[PATCH v7 21/22] x86/boot: Move startup code out of __head section

Ard Biesheuvel
2025-08-28T10:23:00Z

From: Ard Biesheuvel <ardb@kernel.org>

Move startup code out of the __head section, now that this no longer has
a special significance. Move everything into .text or .init.text as
appropriate, so that startup code is not kept around unnecessarily.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/boot/compressed/sev.c | 3 --
arch/x86/boot/startup/gdt_idt.c | 4 +--
arch/x86/boot/startup/map_kernel.c | 4 +--
arch/x86/boot/startup/sev-shared.c | 36 ++++++++++----------
arch/x86/boot/startup/sev-startup.c | 14 ++++----
arch/x86/boot/startup/sme.c | 26 +++++++-------
arch/x86/include/asm/init.h | 6 ----
arch/x86/kernel/head_32.S | 2 +-
arch/x86/kernel/head_64.S | 2 +-
arch/x86/platform/pvh/head.S | 2 +-
10 files changed, 45 insertions(+), 54 deletions(-)

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 6822eb4b9152..235e557fd10c 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -32,9 +32,6 @@ struct ghcb *boot_ghcb;
#undef __init
#define __init

-#undef __head
-#define __head
-
#define __BOOT_COMPRESSED

u8 snp_vmpl;
diff --git a/arch/x86/boot/startup/gdt_idt.c b/arch/x86/boot/startup/gdt_idt.c
index a3112a69b06a..d16102abdaec 100644
--- a/arch/x86/boot/startup/gdt_idt.c
+++ b/arch/x86/boot/startup/gdt_idt.c
@@ -24,7 +24,7 @@
static gate_desc bringup_idt_table[NUM_EXCEPTION_VECTORS] __page_aligned_data;

/* This may run while still in the direct mapping */
-void __head startup_64_load_idt(void *vc_handler)
+void startup_64_load_idt(void *vc_handler)
{
struct desc_ptr desc = {
.address = (unsigned long)rip_rel_ptr(bringup_idt_table),
@@ -46,7 +46,7 @@ void __head startup_64_load_idt(void *vc_handler)
/*
* Setup boot CPU state needed before kernel switches to virtual addresses.
*/
-void __head startup_64_setup_gdt_idt(void)
+void __init startup_64_setup_gdt_idt(void)
{
struct gdt_page *gp = rip_rel_ptr((void *)(__force unsigned long)&gdt_page);
void *handler = NULL;
diff --git a/arch/x86/boot/startup/map_kernel.c b/arch/x86/boot/startup/map_kernel.c
index 332dbe6688c4..83ba98d61572 100644
--- a/arch/x86/boot/startup/map_kernel.c
+++ b/arch/x86/boot/startup/map_kernel.c
@@ -30,7 +30,7 @@ static inline bool check_la57_support(void)
return true;
}

-static unsigned long __head sme_postprocess_startup(struct boot_params *bp,
+static unsigned long __init sme_postprocess_startup(struct boot_params *bp,
pmdval_t *pmd,
unsigned long p2v_offset)
{
@@ -84,7 +84,7 @@ static unsigned long __head sme_postprocess_startup(struct boot_params *bp,
* the 1:1 mapping of memory. Kernel virtual addresses can be determined by
* subtracting p2v_offset from the RIP-relative address.
*/
-unsigned long __head __startup_64(unsigned long p2v_offset,
+unsigned long __init __startup_64(unsigned long p2v_offset,
struct boot_params *bp)
{
pmd_t (*early_pgts)[PTRS_PER_PMD] = rip_rel_ptr(early_dynamic_pgts);
diff --git a/arch/x86/boot/startup/sev-shared.c b/arch/x86/boot/startup/sev-shared.c
index d6d807da2e6e..8d2476e1ad3b 100644
--- a/arch/x86/boot/startup/sev-shared.c
+++ b/arch/x86/boot/startup/sev-shared.c
@@ -31,7 +31,7 @@ static u32 cpuid_std_range_max __ro_after_init;
static u32 cpuid_hyp_range_max __ro_after_init;
static u32 cpuid_ext_range_max __ro_after_init;

