arch: make execmem setup available regardless of CONFIG_MODULES

execmem does not depend on modules, on the contrary modules use
execmem.

To make execmem available when CONFIG_MODULES=n, for instance for
kprobes, split execmem_params initialization out from
arch/*/kernel/module.c and compile it when CONFIG_EXECMEM=y

Signed-off-by: Mike Rapoport (IBM) <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Signed-off-by: Luis Chamberlain <[email protected]>

Author: rppt

arch/arm/kernel/module.c

@@ -12,57 +12,14 @@
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/elf.h>
-#include <linux/vmalloc.h>
 #include <linux/fs.h>
 #include <linux/string.h>
-#include <linux/gfp.h>
-#include <linux/execmem.h>
 
 #include <asm/sections.h>
 #include <asm/smp_plat.h>
 #include <asm/unwind.h>
 #include <asm/opcodes.h>
 
-#ifdef CONFIG_XIP_KERNEL
-/*
- * The XIP kernel text is mapped in the module area for modules and
- * some other stuff to work without any indirect relocations.
- * MODULES_VADDR is redefined here and not in asm/memory.h to avoid
- * recompiling the whole kernel when CONFIG_XIP_KERNEL is turned on/off.
- */
-#undef MODULES_VADDR
-#define MODULES_VADDR	(((unsigned long)_exiprom + ~PMD_MASK) & PMD_MASK)
-#endif
-
-#ifdef CONFIG_MMU
-static struct execmem_info execmem_info __ro_after_init;
-
-struct execmem_info __init *execmem_arch_setup(void)
-{
-	unsigned long fallback_start = 0, fallback_end = 0;
-
-	if (IS_ENABLED(CONFIG_ARM_MODULE_PLTS)) {
-		fallback_start = VMALLOC_START;
-		fallback_end = VMALLOC_END;
-	}
-
-	execmem_info = (struct execmem_info){
-		.ranges = {
-			[EXECMEM_DEFAULT] = {
-				.start	= MODULES_VADDR,
-				.end	= MODULES_END,
-				.pgprot	= PAGE_KERNEL_EXEC,
-				.alignment = 1,
-				.fallback_start	= fallback_start,
-				.fallback_end	= fallback_end,
-			},
-		},
-	};
-
-	return &execmem_info;
-}
-#endif
-
 bool module_init_section(const char *name)
 {
 	return strstarts(name, ".init") ||

arch/arm/mm/init.c

@@ -22,6 +22,7 @@
 #include <linux/sizes.h>
 #include <linux/stop_machine.h>
 #include <linux/swiotlb.h>
+#include <linux/execmem.h>
 
 #include <asm/cp15.h>
 #include <asm/mach-types.h>
@@ -486,3 +487,47 @@ void free_initrd_mem(unsigned long start, unsigned long end)
 	free_reserved_area((void *)start, (void *)end, -1, "initrd");
 }
 #endif
+
+#ifdef CONFIG_EXECMEM
+
+#ifdef CONFIG_XIP_KERNEL
+/*
+ * The XIP kernel text is mapped in the module area for modules and
+ * some other stuff to work without any indirect relocations.
+ * MODULES_VADDR is redefined here and not in asm/memory.h to avoid
+ * recompiling the whole kernel when CONFIG_XIP_KERNEL is turned on/off.
+ */
+#undef MODULES_VADDR
+#define MODULES_VADDR	(((unsigned long)_exiprom + ~PMD_MASK) & PMD_MASK)
+#endif
+
+#ifdef CONFIG_MMU
+static struct execmem_info execmem_info __ro_after_init;
+
+struct execmem_info __init *execmem_arch_setup(void)
+{
+	unsigned long fallback_start = 0, fallback_end = 0;
+
+	if (IS_ENABLED(CONFIG_ARM_MODULE_PLTS)) {
+		fallback_start = VMALLOC_START;
+		fallback_end = VMALLOC_END;
+	}
+
+	execmem_info = (struct execmem_info){
+		.ranges = {
+			[EXECMEM_DEFAULT] = {
+				.start	= MODULES_VADDR,
+				.end	= MODULES_END,
+				.pgprot	= PAGE_KERNEL_EXEC,
+				.alignment = 1,
+				.fallback_start	= fallback_start,
+				.fallback_end	= fallback_end,
+			},
+		},
+	};
+
+	return &execmem_info;
+}
+#endif /* CONFIG_MMU */
+
+#endif /* CONFIG_EXECMEM */

arch/arm64/kernel/module.c

@@ -12,158 +12,18 @@
 #include <linux/bitops.h>
 #include <linux/elf.h>
 #include <linux/ftrace.h>
-#include <linux/gfp.h>
 #include <linux/kasan.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/moduleloader.h>
 #include <linux/random.h>
 #include <linux/scs.h>
-#include <linux/vmalloc.h>
-#include <linux/execmem.h>
 
 #include <asm/alternative.h>
 #include <asm/insn.h>
 #include <asm/scs.h>
 #include <asm/sections.h>
 
