Commit e46b7103 authored by Mark Rutland's avatar Mark Rutland Committed by Catalin Marinas
Browse files

arm64: module: move module randomization to module.c 



When CONFIG_RANDOMIZE_BASE=y, module_alloc_base is a variable which is
configured by kaslr_module_init() in kaslr.c, and otherwise it is an
expression defined in module.h.

As kaslr_module_init() is no longer tightly coupled with the KASLR
initialization code, we can centralize this in module.c.

This patch moves kaslr_module_init() to module.c, making
module_alloc_base a static variable, and removing redundant includes from
kaslr.c. For the defintion of struct arm64_ftr_override we must include
<asm/cpufeature.h>, which was previously included transitively via
another header.

There should be no functional change as a result of this patch.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Reviewed-by: default avatarArd Biesheuvel <ardb@kernel.org>
Cc: Will Deacon <will@kernel.org>
Tested-by: default avatarShanker Donthineni <sdonthineni@nvidia.com>
Link: https://lore.kernel.org/r/20230530110328.2213762-5-mark.rutland@arm.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent 6e13b6b9

arch/arm64/include/asm/module.h

+0 −6
Original line number Diff line number Diff line
@@ -30,12 +30,6 @@ u64 module_emit_plt_entry(struct module *mod, Elf64_Shdr *sechdrs, 
u64 module_emit_veneer_for_adrp(struct module *mod, Elf64_Shdr *sechdrs,

				void *loc, u64 val);



#ifdef CONFIG_RANDOMIZE_BASE

extern u64 module_alloc_base;

#else

#define module_alloc_base	((u64)_etext - MODULES_VSIZE)

#endif



struct plt_entry {

	/*

	 * A program that conforms to the AArch64 Procedure Call Standard

arch/arm64/kernel/kaslr.c

+2 −58
Original line number Diff line number Diff line
@@ -4,23 +4,12 @@ 
 */



#include <linux/cache.h>

#include <linux/crc32.h>

#include <linux/init.h>

#include <linux/libfdt.h>

#include <linux/mm_types.h>

#include <linux/sched.h>

#include <linux/types.h>

#include <linux/pgtable.h>

#include <linux/random.h>

#include <linux/printk.h>



#include <asm/fixmap.h>

#include <asm/kernel-pgtable.h>

#include <asm/cpufeature.h>

#include <asm/memory.h>

#include <asm/mmu.h>

#include <asm/sections.h>

#include <asm/setup.h>



u64 __ro_after_init module_alloc_base;

u16 __initdata memstart_offset_seed;



struct arm64_ftr_override kaslr_feature_override __initdata;
@@ -47,48 +36,3 @@ void __init kaslr_init(void) 
	pr_info("KASLR enabled\n");

	__kaslr_is_enabled = true;

}
 


int kaslr_module_init(void)

{

	u64 module_range;

	u32 seed;



	/*

	 * Set a reasonable default for module_alloc_base in case

	 * we end up running with module randomization disabled.

	 */

	module_alloc_base = (u64)_etext - MODULES_VSIZE;



	seed = get_random_u32();



	if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) {

		/*

		 * Randomize the module region over a 2 GB window covering the

		 * kernel. This reduces the risk of modules leaking information

		 * about the address of the kernel itself, but results in

		 * branches between modules and the core kernel that are

		 * resolved via PLTs. (Branches between modules will be

		 * resolved normally.)

		 */

		module_range = SZ_2G - (u64)(_end - _stext);

		module_alloc_base = max((u64)_end - SZ_2G, (u64)MODULES_VADDR);

	} else {

		/*

		 * Randomize the module region by setting module_alloc_base to

		 * a PAGE_SIZE multiple in the range [_etext - MODULES_VSIZE,

		 * _stext) . This guarantees that the resulting region still

		 * covers [_stext, _etext], and that all relative branches can

		 * be resolved without veneers unless this region is exhausted

		 * and we fall back to a larger 2GB window in module_alloc()

		 * when ARM64_MODULE_PLTS is enabled.

		 */

		module_range = MODULES_VSIZE - (u64)(_etext - _stext);

	}



	/* use the lower 21 bits to randomize the base of the module region */

	module_alloc_base += (module_range * (seed & ((1 << 21) - 1))) >> 21;

	module_alloc_base &= PAGE_MASK;



	return 0;

}

subsys_initcall(kaslr_module_init)

arch/arm64/kernel/module.c

+48 −0
Original line number Diff line number Diff line
@@ -15,13 +15,61 @@ 
#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 <asm/alternative.h>

#include <asm/insn.h>

#include <asm/scs.h>

#include <asm/sections.h>



static u64 __ro_after_init module_alloc_base = (u64)_etext - MODULES_VSIZE;



#ifdef CONFIG_RANDOMIZE_BASE

static int __init kaslr_module_init(void)

{

	u64 module_range;

	u32 seed;



	if (!kaslr_enabled())

		return 0;



	seed = get_random_u32();



	if (IS_ENABLED(CONFIG_RANDOMIZE_MODULE_REGION_FULL)) {

		/*

		 * Randomize the module region over a 2 GB window covering the

		 * kernel. This reduces the risk of modules leaking information

		 * about the address of the kernel itself, but results in

		 * branches between modules and the core kernel that are

		 * resolved via PLTs. (Branches between modules will be

		 * resolved normally.)

		 */

		module_range = SZ_2G - (u64)(_end - _stext);

		module_alloc_base = max((u64)_end - SZ_2G, (u64)MODULES_VADDR);

	} else {

		/*

		 * Randomize the module region by setting module_alloc_base to

		 * a PAGE_SIZE multiple in the range [_etext - MODULES_VSIZE,

		 * _stext) . This guarantees that the resulting region still

		 * covers [_stext, _etext], and that all relative branches can

		 * be resolved without veneers unless this region is exhausted

		 * and we fall back to a larger 2GB window in module_alloc()

		 * when ARM64_MODULE_PLTS is enabled.

		 */

		module_range = MODULES_VSIZE - (u64)(_etext - _stext);

	}



	/* use the lower 21 bits to randomize the base of the module region */

	module_alloc_base += (module_range * (seed & ((1 << 21) - 1))) >> 21;

	module_alloc_base &= PAGE_MASK;



	return 0;

}

subsys_initcall(kaslr_module_init)

#endif



void *module_alloc(unsigned long size)

{

	u64 module_alloc_end = module_alloc_base + MODULES_VSIZE;