linux-kernel - [PATCH RFC 7/8] riscv/kaslr: add cmdline support to disable KASLR

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Date:   Tue, 24 Mar 2020 15:30:52 +0800
From:   Zong Li <zong.li@...ive.com>
To:     palmer@...belt.com, paul.walmsley@...ive.com, alex@...ti.fr,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Zong Li <zong.li@...ive.com>
Subject: [PATCH RFC 7/8] riscv/kaslr: add cmdline support to disable KASLR

Provide a cmdline parameter 'nokaslr' to disable KASLR.

Signed-off-by: Zong Li <zong.li@...ive.com>
---
 arch/riscv/kernel/kaslr.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/arch/riscv/kernel/kaslr.c b/arch/riscv/kernel/kaslr.c
index 0bd30831c455..6920727e4b4a 100644
--- a/arch/riscv/kernel/kaslr.c
+++ b/arch/riscv/kernel/kaslr.c
@@ -156,6 +156,36 @@ static __init u64 kaslr_get_seed(void)
 	return ret;
 }
 
+static __init const u8 *kaslr_get_cmdline(void)
+{
+	static const u8 default_cmdline[] __initconst = CONFIG_CMDLINE;
+
+	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
+		int node;
+		const u8 *prop;
+
+		node = fdt_path_offset(dtb_early_va, "/chosen");
+		if (node < 0)
+			goto out;
+
+		prop = fdt_getprop(dtb_early_va, node, "bootargs", NULL);
+		if (!prop)
+			goto out;
+
+		return prop;
+	}
+
+out:
+	return default_cmdline;
+}
+
+static __init bool kaslr_is_disabled(void)
+{
+	const u8 *cmdline = kaslr_get_cmdline();
+
+	return strstr(cmdline, "nokaslr") != NULL;
+}
+
 static __init bool is_overlap(uintptr_t s1, uintptr_t e1, uintptr_t s2,
 			      uintptr_t e2)
 {
@@ -379,6 +409,10 @@ uintptr_t __init kaslr_early_init(void)
 	if (!seed)
 		return 0;
 
+	/* Check whether disable kaslr by cmdline. */
+	if (kaslr_is_disabled())
+		return 0;
+
 	/* Get the random number for kaslr offset. */
 	kaslr_offset = get_random_offset(seed, kernel_size);
 
-- 
2.25.1