Merge branch 'akpm' (patches from Andrew)

Merge misc fixes from Andrew Morton:
 "16 fixes"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
  mm: don't defer struct page initialization for Xen pv guests
  lib/Kconfig.debug: enable RUNTIME_TESTING_MENU
  vmalloc: fix __GFP_HIGHMEM usage for vmalloc_32 on 32b systems
  selftests/memfd: add run_fuse_test.sh to TEST_FILES
  bug.h: work around GCC PR82365 in BUG()
  mm/swap.c: make functions and their kernel-doc agree (again)
  mm/zpool.c: zpool_evictable: fix mismatch in parameter name and kernel-doc
  ida: do zeroing in ida_pre_get()
  mm, swap, frontswap: fix THP swap if frontswap enabled
  certs/blacklist_nohashes.c: fix const confusion in certs blacklist
  kernel/relay.c: limit kmalloc size to KMALLOC_MAX_SIZE
  mm, mlock, vmscan: no more skipping pagevecs
  mm: memcontrol: fix NR_WRITEBACK leak in memcg and system stats
  Kbuild: always define endianess in kconfig.h
  include/linux/sched/mm.h: re-inline mmdrop()
  tools: fix cross-compile var clobbering

arch/arc/include/asm/bug.h

@@ -23,7 +23,8 @@ void die(const char *str, struct pt_regs *regs, unsigned long address);
 
 #define BUG()	do {								\
 	pr_warn("BUG: failure at %s:%d/%s()!\n", __FILE__, __LINE__, __func__); \
-	dump_stack();								\
+	barrier_before_unreachable();						\
+	__builtin_trap();							\
 } while (0)
 
 #define HAVE_ARCH_BUG

arch/cris/include/arch-v10/arch/bug.h

@@ -44,18 +44,25 @@ struct bug_frame {
  * not be used like this with newer versions of gcc.
  */
 #define BUG()								\
+do {									\
 	__asm__ __volatile__ ("clear.d [" __stringify(BUG_MAGIC) "]\n\t"\
 			      "movu.w " __stringify(__LINE__) ",$r0\n\t"\
 			      "jump 0f\n\t"				\
 			      ".section .rodata\n"			\
 			      "0:\t.string \"" __FILE__ "\"\n\t"	\
-			      ".previous")
+			      ".previous");				\
+	unreachable();							\
+} while (0)
 #endif
 
 #else
 
 /* This just causes an oops. */
-#define BUG() (*(int *)0 = 0)
+#define BUG()								\
+do {									\
+	barrier_before_unreachable();					\
+	__builtin_trap();						\
+} while (0)
 
 #endif
 

arch/ia64/include/asm/bug.h

@@ -4,7 +4,11 @@
 
 #ifdef CONFIG_BUG
 #define ia64_abort()	__builtin_trap()
-#define BUG() do { printk("kernel BUG at %s:%d!\n", __FILE__, __LINE__); ia64_abort(); } while (0)
+#define BUG() do {						\
+	printk("kernel BUG at %s:%d!\n", __FILE__, __LINE__);	\
+	barrier_before_unreachable();				\
+	ia64_abort();						\
+} while (0)
 
 /* should this BUG be made generic? */
 #define HAVE_ARCH_BUG

arch/m68k/include/asm/bug.h

@@ -8,16 +8,19 @@
 #ifndef CONFIG_SUN3
 #define BUG() do { \
 	pr_crit("kernel BUG at %s:%d!\n", __FILE__, __LINE__); \
+	barrier_before_unreachable(); \
 	__builtin_trap(); \
 } while (0)
 #else
 #define BUG() do { \
 	pr_crit("kernel BUG at %s:%d!\n", __FILE__, __LINE__); \
+	barrier_before_unreachable(); \
 	panic("BUG!"); \
 } while (0)
 #endif
 #else
 #define BUG() do { \
+	barrier_before_unreachable(); \
 	__builtin_trap(); \
 } while (0)
 #endif

arch/sparc/include/asm/bug.h

@@ -9,10 +9,14 @@
 void do_BUG(const char *file, int line);
 #define BUG() do {					\
 	do_BUG(__FILE__, __LINE__);			\
+	barrier_before_unreachable();			\
 	__builtin_trap();				\
 } while (0)
 #else
-#define BUG()		__builtin_trap()
+#define BUG() do {					\
+	barrier_before_unreachable();			\
+	__builtin_trap();				\
+} while (0)
 #endif
 
