To make the swapper_pg_dir read only, we will move it to the rodata
section. And force the kernel to set up the initial page table in
the init_pg_dir. After generating all levels page table, we copy
only the top level into the swapper_pg_dir during paging_init().
In this patch, just add the init_pg_dir to vmlinux.lds.S and
boiler-plate clearing/cleaning/invalidating it in head.S.
Signed-off-by: Jun Yao <yaojun8558...@gmail.com>
---
arch/arm64/include/asm/assembler.h | 29 +++++++++++++++++++++++++++++
arch/arm64/kernel/head.S | 22 +++++++++++++++-------
arch/arm64/kernel/vmlinux.lds.S | 8 ++++++++
3 files changed, 52 insertions(+), 7 deletions(-)
diff --git a/arch/arm64/include/asm/assembler.h
b/arch/arm64/include/asm/assembler.h
index 0bcc98dbba56..e7bdc324d538 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -456,6 +456,35 @@ USER(\label, ic ivau, \tmp2) //
invalidate I line PoU
b.ne 9998b
.endm
+/*
+ * clear_page - clear one page
+ *
+ * start: page aligned virtual address
+ */
+ .macro clear_page, start:req
+9996: stp xzr, xzr, [\start], #16
+ stp xzr, xzr, [\start], #16
+ stp xzr, xzr, [\start], #16
+ stp xzr, xzr, [\start], #16
+ tst \start, #(PAGE_SIZE - 1)
+ b.ne 9996b
+ .endm
+
+/*
+ * clear_pages - clear contiguous pages
+ *
+ * start, end: page aligned virtual addresses
+ */
+ .macro clear_pages, start:req, end:req
+ sub \end, \end, \start
+ lsr \end, \end, #(PAGE_SHIFT)
+9997: cbz \end, 9998f
+ clear_page \start
+ sub \end, \end, #1
+ b 9997b
+9998:
+ .endm
+
/*
* Annotate a function as position independent, i.e., safe to be called before
* the kernel virtual mapping is activated.
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index b0853069702f..2c83a8c47e3f 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -295,18 +295,21 @@ __create_page_tables:
sub x1, x1, x0
bl __inval_dcache_area
+ adrp x0, init_pg_dir
+ adrp x1, init_pg_end
+ sub x1, x1, x0
+ bl __inval_dcache_area
+
/*
* Clear the idmap and swapper page tables.
*/
adrp x0, idmap_pg_dir
adrp x1, swapper_pg_end
- sub x1, x1, x0
-1: stp xzr, xzr, [x0], #16
- stp xzr, xzr, [x0], #16
- stp xzr, xzr, [x0], #16
- stp xzr, xzr, [x0], #16
- subs x1, x1, #64
- b.ne 1b
+ clear_pages x0, x1
+
+ adrp x0, init_pg_dir
+ adrp x1, init_pg_end
+ clear_pages x0, x1
mov x7, SWAPPER_MM_MMUFLAGS
@@ -395,6 +398,11 @@ __create_page_tables:
dmb sy
bl __inval_dcache_area
+ adrp x0, init_pg_dir
+ adrp x1, init_pg_end
+ sub x1, x1, x0
+ bl __inval_dcache_area
+
ret x28
ENDPROC(__create_page_tables)
.ltorg
diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
index 605d1b60469c..612ffc0bbe11 100644
--- a/arch/arm64/kernel/vmlinux.lds.S
+++ b/arch/arm64/kernel/vmlinux.lds.S
@@ -68,6 +68,12 @@ jiffies = jiffies_64;
#define TRAMP_TEXT
#endif
+#define INIT_PG_TABLES \
+ . = ALIGN(PAGE_SIZE); \
+ init_pg_dir = .; \
+ . += SWAPPER_DIR_SIZE; \
+ init_pg_end = .;
+
/*
* The size of the PE/COFF section that covers the kernel image, which
* runs from stext to _edata, must be a round multiple of the PE/COFF
@@ -161,6 +167,8 @@ SECTIONS
__inittext_end = .;
__initdata_begin = .;
+ INIT_PG_TABLES
+
.init.data : {
INIT_DATA
INIT_SETUP(16)
--
2.17.1
