[PATCH v6 8/8] x86/module: enable ROX caches for module text on 64 bit

[Mike Rapoport]

From: "Mike Rapoport (Microsoft)" <rppt at kernel.org>

Enable execmem's cache of PMD_SIZE'ed pages mapped as ROX for module
text allocations on 64 bit.

Signed-off-by: Mike Rapoport (Microsoft) <rppt at kernel.org>
---
 arch/x86/Kconfig   |  1 +
 arch/x86/mm/init.c | 37 ++++++++++++++++++++++++++++++++++++-
 2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2852fcd82cbd..ff71d18253ba 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -83,6 +83,7 @@ config X86
 	select ARCH_HAS_DMA_OPS			if GART_IOMMU || XEN
 	select ARCH_HAS_EARLY_DEBUG		if KGDB
 	select ARCH_HAS_ELF_RANDOMIZE
+	select ARCH_HAS_EXECMEM_ROX		if X86_64
 	select ARCH_HAS_FAST_MULTIPLIER
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_GCOV_PROFILE_ALL
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index eb503f53c319..c2e4f389f47f 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -1053,18 +1053,53 @@ unsigned long arch_max_swapfile_size(void)
 #ifdef CONFIG_EXECMEM
 static struct execmem_info execmem_info __ro_after_init;
 
+#ifdef CONFIG_ARCH_HAS_EXECMEM_ROX
+void execmem_fill_trapping_insns(void *ptr, size_t size, bool writeable)
+{
+	/* fill memory with INT3 instructions */
+	if (writeable)
+		memset(ptr, INT3_INSN_OPCODE, size);
+	else
+		text_poke_set(ptr, INT3_INSN_OPCODE, size);
+}
+#endif
+
 struct execmem_info __init *execmem_arch_setup(void)
 {
 	unsigned long start, offset = 0;
+	enum execmem_range_flags flags;
+	pgprot_t pgprot;
 
 	if (kaslr_enabled())
 		offset = get_random_u32_inclusive(1, 1024) * PAGE_SIZE;
 
 	start = MODULES_VADDR + offset;
 
+	if (IS_ENABLED(CONFIG_ARCH_HAS_EXECMEM_ROX)) {
+		pgprot = PAGE_KERNEL_ROX;
+		flags = EXECMEM_KASAN_SHADOW | EXECMEM_ROX_CACHE;
+	} else {
+		pgprot = PAGE_KERNEL;
+		flags = EXECMEM_KASAN_SHADOW;
+	}
+
 	execmem_info = (struct execmem_info){
 		.ranges = {
-			[EXECMEM_DEFAULT] = {
+			[EXECMEM_MODULE_TEXT] = {
+				.flags	= flags,
+				.start	= start,
+				.end	= MODULES_END,
+				.pgprot	= pgprot,
+				.alignment = MODULE_ALIGN,
+			},
+			[EXECMEM_KPROBES ... EXECMEM_BPF] = {
+				.flags	= EXECMEM_KASAN_SHADOW,
+				.start	= start,
+				.end	= MODULES_END,
+				.pgprot	= PAGE_KERNEL,
+				.alignment = MODULE_ALIGN,
+			},
+			[EXECMEM_MODULE_DATA] = {
 				.flags	= EXECMEM_KASAN_SHADOW,
 				.start	= start,
 				.end	= MODULES_END,
-- 
2.43.0