efi/libstub: Unify command line param parsing

Merge the parsing of the command line carried out in arm-stub.c with
the handling in efi_parse_options(). Note that this also fixes the
missing handling of CONFIG_CMDLINE_FORCE=y, in which case the builtin
command line should supersede the one passed by the firmware.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bhe@redhat.com
Cc: bhsharma@redhat.com
Cc: bp@alien8.de
Cc: eugene@hp.com
Cc: evgeny.kalugin@intel.com
Cc: jhugo@codeaurora.org
Cc: leif.lindholm@linaro.org
Cc: linux-efi@vger.kernel.org
Cc: mark.rutland@arm.com
Cc: roy.franz@cavium.com
Cc: rruigrok@codeaurora.org
Link: http://lkml.kernel.org/r/20170404160910.28115-1-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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

@@ -32,6 +32,13 @@
 
 static unsigned long __chunk_size = EFI_READ_CHUNK_SIZE;
 
+static int __section(.data) __nokaslr;
+
+int __pure nokaslr(void)
+{
+	return __nokaslr;
+}
+
 #define EFI_MMAP_NR_SLACK_SLOTS	8
 
 struct file_info {
@@ -409,17 +416,13 @@ static efi_status_t efi_file_close(void *handle)
  * environments, first in the early boot environment of the EFI boot
  * stub, and subsequently during the kernel boot.
  */
-efi_status_t efi_parse_options(char *cmdline)
+efi_status_t efi_parse_options(char const *cmdline)
 {
 	char *str;
 
-	/*
-	 * Currently, the only efi= option we look for is 'nochunk', which
-	 * is intended to work around known issues on certain x86 UEFI
-	 * versions. So ignore for now on other architectures.
-	 */
-	if (!IS_ENABLED(CONFIG_X86))
-		return EFI_SUCCESS;
+	str = strstr(cmdline, "nokaslr");
+	if (str == cmdline || (str && str > cmdline && *(str - 1) == ' '))
+		__nokaslr = 1;
 
 	/*
 	 * If no EFI parameters were specified on the cmdline we've got