 #define HAVE_ARCH_BUG

certs/blacklist_nohashes.c

 // SPDX-License-Identifier: GPL-2.0
 #include "blacklist.h"
 
-const char __initdata *const blacklist_hashes[] = {
+const char __initconst *const blacklist_hashes[] = {
 	NULL
 };

drivers/xen/tmem.c

@@ -284,6 +284,10 @@ static int tmem_frontswap_store(unsigned type, pgoff_t offset,
 	int pool = tmem_frontswap_poolid;
 	int ret;
 
+	/* THP isn't supported */
+	if (PageTransHuge(page))
+		return -1;
+
 	if (pool < 0)
 		return -1;
 	if (ind64 != ind)

include/asm-generic/bug.h

@@ -52,6 +52,7 @@ struct bug_entry {
 #ifndef HAVE_ARCH_BUG
 #define BUG() do { \
 	printk("BUG: failure at %s:%d/%s()!\n", __FILE__, __LINE__, __func__); \
+	barrier_before_unreachable(); \
 	panic("BUG!"); \
 } while (0)
 #endif

include/linux/compiler-gcc.h

@@ -207,6 +207,15 @@
 #endif
 #endif
 
+/*
+ * calling noreturn functions, __builtin_unreachable() and __builtin_trap()
+ * confuse the stack allocation in gcc, leading to overly large stack
+ * frames, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82365
+ *
+ * Adding an empty inline assembly before it works around the problem
+ */
+#define barrier_before_unreachable() asm volatile("")
+
 /*
  * Mark a position in code as unreachable.  This can be used to
  * suppress control flow warnings after asm blocks that transfer
@@ -217,7 +226,11 @@
  * unreleased.  Really, we need to have autoconf for the kernel.
  */
 #define unreachable() \
-	do { annotate_unreachable(); __builtin_unreachable(); } while (0)
+	do {					\
+		annotate_unreachable();		\
+		barrier_before_unreachable();	\
+		__builtin_unreachable();	\
+	} while (0)
 
 /* Mark a function definition as prohibited from being cloned. */
 #define __noclone	__attribute__((__noclone__, __optimize__("no-tracer")))

include/linux/compiler.h

@@ -86,6 +86,11 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 # define barrier_data(ptr) barrier()
 #endif
 
+/* workaround for GCC PR82365 if needed */
+#ifndef barrier_before_unreachable
+# define barrier_before_unreachable() do { } while (0)
+#endif
+
 /* Unreachable code */
 #ifdef CONFIG_STACK_VALIDATION
 /*

include/linux/kconfig.h

@@ -4,6 +4,12 @@
 
 #include <generated/autoconf.h>
 
+#ifdef CONFIG_CPU_BIG_ENDIAN
+#define __BIG_ENDIAN 4321
+#else
+#define __LITTLE_ENDIAN 1234
+#endif
+
 #define __ARG_PLACEHOLDER_1 0,
 #define __take_second_arg(__ignored, val, ...) val
 

include/linux/memcontrol.h

@@ -523,9 +523,11 @@ static inline void __mod_memcg_state(struct mem_cgroup *memcg,
 static inline void mod_memcg_state(struct mem_cgroup *memcg,
 				   int idx, int val)
 {
-	preempt_disable();
+	unsigned long flags;
+
+	local_irq_save(flags);
 	__mod_memcg_state(memcg, idx, val);
-	preempt_enable();
+	local_irq_restore(flags);
 }
 
