From: Ard Biesheuvel <ardb@kernel.org>
Date: Fri, 3 Jan 2020 12:39:45 +0100
Subject: efi/x86: Clean up efi_systab_init() routine for legibility
Patch-mainline: v5.6-rc1
Git-commit: 5b279a262f5413889529802b82e153e87ee6bef8
References: jsc#SLE-16407

Clean up the efi_systab_init() routine which maps the EFI system
table and copies the relevant pieces of data out of it.

The current routine is very difficult to read, so let's clean that
up. Also, switch to a R/O mapping of the system table since that is
all we need.

Finally, use a plain u64 variable to record the physical address of
the system table instead of pointlessly stashing it in a struct efi
that is never used for anything else.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Matthew Garrett <mjg59@google.com>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20200103113953.9571-13-ardb@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
 arch/x86/platform/efi/efi.c |  162 +++++++++++++++++++++-----------------------
 1 file changed, 80 insertions(+), 82 deletions(-)

--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -54,8 +54,8 @@
 #include <asm/x86_init.h>
 #include <asm/uv/uv.h>
 
-struct efi efi_phys __initdata;
 static efi_system_table_t efi_systab __initdata;
+static u64 efi_systab_phys __initdata;
 
 static efi_config_table_type_t arch_tables[] __initdata = {
 #ifdef CONFIG_X86_UV
@@ -328,89 +328,90 @@ void __init efi_print_memmap(void)
 	}
 }
 
-static int __init efi_systab_init(void *phys)
+static int __init efi_systab_init(u64 phys)
 {
+	int size = efi_enabled(EFI_64BIT) ? sizeof(efi_system_table_64_t)
+					  : sizeof(efi_system_table_32_t);
+	bool over4g = false;
+	void *p;
+
+	p = early_memremap_ro(phys, size);
+	if (p == NULL) {
+		pr_err("Couldn't map the system table!\n");
+		return -ENOMEM;
+	}
+
 	if (efi_enabled(EFI_64BIT)) {
-		efi_system_table_64_t *systab64;
-		struct efi_setup_data *data = NULL;
-		u64 tmp = 0;
+		const efi_system_table_64_t *systab64 = p;
+
+		efi_systab.hdr			= systab64->hdr;
+		efi_systab.fw_vendor		= systab64->fw_vendor;
+		efi_systab.fw_revision		= systab64->fw_revision;
+		efi_systab.con_in_handle	= systab64->con_in_handle;
+		efi_systab.con_in		= systab64->con_in;
+		efi_systab.con_out_handle	= systab64->con_out_handle;
+		efi_systab.con_out		= (void *)(unsigned long)systab64->con_out;
+		efi_systab.stderr_handle	= systab64->stderr_handle;
+		efi_systab.stderr		= systab64->stderr;
+		efi_systab.runtime		= (void *)(unsigned long)systab64->runtime;
+		efi_systab.boottime		= (void *)(unsigned long)systab64->boottime;
+		efi_systab.nr_tables		= systab64->nr_tables;
+		efi_systab.tables		= systab64->tables;
+
+		over4g = systab64->con_in_handle	> U32_MAX ||
+			 systab64->con_in		> U32_MAX ||
+			 systab64->con_out_handle	> U32_MAX ||
+			 systab64->con_out		> U32_MAX ||
+			 systab64->stderr_handle	> U32_MAX ||
+			 systab64->stderr		> U32_MAX ||
+			 systab64->boottime		> U32_MAX;
 
 		if (efi_setup) {
-			data = early_memremap(efi_setup, sizeof(*data));
-			if (!data)
+			struct efi_setup_data *data;
+
+			data = early_memremap_ro(efi_setup, sizeof(*data));
+			if (!data) {
+				early_memunmap(p, size);
 				return -ENOMEM;
-		}
-		systab64 = early_memremap((unsigned long)phys,
-					 sizeof(*systab64));
-		if (systab64 == NULL) {
-			pr_err("Couldn't map the system table!\n");
-			if (data)
-				early_memunmap(data, sizeof(*data));
-			return -ENOMEM;
-		}
+			}
 
-		efi_systab.hdr = systab64->hdr;
-		efi_systab.fw_vendor = data ? (unsigned long)data->fw_vendor :
-					      systab64->fw_vendor;
-		tmp |= data ? data->fw_vendor : systab64->fw_vendor;
-		efi_systab.fw_revision = systab64->fw_revision;
-		efi_systab.con_in_handle = systab64->con_in_handle;
-		tmp |= systab64->con_in_handle;
-		efi_systab.con_in = systab64->con_in;
-		tmp |= systab64->con_in;
-		efi_systab.con_out_handle = systab64->con_out_handle;
-		tmp |= systab64->con_out_handle;
-		efi_systab.con_out = (void *)(unsigned long)systab64->con_out;
-		tmp |= systab64->con_out;
-		efi_systab.stderr_handle = systab64->stderr_handle;
-		tmp |= systab64->stderr_handle;
-		efi_systab.stderr = systab64->stderr;
-		tmp |= systab64->stderr;
-		efi_systab.runtime = data ?
-				     (void *)(unsigned long)data->runtime :
-				     (void *)(unsigned long)systab64->runtime;
-		tmp |= data ? data->runtime : systab64->runtime;
-		efi_systab.boottime = (void *)(unsigned long)systab64->boottime;
-		tmp |= systab64->boottime;
-		efi_systab.nr_tables = systab64->nr_tables;
-		efi_systab.tables = data ? (unsigned long)data->tables :
-					   systab64->tables;
-		tmp |= data ? data->tables : systab64->tables;
+			efi_systab.fw_vendor	= (unsigned long)data->fw_vendor;
+			efi_systab.runtime	= (void *)(unsigned long)data->runtime;
+			efi_systab.tables	= (unsigned long)data->tables;
+
+			over4g |= data->fw_vendor	> U32_MAX ||
+				  data->runtime		> U32_MAX ||
+				  data->tables		> U32_MAX;
 