-static u64 module_direct_base __ro_after_init = 0;
-static u64 module_plt_base __ro_after_init = 0;
-
-/*
- * Choose a random page-aligned base address for a window of 'size' bytes which
- * entirely contains the interval [start, end - 1].
- */
-static u64 __init random_bounding_box(u64 size, u64 start, u64 end)
-{
-	u64 max_pgoff, pgoff;
-
-	if ((end - start) >= size)
-		return 0;
-
-	max_pgoff = (size - (end - start)) / PAGE_SIZE;
-	pgoff = get_random_u32_inclusive(0, max_pgoff);
-
-	return start - pgoff * PAGE_SIZE;
-}
-
-/*
- * Modules may directly reference data and text anywhere within the kernel
- * image and other modules. References using PREL32 relocations have a +/-2G
- * range, and so we need to ensure that the entire kernel image and all modules
- * fall within a 2G window such that these are always within range.
- *
- * Modules may directly branch to functions and code within the kernel text,
- * and to functions and code within other modules. These branches will use
- * CALL26/JUMP26 relocations with a +/-128M range. Without PLTs, we must ensure
- * that the entire kernel text and all module text falls within a 128M window
- * such that these are always within range. With PLTs, we can expand this to a
- * 2G window.
- *
- * We chose the 128M region to surround the entire kernel image (rather than
- * just the text) as using the same bounds for the 128M and 2G regions ensures
- * by construction that we never select a 128M region that is not a subset of
- * the 2G region. For very large and unusual kernel configurations this means
- * we may fall back to PLTs where they could have been avoided, but this keeps
- * the logic significantly simpler.
- */
-static int __init module_init_limits(void)
-{
-	u64 kernel_end = (u64)_end;
-	u64 kernel_start = (u64)_text;
-	u64 kernel_size = kernel_end - kernel_start;
-
-	/*
-	 * The default modules region is placed immediately below the kernel
-	 * image, and is large enough to use the full 2G relocation range.
-	 */
-	BUILD_BUG_ON(KIMAGE_VADDR != MODULES_END);
-	BUILD_BUG_ON(MODULES_VSIZE < SZ_2G);
-
-	if (!kaslr_enabled()) {
-		if (kernel_size < SZ_128M)
-			module_direct_base = kernel_end - SZ_128M;
-		if (kernel_size < SZ_2G)
-			module_plt_base = kernel_end - SZ_2G;
-	} else {
-		u64 min = kernel_start;
-		u64 max = kernel_end;
-
-		if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) {
-			pr_info("2G module region forced by RANDOMIZE_MODULE_REGION_FULL\n");
-		} else {
-			module_direct_base = random_bounding_box(SZ_128M, min, max);
-			if (module_direct_base) {
-				min = module_direct_base;
-				max = module_direct_base + SZ_128M;
-			}
-		}
-
-		module_plt_base = random_bounding_box(SZ_2G, min, max);
-	}
-
-	pr_info("%llu pages in range for non-PLT usage",
-		module_direct_base ? (SZ_128M - kernel_size) / PAGE_SIZE : 0);
-	pr_info("%llu pages in range for PLT usage",
-		module_plt_base ? (SZ_2G - kernel_size) / PAGE_SIZE : 0);
-
-	return 0;
-}
-
-static struct execmem_info execmem_info __ro_after_init;
-
-struct execmem_info __init *execmem_arch_setup(void)
-{
-	unsigned long fallback_start = 0, fallback_end = 0;
-	unsigned long start = 0, end = 0;
-
-	module_init_limits();
-
-	/*
-	 * Where possible, prefer to allocate within direct branch range of the
-	 * kernel such that no PLTs are necessary.
-	 */
-	if (module_direct_base) {
-		start = module_direct_base;
-		end = module_direct_base + SZ_128M;
-
-		if (module_plt_base) {
-			fallback_start = module_plt_base;
-			fallback_end = module_plt_base + SZ_2G;
-		}
-	} else if (module_plt_base) {
-		start = module_plt_base;
-		end = module_plt_base + SZ_2G;
-	}
-
-	execmem_info = (struct execmem_info){
-		.ranges = {
-			[EXECMEM_DEFAULT] = {
-				.start	= start,
-				.end	= end,
-				.pgprot	= PAGE_KERNEL,
-				.alignment = 1,
-				.fallback_start	= fallback_start,
-				.fallback_end	= fallback_end,
-			},
-			[EXECMEM_KPROBES] = {
-				.start	= VMALLOC_START,
-				.end	= VMALLOC_END,
-				.pgprot	= PAGE_KERNEL_ROX,
-				.alignment = 1,
-			},
-			[EXECMEM_BPF] = {
-				.start	= VMALLOC_START,
-				.end	= VMALLOC_END,
-				.pgprot	= PAGE_KERNEL,
-				.alignment = 1,
-			},
-		},
-	};
-
-	return &execmem_info;
-}
-
 enum aarch64_reloc_op {
 	RELOC_OP_NONE,
 	RELOC_OP_ABS,