 /**
@@ -606,9 +608,11 @@ static inline void __mod_lruvec_state(struct lruvec *lruvec,
 static inline void mod_lruvec_state(struct lruvec *lruvec,
 				    enum node_stat_item idx, int val)
 {
-	preempt_disable();
+	unsigned long flags;
+
+	local_irq_save(flags);
 	__mod_lruvec_state(lruvec, idx, val);
-	preempt_enable();
+	local_irq_restore(flags);
 }
 
 static inline void __mod_lruvec_page_state(struct page *page,
@@ -630,9 +634,11 @@ static inline void __mod_lruvec_page_state(struct page *page,
 static inline void mod_lruvec_page_state(struct page *page,
 					 enum node_stat_item idx, int val)
 {
-	preempt_disable();
+	unsigned long flags;
+
+	local_irq_save(flags);
 	__mod_lruvec_page_state(page, idx, val);
-	preempt_enable();
+	local_irq_restore(flags);
 }
 
 unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,
@@ -659,9 +665,11 @@ static inline void __count_memcg_events(struct mem_cgroup *memcg,
 static inline void count_memcg_events(struct mem_cgroup *memcg,
 				      int idx, unsigned long count)
 {
-	preempt_disable();
+	unsigned long flags;
+
+	local_irq_save(flags);
 	__count_memcg_events(memcg, idx, count);
-	preempt_enable();
+	local_irq_restore(flags);
 }
 
 /* idx can be of type enum memcg_event_item or vm_event_item */

include/linux/sched/mm.h

@@ -36,7 +36,18 @@ static inline void mmgrab(struct mm_struct *mm)
 	atomic_inc(&mm->mm_count);
 }
 
-extern void mmdrop(struct mm_struct *mm);
+extern void __mmdrop(struct mm_struct *mm);
+
+static inline void mmdrop(struct mm_struct *mm)
+{
+	/*
+	 * The implicit full barrier implied by atomic_dec_and_test() is
+	 * required by the membarrier system call before returning to
+	 * user-space, after storing to rq->curr.
+	 */
+	if (unlikely(atomic_dec_and_test(&mm->mm_count)))
+		__mmdrop(mm);
+}
 
 /**
  * mmget() - Pin the address space associated with a &struct mm_struct.

include/linux/swap.h

@@ -337,8 +337,6 @@ extern void deactivate_file_page(struct page *page);
 extern void mark_page_lazyfree(struct page *page);
 extern void swap_setup(void);
 
-extern void add_page_to_unevictable_list(struct page *page);
-
 extern void lru_cache_add_active_or_unevictable(struct page *page,
 						struct vm_area_struct *vma);
 

kernel/fork.c

@@ -592,7 +592,7 @@ static void check_mm(struct mm_struct *mm)
  * is dropped: either by a lazy thread or by
  * mmput. Free the page directory and the mm.
  */
-static void __mmdrop(struct mm_struct *mm)
+void __mmdrop(struct mm_struct *mm)
 {
 	BUG_ON(mm == &init_mm);
 	mm_free_pgd(mm);
@@ -603,18 +603,7 @@ static void __mmdrop(struct mm_struct *mm)
 	put_user_ns(mm->user_ns);
 	free_mm(mm);
 }
-
-void mmdrop(struct mm_struct *mm)
-{
-	/*
-	 * The implicit full barrier implied by atomic_dec_and_test() is
-	 * required by the membarrier system call before returning to
-	 * user-space, after storing to rq->curr.
-	 */
-	if (unlikely(atomic_dec_and_test(&mm->mm_count)))
-		__mmdrop(mm);
-}
-EXPORT_SYMBOL_GPL(mmdrop);
+EXPORT_SYMBOL_GPL(__mmdrop);
 
 static void mmdrop_async_fn(struct work_struct *work)
 {

kernel/relay.c

@@ -163,7 +163,7 @@ static struct rchan_buf *relay_create_buf(struct rchan *chan)
 {
 	struct rchan_buf *buf;
 