-		early_memunmap(systab64, sizeof(*systab64));
-		if (data)
 			early_memunmap(data, sizeof(*data));
-#ifdef CONFIG_X86_32
-		if (tmp >> 32) {
-			pr_err("EFI data located above 4GB, disabling EFI.\n");
-			return -EINVAL;
+		} else {
+			over4g |= systab64->fw_vendor	> U32_MAX ||
+				  systab64->runtime	> U32_MAX ||
+				  systab64->tables	> U32_MAX;
 		}
-#endif
 	} else {
-		efi_system_table_32_t *systab32;
+		const efi_system_table_32_t *systab32 = p;
 
-		systab32 = early_memremap((unsigned long)phys,
-					 sizeof(*systab32));
-		if (systab32 == NULL) {
-			pr_err("Couldn't map the system table!\n");
-			return -ENOMEM;
-		}
+		efi_systab.hdr			= systab32->hdr;
+		efi_systab.fw_vendor		= systab32->fw_vendor;
+		efi_systab.fw_revision		= systab32->fw_revision;
+		efi_systab.con_in_handle	= systab32->con_in_handle;
+		efi_systab.con_in		= systab32->con_in;
+		efi_systab.con_out_handle	= systab32->con_out_handle;
+		efi_systab.con_out		= (void *)(unsigned long)systab32->con_out;
+		efi_systab.stderr_handle	= systab32->stderr_handle;
+		efi_systab.stderr		= systab32->stderr;
+		efi_systab.runtime		= (void *)(unsigned long)systab32->runtime;
+		efi_systab.boottime		= (void *)(unsigned long)systab32->boottime;
+		efi_systab.nr_tables		= systab32->nr_tables;
+		efi_systab.tables		= systab32->tables;
+	}
 
-		efi_systab.hdr = systab32->hdr;
-		efi_systab.fw_vendor = systab32->fw_vendor;
-		efi_systab.fw_revision = systab32->fw_revision;
-		efi_systab.con_in_handle = systab32->con_in_handle;
-		efi_systab.con_in = systab32->con_in;
-		efi_systab.con_out_handle = systab32->con_out_handle;
-		efi_systab.con_out = (void *)(unsigned long)systab32->con_out;
-		efi_systab.stderr_handle = systab32->stderr_handle;
-		efi_systab.stderr = systab32->stderr;
-		efi_systab.runtime = (void *)(unsigned long)systab32->runtime;
-		efi_systab.boottime = (void *)(unsigned long)systab32->boottime;
-		efi_systab.nr_tables = systab32->nr_tables;
-		efi_systab.tables = systab32->tables;
+	early_memunmap(p, size);
 
-		early_memunmap(systab32, sizeof(*systab32));
+	if (IS_ENABLED(CONFIG_X86_32) && over4g) {
+		pr_err("EFI data located above 4GB, disabling EFI.\n");
+		return -EINVAL;
 	}
 
 	efi.systab = &efi_systab;
@@ -436,20 +437,17 @@ void __init efi_init(void)
 	char vendor[100] = "unknown";
 	int i = 0;
 
-#ifdef CONFIG_X86_32
-	if (boot_params.efi_info.efi_systab_hi ||
-	    boot_params.efi_info.efi_memmap_hi) {
+	if (IS_ENABLED(CONFIG_X86_32) &&
+	    (boot_params.efi_info.efi_systab_hi ||
+	     boot_params.efi_info.efi_memmap_hi)) {
 		pr_info("Table located above 4GB, disabling EFI.\n");
 		return;
 	}
-	efi_phys.systab = (efi_system_table_t *)boot_params.efi_info.efi_systab;
-#else
-	efi_phys.systab = (efi_system_table_t *)
-			  (boot_params.efi_info.efi_systab |
-			  ((__u64)boot_params.efi_info.efi_systab_hi<<32));
-#endif
 
-	if (efi_systab_init(efi_phys.systab))
+	efi_systab_phys = boot_params.efi_info.efi_systab |
+			  ((__u64)boot_params.efi_info.efi_systab_hi << 32);
+
+	if (efi_systab_init(efi_systab_phys))
 		return;
 
 	efi.config_table = (unsigned long)efi.systab->tables;
@@ -602,7 +600,7 @@ static void __init get_systab_virt_addr(
 
 	size = md->num_pages << EFI_PAGE_SHIFT;
 	end = md->phys_addr + size;
-	systab = (u64)(unsigned long)efi_phys.systab;
+	systab = efi_systab_phys;
 	if (md->phys_addr <= systab && systab < end) {
 		systab += md->virt_addr - md->phys_addr;
 		efi.systab = (efi_system_table_t *)(unsigned long)systab;
