PATCH: kexec/i386: fix erroneous memory descriptor message

[Tony Jones]

On non-EFI systems, efi_info section of boot_params is zero filled resulting 
in an erroneous message from kexec regarding "efi memory descriptor" version.

Caused by commit: e1ffc9e9a0769e1f54185003102e9bec428b84e8 "Passing efi related 
data via setup_data"

# od -j 448 -N 32 -v -x /sys/kernel/boot_params/data 
0000700 0000 0000 0000 0000 0000 0000 0000 0000
0000720 0000 0000 0000 0000 0000 0000 0000 0000
0000740

# kexec -l --reuse-cmdline --initrd=/boot/initrd-`uname -r` /boot/vmlinuz-`uname -r`
efi memory descriptor version 0 is not supported!

Signed-off-by: Tony Jones <tonyj at suse.de>

---
 kexec/arch/i386/x86-linux-setup.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

--- a/kexec/arch/i386/x86-linux-setup.c
+++ b/kexec/arch/i386/x86-linux-setup.c
@@ -687,17 +687,25 @@ static void setup_efi_info(struct kexec_
 	ret = get_bootparam(&real_mode->efi_info, offset, 32);
 	if (ret)
 		return;
+	if (((struct efi_info *)real_mode->efi_info)->efi_memmap_size == 0)
+		/* zero filled efi_info */
+		goto out;
 	desc_version = get_efi_mem_desc_version(real_mode);
 	if (desc_version != 1) {
 		fprintf(stderr,
 			"efi memory descriptor version %d is not supported!\n",
 			desc_version);
-		memset(&real_mode->efi_info, 0, 32);
-		return;
+		goto out;
 	}
 	ret = setup_efi_data(info, real_mode);
 	if (ret)
-		memset(&real_mode->efi_info, 0, 32);
+		goto out;
+
+	return;
+
+out:
+	memset(&real_mode->efi_info, 0, 32);
+	return;
 }
 
 void setup_linux_system_parameters(struct kexec_info *info,