linux-kernel - [PATCH 4.9 27/31] arm64: map FDT as RW for early_init_dt

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Date:   Fri,  2 Sep 2022 14:18:53 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hsin-Yi Wang <hsinyi@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Will Deacon <will@...nel.org>,
        Michael Bestas <mkbestas@...il.com>
Subject: [PATCH 4.9 27/31] arm64: map FDT as RW for early_init_dt_scan()

From: Hsin-Yi Wang <hsinyi@...omium.org>

commit e112b032a72c78f15d0c803c5dc6be444c2e6c66 upstream.

Currently in arm64, FDT is mapped to RO before it's passed to
early_init_dt_scan(). However, there might be some codes
(eg. commit "fdt: add support for rng-seed") that need to modify FDT
during init. Map FDT to RO after early fixups are done.

Signed-off-by: Hsin-Yi Wang <hsinyi@...omium.org>
Reviewed-by: Stephen Boyd <swboyd@...omium.org>
Reviewed-by: Mike Rapoport <rppt@...ux.ibm.com>
Signed-off-by: Will Deacon <will@...nel.org>
[mkbestas: fixed trivial conflicts for 4.9 backport]
Signed-off-by: Michael Bestas <mkbestas@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm64/include/asm/mmu.h |    2 +-
 arch/arm64/kernel/kaslr.c    |    5 +----
 arch/arm64/kernel/setup.c    |    9 ++++++++-
 arch/arm64/mm/mmu.c          |   15 +--------------
 4 files changed, 11 insertions(+), 20 deletions(-)

--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -90,7 +90,7 @@ extern void init_mem_pgprot(void);
 extern void create_pgd_mapping(struct mm_struct *mm, phys_addr_t phys,
 			       unsigned long virt, phys_addr_t size,
 			       pgprot_t prot, bool allow_block_mappings);
-extern void *fixmap_remap_fdt(phys_addr_t dt_phys);
+extern void *fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot);
 
 #endif	/* !__ASSEMBLY__ */
 #endif
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -65,9 +65,6 @@ out:
 	return default_cmdline;
 }
 
-extern void *__init __fixmap_remap_fdt(phys_addr_t dt_phys, int *size,
-				       pgprot_t prot);
-
 /*
  * This routine will be executed with the kernel mapped at its default virtual
  * address, and if it returns successfully, the kernel will be remapped, and
@@ -96,7 +93,7 @@ u64 __init kaslr_early_init(u64 dt_phys,
 	 * attempt at mapping the FDT in setup_machine()
 	 */
 	early_fixmap_init();
-	fdt = __fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL);
+	fdt = fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL);
 	if (!fdt)
 		return 0;
 
--- a/arch/arm64/kernel/setup.c
+++ b/arch/arm64/kernel/setup.c
@@ -178,7 +178,11 @@ static void __init smp_build_mpidr_hash(
 
 static void __init setup_machine_fdt(phys_addr_t dt_phys)
 {
-	void *dt_virt = fixmap_remap_fdt(dt_phys);
+	int size;
+	void *dt_virt = fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL);
+
+	if (dt_virt)
+		memblock_reserve(dt_phys, size);
 
 	if (!dt_virt || !early_init_dt_scan(dt_virt)) {
 		pr_crit("\n"
@@ -191,6 +195,9 @@ static void __init setup_machine_fdt(phy
 			cpu_relax();
 	}
 
+	/* Early fixups are done, map the FDT as read-only now */
+	fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL_RO);
+
 	dump_stack_set_arch_desc("%s (DT)", of_flat_dt_get_machine_name());
 }
 
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -718,7 +718,7 @@ void __set_fixmap(enum fixed_addresses i
 	}
 }
 
-void *__init __fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot)
+void *__init fixmap_remap_fdt(phys_addr_t dt_phys, int *size, pgprot_t prot)
 {
 	const u64 dt_virt_base = __fix_to_virt(FIX_FDT);
 	int offset;
@@ -771,19 +771,6 @@ void *__init __fixmap_remap_fdt(phys_add
 	return dt_virt;
 }
 
-void *__init fixmap_remap_fdt(phys_addr_t dt_phys)
-{
-	void *dt_virt;
-	int size;
-
-	dt_virt = __fixmap_remap_fdt(dt_phys, &size, PAGE_KERNEL_RO);
-	if (!dt_virt)
-		return NULL;
-
-	memblock_reserve(dt_phys, size);
-	return dt_virt;
-}
-
 int __init arch_ioremap_pud_supported(void)
 {
 	/*