1 files changed, 65 insertions, 28 deletions

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 3d578c6fefee..e2f2574d8b74 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1091,6 +1091,11 @@ __bpf_kfunc void crash_kexec(struct pt_regs *regs)
 	}
 }
 
+static inline resource_size_t crash_resource_size(const struct resource *res)
+{
+	return !res->end ? 0 : resource_size(res);
+}
+
 ssize_t crash_get_memory_size(void)
 {
 	ssize_t size = 0;
@@ -1098,19 +1103,45 @@ ssize_t crash_get_memory_size(void)
 	if (!kexec_trylock())
 		return -EBUSY;
 
-	if (crashk_res.end != crashk_res.start)
-		size = resource_size(&crashk_res);
+	size += crash_resource_size(&crashk_res);
+	size += crash_resource_size(&crashk_low_res);
 
 	kexec_unlock();
 	return size;
 }
 
+static int __crash_shrink_memory(struct resource *old_res,
+				 unsigned long new_size)
+{
+	struct resource *ram_res;
+
+	ram_res = kzalloc(sizeof(*ram_res), GFP_KERNEL);
+	if (!ram_res)
+		return -ENOMEM;
+
+	ram_res->start = old_res->start + new_size;
+	ram_res->end   = old_res->end;
+	ram_res->flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM;
+	ram_res->name  = "System RAM";
+
+	if (!new_size) {
+		release_resource(old_res);
+		old_res->start = 0;
+		old_res->end   = 0;
+	} else {
+		crashk_res.end = ram_res->start - 1;
+	}
+
+	crash_free_reserved_phys_range(ram_res->start, ram_res->end);
+	insert_resource(&iomem_resource, ram_res);
+
+	return 0;
+}
+
 int crash_shrink_memory(unsigned long new_size)
 {
 	int ret = 0;
-	unsigned long start, end;
-	unsigned long old_size;
-	struct resource *ram_res;
+	unsigned long old_size, low_size;
 
 	if (!kexec_trylock())
 		return -EBUSY;
@@ -1119,36 +1150,42 @@ int crash_shrink_memory(unsigned long new_size)
 		ret = -ENOENT;
 		goto unlock;
 	}
-	start = crashk_res.start;
-	end = crashk_res.end;
-	old_size = (end == 0) ? 0 : end - start + 1;
+
+	low_size = crash_resource_size(&crashk_low_res);
+	old_size = crash_resource_size(&crashk_res) + low_size;
+	new_size = roundup(new_size, KEXEC_CRASH_MEM_ALIGN);
 	if (new_size >= old_size) {
 		ret = (new_size == old_size) ? 0 : -EINVAL;
 		goto unlock;
 	}
 
-	ram_res = kzalloc(sizeof(*ram_res), GFP_KERNEL);
-	if (!ram_res) {
-		ret = -ENOMEM;
-		goto unlock;
-	}
-
-	start = roundup(start, KEXEC_CRASH_MEM_ALIGN);
-	end = roundup(start + new_size, KEXEC_CRASH_MEM_ALIGN);
-
-	crash_free_reserved_phys_range(end, crashk_res.end);
-
-	if ((start == end) && (crashk_res.parent != NULL))
-		release_resource(&crashk_res);
-
-	ram_res->start = end;
-	ram_res->end = crashk_res.end;
-	ram_res->flags = IORESOURCE_BUSY | IORESOURCE_SYSTEM_RAM;
-	ram_res->name = "System RAM";
+	/*
+	 * (low_size > new_size) implies that low_size is greater than zero.
+	 * This also means that if low_size is zero, the else branch is taken.
+	 *
+	 * If low_size is greater than 0, (low_size > new_size) indicates that
+	 * crashk_low_res also needs to be shrunken. Otherwise, only crashk_res
+	 * needs to be shrunken.
+	 */
+	if (low_size > new_size) {
+		ret = __crash_shrink_memory(&crashk_res, 0);
+		if (ret)
+			goto unlock;
 
-	crashk_res.end = end - 1;
+		ret = __crash_shrink_memory(&crashk_low_res, new_size);
+	} else {
+		ret = __crash_shrink_memory(&crashk_res, new_size - low_size);
+	}
 
-	insert_resource(&iomem_resource, ram_res);
+	/* Swap crashk_res and crashk_low_res if needed */
+	if (!crashk_res.end && crashk_low_res.end) {
+		crashk_res.start = crashk_low_res.start;
+		crashk_res.end   = crashk_low_res.end;
+		release_resource(&crashk_low_res);
+		crashk_low_res.start = 0;
+		crashk_low_res.end   = 0;
+		insert_resource(&iomem_resource, &crashk_res);
+	}
 
 unlock:
 	kexec_unlock();