Update Linux to v5.10.109
Sourced from [1]
[1] https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.109.tar.xz
Change-Id: I19bca9fc6762d4e63bcf3e4cba88bbe560d9c76c
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
diff --git a/kernel/scs.c b/kernel/scs.c
new file mode 100644
index 0000000..4ff4a7b
--- /dev/null
+++ b/kernel/scs.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Shadow Call Stack support.
+ *
+ * Copyright (C) 2019 Google LLC
+ */
+
+#include <linux/kasan.h>
+#include <linux/mm.h>
+#include <linux/scs.h>
+#include <linux/slab.h>
+#include <linux/vmstat.h>
+
+static struct kmem_cache *scs_cache;
+
+static void __scs_account(void *s, int account)
+{
+ struct page *scs_page = virt_to_page(s);
+
+ mod_node_page_state(page_pgdat(scs_page), NR_KERNEL_SCS_KB,
+ account * (SCS_SIZE / SZ_1K));
+}
+
+static void *scs_alloc(int node)
+{
+ void *s = kmem_cache_alloc_node(scs_cache, GFP_SCS, node);
+
+ if (!s)
+ return NULL;
+
+ *__scs_magic(s) = SCS_END_MAGIC;
+
+ /*
+ * Poison the allocation to catch unintentional accesses to
+ * the shadow stack when KASAN is enabled.
+ */
+ kasan_poison_object_data(scs_cache, s);
+ __scs_account(s, 1);
+ return s;
+}
+
+static void scs_free(void *s)
+{
+ __scs_account(s, -1);
+ kasan_unpoison_object_data(scs_cache, s);
+ kmem_cache_free(scs_cache, s);
+}
+
+void __init scs_init(void)
+{
+ scs_cache = kmem_cache_create("scs_cache", SCS_SIZE, 0, 0, NULL);
+}
+
+int scs_prepare(struct task_struct *tsk, int node)
+{
+ void *s = scs_alloc(node);
+
+ if (!s)
+ return -ENOMEM;
+
+ task_scs(tsk) = task_scs_sp(tsk) = s;
+ return 0;
+}
+
+static void scs_check_usage(struct task_struct *tsk)
+{
+ static unsigned long highest;
+
+ unsigned long *p, prev, curr = highest, used = 0;
+
+ if (!IS_ENABLED(CONFIG_DEBUG_STACK_USAGE))
+ return;
+
+ for (p = task_scs(tsk); p < __scs_magic(tsk); ++p) {
+ if (!READ_ONCE_NOCHECK(*p))
+ break;
+ used += sizeof(*p);
+ }
+
+ while (used > curr) {
+ prev = cmpxchg_relaxed(&highest, curr, used);
+
+ if (prev == curr) {
+ pr_info("%s (%d): highest shadow stack usage: %lu bytes\n",
+ tsk->comm, task_pid_nr(tsk), used);
+ break;
+ }
+
+ curr = prev;
+ }
+}
+
+void scs_release(struct task_struct *tsk)
+{
+ void *s = task_scs(tsk);
+
+ if (!s)
+ return;
+
+ WARN(task_scs_end_corrupted(tsk),
+ "corrupted shadow stack detected when freeing task\n");
+ scs_check_usage(tsk);
+ scs_free(s);
+}