linux-kernel - Re: [PATCH v2] x86/boot: Use EFI setup data if provided

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Message-ID: <20190328155256.GP22720@zn.tnic>
Date:   Thu, 28 Mar 2019 16:52:56 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Junichi Nomura <j-nomura@...jp.nec.com>
Cc:     "bhe@...hat.com" <bhe@...hat.com>, Dave Young <dyoung@...hat.com>,
        "fanc.fnst@...fujitsu.com" <fanc.fnst@...fujitsu.com>,
        "kasong@...hat.com" <kasong@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] x86/boot: Use EFI setup data if provided

On Thu, Mar 28, 2019 at 07:43:38AM +0000, Junichi Nomura wrote:
>  /* Search EFI system tables for RSDP. */
> -static acpi_physical_address efi_get_rsdp_addr(void)
> +static acpi_physical_address __efi_get_rsdp_addr(unsigned long config_tables, unsigned int nr_tables, int size, bool efi_64)

Break this line like this:

static acpi_physical_address
__efi_get_rsdp_addr(unsigned long config_tables, unsigned int nr_tables,
                    int size, bool efi_64)


>  {
>  	acpi_physical_address rsdp_addr = 0;

You don't need that variable and can return "table" or 0 after the endif
below.

>  #ifdef CONFIG_EFI
> -	unsigned long systab, systab_tables, config_tables;
> +	int i;
> +
> +	/* Get EFI tables from systab. */
> +	for (i = 0; i < nr_tables; i++) {
> +		acpi_physical_address table;
> +		efi_guid_t guid;
> +
> +		config_tables += size;
> +
> +		if (efi_64) {
> +			efi_config_table_64_t *tbl = (efi_config_table_64_t *)config_tables;
> +
> +			guid  = tbl->guid;
> +			table = tbl->table;
> +
> +			if (!IS_ENABLED(CONFIG_X86_64) && table >> 32) {
> +				debug_putstr("Error getting RSDP address: EFI config table located above 4GB.\n");
> +				return 0;
> +			}
> +		} else {
> +			efi_config_table_32_t *tbl = (efi_config_table_32_t *)config_tables;
> +
> +			guid  = tbl->guid;
> +			table = tbl->table;
> +		}
> +
> +		if (!(efi_guidcmp(guid, ACPI_TABLE_GUID)))
> +			rsdp_addr = table;
> +		else if (!(efi_guidcmp(guid, ACPI_20_TABLE_GUID)))
> +			return table;
> +	}
> +#endif
> +	return rsdp_addr;
> +}
> +
> +static acpi_physical_address kexec_get_rsdp_addr(void)
> +{
> +#ifdef CONFIG_EFI
> +	struct efi_setup_data *esd;
> +	efi_system_table_64_t *systab;
> +	struct efi_info *ei;
> +	char *sig;

Please sort function local variables declaration in a reverse christmas
tree order:

	<type A> longest_variable_name;
	<type B> shorter_var_name;
	<type C> even_shorter;
	<type D> i;

> +
> +	esd = (struct efi_setup_data *) efi_get_kexec_setup_data_addr();
> +	if (!esd)
> +		return 0;

<---- newline here.

> +	if (!esd->tables) {
> +		debug_putstr("Wrong kexec SETUP_EFI data.\n");
> +		return 0;
> +	}
> +
> +	ei = &boot_params->efi_info;
> +	sig = (char *)&ei->efi_loader_signature;
> +	if (strncmp(sig, EFI64_LOADER_SIGNATURE, 4)) {
> +		debug_putstr("Wrong EFI loader signature.\n");

  "Wrong kexec EFI loader signature."

so that it differs from the other error message and we can know where we
are when debugging.

> +		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.");

Ditto.

> +
> +	return __efi_get_rsdp_addr((unsigned long) esd->tables, systab->nr_tables, sizeof(efi_config_table_64_t), true);

You can easily break that line - no need to let it stick out.

> +#else
> +	return 0;
> +#endif
> +}

Other than those nitpicks, yes, it looks ok to me. Please send a proper
patch.

Thx.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.