Commit d6d1e3e6 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Dave Hansen
Browse files

mm/execmem: Unify early execmem_cache behaviour 



Early kernel memory is RWX, only at the end of early boot (before SMP)
do we mark things ROX. Have execmem_cache mirror this behaviour for
early users.

This avoids having to remember what code is execmem and what is not --
we can poke everything with impunity ;-) Also performance for not
having to do endless text_poke_mm switches.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarPawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: default avatarDave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: default avatarAlexandre Chartre <alexandre.chartre@oracle.com>
parent f0cd7091

arch/x86/mm/init_32.c

+3 −0
Original line number Diff line number Diff line
@@ -30,6 +30,7 @@ 
#include <linux/initrd.h>

#include <linux/cpumask.h>

#include <linux/gfp.h>

#include <linux/execmem.h>



#include <asm/asm.h>

#include <asm/bios_ebda.h>
@@ -755,6 +756,8 @@ void mark_rodata_ro(void) 
	pr_info("Write protecting kernel text and read-only data: %luk\n",

		size >> 10);



	execmem_cache_make_ro();



	kernel_set_to_readonly = 1;



#ifdef CONFIG_CPA_DEBUG

arch/x86/mm/init_64.c

+3 −0
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ 
#include <linux/gfp.h>

#include <linux/kcore.h>

#include <linux/bootmem_info.h>

#include <linux/execmem.h>



#include <asm/processor.h>

#include <asm/bios_ebda.h>
@@ -1391,6 +1392,8 @@ void mark_rodata_ro(void) 
	       (end - start) >> 10);

	set_memory_ro(start, (end - start) >> PAGE_SHIFT);



	execmem_cache_make_ro();



	kernel_set_to_readonly = 1;



	/*

include/linux/execmem.h

+7 −1
Original line number Diff line number Diff line
@@ -53,7 +53,7 @@ enum execmem_range_flags { 
	EXECMEM_ROX_CACHE	= (1 << 1),

};



#ifdef CONFIG_ARCH_HAS_EXECMEM_ROX

#if defined(CONFIG_ARCH_HAS_EXECMEM_ROX) && defined(CONFIG_EXECMEM)

/**

 * execmem_fill_trapping_insns - set memory to contain instructions that

 *				 will trap
@@ -93,9 +93,15 @@ int execmem_make_temp_rw(void *ptr, size_t size); 
 * Return: 0 on success or negative error code on failure.

 */

int execmem_restore_rox(void *ptr, size_t size);



/*

 * Called from mark_readonly(), where the system transitions to ROX.

 */

void execmem_cache_make_ro(void);

#else

static inline int execmem_make_temp_rw(void *ptr, size_t size) { return 0; }

static inline int execmem_restore_rox(void *ptr, size_t size) { return 0; }

static inline void execmem_cache_make_ro(void) { }

#endif



/**

mm/execmem.c

+37 −3
Original line number Diff line number Diff line
@@ -254,6 +254,34 @@ static void *__execmem_cache_alloc(struct execmem_range *range, size_t size) 
	return ptr;

}



static bool execmem_cache_rox = false;



void execmem_cache_make_ro(void)

{

	struct maple_tree *free_areas = &execmem_cache.free_areas;

	struct maple_tree *busy_areas = &execmem_cache.busy_areas;

	MA_STATE(mas_free, free_areas, 0, ULONG_MAX);

	MA_STATE(mas_busy, busy_areas, 0, ULONG_MAX);

	struct mutex *mutex = &execmem_cache.mutex;

	void *area;



	execmem_cache_rox = true;



	mutex_lock(mutex);



	mas_for_each(&mas_free, area, ULONG_MAX) {

		unsigned long pages = mas_range_len(&mas_free) >> PAGE_SHIFT;

		set_memory_ro(mas_free.index, pages);

	}



	mas_for_each(&mas_busy, area, ULONG_MAX) {

		unsigned long pages = mas_range_len(&mas_busy) >> PAGE_SHIFT;

		set_memory_ro(mas_busy.index, pages);

	}



	mutex_unlock(mutex);

}



static int execmem_cache_populate(struct execmem_range *range, size_t size)

{

	unsigned long vm_flags = VM_ALLOW_HUGE_VMAP;
@@ -274,9 +302,15 @@ static int execmem_cache_populate(struct execmem_range *range, size_t size) 
	/* fill memory with instructions that will trap */

	execmem_fill_trapping_insns(p, alloc_size, /* writable = */ true);



	if (execmem_cache_rox) {

		err = set_memory_rox((unsigned long)p, vm->nr_pages);

		if (err)

			goto err_free_mem;

	} else {

		err = set_memory_x((unsigned long)p, vm->nr_pages);

		if (err)

			goto err_free_mem;

	}



	err = execmem_cache_add(p, alloc_size);

	if (err)