linux-kernel - [PATCH] x86/boot: minor improvement in kaslr

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Message-ID: <20190201054853.28541-1-caoj.fnst@cn.fujitsu.com>
Date:   Fri, 1 Feb 2019 13:48:53 +0800
From:   Cao jin <caoj.fnst@...fujitsu.com>
To:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC:     <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <hpa@...or.com>, <bhe@...hat.com>, <keescook@...omium.org>,
        <fanc.fnst@...fujitsu.com>
Subject: [PATCH] x86/boot: minor improvement in kaslr

comments fix: input_size is ZO image size which just don't count .bss
in, but has .text, .data, etc;
drop unecessary alignment: minimum is either 512M or output, both are
CONFIG_PHYSICAL_ALIGN aligned(output is aligned in head_32/64.S). But
mention it in earlier comments.

Signed-off-by: Cao jin <caoj.fnst@...fujitsu.com>
---
 arch/x86/boot/compressed/kaslr.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/x86/boot/compressed/kaslr.c b/arch/x86/boot/compressed/kaslr.c
index 9ed9709d9947..a947c5aba34e 100644
--- a/arch/x86/boot/compressed/kaslr.c
+++ b/arch/x86/boot/compressed/kaslr.c
@@ -360,7 +360,7 @@ static void handle_mem_options(void)
  * (i.e. it does not include its run size). This range must be avoided
  * because it contains the data used for decompression.
  *
- * [input+input_size, output+init_size) is [_text, _end) for ZO. This
+ * [input+input_size, output+init_size) is [_bss, _end) for ZO. This
  * range includes ZO's heap and stack, and must be avoided since it
  * performs the decompression.
  *
@@ -763,9 +763,6 @@ static unsigned long find_random_phys_addr(unsigned long minimum,
 		return 0;
 	}
 
-	/* Make sure minimum is aligned. */
-	minimum = ALIGN(minimum, CONFIG_PHYSICAL_ALIGN);
-
 	if (process_efi_entries(minimum, image_size))
 		return slots_fetch_random();
 
@@ -831,8 +828,8 @@ void choose_random_location(unsigned long input,
 
 	/*
 	 * Low end of the randomization range should be the
-	 * smaller of 512M or the initial kernel image
-	 * location:
+	 * smaller of 512M or the initial kernel image location.
+	 * Should be aligned to CONFIG_PHYSICAL_ALIGN.
 	 */
 	min_addr = min(*output, 512UL << 20);
 
-- 
2.17.0