Merge branch 'mm-hotfixes-stable' into mm-nonmm-stable in order to be able

to merge "kho: make debugfs interface optional" into mm-nonmm-stable.

7 files changed, 117 insertions, 39 deletions

diff --git a/kernel/Kconfig.kexec b/kernel/Kconfig.kexec
index 422270d64820..54e581072617 100644
--- a/kernel/Kconfig.kexec
+++ b/kernel/Kconfig.kexec
@@ -109,6 +109,15 @@ config KEXEC_HANDOVER
 	  to keep data or state alive across the kexec. For this to work,
 	  both source and target kernels need to have this option enabled.
 
+config KEXEC_HANDOVER_DEBUG
+	bool "Enable Kexec Handover debug checks"
+	depends on KEXEC_HANDOVER
+	help
+	  This option enables extra sanity checks for the Kexec Handover
+	  subsystem. Since, KHO performance is crucial in live update
+	  scenarios and the extra code might be adding overhead it is
+	  only optionally enabled.
+
 config CRASH_DUMP
 	bool "kernel crash dumps"
 	default ARCH_DEFAULT_CRASH_DUMP
diff --git a/kernel/Makefile b/kernel/Makefile
index df3dd8291bb6..9fe722305c9b 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -83,6 +83,7 @@ obj-$(CONFIG_KEXEC) += kexec.o
 obj-$(CONFIG_KEXEC_FILE) += kexec_file.o
 obj-$(CONFIG_KEXEC_ELF) += kexec_elf.o
 obj-$(CONFIG_KEXEC_HANDOVER) += kexec_handover.o
+obj-$(CONFIG_KEXEC_HANDOVER_DEBUG) += kexec_handover_debug.o
 obj-$(CONFIG_BACKTRACE_SELF_TEST) += backtracetest.o
 obj-$(CONFIG_COMPAT) += compat.o
 obj-$(CONFIG_CGROUPS) += cgroup/
diff --git a/kernel/crash_core.c b/kernel/crash_core.c
index 3b1c43382eec..99dac1aa972a 100644
--- a/kernel/crash_core.c
+++ b/kernel/crash_core.c
@@ -373,7 +373,7 @@ static int __crash_shrink_memory(struct resource *old_res,
 		old_res->start = 0;
 		old_res->end   = 0;
 	} else {
-		crashk_res.end = ram_res->start - 1;
+		old_res->end = ram_res->start - 1;
 	}
 
 	crash_free_reserved_phys_range(ram_res->start, ram_res->end);
diff --git a/kernel/gcov/gcc_4_7.c b/kernel/gcov/gcc_4_7.c
index a08cc076f332..ffde93d051a4 100644
--- a/kernel/gcov/gcc_4_7.c
+++ b/kernel/gcov/gcc_4_7.c
@@ -18,7 +18,9 @@
 #include <linux/mm.h>
 #include "gcov.h"
 
-#if (__GNUC__ >= 14)
+#if (__GNUC__ >= 15)
+#define GCOV_COUNTERS			10
+#elif (__GNUC__ >= 14)
 #define GCOV_COUNTERS			9
 #elif (__GNUC__ >= 10)
 #define GCOV_COUNTERS			8
diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index 76f0940fb485..03d12e27189f 100644
--- a/kernel/kexec_handover.c
+++ b/kernel/kexec_handover.c
@@ -8,6 +8,7 @@
 
 #define pr_fmt(fmt) "KHO: " fmt
 
+#include <linux/cleanup.h>
 #include <linux/cma.h>
 #include <linux/count_zeros.h>
 #include <linux/debugfs.h>
@@ -22,6 +23,7 @@
 
