Commit 7cd9a11d authored by Mike Rapoport (Microsoft)'s avatar Mike Rapoport (Microsoft) Committed by Peter Zijlstra
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Revert "mm/execmem: Unify early execmem_cache behaviour" 



The commit d6d1e3e6 ("mm/execmem: Unify early execmem_cache
behaviour") changed early behaviour of execemem ROX cache to allow its
usage in early x86 code that allocates text pages when
CONFIG_MITGATION_ITS is enabled.

The permission management of the pages allocated from execmem for ITS
mitigation is now completely contained in arch/x86/kernel/alternatives.c
and therefore there is no need to special case early allocations in
execmem.

This reverts commit d6d1e3e6.

Signed-off-by: default avatarMike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20250603111446.2609381-6-rppt@kernel.org
parent a82b2645

arch/x86/mm/init_32.c

+0 −3
Original line number Diff line number Diff line
@@ -30,7 +30,6 @@ 
#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>
@@ -749,8 +748,6 @@ 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

+0 −3
Original line number Diff line number Diff line
@@ -34,7 +34,6 @@ 
#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>
@@ -1392,8 +1391,6 @@ 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

+1 −7
Original line number Diff line number Diff line
@@ -54,7 +54,7 @@ enum execmem_range_flags { 
	EXECMEM_ROX_CACHE	= (1 << 1),

};



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

#ifdef CONFIG_ARCH_HAS_EXECMEM_ROX

/**

 * execmem_fill_trapping_insns - set memory to contain instructions that

 *				 will trap
@@ -94,15 +94,9 @@ 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

+3 −37
Original line number Diff line number Diff line
@@ -254,34 +254,6 @@ 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;
@@ -302,15 +274,9 @@ 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)