1 files changed, 37 insertions, 10 deletions

diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c
index 765004b60513..575e71d6c8ae 100644
--- a/arch/riscv/kernel/patch.c
+++ b/arch/riscv/kernel/patch.c
@@ -11,14 +11,18 @@
 #include <asm/kprobes.h>
 #include <asm/cacheflush.h>
 #include <asm/fixmap.h>
+#include <asm/ftrace.h>
 #include <asm/patch.h>
 
 struct patch_insn {
 	void *addr;
-	u32 insn;
+	u32 *insns;
+	int ninsns;
 	atomic_t cpu_count;
 };
 
+int riscv_patch_in_stop_machine = false;
+
 #ifdef CONFIG_MMU
 /*
  * The fix_to_virt(, idx) needs a const value (not a dynamic variable of
@@ -59,8 +63,15 @@ static int patch_insn_write(void *addr, const void *insn, size_t len)
 	 * Before reaching here, it was expected to lock the text_mutex
 	 * already, so we don't need to give another lock here and could
 	 * ensure that it was safe between each cores.
+	 *
+	 * We're currently using stop_machine() for ftrace & kprobes, and while
+	 * that ensures text_mutex is held before installing the mappings it
+	 * does not ensure text_mutex is held by the calling thread.  That's
+	 * safe but triggers a lockdep failure, so just elide it for that
+	 * specific case.
 	 */
-	lockdep_assert_held(&text_mutex);
+	if (!riscv_patch_in_stop_machine)
+		lockdep_assert_held(&text_mutex);
 
 	if (across_pages)
 		patch_map(addr + len, FIX_TEXT_POKE1);
@@ -102,12 +113,15 @@ NOKPROBE_SYMBOL(patch_text_nosync);
 static int patch_text_cb(void *data)
 {
 	struct patch_insn *patch = data;
-	int ret = 0;
+	unsigned long len;
+	int i, ret = 0;
 
 	if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
-		ret =
-		    patch_text_nosync(patch->addr, &patch->insn,
-					    GET_INSN_LENGTH(patch->insn));
+		for (i = 0; ret == 0 && i < patch->ninsns; i++) {
+			len = GET_INSN_LENGTH(patch->insns[i]);
+			ret = patch_text_nosync(patch->addr + i * len,
+						&patch->insns[i], len);
+		}
 		atomic_inc(&patch->cpu_count);
 	} else {
 		while (atomic_read(&patch->cpu_count) <= num_online_cpus())
@@ -119,15 +133,28 @@ static int patch_text_cb(void *data)
 }
 NOKPROBE_SYMBOL(patch_text_cb);
 
-int patch_text(void *addr, u32 insn)
+int patch_text(void *addr, u32 *insns, int ninsns)
 {
+	int ret;
 	struct patch_insn patch = {
 		.addr = addr,
-		.insn = insn,
+		.insns = insns,
+		.ninsns = ninsns,
 		.cpu_count = ATOMIC_INIT(0),
 	};
 
-	return stop_machine_cpuslocked(patch_text_cb,
-				       &patch, cpu_online_mask);
+	/*
+	 * kprobes takes text_mutex, before calling patch_text(), but as we call
+	 * calls stop_machine(), the lockdep assertion in patch_insn_write()
+	 * gets confused by the context in which the lock is taken.
+	 * Instead, ensure the lock is held before calling stop_machine(), and
+	 * set riscv_patch_in_stop_machine to skip the check in
+	 * patch_insn_write().
+	 */
+	lockdep_assert_held(&text_mutex);
+	riscv_patch_in_stop_machine = true;
+	ret = stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask);
+	riscv_patch_in_stop_machine = false;
+	return ret;
 }
 NOKPROBE_SYMBOL(patch_text);