Merge: x86/efistub: Omit physical KASLR when memory reservations exist

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/6577

JIRA: https://issues.redhat.com/browse/RHEL-83461

This patch is a backport of the following upstream commit:
commit 15aa8fb
Author: Ard Biesheuvel <ardb@kernel.org>
Date:   Thu May 16 11:05:42 2024 +0200

Signed-off-by: Charles Haithcock <chaithco@redhat.com>

Approved-by: Ricardo Robaina <rrobaina@redhat.com>
Approved-by: Rafael Aquini <raquini@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Augusto Caringi <acaringi@redhat.com>

Author: caringi

drivers/firmware/efi/libstub/x86-stub.c

@@ -770,6 +770,26 @@ static void error(char *str)
 	efi_warn("Decompression failed: %s\n", str);
 }
 
+static const char *cmdline_memmap_override;
+
+static efi_status_t parse_options(const char *cmdline)
+{
+	static const char opts[][14] = {
+		"mem=", "memmap=", "efi_fake_mem=", "hugepages="
+	};
+
+	for (int i = 0; i < ARRAY_SIZE(opts); i++) {
+		const char *p = strstr(cmdline, opts[i]);
+
+		if (p == cmdline || (p > cmdline && isspace(p[-1]))) {
+			cmdline_memmap_override = opts[i];
+			break;
+		}
+	}
+
+	return efi_parse_options(cmdline);
+}
+
 static efi_status_t efi_decompress_kernel(unsigned long *kernel_entry)
 {
 	unsigned long virt_addr = LOAD_PHYSICAL_ADDR;
@@ -801,6 +821,10 @@ static efi_status_t efi_decompress_kernel(unsigned long *kernel_entry)
 		    !memcmp(efistub_fw_vendor(), ami, sizeof(ami))) {
 			efi_debug("AMI firmware v2.0 or older detected - disabling physical KASLR\n");
 			seed[0] = 0;
+		} else if (cmdline_memmap_override) {
+			efi_info("%s detected on the kernel command line - disabling physical KASLR\n",
+				 cmdline_memmap_override);
+			seed[0] = 0;
 		}
 
 		boot_params_ptr->hdr.loadflags |= KASLR_FLAG;
@@ -877,7 +901,7 @@ void __noreturn efi_stub_entry(efi_handle_t handle,
 	}
 
 #ifdef CONFIG_CMDLINE_BOOL
-	status = efi_parse_options(CONFIG_CMDLINE);
+	status = parse_options(CONFIG_CMDLINE);
 	if (status != EFI_SUCCESS) {
 		efi_err("Failed to parse options\n");
 		goto fail;
@@ -886,7 +910,7 @@ void __noreturn efi_stub_entry(efi_handle_t handle,
 	if (!IS_ENABLED(CONFIG_CMDLINE_OVERRIDE)) {
 		unsigned long cmdline_paddr = ((u64)hdr->cmd_line_ptr |
 					       ((u64)boot_params->ext_cmd_line_ptr << 32));
-		status = efi_parse_options((char *)cmdline_paddr);
+		status = parse_options((char *)cmdline_paddr);
 		if (status != EFI_SUCCESS) {
 			efi_err("Failed to parse options\n");
 			goto fail;