[PATCH v3 4/6] powerpc/fsl_booke/64: do not clear the BSS for the second pass

[Jason Yan]

The BSS section has already cleared out in the first pass. No need to
clear it again. This can save some time when booting with KASLR
enabled.

Signed-off-by: Jason Yan <yanaijie at huawei.com>
Cc: Scott Wood <oss at buserror.net>
Cc: Diana Craciun <diana.craciun at nxp.com>
Cc: Michael Ellerman <mpe at ellerman.id.au>
Cc: Christophe Leroy <christophe.leroy at c-s.fr>
Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
Cc: Paul Mackerras <paulus at samba.org>
Cc: Nicholas Piggin <npiggin at gmail.com>
Cc: Kees Cook <keescook at chromium.org>
---
 arch/powerpc/kernel/head_64.S | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index 744624140fb8..8c644e7c3eaf 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -914,6 +914,13 @@ start_here_multiplatform:
 	bl      relative_toc
 	tovirt(r2,r2)
 
+	/* Do not clear the BSS for the second pass if randomized */
+	LOAD_REG_ADDR(r3, kernstart_virt_addr)
+	lwz     r3,0(r3)
+	LOAD_REG_IMMEDIATE(r4, KERNELBASE)
+	cmpw	r3,r4
+	bne	4f
+
 	/* Clear out the BSS. It may have been done in prom_init,
 	 * already but that's irrelevant since prom_init will soon
 	 * be detached from the kernel completely. Besides, we need
-- 
2.17.2