[PATCH v12 24/46] x86/compressed/acpi: Move EFI detection to helper

Brijesh Singh
2022-03-07T21:35:59Z

From: Michael Roth <michael.roth@amd.com>

Future patches for SEV-SNP-validated CPUID will also require early
parsing of the EFI configuration. Incrementally move the related
code into a set of helpers that can be re-used for that purpose.

Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
arch/x86/boot/compressed/Makefile | 1 +
arch/x86/boot/compressed/acpi.c | 28 +++++++----------
arch/x86/boot/compressed/efi.c | 50 +++++++++++++++++++++++++++++++
arch/x86/boot/compressed/misc.h | 16 ++++++++++
4 files changed, 77 insertions(+), 18 deletions(-)
create mode 100644 arch/x86/boot/compressed/efi.c

diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
index 6115274fe10f..e69c3d2e0628 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -103,6 +103,7 @@ endif
vmlinux-objs-$(CONFIG_ACPI) += $(obj)/acpi.o

vmlinux-objs-$(CONFIG_EFI_MIXED) += $(obj)/efi_thunk_$(BITS).o
+vmlinux-objs-$(CONFIG_EFI) += $(obj)/efi.o
efi-obj-$(CONFIG_EFI_STUB) = $(objtree)/drivers/firmware/efi/libstub/lib.a

$(obj)/vmlinux: $(vmlinux-objs-y) $(efi-obj-y) FORCE
diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index 8bcbcee54aa1..db6c561920f0 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -87,7 +87,7 @@ static acpi_physical_address kexec_get_rsdp_addr(void)
efi_system_table_64_t *systab;
struct efi_setup_data *esd;
struct efi_info *ei;
- char *sig;
+ enum efi_type et;

esd = (struct efi_setup_data *)get_kexec_setup_data_addr();
if (!esd)
@@ -98,10 +98,9 @@ static acpi_physical_address kexec_get_rsdp_addr(void)
return 0;
}

- ei = &boot_params->efi_info;
- sig = (char *)&ei->efi_loader_signature;
- if (strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
- debug_putstr("Wrong kexec EFI loader signature.\n");
+ et = efi_get_type(boot_params);
+ if (et != EFI_TYPE_64) {
+ debug_putstr("Unexpected kexec EFI environment (expected 64-bit EFI).\n");
return 0;
}

@@ -122,29 +121,22 @@ static acpi_physical_address efi_get_rsdp_addr(void)
unsigned long systab, config_tables;
unsigned int nr_tables;
struct efi_info *ei;
+ enum efi_type et;
bool efi_64;
- char *sig;
-
- ei = &boot_params->efi_info;
- sig = (char *)&ei->efi_loader_signature;

- if (!strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
+ et = efi_get_type(boot_params);
+ if (et == EFI_TYPE_64)
efi_64 = true;
- } else if (!strncmp(sig, EFI32_LOADER_SIGNATURE, 4)) {
+ else if (et == EFI_TYPE_32)
efi_64 = false;
- } else {
- debug_putstr("Wrong EFI loader signature.\n");
+ else
return 0;
- }

/* Get systab from boot params. */
+ ei = &boot_params->efi_info;
#ifdef CONFIG_X86_64
systab = ei->efi_systab | ((__u64)ei->efi_systab_hi << 32);
#else
- if (ei->efi_systab_hi || ei->efi_memmap_hi) {
- debug_putstr("Error getting RSDP address: EFI system table located above 4GB.\n");
- return 0;
- }
systab = ei->efi_systab;
#endif
if (!systab)
diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
new file mode 100644
index 000000000000..bad0ce3e2ef6
--- /dev/null
+++ b/arch/x86/boot/compressed/efi.c
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Helpers for early access to EFI configuration table.
+ *
+ * Originally derived from arch/x86/boot/compressed/acpi.c
+ */
+
+#include "misc.h"
+#include <linux/efi.h>
+#include <asm/efi.h>
+
+/**
+ * efi_get_type - Given a pointer to boot_params, determine the type of EFI environment.
+ *
+ * @bp: pointer to boot_params
+ *
+ * Return: EFI_TYPE_{32,64} for valid EFI environments, EFI_TYPE_NONE otherwise.
+ */
+enum efi_type efi_get_type(struct boot_params *bp)
+{
+ struct efi_info *ei;
+ enum efi_type et;
+ const char *sig;
+
+ ei = &bp->efi_info;
+ sig = (char *)&ei->efi_loader_signature;
+
+ if (!strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
+ et = EFI_TYPE_64;
+ } else if (!strncmp(sig, EFI32_LOADER_SIGNATURE, 4)) {
+ et = EFI_TYPE_32;
+ } else {
+ debug_putstr("No EFI environment detected.\n");
+ et = EFI_TYPE_NONE;
+ }
+
+#ifndef CONFIG_X86_64
+ /*
+ * Existing callers like acpi.c treat this case as an indicator to
+ * fall-through to non-EFI, rather than an error, so maintain that
+ * functionality here as well.
+ */
+ if (ei->efi_systab_hi || ei->efi_memmap_hi) {
+ debug_putstr("EFI system table is located above 4GB and cannot be accessed.\n");
+ et = EFI_TYPE_NONE;
+ }
+#endif
+
+ return et;
+}
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 01cc13c12059..fede1afa39e9 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -176,4 +176,20 @@ void boot_stage2_vc(void);

unsigned long sev_verify_cbit(unsigned long cr3);

+enum efi_type {
+ EFI_TYPE_64,
+ EFI_TYPE_32,
+ EFI_TYPE_NONE,
+};
+
+#ifdef CONFIG_EFI
+/* helpers for early EFI config table access */
+enum efi_type efi_get_type(struct boot_params *bp);
+#else
+static inline enum efi_type efi_get_type(struct boot_params *bp)
+{
+ return EFI_TYPE_NONE;
+}
+#endif /* CONFIG_EFI */
+
#endif /* BOOT_COMPRESSED_MISC_H */
--
2.25.1