[PATCH v6 28/42] x86/compressed/acpi: move EFI system table lookup to helper

Brijesh Singh
2021-10-08T18:06:05Z

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 | 18 ++++-----
arch/x86/boot/compressed/efi.c | 64 +++++++++++++++++++++++++++++++
arch/x86/boot/compressed/misc.h | 14 +++++++
4 files changed, 87 insertions(+), 10 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 431bf7f846c3..d364192c2367 100644
--- a/arch/x86/boot/compressed/Makefile
+++ b/arch/x86/boot/compressed/Makefile
@@ -100,6 +100,7 @@ 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..255f6959c090 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -86,8 +86,8 @@ 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;
+ bool efi_64;
+ int ret;

esd = (struct efi_setup_data *)get_kexec_setup_data_addr();
if (!esd)
@@ -98,18 +98,16 @@ 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)) {
+ /* Get systab from boot params. */
+ ret = efi_get_system_table(boot_params, (unsigned long *)&systab, &efi_64);
+ if (ret)
+ error("EFI system table not found in kexec boot_params.");
+
+ if (!efi_64) {
debug_putstr("Wrong kexec EFI loader signature.\n");
return 0;
}

- /* Get systab from boot params. */
- systab = (efi_system_table_64_t *) (ei->efi_systab | ((__u64)ei->efi_systab_hi << 32));
- if (!systab)
- error("EFI system table not found in kexec boot_params.");
-
return __efi_get_rsdp_addr((unsigned long)esd->tables, systab->nr_tables, true);
}
#else
diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
new file mode 100644
index 000000000000..306b287b7368
--- /dev/null
+++ b/arch/x86/boot/compressed/efi.c
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Helpers for early access to EFI configuration table
+ *
+ * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ *
+ * Author: Michael Roth <michael.roth@amd.com>
+ */
+
+#include "misc.h"
+#include <linux/efi.h>
+#include <asm/efi.h>
+
+/**
+ * Given boot_params, retrieve the physical address of EFI system table.
+ *
+ * @boot_params: pointer to boot_params
+ * @sys_tbl_pa: location to store physical address of system table
+ * @is_efi_64: location to store whether using 64-bit EFI or not
+ *
+ * Returns 0 on success. On error, return params are left unchanged.
+ */
+int efi_get_system_table(struct boot_params *boot_params, unsigned long *sys_tbl_pa,
+ bool *is_efi_64)
+{
+ unsigned long sys_tbl;
+ struct efi_info *ei;
+ bool efi_64;
+ char *sig;
+
+ if (!sys_tbl_pa || !is_efi_64)
+ return -EINVAL;
+
+ ei = &boot_params->efi_info;
+ sig = (char *)&ei->efi_loader_signature;
+
+ if (!strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
+ efi_64 = true;
+ } else if (!strncmp(sig, EFI32_LOADER_SIGNATURE, 4)) {
+ efi_64 = false;
+ } else {
+ debug_putstr("Wrong EFI loader signature.\n");
+ return -ENOENT;
+ }
+
+ /* Get systab from boot params. */
+#ifdef CONFIG_X86_64
+ sys_tbl = ei->efi_systab | ((__u64)ei->efi_systab_hi << 32);
+#else
+ if (ei->efi_systab_hi || ei->efi_memmap_hi) {
+ debug_putstr("Error: EFI system table located above 4GB.\n");
+ return -EINVAL;
+ }
+ sys_tbl = ei->efi_systab;
+#endif
+ if (!sys_tbl) {
+ debug_putstr("EFI system table not found.");
+ return -ENOENT;
+ }
+
+ *sys_tbl_pa = sys_tbl;
+ *is_efi_64 = efi_64;
+ return 0;
+}
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 822e0c254b9a..f86ff866fd7a 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -21,6 +21,7 @@
#include <linux/screen_info.h>
#include <linux/elf.h>
#include <linux/io.h>
+#include <linux/efi.h>
#include <asm/page.h>
#include <asm/boot.h>
#include <asm/bootparam.h>
@@ -174,4 +175,17 @@ void boot_stage2_vc(void);

unsigned long sev_verify_cbit(unsigned long cr3);

+#ifdef CONFIG_EFI
+/* helpers for early EFI config table access */
+int efi_get_system_table(struct boot_params *boot_params,
+ unsigned long *sys_tbl_pa, bool *is_efi_64);
+#else
+static inline int
+efi_get_system_table(struct boot_params *boot_params,
+ unsigned long *sys_tbl_pa, bool *is_efi_64)
+{
+ return -ENOENT;
+}
+#endif /* CONFIG_EFI */
+
#endif /* BOOT_COMPRESSED_MISC_H */
--
2.25.1