-	if (chan->n_subbufs > UINT_MAX / sizeof(size_t *))
+	if (chan->n_subbufs > KMALLOC_MAX_SIZE / sizeof(size_t *))
 		return NULL;
 
 	buf = kzalloc(sizeof(struct rchan_buf), GFP_KERNEL);

lib/Kconfig.debug

@@ -1642,6 +1642,7 @@ config DMA_API_DEBUG
 
 menuconfig RUNTIME_TESTING_MENU
 	bool "Runtime Testing"
+	def_bool y
 
 if RUNTIME_TESTING_MENU
 

lib/idr.c

@@ -431,7 +431,6 @@ int ida_get_new_above(struct ida *ida, int start, int *id)
 			bitmap = this_cpu_xchg(ida_bitmap, NULL);
 			if (!bitmap)
 				return -EAGAIN;
-			memset(bitmap, 0, sizeof(*bitmap));
 			bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
 			rcu_assign_pointer(*slot, bitmap);
 		}
@@ -464,7 +463,6 @@ int ida_get_new_above(struct ida *ida, int start, int *id)
 			bitmap = this_cpu_xchg(ida_bitmap, NULL);
 			if (!bitmap)
 				return -EAGAIN;
-			memset(bitmap, 0, sizeof(*bitmap));
 			__set_bit(bit, bitmap->bitmap);
 			radix_tree_iter_replace(root, &iter, slot, bitmap);
 		}

lib/radix-tree.c

@@ -2125,7 +2125,7 @@ int ida_pre_get(struct ida *ida, gfp_t gfp)
 		preempt_enable();
 
 	if (!this_cpu_read(ida_bitmap)) {
-		struct ida_bitmap *bitmap = kmalloc(sizeof(*bitmap), gfp);
+		struct ida_bitmap *bitmap = kzalloc(sizeof(*bitmap), gfp);
 		if (!bitmap)
 			return 0;
 		if (this_cpu_cmpxchg(ida_bitmap, NULL, bitmap))

mm/mlock.c

@@ -64,6 +64,12 @@ void clear_page_mlock(struct page *page)
 	mod_zone_page_state(page_zone(page), NR_MLOCK,
 			    -hpage_nr_pages(page));
 	count_vm_event(UNEVICTABLE_PGCLEARED);
+	/*
+	 * The previous TestClearPageMlocked() corresponds to the smp_mb()
+	 * in __pagevec_lru_add_fn().
+	 *
+	 * See __pagevec_lru_add_fn for more explanation.
+	 */
 	if (!isolate_lru_page(page)) {
 		putback_lru_page(page);
 	} else {

mm/page_alloc.c

@@ -46,6 +46,7 @@
 #include <linux/stop_machine.h>
 #include <linux/sort.h>
 #include <linux/pfn.h>
+#include <xen/xen.h>
 #include <linux/backing-dev.h>
 #include <linux/fault-inject.h>
 #include <linux/page-isolation.h>
@@ -347,6 +348,9 @@ static inline bool update_defer_init(pg_data_t *pgdat,
 	/* Always populate low zones for address-constrained allocations */
 	if (zone_end < pgdat_end_pfn(pgdat))
 		return true;
+	/* Xen PV domains need page structures early */
+	if (xen_pv_domain())
+		return true;
 	(*nr_initialised)++;
 	if ((*nr_initialised > pgdat->static_init_pgcnt) &&
 	    (pfn & (PAGES_PER_SECTION - 1)) == 0) {

mm/swap.c

@@ -445,30 +445,6 @@ void lru_cache_add(struct page *page)
 	__lru_cache_add(page);
 }
 