-void __head __noreturn
+void __noreturn
sev_es_terminate(unsigned int set, unsigned int reason)
{
u64 val = GHCB_MSR_TERM_REQ;
@@ -50,7 +50,7 @@ sev_es_terminate(unsigned int set, unsigned int reason)
/*
* The hypervisor features are available from GHCB version 2 onward.
*/
-u64 get_hv_features(void)
+u64 __init get_hv_features(void)
{
u64 val;

@@ -220,7 +220,7 @@ const struct snp_cpuid_table *snp_cpuid_get_table(void)
*
* Return: XSAVE area size on success, 0 otherwise.
*/
-static u32 __head snp_cpuid_calc_xsave_size(u64 xfeatures_en, bool compacted)
+static u32 snp_cpuid_calc_xsave_size(u64 xfeatures_en, bool compacted)
{
const struct snp_cpuid_table *cpuid_table = snp_cpuid_get_table();
u64 xfeatures_found = 0;
@@ -256,7 +256,7 @@ static u32 __head snp_cpuid_calc_xsave_size(u64 xfeatures_en, bool compacted)
return xsave_size;
}

-static bool __head
+static bool
snp_cpuid_get_validated_func(struct cpuid_leaf *leaf)
{
const struct snp_cpuid_table *cpuid_table = snp_cpuid_get_table();
@@ -298,7 +298,7 @@ static void snp_cpuid_hv_msr(void *ctx, struct cpuid_leaf *leaf)
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_CPUID_HV);
}

-static int __head
+static int
snp_cpuid_postprocess(void (*cpuid_fn)(void *ctx, struct cpuid_leaf *leaf),
void *ctx, struct cpuid_leaf *leaf)
{
@@ -394,8 +394,8 @@ snp_cpuid_postprocess(void (*cpuid_fn)(void *ctx, struct cpuid_leaf *leaf),
* Returns -EOPNOTSUPP if feature not enabled. Any other non-zero return value
* should be treated as fatal by caller.
*/
-int __head snp_cpuid(void (*cpuid_fn)(void *ctx, struct cpuid_leaf *leaf),
- void *ctx, struct cpuid_leaf *leaf)
+int snp_cpuid(void (*cpuid_fn)(void *ctx, struct cpuid_leaf *leaf),
+ void *ctx, struct cpuid_leaf *leaf)
{
const struct snp_cpuid_table *cpuid_table = snp_cpuid_get_table();

@@ -437,7 +437,7 @@ int __head snp_cpuid(void (*cpuid_fn)(void *ctx, struct cpuid_leaf *leaf),
* page yet, so it only supports the MSR based communication with the
* hypervisor and only the CPUID exit-code.
*/
-void __head do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code)
+void do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code)
{
unsigned int subfn = lower_bits(regs->cx, 32);
unsigned int fn = lower_bits(regs->ax, 32);
@@ -513,7 +513,7 @@ struct cc_setup_data {
* Search for a Confidential Computing blob passed in as a setup_data entry
* via the Linux Boot Protocol.
*/
-static __head
+static __init
struct cc_blob_sev_info *find_cc_blob_setup_data(struct boot_params *bp)
{
struct cc_setup_data *sd = NULL;
@@ -541,7 +541,7 @@ struct cc_blob_sev_info *find_cc_blob_setup_data(struct boot_params *bp)
* mapping needs to be updated in sync with all the changes to virtual memory
* layout and related mapping facilities throughout the boot process.
*/
-static void __head setup_cpuid_table(const struct cc_blob_sev_info *cc_info)
+static void __init setup_cpuid_table(const struct cc_blob_sev_info *cc_info)
{
const struct snp_cpuid_table *cpuid_table_fw, *cpuid_table;
int i;
@@ -569,7 +569,7 @@ static void __head setup_cpuid_table(const struct cc_blob_sev_info *cc_info)
}
}

