x86/efi: Drop support for fake EFI memory maps

Between kexec and confidential VM support, handling the EFI memory maps
correctly on x86 is already proving to be rather difficult (as opposed
to other EFI architectures which manage to never modify the EFI memory
map to begin with)

EFI fake memory map support is essentially a development hack (for
testing new support for the 'special purpose' and 'more reliable' EFI
memory attributes) that leaked into production code. The regions marked
in this manner are not actually recognized as such by the firmware
itself or the EFI stub (and never have), and marking memory as 'more
reliable' seems rather futile if the underlying memory is just ordinary
RAM.

Marking memory as 'special purpose' in this way is also dubious, but may
be in use in production code nonetheless. However, the same should be
achievable by using the memmap= command line option with the ! operator.

EFI fake memmap support is not enabled by any of the major distros
(Debian, Fedora, SUSE, Ubuntu) and does not exist on other
architectures, so let's drop support for it.

Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

1 files changed, 9 insertions, 34 deletions

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index dec961c6d16a..f4d82379bf44 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -119,13 +119,8 @@ char *skip_spaces(const char *str)
 #include "../../../../lib/ctype.c"
 #include "../../../../lib/cmdline.c"
 
-enum parse_mode {
-	PARSE_MEMMAP,
-	PARSE_EFI,
-};
-
 static int
-parse_memmap(char *p, u64 *start, u64 *size, enum parse_mode mode)
+parse_memmap(char *p, u64 *start, u64 *size)
 {
 	char *oldp;
 
@@ -148,29 +143,11 @@ parse_memmap(char *p, u64 *start, u64 *size, enum parse_mode mode)
 		*start = memparse(p + 1, &p);
 		return 0;
 	case '@':
-		if (mode == PARSE_MEMMAP) {
-			/*
-			 * memmap=nn@ss specifies usable region, should
-			 * be skipped
-			 */
-			*size = 0;
-		} else {
-			u64 flags;
-
-			/*
-			 * efi_fake_mem=nn@ss:attr the attr specifies
-			 * flags that might imply a soft-reservation.
-			 */
-			*start = memparse(p + 1, &p);
-			if (p && *p == ':') {
-				p++;
-				if (kstrtoull(p, 0, &flags) < 0)
-					*size = 0;
-				else if (flags & EFI_MEMORY_SP)
-					return 0;
-			}
-			*size = 0;
-		}
+		/*
+		 * memmap=nn@ss specifies usable region, should
+		 * be skipped
+		 */
+		*size = 0;
 		fallthrough;
 	default:
 		/*
@@ -185,7 +162,7 @@ parse_memmap(char *p, u64 *start, u64 *size, enum parse_mode mode)
 	return -EINVAL;
 }
 
-static void mem_avoid_memmap(enum parse_mode mode, char *str)
+static void mem_avoid_memmap(char *str)
 {
 	static int i;
 
@@ -200,7 +177,7 @@ static void mem_avoid_memmap(enum parse_mode mode, char *str)
 		if (k)
 			*k++ = 0;
 
-		rc = parse_memmap(str, &start, &size, mode);
+		rc = parse_memmap(str, &start, &size);
 		if (rc < 0)
 			break;
 		str = k;
@@ -281,7 +258,7 @@ static void handle_mem_options(void)
 			break;
 
 		if (!strcmp(param, "memmap")) {
-			mem_avoid_memmap(PARSE_MEMMAP, val);
+			mem_avoid_memmap(val);
 		} else if (IS_ENABLED(CONFIG_X86_64) && strstr(param, "hugepages")) {
 			parse_gb_huge_pages(param, val);
 		} else if (!strcmp(param, "mem")) {
@@ -295,8 +272,6 @@ static void handle_mem_options(void)
 
 			if (mem_size < mem_limit)
 				mem_limit = mem_size;
-		} else if (!strcmp(param, "efi_fake_mem")) {
-			mem_avoid_memmap(PARSE_EFI, val);
 		}
 	}