[PATCH v6 11/21] arm64: Extract early FDT mapping from kaslr_early_init()

[Marc Zyngier]

As we want to parse more options very early in the kernel lifetime,
let's always map the FDT early. This is achieved by moving that
code out of kaslr_early_init().

No functionnal change expected.

Signed-off-by: Marc Zyngier <maz at kernel.org>
Acked-by: Catalin Marinas <catalin.marinas at arm.com>
Acked-by: David Brazdil <dbrazdil at google.com>
---
 arch/arm64/include/asm/setup.h | 11 +++++++++++
 arch/arm64/kernel/head.S       |  3 ++-
 arch/arm64/kernel/kaslr.c      |  7 +++----
 arch/arm64/kernel/setup.c      | 15 +++++++++++++++
 4 files changed, 31 insertions(+), 5 deletions(-)
 create mode 100644 arch/arm64/include/asm/setup.h

diff --git a/arch/arm64/include/asm/setup.h b/arch/arm64/include/asm/setup.h
new file mode 100644
index 000000000000..d3320618ed14
--- /dev/null
+++ b/arch/arm64/include/asm/setup.h
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef __ARM64_ASM_SETUP_H
+#define __ARM64_ASM_SETUP_H
+
+#include <uapi/asm/setup.h>
+
+void *get_early_fdt_ptr(void);
+void early_fdt_map(u64 dt_phys);
+
+#endif
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index b425d2587cdb..d74e5f84042e 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -433,6 +433,8 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 	bl	__pi_memset
 	dsb	ishst				// Make zero page visible to PTW
 
+	mov	x0, x21				// pass FDT address in x0
+	bl	early_fdt_map			// Try mapping the FDT early
 	bl	switch_to_vhe
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 	bl	kasan_early_init
@@ -440,7 +442,6 @@ SYM_FUNC_START_LOCAL(__primary_switched)
 #ifdef CONFIG_RANDOMIZE_BASE
 	tst	x23, ~(MIN_KIMG_ALIGN - 1)	// already running randomized?
 	b.ne	0f
-	mov	x0, x21				// pass FDT address in x0
 	bl	kaslr_early_init		// parse FDT for KASLR options
 	cbz	x0, 0f				// KASLR disabled? just proceed
 	orr	x23, x23, x0			// record KASLR offset
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index 1c74c45b9494..5fc86e7d01a1 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -19,6 +19,7 @@
 #include <asm/memory.h>
 #include <asm/mmu.h>
 #include <asm/sections.h>
+#include <asm/setup.h>
 
 enum kaslr_status {
 	KASLR_ENABLED,
@@ -92,12 +93,11 @@ static __init bool is_kaslr_disabled_cmdline(void *fdt)
  * containing function pointers) to be reinitialized, and zero-initialized
  * .bss variables will be reset to 0.
  */
-u64 __init kaslr_early_init(u64 dt_phys)
+u64 __init kaslr_early_init(void)
 {
 	void *fdt;
 	u64 seed, offset, mask, module_range;
 	unsigned long raw;
-	int size;
 
 	/*
 	 * Set a reasonable default for module_alloc_base in case
@@ -111,8 +111,7 @@ u64 __init kaslr_early_init(u64 dt_phys)
 	 * and proceed with KASLR disabled. We will make another
 	 * attempt at mapping the FDT in setup_machine()
 	 */
-	early_fixmap_init();
-	fdt = fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL);
+	fdt = get_early_fdt_ptr();
 	if (!fdt) {
 		kaslr_status = KASLR_DISABLED_FDT_REMAP;
 		return 0;
diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
index c18aacde8bb0..61845c0821d9 100644
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -168,6 +168,21 @@ static void __init smp_build_mpidr_hash(void)
 		pr_warn("Large number of MPIDR hash buckets detected\n");
 }
 
+static void *early_fdt_ptr __initdata;
+
+void __init *get_early_fdt_ptr(void)
+{
+	return early_fdt_ptr;
+}
+
+asmlinkage void __init early_fdt_map(u64 dt_phys)
+{
+	int fdt_size;
+
+	early_fixmap_init();
+	early_fdt_ptr = fixmap_remap_fdt(dt_phys, &fdt_size, PAGE_KERNEL);
+}
+
 static void __init setup_machine_fdt(phys_addr_t dt_phys)
 {
 	int size;
-- 
2.29.2