-static int __head svsm_call_msr_protocol(struct svsm_call *call)
+static int svsm_call_msr_protocol(struct svsm_call *call)
{
int ret;

@@ -580,8 +580,8 @@ static int __head svsm_call_msr_protocol(struct svsm_call *call)
return ret;
}

-static void __head svsm_pval_4k_page(unsigned long paddr, bool validate,
- struct svsm_ca *caa, u64 caa_pa)
+static void svsm_pval_4k_page(unsigned long paddr, bool validate,
+ struct svsm_ca *caa, u64 caa_pa)
{
struct svsm_pvalidate_call *pc;
struct svsm_call call = {};
@@ -622,8 +622,8 @@ static void __head svsm_pval_4k_page(unsigned long paddr, bool validate,
native_local_irq_restore(flags);
}

-static void __head pvalidate_4k_page(unsigned long vaddr, unsigned long paddr,
- bool validate, struct svsm_ca *caa, u64 caa_pa)
+static void pvalidate_4k_page(unsigned long vaddr, unsigned long paddr,
+ bool validate, struct svsm_ca *caa, u64 caa_pa)
{
int ret;

@@ -643,8 +643,8 @@ static void __head pvalidate_4k_page(unsigned long vaddr, unsigned long paddr,
sev_evict_cache((void *)vaddr, 1);
}

-static void __head __page_state_change(unsigned long vaddr, unsigned long paddr,
- const struct psc_desc *desc)
+static void __page_state_change(unsigned long vaddr, unsigned long paddr,
+ const struct psc_desc *desc)
{
u64 val, msr;

@@ -682,7 +682,7 @@ static void __head __page_state_change(unsigned long vaddr, unsigned long paddr,
* Maintain the GPA of the SVSM Calling Area (CA) in order to utilize the SVSM
* services needed when not running in VMPL0.
*/
-static bool __head svsm_setup_ca(const struct cc_blob_sev_info *cc_info,
+static bool __init svsm_setup_ca(const struct cc_blob_sev_info *cc_info,
void *page)
{
struct snp_secrets_page *secrets_page;
diff --git a/arch/x86/boot/startup/sev-startup.c b/arch/x86/boot/startup/sev-startup.c
index 9f4b4ca7deaa..39465a0ff4e5 100644
--- a/arch/x86/boot/startup/sev-startup.c
+++ b/arch/x86/boot/startup/sev-startup.c
@@ -44,7 +44,7 @@
/* Include code shared with pre-decompression boot stage */
#include "sev-shared.c"

-void __head
+void __init
early_set_pages_state(unsigned long vaddr, unsigned long paddr,
unsigned long npages, const struct psc_desc *desc)
{
@@ -63,7 +63,7 @@ early_set_pages_state(unsigned long vaddr, unsigned long paddr,
}
}

-void __head early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr,
+void __init early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr,
unsigned long npages)
{
struct psc_desc d = {
@@ -88,7 +88,7 @@ void __head early_snp_set_memory_private(unsigned long vaddr, unsigned long padd
early_set_pages_state(vaddr, paddr, npages, &d);
}

-void __head early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
+void __init early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
unsigned long npages)
{
struct psc_desc d = {
@@ -123,7 +123,7 @@ void __head early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr
*
* Scan for the blob in that order.
*/
-static __head struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
+static struct cc_blob_sev_info *__init find_cc_blob(struct boot_params *bp)
{
struct cc_blob_sev_info *cc_info;

@@ -149,7 +149,7 @@ static __head struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
return cc_info;
}