-/**
- * add_page_to_unevictable_list - add a page to the unevictable list
- * @page:  the page to be added to the unevictable list
- *
- * Add page directly to its zone's unevictable list.  To avoid races with
- * tasks that might be making the page evictable, through eg. munlock,
- * munmap or exit, while it's not on the lru, we want to add the page
- * while it's locked or otherwise "invisible" to other tasks.  This is
- * difficult to do when using the pagevec cache, so bypass that.
- */
-void add_page_to_unevictable_list(struct page *page)
-{
-	struct pglist_data *pgdat = page_pgdat(page);
-	struct lruvec *lruvec;
-
-	spin_lock_irq(&pgdat->lru_lock);
-	lruvec = mem_cgroup_page_lruvec(page, pgdat);
-	ClearPageActive(page);
-	SetPageUnevictable(page);
-	SetPageLRU(page);
-	add_page_to_lru_list(page, lruvec, LRU_UNEVICTABLE);
-	spin_unlock_irq(&pgdat->lru_lock);
-}
-
 /**
  * lru_cache_add_active_or_unevictable
  * @page:  the page to be added to LRU
@@ -484,13 +460,9 @@ void lru_cache_add_active_or_unevictable(struct page *page,
 {
 	VM_BUG_ON_PAGE(PageLRU(page), page);
 
-	if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED)) {
+	if (likely((vma->vm_flags & (VM_LOCKED | VM_SPECIAL)) != VM_LOCKED))
 		SetPageActive(page);
-		lru_cache_add(page);
-		return;
-	}
-
-	if (!TestSetPageMlocked(page)) {
+	else if (!TestSetPageMlocked(page)) {
 		/*
 		 * We use the irq-unsafe __mod_zone_page_stat because this
 		 * counter is not modified from interrupt context, and the pte
@@ -500,7 +472,7 @@ void lru_cache_add_active_or_unevictable(struct page *page,
 				    hpage_nr_pages(page));
 		count_vm_event(UNEVICTABLE_PGMLOCKED);
 	}
-	add_page_to_unevictable_list(page);
+	lru_cache_add(page);
 }
 
 /*
@@ -886,15 +858,55 @@ void lru_add_page_tail(struct page *page, struct page *page_tail,
 static void __pagevec_lru_add_fn(struct page *page, struct lruvec *lruvec,
 				 void *arg)
 {
-	int file = page_is_file_cache(page);
-	int active = PageActive(page);
-	enum lru_list lru = page_lru(page);
+	enum lru_list lru;
+	int was_unevictable = TestClearPageUnevictable(page);
 
 	VM_BUG_ON_PAGE(PageLRU(page), page);
 
 	SetPageLRU(page);
+	/*
+	 * Page becomes evictable in two ways:
+	 * 1) Within LRU lock [munlock_vma_pages() and __munlock_pagevec()].
+	 * 2) Before acquiring LRU lock to put the page to correct LRU and then
+	 *   a) do PageLRU check with lock [check_move_unevictable_pages]
+	 *   b) do PageLRU check before lock [clear_page_mlock]
+	 *
+	 * (1) & (2a) are ok as LRU lock will serialize them. For (2b), we need
+	 * following strict ordering:
+	 *
+	 * #0: __pagevec_lru_add_fn		#1: clear_page_mlock
+	 *
+	 * SetPageLRU()				TestClearPageMlocked()
+	 * smp_mb() // explicit ordering	// above provides strict
+	 *					// ordering
+	 * PageMlocked()			PageLRU()
+	 *
+	 *
+	 * if '#1' does not observe setting of PG_lru by '#0' and fails
+	 * isolation, the explicit barrier will make sure that page_evictable
+	 * check will put the page in correct LRU. Without smp_mb(), SetPageLRU
+	 * can be reordered after PageMlocked check and can make '#1' to fail
+	 * the isolation of the page whose Mlocked bit is cleared (#0 is also
+	 * looking at the same page) and the evictable page will be stranded
+	 * in an unevictable LRU.
+	 */
+	smp_mb();
+
+	if (page_evictable(page)) {
+		lru = page_lru(page);
+		update_page_reclaim_stat(lruvec, page_is_file_cache(page),
+					 PageActive(page));
+		if (was_unevictable)
+			count_vm_event(UNEVICTABLE_PGRESCUED);
+	} else {
+		lru = LRU_UNEVICTABLE;
+		ClearPageActive(page);
+		SetPageUnevictable(page);
+		if (!was_unevictable)
+			count_vm_event(UNEVICTABLE_PGCULLED);
+	}
+
 	add_page_to_lru_list(page, lruvec, lru);
-	update_page_reclaim_stat(lruvec, file, active);
 	trace_mm_lru_insertion(page, lru);
 }
 