 #include <asm/early_ioremap.h>
 
+#include "kexec_handover_internal.h"
 /*
  * KHO is tightly coupled with mm init and needs access to some of mm
  * internal APIs.
@@ -67,10 +69,10 @@ early_param("kho", kho_parse_enable);
  * Keep track of memory that is to be preserved across KHO.
  *
  * The serializing side uses two levels of xarrays to manage chunks of per-order
- * 512 byte bitmaps. For instance if PAGE_SIZE = 4096, the entire 1G order of a
- * 1TB system would fit inside a single 512 byte bitmap. For order 0 allocations
- * each bitmap will cover 16M of address space. Thus, for 16G of memory at most
- * 512K of bitmap memory will be needed for order 0.
+ * PAGE_SIZE byte bitmaps. For instance if PAGE_SIZE = 4096, the entire 1G order
+ * of a 8TB system would fit inside a single 4096 byte bitmap. For order 0
+ * allocations each bitmap will cover 128M of address space. Thus, for 16G of
+ * memory at most 512K of bitmap memory will be needed for order 0.
  *
  * This approach is fully incremental, as the serialization progresses folios
  * can continue be aggregated to the tracker. The final step, immediately prior
@@ -78,12 +80,14 @@ early_param("kho", kho_parse_enable);
  * successor kernel to parse.
  */
 
-#define PRESERVE_BITS (512 * 8)
+#define PRESERVE_BITS (PAGE_SIZE * 8)
 
 struct kho_mem_phys_bits {
 	DECLARE_BITMAP(preserve, PRESERVE_BITS);
 };
 
+static_assert(sizeof(struct kho_mem_phys_bits) == PAGE_SIZE);
+
 struct kho_mem_phys {
 	/*
 	 * Points to kho_mem_phys_bits, a sparse bitmap array. Each bit is sized
@@ -131,28 +135,28 @@ static struct kho_out kho_out = {
 	.finalized = false,
 };
 
-static void *xa_load_or_alloc(struct xarray *xa, unsigned long index, size_t sz)
+static void *xa_load_or_alloc(struct xarray *xa, unsigned long index)
 {
-	void *elm, *res;
+	void *res = xa_load(xa, index);
+
+	if (res)
+		return res;
 
-	elm = xa_load(xa, index);
-	if (elm)
-		return elm;
+	void *elm __free(free_page) = (void *)get_zeroed_page(GFP_KERNEL);
 
-	elm = kzalloc(sz, GFP_KERNEL);
 	if (!elm)
 		return ERR_PTR(-ENOMEM);
 
+	if (WARN_ON(kho_scratch_overlap(virt_to_phys(elm), PAGE_SIZE)))
+		return ERR_PTR(-EINVAL);
+
 	res = xa_cmpxchg(xa, index, NULL, elm, GFP_KERNEL);
 	if (xa_is_err(res))
-		res = ERR_PTR(xa_err(res));
-
-	if (res) {
-		kfree(elm);
+		return ERR_PTR(xa_err(res));
+	else if (res)
 		return res;
-	}
 
-	return elm;
+	return no_free_ptr(elm);
 }
 
 static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn,
@@ -167,12 +171,12 @@ static void __kho_unpreserve(struct kho_mem_track *track, unsigned long pfn,
 		const unsigned long pfn_high = pfn >> order;
 
 		physxa = xa_load(&track->orders, order);
-		if (!physxa)
-			continue;
+		if (WARN_ON_ONCE(!physxa))
+			return;
 
 		bits = xa_load(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
-		if (!bits)
-			continue;
+		if (WARN_ON_ONCE(!bits))
+			return;
 
 		clear_bit(pfn_high % PRESERVE_BITS, bits->preserve);
 
@@ -216,8 +220,7 @@ static int __kho_preserve_order(struct kho_mem_track *track, unsigned long pfn,
 		}
 	}
 
-	bits = xa_load_or_alloc(&physxa->phys_bits, pfn_high / PRESERVE_BITS,
-				sizeof(*bits));
+	bits = xa_load_or_alloc(&physxa->phys_bits, pfn_high / PRESERVE_BITS);
 	if (IS_ERR(bits))
 		return PTR_ERR(bits);
 
