summaryrefslogtreecommitdiffstats
path: root/kernel/scs.c
diff options
context:
space:
mode:
authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /kernel/scs.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'kernel/scs.c')
-rw-r--r--kernel/scs.c168
1 files changed, 168 insertions, 0 deletions
diff --git a/kernel/scs.c b/kernel/scs.c
new file mode 100644
index 0000000000..d7809affe7
--- /dev/null
+++ b/kernel/scs.c
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Shadow Call Stack support.
+ *
+ * Copyright (C) 2019 Google LLC
+ */
+
+#include <linux/cpuhotplug.h>
+#include <linux/kasan.h>
+#include <linux/mm.h>
+#include <linux/scs.h>
+#include <linux/vmalloc.h>
+#include <linux/vmstat.h>
+
+#ifdef CONFIG_DYNAMIC_SCS
+DEFINE_STATIC_KEY_FALSE(dynamic_scs_enabled);
+#endif
+
+static void __scs_account(void *s, int account)
+{
+ struct page *scs_page = vmalloc_to_page(s);
+
+ mod_node_page_state(page_pgdat(scs_page), NR_KERNEL_SCS_KB,
+ account * (SCS_SIZE / SZ_1K));
+}
+
+/* Matches NR_CACHED_STACKS for VMAP_STACK */
+#define NR_CACHED_SCS 2
+static DEFINE_PER_CPU(void *, scs_cache[NR_CACHED_SCS]);
+
+static void *__scs_alloc(int node)
+{
+ int i;
+ void *s;
+
+ for (i = 0; i < NR_CACHED_SCS; i++) {
+ s = this_cpu_xchg(scs_cache[i], NULL);
+ if (s) {
+ s = kasan_unpoison_vmalloc(s, SCS_SIZE,
+ KASAN_VMALLOC_PROT_NORMAL);
+ memset(s, 0, SCS_SIZE);
+ goto out;
+ }
+ }
+
+ s = __vmalloc_node_range(SCS_SIZE, 1, VMALLOC_START, VMALLOC_END,
+ GFP_SCS, PAGE_KERNEL, 0, node,
+ __builtin_return_address(0));
+
+out:
+ return kasan_reset_tag(s);
+}
+
+void *scs_alloc(int node)
+{
+ void *s;
+
+ s = __scs_alloc(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_vmalloc(s, SCS_SIZE);
+ __scs_account(s, 1);
+ return s;
+}
+
+void scs_free(void *s)
+{
+ int i;
+
+ __scs_account(s, -1);
+
+ /*
+ * We cannot sleep as this can be called in interrupt context,
+ * so use this_cpu_cmpxchg to update the cache, and vfree_atomic
+ * to free the stack.
+ */
+
+ for (i = 0; i < NR_CACHED_SCS; i++)
+ if (this_cpu_cmpxchg(scs_cache[i], 0, s) == NULL)
+ return;
+
+ kasan_unpoison_vmalloc(s, SCS_SIZE, KASAN_VMALLOC_PROT_NORMAL);
+ vfree_atomic(s);
+}
+
+static int scs_cleanup(unsigned int cpu)
+{
+ int i;
+ void **cache = per_cpu_ptr(scs_cache, cpu);
+
+ for (i = 0; i < NR_CACHED_SCS; i++) {
+ vfree(cache[i]);
+ cache[i] = NULL;
+ }
+
+ return 0;
+}
+
+void __init scs_init(void)
+{
+ if (!scs_is_enabled())
+ return;
+ cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "scs:scs_cache", NULL,
+ scs_cleanup);
+}
+
+int scs_prepare(struct task_struct *tsk, int node)
+{
+ void *s;
+
+ if (!scs_is_enabled())
+ return 0;
+
+ 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 (!scs_is_enabled() || !s)
+ return;
+
+ WARN(task_scs_end_corrupted(tsk),
+ "corrupted shadow stack detected when freeing task\n");
+ scs_check_usage(tsk);
+ scs_free(s);
+}