linux-kernel - [PATCH v4 6/7] LoongArch: Automatically disable kaslr when the kernel loads from kexec

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Message-Id: <20250903030100.196744-7-youling.tang@linux.dev>
Date: Wed,  3 Sep 2025 11:00:59 +0800
From: Youling Tang <youling.tang@...ux.dev>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: WANG Xuerui <kernel@...0n.name>,
	Baoquan He <bhe@...hat.com>,
	Yao Zi <ziyao@...root.org>,
	kexec@...ts.infradead.org,
	loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	youling.tang@...ux.dev,
	Youling Tang <tangyouling@...inos.cn>,
	stable@...r.kernel.org
Subject: [PATCH v4 6/7] LoongArch: Automatically disable kaslr when the kernel loads from kexec_file

From: Youling Tang <tangyouling@...inos.cn>

Automatically disable kaslr when the kernel loads from kexec_file.

kexec_file loads the secondary kernel image to a non-linked address,
inherently providing KASLR-like randomization.

However, on LoongArch where System RAM may be non-contiguous, enabling
KASLR for the second kernel could relocate it to an invalid memory
region and cause boot failure. Thus, we disable KASLR when
"kexec_file" is detected in the command line.

To ensure compatibility with older kernels loaded via kexec_file,
this patch need be backported to stable branches.

Cc: stable@...r.kernel.org
Signed-off-by: Youling Tang <tangyouling@...inos.cn>
---
 arch/loongarch/kernel/relocate.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/relocate.c
index 50c469067f3a..4c097532cb88 100644
--- a/arch/loongarch/kernel/relocate.c
+++ b/arch/loongarch/kernel/relocate.c
@@ -140,6 +140,10 @@ static inline __init bool kaslr_disabled(void)
 	if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' '))
 		return true;
 
+	str = strstr(boot_command_line, "kexec_file");
+	if (str == boot_command_line || (str > boot_command_line && *(str - 1) == ' '))
+		return true;
+
 #ifdef CONFIG_HIBERNATION
 	str = strstr(builtin_cmdline, "nohibernate");
 	if (str == builtin_cmdline || (str > builtin_cmdline && *(str - 1) == ' '))
-- 
2.43.0