@@ -345,15 +348,19 @@ static_assert(sizeof(struct khoser_mem_chunk) == PAGE_SIZE);
 static struct khoser_mem_chunk *new_chunk(struct khoser_mem_chunk *cur_chunk,
 					  unsigned long order)
 {
-	struct khoser_mem_chunk *chunk;
+	struct khoser_mem_chunk *chunk __free(free_page) = NULL;
 
-	chunk = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	chunk = (void *)get_zeroed_page(GFP_KERNEL);
 	if (!chunk)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
+
+	if (WARN_ON(kho_scratch_overlap(virt_to_phys(chunk), PAGE_SIZE)))
+		return ERR_PTR(-EINVAL);
+
 	chunk->hdr.order = order;
 	if (cur_chunk)
 		KHOSER_STORE_PTR(cur_chunk->hdr.next, chunk);
-	return chunk;
+	return no_free_ptr(chunk);
 }
 
 static void kho_mem_ser_free(struct khoser_mem_chunk *first_chunk)
@@ -374,14 +381,17 @@ static int kho_mem_serialize(struct kho_serialization *ser)
 	struct khoser_mem_chunk *chunk = NULL;
 	struct kho_mem_phys *physxa;
 	unsigned long order;
+	int err = -ENOMEM;
 
 	xa_for_each(&ser->track.orders, order, physxa) {
 		struct kho_mem_phys_bits *bits;
 		unsigned long phys;
 
 		chunk = new_chunk(chunk, order);
-		if (!chunk)
+		if (IS_ERR(chunk)) {
+			err = PTR_ERR(chunk);
 			goto err_free;
+		}
 
 		if (!first_chunk)
 			first_chunk = chunk;
@@ -391,8 +401,10 @@ static int kho_mem_serialize(struct kho_serialization *ser)
 
 			if (chunk->hdr.num_elms == ARRAY_SIZE(chunk->bitmaps)) {
 				chunk = new_chunk(chunk, order);
-				if (!chunk)
+				if (IS_ERR(chunk)) {
+					err = PTR_ERR(chunk);
 					goto err_free;
+				}
 			}
 
 			elm = &chunk->bitmaps[chunk->hdr.num_elms];
@@ -409,7 +421,7 @@ static int kho_mem_serialize(struct kho_serialization *ser)
 
 err_free:
 	kho_mem_ser_free(first_chunk);
-	return -ENOMEM;
+	return err;
 }
 
 static void __init deserialize_bitmap(unsigned int order,
@@ -465,8 +477,8 @@ static void __init kho_mem_deserialize(const void *fdt)
  * area for early allocations that happen before page allocator is
  * initialized.
  */
-static struct kho_scratch *kho_scratch;
-static unsigned int kho_scratch_cnt;
+struct kho_scratch *kho_scratch;
+unsigned int kho_scratch_cnt;
 
 /*
  * The scratch areas are scaled by default as percent of memory allocated from
@@ -752,6 +764,9 @@ int kho_preserve_folio(struct folio *folio)
 	const unsigned int order = folio_order(folio);
 	struct kho_mem_track *track = &kho_out.ser.track;
 
+	if (WARN_ON(kho_scratch_overlap(pfn << PAGE_SHIFT, PAGE_SIZE << order)))
+		return -EINVAL;
+
 	return __kho_preserve_order(track, pfn, order);
 }
 EXPORT_SYMBOL_GPL(kho_preserve_folio);
@@ -775,6 +790,11 @@ int kho_preserve_pages(struct page *page, unsigned int nr_pages)
 	unsigned long failed_pfn = 0;
 	int err = 0;
 
+	if (WARN_ON(kho_scratch_overlap(start_pfn << PAGE_SHIFT,
+					nr_pages << PAGE_SHIFT))) {
+		return -EINVAL;
+	}
+
 	while (pfn < end_pfn) {
 		const unsigned int order =
 			min(count_trailing_zeros(pfn), ilog2(end_pfn - pfn));
@@ -862,16 +882,17 @@ err_free:
 	return NULL;
 }
 
