[RFC PATCH 2/3] arm64: hibernate: Split create_safe_exec_page() and its mapping code

[James Morse <james.morse@arm.com>]

Kexec wants to share hibernate's page table setup code, but needs its
memory-copy buffer idmapped as it also has to turn the MMU off.

Split the copy of this buffer from the code that maps it.

Signed-off-by: James Morse <james.morse@arm.com>
---
 arch/arm64/kernel/hibernate.c | 57 +++++++++++++++++++++--------------
 1 file changed, 34 insertions(+), 23 deletions(-)

diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
index a96b2921d22c..7f8cb7596f9e 100644
--- a/arch/arm64/kernel/hibernate.c
+++ b/arch/arm64/kernel/hibernate.c
@@ -183,19 +183,9 @@ int arch_hibernation_header_restore(void *addr)
 EXPORT_SYMBOL(arch_hibernation_header_restore);
 
 /*
- * Copies length bytes, starting at src_start into an new page,
- * perform cache maintentance, then maps it at the specified address low
- * address as executable.
- *
- * This is used by hibernate to copy the code it needs to execute when
- * overwriting the kernel text. This function generates a new set of page
- * tables, which it loads into ttbr0.
- *
- * Length is provided as we probably only want 4K of data, even on a 64K
- * page system.
+ * Create a set of page tables that map page to dst_addr.
  */
-static int create_safe_exec_page(void *src_start, size_t length,
-				 unsigned long dst_addr,
+static int create_single_mapping(unsigned long page, unsigned long dst_addr,
 				 phys_addr_t *phys_dst_addr,
 				 void *(*allocator)(gfp_t mask),
 				 gfp_t mask)
@@ -206,15 +196,6 @@ static int create_safe_exec_page(void *src_start, size_t length,
 	pud_t *pudp;
 	pmd_t *pmdp;
 	pte_t *ptep;
-	unsigned long dst = (unsigned long)allocator(mask);
-
-	if (!dst) {
-		rc = -ENOMEM;
-		goto out;
-	}
-
-	memcpy((void *)dst, src_start, length);
-	__flush_icache_range(dst, dst + length);
 
 	trans_pgd = allocator(mask);
 	if (!trans_pgd) {
@@ -253,7 +234,7 @@ static int create_safe_exec_page(void *src_start, size_t length,
 	}
 
 	ptep = pte_offset_kernel(pmdp, dst_addr);
-	set_pte(ptep, pfn_pte(virt_to_pfn(dst), PAGE_KERNEL_EXEC));
+	set_pte(ptep, pfn_pte(virt_to_pfn(page), PAGE_KERNEL_EXEC));
 
 	/*
 	 * Load our new page tables. A strict BBM approach requires that we
@@ -272,12 +253,42 @@ static int create_safe_exec_page(void *src_start, size_t length,
 	write_sysreg(phys_to_ttbr(virt_to_phys(pgdp)), ttbr0_el1);
 	isb();
 
-	*phys_dst_addr = virt_to_phys((void *)dst);
+	*phys_dst_addr = virt_to_phys((void *)page);
 
 out:
 	return rc;
 }
 
+/*
+ * Copies length bytes, starting at src_start into an new page,
+ * perform cache maintentance, then maps it at the specified address low
+ * address as executable.
+ *
+ * This is used by hibernate to copy the code it needs to execute when
+ * overwriting the kernel text. This function generates a new set of page
+ * tables, which it loads into ttbr0.
+ *
+ * Length is provided as we probably only want 4K of data, even on a 64K
+ * page system.
+ */
+static int create_safe_exec_page(void *src_start, size_t length,
+				 unsigned long dst_addr,
+				 phys_addr_t *phys_dst_addr,
+				 void *(*allocator)(gfp_t mask),
+				 gfp_t mask)
+{
+	unsigned long page = (unsigned long)allocator(mask);
+
+	if (!page)
+		return -ENOMEM;
+
+	memcpy((void *)page, src_start, length);
+	__flush_icache_range(page, page + length);
+
+	return create_single_mapping(page, dst_addr, phys_dst_addr,
+				     allocator, gfp_t mask)
+}
+
 #define dcache_clean_range(start, end)	__flush_dcache_area(start, (end - start))
 
 int swsusp_arch_suspend(void)
-- 
2.24.1


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