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    Subject[PATCH v8 24/40] x86/compressed/acpi: move EFI system table lookup to helper
    Date
    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 | 60 ++++++++++----------------
    arch/x86/boot/compressed/efi.c | 72 +++++++++++++++++++++++++++++++
    arch/x86/boot/compressed/misc.h | 14 ++++++
    4 files changed, 109 insertions(+), 38 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..9e784bd7b2e6 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
    @@ -119,45 +117,31 @@ static acpi_physical_address kexec_get_rsdp_addr(void) { return 0; }
    static acpi_physical_address efi_get_rsdp_addr(void)
    {
    #ifdef CONFIG_EFI
    - unsigned long systab, config_tables;
    + unsigned long systab_tbl_pa, config_tables;
    unsigned int nr_tables;
    - struct efi_info *ei;
    bool efi_64;
    - char *sig;
    -
    - 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 0;
    - }
    + int ret;

    - /* Get systab from boot params. */
    -#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");
    + /*
    + * This function is called even for non-EFI BIOSes, and callers expect
    + * failure to locate the EFI system table to result in 0 being returned
    + * as indication that EFI is not available, rather than outright
    + * failure/abort.
    + */
    + ret = efi_get_system_table(boot_params, &systab_tbl_pa, &efi_64);
    + if (ret == -EOPNOTSUPP)
    return 0;
    - }
    - systab = ei->efi_systab;
    -#endif
    - if (!systab)
    - error("EFI system table not found.");
    + if (ret)
    + error("EFI support advertised, but unable to locate system table.");

    /* Handle EFI bitness properly */
    if (efi_64) {
    - efi_system_table_64_t *stbl = (efi_system_table_64_t *)systab;
    + efi_system_table_64_t *stbl = (efi_system_table_64_t *)systab_tbl_pa;

    config_tables = stbl->tables;
    nr_tables = stbl->nr_tables;
    } else {
    - efi_system_table_32_t *stbl = (efi_system_table_32_t *)systab;
    + efi_system_table_32_t *stbl = (efi_system_table_32_t *)systab_tbl_pa;

    config_tables = stbl->tables;
    nr_tables = stbl->nr_tables;
    diff --git a/arch/x86/boot/compressed/efi.c b/arch/x86/boot/compressed/efi.c
    new file mode 100644
    index 000000000000..1c626d28f07e
    --- /dev/null
    +++ b/arch/x86/boot/compressed/efi.c
    @@ -0,0 +1,72 @@
    +// 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>
    +
    +/**
    + * efi_get_system_table - 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
    + *
    + * Return: 0 on success. On error, return params are left unchanged.
    + *
    + * Note: Existing callers like ACPI will call this unconditionally even for
    + * non-EFI BIOSes. In such cases, those callers may treat cases where
    + * bootparams doesn't indicate that a valid EFI system table is available as
    + * non-fatal errors to allow fall-through to non-EFI alternatives. This
    + * class of errors are reported as EOPNOTSUPP and should be kept in sync with
    + * callers who check for that specific error.
    + */
    +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 -EOPNOTSUPP;
    + }
    +
    + /* 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 -EOPNOTSUPP;
    + }
    + 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 01cc13c12059..165640f64b71 100644
    --- a/arch/x86/boot/compressed/misc.h
    +++ b/arch/x86/boot/compressed/misc.h
    @@ -23,6 +23,7 @@
    #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>
    @@ -176,4 +177,17 @@ 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
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