-static void kho_vmalloc_unpreserve_chunk(struct kho_vmalloc_chunk *chunk)
+static void kho_vmalloc_unpreserve_chunk(struct kho_vmalloc_chunk *chunk,
+					 unsigned short order)
 {
 	struct kho_mem_track *track = &kho_out.ser.track;
 	unsigned long pfn = PHYS_PFN(virt_to_phys(chunk));
 
 	__kho_unpreserve(track, pfn, pfn + 1);
 
-	for (int i = 0; chunk->phys[i]; i++) {
+	for (int i = 0; i < ARRAY_SIZE(chunk->phys) && chunk->phys[i]; i++) {
 		pfn = PHYS_PFN(chunk->phys[i]);
-		__kho_unpreserve(track, pfn, pfn + 1);
+		__kho_unpreserve(track, pfn, pfn + (1 << order));
 	}
 }
 
@@ -882,7 +903,7 @@ static void kho_vmalloc_free_chunks(struct kho_vmalloc *kho_vmalloc)
 	while (chunk) {
 		struct kho_vmalloc_chunk *tmp = chunk;
 
-		kho_vmalloc_unpreserve_chunk(chunk);
+		kho_vmalloc_unpreserve_chunk(chunk, kho_vmalloc->order);
 
 		chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
 		free_page((unsigned long)tmp);
@@ -992,7 +1013,7 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
 	while (chunk) {
 		struct page *page;
 
-		for (int i = 0; chunk->phys[i]; i++) {
+		for (int i = 0; i < ARRAY_SIZE(chunk->phys) && chunk->phys[i]; i++) {
 			phys_addr_t phys = chunk->phys[i];
 
 			if (idx + contig_pages > total_pages)
diff --git a/kernel/kexec_handover_debug.c b/kernel/kexec_handover_debug.c
new file mode 100644
index 000000000000..6efb696f5426
--- /dev/null
+++ b/kernel/kexec_handover_debug.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * kexec_handover_debug.c - kexec handover optional debug functionality
+ * Copyright (C) 2025 Google LLC, Pasha Tatashin <pasha.tatashin@soleen.com>
+ */
+
+#define pr_fmt(fmt) "KHO: " fmt
+
+#include "kexec_handover_internal.h"
+
+bool kho_scratch_overlap(phys_addr_t phys, size_t size)
+{
+	phys_addr_t scratch_start, scratch_end;
+	unsigned int i;
+
+	for (i = 0; i < kho_scratch_cnt; i++) {
+		scratch_start = kho_scratch[i].addr;
+		scratch_end = kho_scratch[i].addr + kho_scratch[i].size;
+
+		if (phys < scratch_end && (phys + size) > scratch_start)
+			return true;
+	}
+
+	return false;
+}
diff --git a/kernel/kexec_handover_internal.h b/kernel/kexec_handover_internal.h
new file mode 100644
index 000000000000..3c3c7148ceed
--- /dev/null
+++ b/kernel/kexec_handover_internal.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef LINUX_KEXEC_HANDOVER_INTERNAL_H
+#define LINUX_KEXEC_HANDOVER_INTERNAL_H
+
+#include <linux/kexec_handover.h>
+#include <linux/types.h>
+
+extern struct kho_scratch *kho_scratch;
+extern unsigned int kho_scratch_cnt;
+
+#ifdef CONFIG_KEXEC_HANDOVER_DEBUG
+bool kho_scratch_overlap(phys_addr_t phys, size_t size);
+#else
+static inline bool kho_scratch_overlap(phys_addr_t phys, size_t size)
+{
+	return false;
+}
+#endif /* CONFIG_KEXEC_HANDOVER_DEBUG */
+
+#endif /* LINUX_KEXEC_HANDOVER_INTERNAL_H */