@@ -913,7 +925,7 @@ EXPORT_SYMBOL(__pagevec_lru_add);
  * @pvec:	Where the resulting entries are placed
  * @mapping:	The address_space to search
  * @start:	The starting entry index
- * @nr_pages:	The maximum number of pages
+ * @nr_entries:	The maximum number of pages
  * @indices:	The cache indices corresponding to the entries in @pvec
  *
  * pagevec_lookup_entries() will search for and return a group of up

mm/vmalloc.c

@@ -1943,11 +1943,15 @@ void *vmalloc_exec(unsigned long size)
 }
 
 #if defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA32)
-#define GFP_VMALLOC32 GFP_DMA32 | GFP_KERNEL
+#define GFP_VMALLOC32 (GFP_DMA32 | GFP_KERNEL)
 #elif defined(CONFIG_64BIT) && defined(CONFIG_ZONE_DMA)
-#define GFP_VMALLOC32 GFP_DMA | GFP_KERNEL
+#define GFP_VMALLOC32 (GFP_DMA | GFP_KERNEL)
 #else
-#define GFP_VMALLOC32 GFP_KERNEL
+/*
+ * 64b systems should always have either DMA or DMA32 zones. For others
+ * GFP_DMA32 should do the right thing and use the normal zone.
+ */
+#define GFP_VMALLOC32 GFP_DMA32 | GFP_KERNEL
 #endif
 
 /**

mm/vmscan.c

@@ -769,64 +769,7 @@ int remove_mapping(struct address_space *mapping, struct page *page)
  */
 void putback_lru_page(struct page *page)
 {
-	bool is_unevictable;
-	int was_unevictable = PageUnevictable(page);
-
-	VM_BUG_ON_PAGE(PageLRU(page), page);
-
-redo:
-	ClearPageUnevictable(page);
-
-	if (page_evictable(page)) {
-		/*
-		 * For evictable pages, we can use the cache.
-		 * In event of a race, worst case is we end up with an
-		 * unevictable page on [in]active list.
-		 * We know how to handle that.
-		 */
-		is_unevictable = false;
-		lru_cache_add(page);
-	} else {
-		/*
-		 * Put unevictable pages directly on zone's unevictable
-		 * list.
-		 */
-		is_unevictable = true;
-		add_page_to_unevictable_list(page);
-		/*
-		 * When racing with an mlock or AS_UNEVICTABLE clearing
-		 * (page is unlocked) make sure that if the other thread
-		 * does not observe our setting of PG_lru and fails
-		 * isolation/check_move_unevictable_pages,
-		 * we see PG_mlocked/AS_UNEVICTABLE cleared below and move
-		 * the page back to the evictable list.
-		 *
-		 * The other side is TestClearPageMlocked() or shmem_lock().
-		 */
-		smp_mb();
-	}
-
-	/*
-	 * page's status can change while we move it among lru. If an evictable
-	 * page is on unevictable list, it never be freed. To avoid that,
-	 * check after we added it to the list, again.
-	 */
-	if (is_unevictable && page_evictable(page)) {
-		if (!isolate_lru_page(page)) {
-			put_page(page);
-			goto redo;
-		}
-		/* This means someone else dropped this page from LRU
-		 * So, it will be freed or putback to LRU again. There is
-		 * nothing to do here.
-		 */
-	}
-
-	if (was_unevictable && !is_unevictable)
-		count_vm_event(UNEVICTABLE_PGRESCUED);
-	else if (!was_unevictable && is_unevictable)
-		count_vm_event(UNEVICTABLE_PGCULLED);
-
+	lru_cache_add(page);
 	put_page(page);		/* drop ref from isolate */
 }
 

