linux-kernel - [PATCH v2 2/4] mips: kdump: Capture kernel should be able to see old memories

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1619058274-6996-3-git-send-email-tangyouling@loongson.cn>
Date:   Thu, 22 Apr 2021 10:24:32 +0800
From:   Youling Tang <tangyouling@...ngson.cn>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Jiaxun Yang <jiaxun.yang@...goat.com>, Baoquan He <bhe@...hat.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Jinyang He <hejinyang@...ngson.cn>, kexec@...ts.infradead.org,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/4] mips: kdump: Capture kernel should be able to see old memories

From: Huacai Chen <chenhc@...ote.com>

kexec-tools use mem=X@Y to pass usable memories to capture kernel, but
in commit a94e4f24ec836c8984f83959 ("MIPS: init: Drop boot_mem_map") all
BIOS passed memories are removed by early_parse_mem(). I think this is
reasonable for a normal kernel but not for a capture kernel, because a
capture kernel should be able to see all old memories, even though it is
not supposed to use them.

Fixes: a94e4f24ec836c8984f83959 ("MIPS: init: Drop boot_mem_map")
Signed-off-by: Huacai Chen <chenhuacai@...nel.org>
Signed-off-by: Youling Tang <tangyouling@...ngson.cn>
---
v2:
- Determine whether it is a capture kernel by judging whether there
  is an "elfcorehdr" parameter in the cmdline.

 arch/mips/kernel/setup.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 9338520..1bc8a9cc 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -352,8 +352,13 @@ static int __init early_parse_mem(char *p)
 	 */
 	if (usermem == 0) {
 		usermem = 1;
-		memblock_remove(memblock_start_of_DRAM(),
-			memblock_end_of_DRAM() - memblock_start_of_DRAM());
+		/*
+		 * During the kdump operation, the old memory should be
+		 * visible to the capture kernel.
+		 */
+		if (!strstr(boot_command_line, "elfcorehdr"))
+			memblock_remove(memblock_start_of_DRAM(),
+				memblock_end_of_DRAM() - memblock_start_of_DRAM());
 	}
 	start = 0;
 	size = memparse(p, &p);
-- 
2.1.0