-static __head void svsm_setup(struct cc_blob_sev_info *cc_info)
+static void __init svsm_setup(struct cc_blob_sev_info *cc_info)
{
struct snp_secrets_page *secrets = (void *)cc_info->secrets_phys;
struct svsm_call call = {};
@@ -190,7 +190,7 @@ static __head void svsm_setup(struct cc_blob_sev_info *cc_info)
boot_svsm_caa_pa = pa;
}

-bool __head snp_init(struct boot_params *bp)
+bool __init snp_init(struct boot_params *bp)
{
struct cc_blob_sev_info *cc_info;

@@ -219,7 +219,7 @@ bool __head snp_init(struct boot_params *bp)
return true;
}

-void __head __noreturn snp_abort(void)
+void __init __noreturn snp_abort(void)
{
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
}
diff --git a/arch/x86/boot/startup/sme.c b/arch/x86/boot/startup/sme.c
index eb6a758ba660..39e7e9d18974 100644
--- a/arch/x86/boot/startup/sme.c
+++ b/arch/x86/boot/startup/sme.c
@@ -91,7 +91,7 @@ struct sme_populate_pgd_data {
*/
static char sme_workarea[2 * PMD_SIZE] __section(".init.scratch");

-static void __head sme_clear_pgd(struct sme_populate_pgd_data *ppd)
+static void __init sme_clear_pgd(struct sme_populate_pgd_data *ppd)
{
unsigned long pgd_start, pgd_end, pgd_size;
pgd_t *pgd_p;
@@ -106,7 +106,7 @@ static void __head sme_clear_pgd(struct sme_populate_pgd_data *ppd)
memset(pgd_p, 0, pgd_size);
}

-static pud_t __head *sme_prepare_pgd(struct sme_populate_pgd_data *ppd)
+static pud_t __init *sme_prepare_pgd(struct sme_populate_pgd_data *ppd)
{
pgd_t *pgd;
p4d_t *p4d;
@@ -143,7 +143,7 @@ static pud_t __head *sme_prepare_pgd(struct sme_populate_pgd_data *ppd)
return pud;
}

-static void __head sme_populate_pgd_large(struct sme_populate_pgd_data *ppd)
+static void __init sme_populate_pgd_large(struct sme_populate_pgd_data *ppd)
{
pud_t *pud;
pmd_t *pmd;
@@ -159,7 +159,7 @@ static void __head sme_populate_pgd_large(struct sme_populate_pgd_data *ppd)
set_pmd(pmd, __pmd(ppd->paddr | ppd->pmd_flags));
}

-static void __head sme_populate_pgd(struct sme_populate_pgd_data *ppd)
+static void __init sme_populate_pgd(struct sme_populate_pgd_data *ppd)
{
pud_t *pud;
pmd_t *pmd;
@@ -185,7 +185,7 @@ static void __head sme_populate_pgd(struct sme_populate_pgd_data *ppd)
set_pte(pte, __pte(ppd->paddr | ppd->pte_flags));
}

-static void __head __sme_map_range_pmd(struct sme_populate_pgd_data *ppd)
+static void __init __sme_map_range_pmd(struct sme_populate_pgd_data *ppd)
{
while (ppd->vaddr < ppd->vaddr_end) {
sme_populate_pgd_large(ppd);
@@ -195,7 +195,7 @@ static void __head __sme_map_range_pmd(struct sme_populate_pgd_data *ppd)
}
}

-static void __head __sme_map_range_pte(struct sme_populate_pgd_data *ppd)
+static void __init __sme_map_range_pte(struct sme_populate_pgd_data *ppd)
{
while (ppd->vaddr < ppd->vaddr_end) {
sme_populate_pgd(ppd);
@@ -205,7 +205,7 @@ static void __head __sme_map_range_pte(struct sme_populate_pgd_data *ppd)
}
}