mm/zpool.c

@@ -360,7 +360,7 @@ u64 zpool_get_total_size(struct zpool *zpool)
 
 /**
  * zpool_evictable() - Test if zpool is potentially evictable
- * @pool	The zpool to test
+ * @zpool:	The zpool to test
  *
  * Zpool is only potentially evictable when it's created with struct
  * zpool_ops.evict and its driver implements struct zpool_driver.shrink.

mm/zswap.c

@@ -1007,6 +1007,12 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
 	u8 *src, *dst;
 	struct zswap_header zhdr = { .swpentry = swp_entry(type, offset) };
 
+	/* THP isn't supported */
+	if (PageTransHuge(page)) {
+		ret = -EINVAL;
+		goto reject;
+	}
+
 	if (!zswap_enabled || !tree) {
 		ret = -ENODEV;
 		goto reject;

tools/cgroup/Makefile

 # SPDX-License-Identifier: GPL-2.0
 # Makefile for cgroup tools
 
-CC = $(CROSS_COMPILE)gcc
 CFLAGS = -Wall -Wextra
 
 all: cgroup_event_listener

tools/gpio/Makefile

@@ -12,8 +12,6 @@ endif
 # (this improves performance and avoids hard-to-debug behaviour);
 MAKEFLAGS += -r
 
-CC = $(CROSS_COMPILE)gcc
-LD = $(CROSS_COMPILE)ld
 CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
 
 ALL_TARGETS := lsgpio gpio-hammer gpio-event-mon

tools/hv/Makefile

 # SPDX-License-Identifier: GPL-2.0
 # Makefile for Hyper-V tools
 
-CC = $(CROSS_COMPILE)gcc
 WARNINGS = -Wall -Wextra
 CFLAGS = $(WARNINGS) -g $(shell getconf LFS_CFLAGS)
 

tools/iio/Makefile

@@ -12,8 +12,6 @@ endif
 # (this improves performance and avoids hard-to-debug behaviour);
 MAKEFLAGS += -r
 
-CC = $(CROSS_COMPILE)gcc
-LD = $(CROSS_COMPILE)ld
 CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
 
 ALL_TARGETS := iio_event_monitor lsiio iio_generic_buffer

tools/laptop/freefall/Makefile

@@ -2,7 +2,6 @@
 PREFIX ?= /usr
 SBINDIR ?= sbin
 INSTALL ?= install
-CC = $(CROSS_COMPILE)gcc
 
 TARGET = freefall
 

tools/leds/Makefile

 # SPDX-License-Identifier: GPL-2.0
 # Makefile for LEDs tools
 
-CC = $(CROSS_COMPILE)gcc
 CFLAGS = -Wall -Wextra -g -I../../include/uapi
 
 all: uledmon led_hw_brightness_mon

tools/perf/Makefile.perf

@@ -146,12 +146,6 @@ define allow-override
     $(eval $(1) = $(2)))
 endef
 
-# Allow setting CC and AR and LD, or setting CROSS_COMPILE as a prefix.
-$(call allow-override,CC,$(CROSS_COMPILE)gcc)
-$(call allow-override,AR,$(CROSS_COMPILE)ar)
-$(call allow-override,LD,$(CROSS_COMPILE)ld)
-$(call allow-override,CXX,$(CROSS_COMPILE)g++)
-
 LD += $(EXTRA_LDFLAGS)
 
