ARM: Allow SMP kernels to boot on UP systems
UP systems do not implement all the instructions that SMP systems have,
so in order to boot a SMP kernel on a UP system, we need to rewrite
parts of the kernel.
Do this using an 'alternatives' scheme, where the kernel code and data
is modified prior to initialization to replace the SMP instructions,
thereby rendering the problematical code ineffectual. We use the linker
to generate a list of 32-bit word locations and their replacement values,
and run through these replacements when we detect a UP system.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index bb8e93a..c09e357 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -46,7 +46,8 @@
* this macro assumes that irqstat (r6) and base (r5) are
* preserved from get_irqnr_and_base above
*/
- test_for_ipi r0, r6, r5, lr
+ ALT_SMP(test_for_ipi r0, r6, r5, lr)
+ ALT_UP_B(9997f)
movne r0, sp
adrne lr, BSYM(1b)
bne do_IPI
@@ -57,6 +58,7 @@
adrne lr, BSYM(1b)
bne do_local_timer
#endif
+9997:
#endif
.endm
@@ -965,11 +967,8 @@
beq 1b
rsbs r0, r3, #0
/* beware -- each __kuser slot must be 8 instructions max */
-#ifdef CONFIG_SMP
- b __kuser_memory_barrier
-#else
- usr_ret lr
-#endif
+ ALT_SMP(b __kuser_memory_barrier)
+ ALT_UP(usr_ret lr)
#endif