[PATCH v1] arm64:mm: enable the kernel execute attribute for HEAD_TEXT segment

[Zhichang Yuan]

From: yuanzhichang <yuanzhichang@xxxxxxxxxxxxx>

In the patch whose title is "add better page protections to arm64"
(commit da141706aea52c1a9fbd28cb8d289b78819f5436), The direct mapping
page table entries for HEAD_TEXT segment were configured as PAGE_KERNEL,
without the executable attribute. But when the secondary CPUs are booting
based on spin-table mechanism, some functions in head.S are needed to run.
Only PAGE_KERNEL dosen't work for this case.
This patch will configure the page attributes as PAGE_KERNEL_EXEC for
HEAD_TEXT segment.

Signed-off-by: Zhichang Yuan <yuanzhichang@xxxxxxxxxxxxx>
---
 arch/arm64/mm/mmu.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index c6daaf6..ad08dfd 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -305,8 +305,8 @@ static void __init __map_memblock(phys_addr_t start, phys_addr_t end)
 	 * for now. This will get more fine grained later once all memory
 	 * is mapped
 	 */
-	unsigned long kernel_x_start = round_down(__pa(_stext), SECTION_SIZE);
-	unsigned long kernel_x_end = round_up(__pa(__init_end), SECTION_SIZE);
+	phys_addr_t kernel_x_start = round_down(__pa(_text), SECTION_SIZE);
+	phys_addr_t kernel_x_end = round_up(__pa(__init_end), SECTION_SIZE);
 
 	if (end < kernel_x_start) {
 		create_mapping(start, __phys_to_virt(start),
@@ -315,6 +315,18 @@ static void __init __map_memblock(phys_addr_t start, phys_addr_t end)
 		create_mapping(start, __phys_to_virt(start),
 			end - start, PAGE_KERNEL);
 	} else {
+	/*
+	 * At this moment, the text segment must reside in valid physical
+	 * memory section range to make sure the text are totally mapped. 
+	 * If mapping from non-section aligned address is support, then
+	 * _text can be used here directly in replace to kernel_x_start.
+	 */
+		phys_addr_t max_left, min_right;
+
+		max_left = max(kernel_x_start, start);
+		min_right = min(kernel_x_end, end);
+		BUG_ON(max_left != kernel_x_start || min_right != kernel_x_end);
+
 		if (start < kernel_x_start)
 			create_mapping(start, __phys_to_virt(start),
 				kernel_x_start - start,
@@ -394,12 +406,12 @@ void __init fixup_executable(void)
 {
 #ifdef CONFIG_DEBUG_RODATA
 	/* now that we are actually fully mapped, make the start/end more fine grained */
-	if (!IS_ALIGNED((unsigned long)_stext, SECTION_SIZE)) {
-		unsigned long aligned_start = round_down(__pa(_stext),
+	if (!IS_ALIGNED((unsigned long)_text, SECTION_SIZE)) {
+		unsigned long aligned_start = round_down(__pa(_text),
 							SECTION_SIZE);
 
 		create_mapping(aligned_start, __phys_to_virt(aligned_start),
-				__pa(_stext) - aligned_start,
+				__pa(_text) - aligned_start,
 				PAGE_KERNEL);
 	}
 
@@ -418,7 +430,7 @@ void mark_rodata_ro(void)
 {
 	create_mapping_late(__pa(_stext), (unsigned long)_stext,
 				(unsigned long)_etext - (unsigned long)_stext,
-				PAGE_KERNEL_EXEC | PTE_RDONLY);
+				(PAGE_KERNEL_EXEC | PTE_RDONLY) & ~PTE_WRITE);
 
 }
 #endif
-- 
1.9.1

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