 HOSTCC  ?= gcc

tools/power/acpi/Makefile.config

@@ -56,9 +56,6 @@ INSTALL_SCRIPT = ${INSTALL_PROGRAM}
 # to compile vs uClibc, that can be done here as well.
 CROSS = #/usr/i386-linux-uclibc/usr/bin/i386-uclibc-
 CROSS_COMPILE ?= $(CROSS)
-CC = $(CROSS_COMPILE)gcc
-LD = $(CROSS_COMPILE)gcc
-STRIP = $(CROSS_COMPILE)strip
 HOSTCC = gcc
 
 # check if compiler option is supported

tools/scripts/Makefile.include

@@ -42,6 +42,24 @@ EXTRA_WARNINGS += -Wformat
 
 CC_NO_CLANG := $(shell $(CC) -dM -E -x c /dev/null | grep -Fq "__clang__"; echo $$?)
 
+# Makefiles suck: This macro sets a default value of $(2) for the
+# variable named by $(1), unless the variable has been set by
+# environment or command line. This is necessary for CC and AR
+# because make sets default values, so the simpler ?= approach
+# won't work as expected.
+define allow-override
+  $(if $(or $(findstring environment,$(origin $(1))),\
+            $(findstring command line,$(origin $(1)))),,\
+    $(eval $(1) = $(2)))
+endef
+
+# Allow setting various cross-compile vars or setting CROSS_COMPILE as a prefix.
+$(call allow-override,CC,$(CROSS_COMPILE)gcc)
+$(call allow-override,AR,$(CROSS_COMPILE)ar)
+$(call allow-override,LD,$(CROSS_COMPILE)ld)
+$(call allow-override,CXX,$(CROSS_COMPILE)g++)
+$(call allow-override,STRIP,$(CROSS_COMPILE)strip)
+
 ifeq ($(CC_NO_CLANG), 1)
 EXTRA_WARNINGS += -Wstrict-aliasing=3
 endif

tools/spi/Makefile

@@ -11,8 +11,6 @@ endif
 # (this improves performance and avoids hard-to-debug behaviour);
 MAKEFLAGS += -r
 
-CC = $(CROSS_COMPILE)gcc
-LD = $(CROSS_COMPILE)ld
 CFLAGS += -O2 -Wall -g -D_GNU_SOURCE -I$(OUTPUT)include
 
 ALL_TARGETS := spidev_test spidev_fdx

tools/testing/selftests/memfd/Makefile

@@ -5,6 +5,7 @@ CFLAGS += -I../../../../include/
 CFLAGS += -I../../../../usr/include/
 
 TEST_PROGS := run_tests.sh
+TEST_FILES := run_fuse_test.sh
 TEST_GEN_FILES := memfd_test fuse_mnt fuse_test
 
 fuse_mnt.o: CFLAGS += $(shell pkg-config fuse --cflags)

tools/usb/Makefile

 # SPDX-License-Identifier: GPL-2.0
 # Makefile for USB tools
 
-CC = $(CROSS_COMPILE)gcc
 PTHREAD_LIBS = -lpthread
 WARNINGS = -Wall -Wextra
 CFLAGS = $(WARNINGS) -g -I../include

tools/vm/Makefile

@@ -6,7 +6,6 @@ TARGETS=page-types slabinfo page_owner_sort
 LIB_DIR = ../lib/api
 LIBS = $(LIB_DIR)/libapi.a
 
-CC = $(CROSS_COMPILE)gcc
 CFLAGS = -Wall -Wextra -I../lib/
 LDFLAGS = $(LIBS)
 

tools/wmi/Makefile

@@ -2,7 +2,6 @@ PREFIX ?= /usr
 SBINDIR ?= sbin
 INSTALL ?= install
 CFLAGS += -D__EXPORTED_HEADERS__ -I../../include/uapi -I../../include
-CC = $(CROSS_COMPILE)gcc
 
 TARGET = dell-smbios-example