[PATCH v6 09/10] x86/sev: Move early startup code into .head.text section

Ard Biesheuvel
2024-02-26T14:30:22Z

In preparation for implementing rigorous build time checks to enforce
that only code that can support it will be called from the early 1:1
mapping of memory, move SEV init code that is called in this manner to
the .head.text section.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
arch/x86/boot/compressed/sev.c | 3 +++
arch/x86/include/asm/sev.h | 10 ++++-----
arch/x86/kernel/sev-shared.c | 23 +++++++++-----------
arch/x86/kernel/sev.c | 14 +++++++-----
4 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 073291832f44..bea0719d70f2 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -116,6 +116,9 @@ static bool fault_in_kernel_space(unsigned long address)
#undef __init
#define __init

+#undef __head
+#define __head
+
#define __BOOT_COMPRESSED

/* Basic instruction decoding support needed */
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index bed95e1f4d52..cf671138feef 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -213,16 +213,16 @@ static inline int pvalidate(unsigned long vaddr, bool rmp_psize, bool validate)
struct snp_guest_request_ioctl;

void setup_ghcb(void);
-void __init early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr,
- unsigned long npages);
-void __init early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
- unsigned long npages);
+void early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr,
+ unsigned long npages);
+void early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
+ unsigned long npages);
void __init snp_prep_memory(unsigned long paddr, unsigned int sz, enum psc_op op);
void snp_set_memory_shared(unsigned long vaddr, unsigned long npages);
void snp_set_memory_private(unsigned long vaddr, unsigned long npages);
void snp_set_wakeup_secondary_cpu(void);
bool snp_init(struct boot_params *bp);
-void __init __noreturn snp_abort(void);
+void __noreturn snp_abort(void);
int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio);
void snp_accept_memory(phys_addr_t start, phys_addr_t end);
u64 snp_get_unsupported_features(u64 status);
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index ae79f9505298..0bd7ccbe8732 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -93,7 +93,8 @@ static bool __init sev_es_check_cpu_features(void)
return true;
}

-static void __noreturn sev_es_terminate(unsigned int set, unsigned int reason)
+static void __head __noreturn
+sev_es_terminate(unsigned int set, unsigned int reason)
{
u64 val = GHCB_MSR_TERM_REQ;

@@ -330,13 +331,7 @@ static int sev_cpuid_hv(struct ghcb *ghcb, struct es_em_ctxt *ctxt, struct cpuid
*/
static const struct snp_cpuid_table *snp_cpuid_get_table(void)
{
- void *ptr;
-
- asm ("lea cpuid_table_copy(%%rip), %0"
- : "=r" (ptr)
- : "p" (&cpuid_table_copy));
-
- return ptr;
+ return &RIP_REL_REF(cpuid_table_copy);
}

/*
@@ -395,7 +390,7 @@ static u32 snp_cpuid_calc_xsave_size(u64 xfeatures_en, bool compacted)
return xsave_size;
}

-static bool
+static bool __head
snp_cpuid_get_validated_func(struct cpuid_leaf *leaf)
{
const struct snp_cpuid_table *cpuid_table = snp_cpuid_get_table();
@@ -532,7 +527,8 @@ static int snp_cpuid_postprocess(struct ghcb *ghcb, struct es_em_ctxt *ctxt,
* Returns -EOPNOTSUPP if feature not enabled. Any other non-zero return value
* should be treated as fatal by caller.
*/
-static int snp_cpuid(struct ghcb *ghcb, struct es_em_ctxt *ctxt, struct cpuid_leaf *leaf)
+static int __head
+snp_cpuid(struct ghcb *ghcb, struct es_em_ctxt *ctxt, struct cpuid_leaf *leaf)
{
const struct snp_cpuid_table *cpuid_table = snp_cpuid_get_table();

@@ -574,7 +570,7 @@ static int snp_cpuid(struct ghcb *ghcb, struct es_em_ctxt *ctxt, struct cpuid_le
* page yet, so it only supports the MSR based communication with the
* hypervisor and only the CPUID exit-code.
*/
-void __init do_vc_no_ghcb(struct pt_regs *regs, unsigned long exit_code)
+void __head 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);
@@ -1025,7 +1021,8 @@ struct cc_setup_data {
* Search for a Confidential Computing blob passed in as a setup_data entry
* via the Linux Boot Protocol.
*/
-static struct cc_blob_sev_info *find_cc_blob_setup_data(struct boot_params *bp)
+static __head
+struct cc_blob_sev_info *find_cc_blob_setup_data(struct boot_params *bp)
{
struct cc_setup_data *sd = NULL;
struct setup_data *hdr;
@@ -1052,7 +1049,7 @@ static 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 __init setup_cpuid_table(const struct cc_blob_sev_info *cc_info)
+static void __head setup_cpuid_table(const struct cc_blob_sev_info *cc_info)
{
const struct snp_cpuid_table *cpuid_table_fw, *cpuid_table;
int i;
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 1ef7ae806a01..33c14aa1f06c 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -25,6 +25,7 @@
#include <linux/psp-sev.h>
#include <uapi/linux/sev-guest.h>

+#include <asm/init.h>
#include <asm/cpu_entry_area.h>
#include <asm/stacktrace.h>
#include <asm/sev.h>
@@ -682,8 +683,9 @@ static u64 __init get_jump_table_addr(void)
return ret;
}

-static void early_set_pages_state(unsigned long vaddr, unsigned long paddr,
- unsigned long npages, enum psc_op op)
+static void __head
+early_set_pages_state(unsigned long vaddr, unsigned long paddr,
+ unsigned long npages, enum psc_op op)
{
unsigned long paddr_end;
u64 val;
@@ -739,7 +741,7 @@ static void early_set_pages_state(unsigned long vaddr, unsigned long paddr,
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_PSC);
}

-void __init early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr,
+void __head early_snp_set_memory_private(unsigned long vaddr, unsigned long paddr,
unsigned long npages)
{
/*
@@ -2062,7 +2064,7 @@ bool __init handle_vc_boot_ghcb(struct pt_regs *regs)
*
* Scan for the blob in that order.
*/
-static __init struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
+static __head struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
{
struct cc_blob_sev_info *cc_info;

@@ -2088,7 +2090,7 @@ static __init struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
return cc_info;
}

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

@@ -2110,7 +2112,7 @@ bool __init snp_init(struct boot_params *bp)
return true;
}

-void __init __noreturn snp_abort(void)
+void __head __noreturn snp_abort(void)
{
sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
}
--
2.44.0.rc0.258.g7320e95886-goog