Currently, the "module_blacklist=" command-line parameter only applies to loadable modules. If a module is built-in, the parameter is silently ignored. This patch extends the blacklisting functionality to built-in modules by intercepting their initialisation routines during early boot.
To achieve this, we introduce a new ".initcall.modnames" memory section. For each built-in module, we use a standard C structure (i.e., struct initcall_modname) to map its initcall function pointer to its associated KBUILD_MODNAME string. This mapping is restricted only to files implementing built-in modules via module_init() to avoid mapping core kernel subsystems and save memory. During boot, built-in initcalls are executed sequentially via do_initcall_level() and do_pre_smp_initcalls(). We introduce a new wrapper function, do_one_initcall_builtin(), to cross-reference the initcall function pointer against the ".initcall.modnames" table. If a match is found and the module is present in the blacklist, the initcall is skipped. To make the blacklist functional on monolithic kernels, the command-line parameter parsing and the module_is_blacklisted() lookup function are decoupled from the loadable module subsystem and moved to init/main.c. This enables "module_blacklist=" to intercept built-in modules even on kernels built with CONFIG_MODULES=n. Signed-off-by: Aaron Tomlin <[email protected]> --- include/asm-generic/vmlinux.lds.h | 3 +- include/linux/init.h | 25 +++++++++++++- include/linux/module.h | 4 ++- init/main.c | 54 +++++++++++++++++++++++++++++-- kernel/module/main.c | 23 +------------ rust/bindings/bindings_helper.h | 1 + rust/macros/module.rs | 17 ++++++++++ 7 files changed, 100 insertions(+), 27 deletions(-) diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index b2988aa12f66..7490278b7a2d 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -734,7 +734,8 @@ EARLYCON_TABLE() \ LSM_TABLE() \ EARLY_LSM_TABLE() \ - KUNIT_INIT_TABLE() + KUNIT_INIT_TABLE() \ + BOUNDED_SECTION_BY(.initcall.modnames, _initcall_modnames) #define INIT_TEXT \ *(.init.text .init.text.*) \ diff --git a/include/linux/init.h b/include/linux/init.h index 6326c61e2332..833b837ce11d 100644 --- a/include/linux/init.h +++ b/include/linux/init.h @@ -252,6 +252,7 @@ extern struct module __this_module; #endif #ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS +#define __initcall_fn_ptr(fn, __iid, id) __initcall_stub(fn, __iid, id) #define ____define_initcall(fn, __stub, __name, __sec) \ __define_initcall_stub(__stub, fn) \ asm(".section \"" __sec "\", \"a\" \n" \ @@ -260,6 +261,7 @@ extern struct module __this_module; ".previous \n"); \ static_assert(__same_type(initcall_t, &fn)); #else +#define __initcall_fn_ptr(fn, __iid, id) fn #define ____define_initcall(fn, __unused, __name, __sec) \ static initcall_t __name __used \ __attribute__((__section__(__sec))) = fn; @@ -271,7 +273,28 @@ extern struct module __this_module; __initcall_name(initcall, __iid, id), \ __initcall_section(__sec, __iid)) -#define ___define_initcall(fn, id, __sec) \ +struct initcall_modname { + initcall_t initcall_fn; + const char *modname; +}; + +#define ____define_initcall_modname(fn, id, __sec, __iid) \ + __unique_initcall(fn, id, __sec, __iid) \ + static const char __initstr_##fn[] __used __aligned(1) \ + __section(".init.rodata") = KBUILD_MODNAME; \ + static const struct initcall_modname __modname_##fn __used \ + __section(".initcall.modnames") \ + __aligned(__alignof__(struct initcall_modname)) = { \ + .initcall_fn = __initcall_fn_ptr(fn, __iid, id),\ + .modname = __initstr_##fn \ + }; + +#define __define_initcall_modname(fn, id) \ + ____define_initcall_modname(fn, id, .initcall##id, __initcall_id(fn)) + +#define __builtin_module_initcall(fn) __define_initcall_modname(fn, 6) + +#define ___define_initcall(fn, id, __sec) \ __unique_initcall(fn, id, __sec, __initcall_id(fn)) #define __define_initcall(fn, id) ___define_initcall(fn, id, .initcall##id) diff --git a/include/linux/module.h b/include/linux/module.h index 96cc98568eea..bcc54edbde7d 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -86,7 +86,7 @@ extern void cleanup_module(void); * builtin) or at module insertion time (if a module). There can only * be one per module. */ -#define module_init(x) __initcall(x); +#define module_init(x) __builtin_module_initcall(x); /** * module_exit() - driver exit entry point @@ -879,6 +879,8 @@ static inline void module_for_each_mod(int(*func)(struct module *mod, void *data } #endif /* CONFIG_MODULES */ +bool module_is_blacklisted(const char *module_name); + #ifdef CONFIG_SYSFS extern struct kset *module_kset; extern const struct kobj_type module_ktype; diff --git a/init/main.c b/init/main.c index 2613d3f9b3ce..0ee3b23bcd2b 100644 --- a/init/main.c +++ b/init/main.c @@ -1344,6 +1344,56 @@ static inline void do_trace_initcall_level(const char *level) } #endif /* !TRACEPOINTS_ENABLED */ +extern struct initcall_modname __start_initcall_modnames[]; +extern struct initcall_modname __stop_initcall_modnames[]; + +/* module_blacklist is a comma-separated list of module names */ +static char *module_blacklist; +bool __init_or_module module_is_blacklisted(const char *module_name) +{ + const char *p; + size_t len; + + if (!module_blacklist) + return false; + + for (p = module_blacklist; *p; p += len) { + len = strcspn(p, ","); + if (strlen(module_name) == len && !memcmp(module_name, p, len)) + return true; + if (p[len] == ',') + len++; + } + return false; +} +core_param(module_blacklist, module_blacklist, charp, 0400); + +static const char *__init get_builtin_modname(initcall_t fn) +{ + struct initcall_modname *p; + + for (p = __start_initcall_modnames; p < __stop_initcall_modnames; p++) { + if (p->initcall_fn == fn) + return p->modname; + } + return NULL; +} + +static void __init do_one_initcall_builtin(initcall_t fn) +{ + const char *modname; + + if (module_blacklist) { + modname = get_builtin_modname(fn); + if (modname && module_is_blacklisted(modname)) { + pr_info("Skipping initcall for blacklisted built-in module %s\n", + modname); + return; + } + } + do_one_initcall(fn); +} + int __init_or_module do_one_initcall(initcall_t fn) { int count = preempt_count(); @@ -1416,7 +1466,7 @@ static void __init do_initcall_level(int level, char *command_line) do_trace_initcall_level(initcall_level_names[level]); for (fn = initcall_levels[level]; fn < initcall_levels[level+1]; fn++) - do_one_initcall(initcall_from_entry(fn)); + do_one_initcall_builtin(initcall_from_entry(fn)); } static void __init do_initcalls(void) @@ -1461,7 +1511,7 @@ static void __init do_pre_smp_initcalls(void) do_trace_initcall_level("early"); for (fn = __initcall_start; fn < __initcall0_start; fn++) - do_one_initcall(initcall_from_entry(fn)); + do_one_initcall_builtin(initcall_from_entry(fn)); } static int run_init_process(const char *init_filename) diff --git a/kernel/module/main.c b/kernel/module/main.c index d0e1e0bd2ad0..a9fd6aaedc69 100644 --- a/kernel/module/main.c +++ b/kernel/module/main.c @@ -2930,27 +2930,6 @@ int __weak module_frob_arch_sections(Elf_Ehdr *hdr, return 0; } -/* module_blacklist is a comma-separated list of module names */ -static char *module_blacklist; -static bool blacklisted(const char *module_name) -{ - const char *p; - size_t len; - - if (!module_blacklist) - return false; - - for (p = module_blacklist; *p; p += len) { - len = strcspn(p, ","); - if (strlen(module_name) == len && !memcmp(module_name, p, len)) - return true; - if (p[len] == ',') - len++; - } - return false; -} -core_param(module_blacklist, module_blacklist, charp, 0400); - static struct module *layout_and_allocate(struct load_info *info, int flags) { struct module *mod; @@ -3402,7 +3381,7 @@ static int early_mod_check(struct load_info *info, int flags) * Now that we know we have the correct module name, check * if it's blacklisted. */ - if (blacklisted(info->name)) { + if (module_is_blacklisted(info->name)) { pr_err("Module %s is blacklisted\n", info->name); return -EPERM; } diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index 4b31aa7f432f..1075b26e53ac 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -63,6 +63,7 @@ #include <linux/fwctl.h> #include <linux/fs.h> #include <linux/i2c.h> +#include <linux/init.h> #include <linux/interrupt.h> #include <linux/io-pgtable.h> #include <linux/ioport.h> diff --git a/rust/macros/module.rs b/rust/macros/module.rs index bc7027f8dbb2..a96157598197 100644 --- a/rust/macros/module.rs +++ b/rust/macros/module.rs @@ -480,6 +480,8 @@ pub(crate) fn module(info: ModuleInfo) -> Result<TokenStream> { let ident_init = format_ident!("__{ident}_init"); let ident_exit = format_ident!("__{ident}_exit"); let ident_initcall = format_ident!("__{ident}_initcall"); + let ident_modname = format_ident!("__{ident}_modname"); + let ident_modname_str = format_ident!("__{ident}_modname_str"); let initcall_section = ".initcall6.init"; let global_asm = format!( @@ -491,6 +493,7 @@ pub(crate) fn module(info: ModuleInfo) -> Result<TokenStream> { ); let name_cstr = CString::new(name.value()).expect("name contains NUL-terminator"); + let name_len = name_cstr.to_bytes_with_nul().len(); Ok(quote! { /// The module name. @@ -591,6 +594,20 @@ pub extern "C" fn cleanup_module() { #[cfg(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)] ::core::arch::global_asm!(#global_asm); + #[cfg(not(MODULE))] + #[used(compiler)] + #[link_section = ".init.rodata"] + static #ident_modname_str: [u8; #name_len] = *#name_cstr.to_bytes_with_nul(); + + #[cfg(not(MODULE))] + #[used(compiler)] + #[link_section = ".initcall.modnames"] + static #ident_modname: ::kernel::bindings::initcall_modname = + ::kernel::bindings::initcall_modname { + initcall_fn: Some(#ident_init), + modname: #ident_modname_str.as_ptr().cast(), + }; + #[cfg(not(MODULE))] #[no_mangle] pub extern "C" fn #ident_init() -> ::kernel::ffi::c_int { -- 2.55.0
