; - } + __klp_objects 0: ALIGN(8) { KEEP(*(__klp_objects)) } #ifdef CONFIG_ARCH_USES_CFI_TRAPS __kcfi_traps : { KEEP(*(.kcfi_traps)) } -- cgit v1.2.3 From b525fcaf0a76507f152d58c6f9e5ef67b3ff552c Mon Sep 17 00:00:00 2001 From: Petr Pavlu Date: Fri, 23 Jan 2026 11:26:57 +0100 Subject: livepatch: Free klp_{object,func}_ext data after initialization The klp_object_ext and klp_func_ext data, which are stored in the __klp_objects and __klp_funcs sections, respectively, are not needed after they are used to create the actual klp_object and klp_func instances. This operation is implemented by the init function in scripts/livepatch/init.c. Prefix the two sections with ".init" so they are freed after the module is initializated. Signed-off-by: Petr Pavlu Acked-by: Joe Lawrence Acked-by: Miroslav Benes Reviewed-by: Aaron Tomlin Link: https://patch.msgid.link/20260123102825.3521961-3-petr.pavlu@suse.com Signed-off-by: Josh Poimboeuf --- scripts/livepatch/init.c | 2 +- scripts/module.lds.S | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) (limited to 'scripts') diff --git a/scripts/livepatch/init.c b/scripts/livepatch/init.c index 9e315fc857bd..638c95cffe76 100644 --- a/scripts/livepatch/init.c +++ b/scripts/livepatch/init.c @@ -19,7 +19,7 @@ static int __init livepatch_mod_init(void) unsigned int nr_objs; int ret; - obj_exts = klp_find_section_by_name(THIS_MODULE, "__klp_objects", + obj_exts = klp_find_section_by_name(THIS_MODULE, ".init.klp_objects", &obj_exts_sec_size); nr_objs = obj_exts_sec_size / sizeof(*obj_exts); if (!nr_objs) { diff --git a/scripts/module.lds.S b/scripts/module.lds.S index 383d19beffb4..054ef99e8288 100644 --- a/scripts/module.lds.S +++ b/scripts/module.lds.S @@ -34,8 +34,8 @@ SECTIONS { __patchable_function_entries : { *(__patchable_function_entries) } - __klp_funcs 0: ALIGN(8) { KEEP(*(__klp_funcs)) } - __klp_objects 0: ALIGN(8) { KEEP(*(__klp_objects)) } + .init.klp_funcs 0 : ALIGN(8) { KEEP(*(.init.klp_funcs)) } + .init.klp_objects 0 : ALIGN(8) { KEEP(*(.init.klp_objects)) } #ifdef CONFIG_ARCH_USES_CFI_TRAPS __kcfi_traps : { KEEP(*(.kcfi_traps)) } -- cgit v1.2.3