ARM: 5739/1: ARM: allow empty ATAG_CORE

From: David Brown <davidb@quicinc.com>

The ATAG_CORE is allowed to be empty.  Although this is handled
by parse_tag_core(), __vet_atags during startup rejects this tag
unless it contains data.  Allow the initial tag to be either the
full size, or empty.

Signed-off-by: David Brown <davidb@quicinc.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/arm/kernel/head-common.S b/arch/arm/kernel/head-common.S
index 93ad576b2d74..885a7214418d 100644
--- a/arch/arm/kernel/head-common.S
+++ b/arch/arm/kernel/head-common.S
@@ -13,6 +13,7 @@
 
 #define ATAG_CORE 0x54410001
 #define ATAG_CORE_SIZE ((2*4 + 3*4) >> 2)
+#define ATAG_CORE_SIZE_EMPTY ((2*4) >> 2)
 
         .align  2
         .type   __switch_data, %object
@@ -251,7 +252,8 @@ __vet_atags:
         bne     1f
 
         ldr     r5, [r2, #0]                    @ is first tag ATAG_CORE?
-        subs    r5, r5, #ATAG_CORE_SIZE
+        cmp     r5, #ATAG_CORE_SIZE
+        cmpne   r5, #ATAG_CORE_SIZE_EMPTY
         bne     1f
         ldr     r5, [r2, #4]
         ldr     r6, =ATAG_CORE