On Thu, Sep 03, 2026 at 07:13:02PM +0000, [email protected] wrote:
> commit 828a4fa4f29a0a3c5aba9065f4ba35eb845dddef
> Author: Aaron Tomlin <[email protected]>
>
> module: Extend module_blacklist parameter to built-in modules
>
> This commit extends the module_blacklist command-line parameter to apply to
> built-in modules. It achieves this by creating a new .initcall.modnames
> section to map initcalls to module names, intercepting blacklisted builtin
> initcalls during early boot.
>
> > diff --git a/include/asm-generic/vmlinux.lds.h
> > b/include/asm-generic/vmlinux.lds.h
> > index b2988aa12f664..7490278b7a2df 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)
>
> [Severity: High]
> Does this section declaration need an alignment constraint? Without a
> preceding
> . = ALIGN(8); or similar, the __start_initcall_modnames label might capture
> the unaligned location counter before padding is inserted by the linker.
>
> When iterating over this section during early boot in do_initcall_level(),
> could the kernel read padding bytes as garbage pointers, breaking the
> builtin module blacklist feature or causing an unaligned memory access panic?
Hi Petr,
I forgot to restore ". = ALIGN(8)" in this iteration.
The following ensures the location counter . within .init.data is aligned
to an 8-byte boundary before __start_initcall_modnames = . is captured,
preventing any linker padding from preceding the first element of the
table.
Are you okay with the following?
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -735,6 +735,7 @@
LSM_TABLE() \
EARLY_LSM_TABLE() \
KUNIT_INIT_TABLE() \
+ . = ALIGN(8); \
BOUNDED_SECTION_BY(.initcall.modnames, _initcall_modnames)
#define INIT_TEXT \
> > diff --git a/rust/macros/module.rs b/rust/macros/module.rs
> > index bc7027f8dbb2c..a96157598197f 100644
> > --- a/rust/macros/module.rs
> > +++ b/rust/macros/module.rs
> [ ... ]
> > @@ -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();
>
> [Severity: Low]
> Will this cause a compilation failure for built-in Rust modules?
>
> It attempts to initialize a fixed-size array by dereferencing a dynamically
> sized slice returned by to_bytes_with_nul(). This could break the build when
> CONFIG_MODULES=n or when a Rust module is configured as built-in.
Hi Gary,
Calling .to_bytes_with_nul() on &CStr returns a slice reference (&[u8]), so
dereferencing it yields an unsized slice ([u8]).
To resolve this, we can follow the pattern already used in
rust/macros/module.rs for emitting '.modinfo' entries construct a byte
string literal at macro-expansion time using Literal::byte_string(). In
Rust, a byte string literal (b"...\0") has type &'static [u8; N], which can
be cleanly dereferenced with '*' into a fixed-size array [u8; N].
Would the following be appropriate?
diff --git a/rust/macros/module.rs b/rust/macros/module.rs
index a96157598197..67e3df8d4389 100644
--- a/rust/macros/module.rs
+++ b/rust/macros/module.rs
@@ -493,7 +493,9 @@ 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();
+ let name_bytes = name_cstr.to_bytes_with_nul();
+ let name_len = name_bytes.len();
+ let name_byte_literal = Literal::byte_string(name_bytes);
Ok(quote! {
/// The module name.
@@ -596,7 +598,7 @@ pub extern "C" fn cleanup_module() {
#[cfg(not(MODULE))]
#[used(compiler)]
#[link_section = ".init.rodata"]
- static #ident_modname_str: [u8; #name_len] =
*#name_cstr.to_bytes_with_nul();
+ static #ident_modname_str: [u8; #name_len] =
*#name_byte_literal;
#[cfg(not(MODULE))]
#[used(compiler)]
Kind regards,
--
Aaron Tomlin
