x86: Handle KCOV __init vs inline mismatches

GCC appears to have kind of fragile inlining heuristics, in the
sense that it can change whether or not it inlines something based on
optimizations. It looks like the kcov instrumentation being added (or in
this case, removed) from a function changes the optimization results,
and some functions marked "inline" are _not_ inlined. In that case,
we end up with __init code calling a function not marked __init, and we
get the build warnings I'm trying to eliminate in the coming patch that
adds __no_sanitize_coverage to __init functions:

WARNING: modpost: vmlinux: section mismatch in reference: xbc_exit+0x8 (section: .text.unlikely) -> _xbc_exit (section: .init.text)
WARNING: modpost: vmlinux: section mismatch in reference: real_mode_size_needed+0x15 (section: .text.unlikely) -> real_mode_blob_end (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: __set_percpu_decrypted+0x16 (section: .text.unlikely) -> early_set_memory_decrypted (section: .init.text)
WARNING: modpost: vmlinux: section mismatch in reference: memblock_alloc_from+0x26 (section: .text.unlikely) -> memblock_alloc_try_nid (section: .init.text)
WARNING: modpost: vmlinux: section mismatch in reference: acpi_arch_set_root_pointer+0xc (section: .text.unlikely) -> x86_init (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: acpi_arch_get_root_pointer+0x8 (section: .text.unlikely) -> x86_init (section: .init.data)
WARNING: modpost: vmlinux: section mismatch in reference: efi_config_table_is_usable+0x16 (section: .text.unlikely) -> xen_efi_config_table_is_usable (section: .init.text)

This problem is somewhat fragile (though using either __always_inline
or __init will deterministically solve it), but we've tripped over
this before with GCC and the solution has usually been to just use
__always_inline and move on.

For x86 this means forcing several functions to be inline with
__always_inline.

Link: https://lore.kernel.org/r/20250724055029.3623499-2-kees@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>

4 files changed, 5 insertions, 5 deletions

diff --git a/arch/x86/include/asm/acpi.h b/arch/x86/include/asm/acpi.h
index 5ab1a4598d00..a03aa6f999d1 100644
--- a/arch/x86/include/asm/acpi.h
+++ b/arch/x86/include/asm/acpi.h
@@ -158,13 +158,13 @@ static inline bool acpi_has_cpu_in_madt(void)
 }
 
 #define ACPI_HAVE_ARCH_SET_ROOT_POINTER
-static inline void acpi_arch_set_root_pointer(u64 addr)
+static __always_inline void acpi_arch_set_root_pointer(u64 addr)
 {
 	x86_init.acpi.set_root_pointer(addr);
 }
 
 #define ACPI_HAVE_ARCH_GET_ROOT_POINTER
-static inline u64 acpi_arch_get_root_pointer(void)
+static __always_inline u64 acpi_arch_get_root_pointer(void)
 {
 	return x86_init.acpi.get_root_pointer();
 }
diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h
index f607081a022a..e406a1e92c63 100644
--- a/arch/x86/include/asm/realmode.h
+++ b/arch/x86/include/asm/realmode.h
@@ -78,7 +78,7 @@ extern unsigned char secondary_startup_64[];
 extern unsigned char secondary_startup_64_no_verify[];
 #endif
 
-static inline size_t real_mode_size_needed(void)
+static __always_inline size_t real_mode_size_needed(void)
 {
 	if (real_mode_header)
 		return 0;	/* already allocated. */
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 921c1c783bc1..8ae750cde0c6 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -420,7 +420,7 @@ static u64 kvm_steal_clock(int cpu)
 	return steal;
 }
 
-static inline void __set_percpu_decrypted(void *ptr, unsigned long size)
+static inline __init void __set_percpu_decrypted(void *ptr, unsigned long size)
 {
 	early_set_memory_decrypted((unsigned long) ptr, size);
 }
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index ee66fae9ebcc..c02029cd27e1 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -806,7 +806,7 @@ kernel_physical_mapping_change(unsigned long paddr_start,
 }
 
 #ifndef CONFIG_NUMA
-static inline void x86_numa_init(void)
+static __always_inline void x86_numa_init(void)
 {
 	memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);
 }