linux-kernel - Re: [tip:x86/boot] x86/boot: Early parse RSDP and save it in boot

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Message-ID: <20190211112009.GE19618@zn.tnic>
Date:   Mon, 11 Feb 2019 12:20:09 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Chao Fan <fanc.fnst@...fujitsu.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        "Lendacky, Thomas" <thomas.lendacky@....com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        caoj.fnst@...fujitsu.com, Juergen Gross <jgross@...e.com>,
        Ingo Molnar <mingo@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        linux-tip-commits@...r.kernel.org,
        Matt Fleming <matt@...eblueprint.co.uk>
Subject: Re: [tip:x86/boot] x86/boot: Early parse RSDP and save it in
 boot_params

On Mon, Feb 11, 2019 at 10:46:18AM +0000, Ard Biesheuvel wrote:
> As I pointed out in my previous reply, systab will be the wrong type
> on 32-bit firmware, it needs to be efi_system_table_32_t

This seems to work. Chao, please run it too.

Thx.

---
diff --git a/arch/x86/boot/compressed/acpi.c b/arch/x86/boot/compressed/acpi.c
index c5a949335d8b..0d97aa8bd01f 100644
--- a/arch/x86/boot/compressed/acpi.c
+++ b/arch/x86/boot/compressed/acpi.c
@@ -50,7 +50,8 @@ static acpi_physical_address efi_get_rsdp_addr(void)
 	acpi_physical_address rsdp_addr = 0;
 
 #ifdef CONFIG_EFI
-	efi_system_table_t *systab;
+	unsigned long systab, systab_tables, config_tables;
+	unsigned int nr_tables;
 	struct efi_info *ei;
 	bool efi_64;
 	int size, i;
@@ -70,13 +71,13 @@ static acpi_physical_address efi_get_rsdp_addr(void)
 
 	/* Get systab from boot params. */
 #ifdef CONFIG_X86_64
-	systab = (efi_system_table_t *)(ei->efi_systab | ((__u64)ei->efi_systab_hi<<32));
+	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 = (efi_system_table_t *)ei->efi_systab;
+	systab = ei->efi_systab;
 #endif
 	if (!systab)
 		error("EFI system table not found.");
@@ -87,16 +88,30 @@ static acpi_physical_address efi_get_rsdp_addr(void)
 	size = efi_64 ? sizeof(efi_config_table_64_t) :
 			sizeof(efi_config_table_32_t);
 
-	for (i = 0; i < systab->nr_tables; i++) {
+	if (efi_64) {
+		efi_system_table_64_t *st_tbl = (efi_system_table_64_t *)systab;
+
+		config_tables	= st_tbl->tables;
+		nr_tables	= st_tbl->nr_tables;
+	} else {
+		efi_system_table_32_t *st_tbl = (efi_system_table_32_t *)systab;
+
+		config_tables	= st_tbl->tables;
+		nr_tables	= st_tbl->nr_tables;
+	}
+
+	if (!config_tables)
+		error("EFI config tables not found.");
+
+	for (i = 0; i < nr_tables; i++) {
 		acpi_physical_address table;
-		void *config_tables;
 		efi_guid_t guid;
 
-		config_tables = (void *)(systab->tables + size * i);
+		config_tables += size * i;
+
 		if (efi_64) {
-			efi_config_table_64_t *tmp_table;
+			efi_config_table_64_t *tmp_table = (efi_config_table_64_t *)config_tables;
 
-			tmp_table = config_tables;
 			guid = tmp_table->guid;
 			table = tmp_table->table;
 
@@ -105,9 +120,8 @@ static acpi_physical_address efi_get_rsdp_addr(void)
 				return 0;
 			}
 		} else {
-			efi_config_table_32_t *tmp_table;
+			efi_config_table_32_t *tmp_table = (efi_config_table_32_t *)config_tables;
 
-			tmp_table = config_tables;
 			guid = tmp_table->guid;
 			table = tmp_table->table;
 		}

-- 
Regards/Gruss,
    Boris.

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