Re: [PATCH v8 24/40] x86/compressed/acpi: move EFI system table lookup to helper

Venu Busireddy
2022-01-06T19:59:49Z

On 2021-12-10 09:43:16 -0600, Brijesh Singh wrote:
> 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>

Reviewed-by: Venu Busireddy <venu.busireddy@oracle.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
>