[RFC,15/17] arm64: text replication: include most of read-only data as well

Commit Message

Russell King (Oracle) May 30, 2023, 2:05 p.m. UTC

Include as much of the read-only data in the replication as we can
without needing to move away from the generic RO_DATA() macro in
the linker script.

Unfortunately, the read-only data section is immedaitely followed
by the read-only after init data with no page alignment, which
means we can't have separate mappings for the read-only data
section and everything else. Changing that would mean replacing
the generic RO_DATA() macro which increases the maintenance burden.

however, this is likely not worth the effort as the majority of
read-only data will be covered.

Signed-off-by: Russell King (Oracle) <[e-mail]>
---
 arch/arm64/mm/ktext.c |  2 +-
 arch/arm64/mm/mmu.c   | 21 ++++++++++++++++++---
 2 files changed, 19 insertions(+), 4 deletions(-)

Patch

diff --git a/arch/arm64/mm/ktext.c b/arch/arm64/mm/ktext.c
index 11eba88fdd49..f64a649f06a4 100644
--- a/arch/arm64/mm/ktext.c
+++ b/arch/arm64/mm/ktext.c
@@ -101,7 +101,7 @@  void ktext_replication_patch_alternative(__le32 *src, int nr_inst)
 /* Allocate page tables and memory for the replicated kernel texts. */
 void __init ktext_replication_init(void)
 {
-	size_t size = _etext - _stext;
+	size_t size = __end_rodata - _stext;
 	int kidx = pgd_index((phys_addr_t)KERNEL_START);
 	int nid;
 
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 2ba5cdfa28ce..5e4cb28f3e5f 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -753,11 +753,26 @@  static pgprot_t __init kernel_text_pgprot(void)
 #ifdef CONFIG_REPLICATE_KTEXT
 void __init create_kernel_nid_map(pgd_t *pgdp, void *ktext)
 {
+	phys_addr_t pa_ktext;
+	size_t ro_offset;
+	void *ro_end;
 	pgprot_t text_prot = kernel_text_pgprot();
 
-	create_kernel_mapping(pgdp, __pa(ktext), _stext, _etext, text_prot, 0);
-	create_kernel_mapping(pgdp, __pa_symbol(__start_rodata),
-			      __start_rodata, __inittext_begin,
+	pa_ktext = __pa(ktext);
+	ro_offset = __pa_symbol(__start_rodata) - __pa_symbol(_stext);
+	/*
+	 * We must not cover the read-only data after init, since this
+	 * is written to during boot, and thus must be shared between
+	 * the NUMA nodes.
+	 */
+	ro_end = PTR_ALIGN_DOWN((void *)__start_ro_after_init, PAGE_SIZE);
+
+	create_kernel_mapping(pgdp, pa_ktext, _stext, _etext, text_prot, 0);
+	create_kernel_mapping(pgdp, pa_ktext + ro_offset,
+			      __start_rodata, ro_end,
+			      PAGE_KERNEL, NO_CONT_MAPPINGS);
+	create_kernel_mapping(pgdp, __pa_symbol(ro_end),
+			      ro_end, __inittext_begin,
 			      PAGE_KERNEL, NO_CONT_MAPPINGS);
 	create_kernel_mapping(pgdp, __pa_symbol(__inittext_begin),
 			      __inittext_begin, __inittext_end,