Revert "mm/execmem: Unify early execmem_cache behaviour"

The commit d6d1e3e ("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 d6d1e3e.

Signed-off-by: Mike Rapoport (Microsoft) <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]

Author: rppt

arch/x86/mm/init_32.c

@@ -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

@@ -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

@@ -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

@@ -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 = set_memory_rox((unsigned long)p, vm->nr_pages);
+	if (err)
+		goto err_free_mem;
 
 	err = execmem_cache_add(p, alloc_size);
 	if (err)