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

在 2020/3/5 5:49, Scott Wood 写道:

On Thu, 2020-02-06 at 10:58 +0800, Jason Yan wrote:

quoted

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@huawei.com>
Cc: Scott Wood <oss@buserror.net>
Cc: Diana Craciun <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Christophe Leroy <redacted>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <redacted>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Kees Cook <redacted>
---
  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

These are 64-bit values.

Oh yes, will fix. Thanks.

-Scott



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