-static void __head __sme_map_range(struct sme_populate_pgd_data *ppd,
+static void __init __sme_map_range(struct sme_populate_pgd_data *ppd,
pmdval_t pmd_flags, pteval_t pte_flags)
{
unsigned long vaddr_end;
@@ -229,22 +229,22 @@ static void __head __sme_map_range(struct sme_populate_pgd_data *ppd,
__sme_map_range_pte(ppd);
}

-static void __head sme_map_range_encrypted(struct sme_populate_pgd_data *ppd)
+static void __init sme_map_range_encrypted(struct sme_populate_pgd_data *ppd)
{
__sme_map_range(ppd, PMD_FLAGS_ENC, PTE_FLAGS_ENC);
}

-static void __head sme_map_range_decrypted(struct sme_populate_pgd_data *ppd)
+static void __init sme_map_range_decrypted(struct sme_populate_pgd_data *ppd)
{
__sme_map_range(ppd, PMD_FLAGS_DEC, PTE_FLAGS_DEC);
}

-static void __head sme_map_range_decrypted_wp(struct sme_populate_pgd_data *ppd)
+static void __init sme_map_range_decrypted_wp(struct sme_populate_pgd_data *ppd)
{
__sme_map_range(ppd, PMD_FLAGS_DEC_WP, PTE_FLAGS_DEC_WP);
}

-static unsigned long __head sme_pgtable_calc(unsigned long len)
+static unsigned long __init sme_pgtable_calc(unsigned long len)
{
unsigned long entries = 0, tables = 0;

@@ -281,7 +281,7 @@ static unsigned long __head sme_pgtable_calc(unsigned long len)
return entries + tables;
}

-void __head sme_encrypt_kernel(struct boot_params *bp)
+void __init sme_encrypt_kernel(struct boot_params *bp)
{
unsigned long workarea_start, workarea_end, workarea_len;
unsigned long execute_start, execute_end, execute_len;
@@ -485,7 +485,7 @@ void __head sme_encrypt_kernel(struct boot_params *bp)
native_write_cr3(__native_read_cr3());
}

-void __head sme_enable(struct boot_params *bp)
+void __init sme_enable(struct boot_params *bp)
{
unsigned int eax, ebx, ecx, edx;
unsigned long feature_mask;
diff --git a/arch/x86/include/asm/init.h b/arch/x86/include/asm/init.h
index 5a68e9db6518..01ccdd168df0 100644
--- a/arch/x86/include/asm/init.h
+++ b/arch/x86/include/asm/init.h
@@ -2,12 +2,6 @@
#ifndef _ASM_X86_INIT_H
#define _ASM_X86_INIT_H

-#if defined(CONFIG_CC_IS_CLANG) && CONFIG_CLANG_VERSION < 170000
-#define __head __section(".head.text") __no_sanitize_undefined __no_stack_protector
-#else
-#define __head __section(".head.text") __no_sanitize_undefined __no_kstack_erase
-#endif
-
struct x86_mapping_info {
void *(*alloc_pgt_page)(void *); /* allocate buf for page table */
void (*free_pgt_page)(void *, void *); /* free buf for page table */
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 76743dfad6ab..437effb1ef03 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -61,7 +61,7 @@ RESERVE_BRK(pagetables, INIT_MAP_SIZE)
* any particular GDT layout, because we load our own as soon as we
* can.
*/
-__HEAD
+ __INIT
SYM_CODE_START(startup_32)
movl pa(initial_stack),%ecx

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index d219963ecb60..21816b48537c 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -33,7 +33,7 @@
* because we need identity-mapped pages.
*/

- __HEAD
+ __INIT
.code64
SYM_CODE_START_NOALIGN(startup_64)
UNWIND_HINT_END_OF_STACK
diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index 1d78e5631bb8..344030c1a81d 100644
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -24,7 +24,7 @@
#include <asm/nospec-branch.h>
#include <xen/interface/elfnote.h>

- __HEAD
+ __INIT

/*
* Entry point for PVH guests.
--
2.51.0.268.g9569e192d0-goog