add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/arch/riscv/kernel/patch.c
..
..
@@ -11,6 +11,7 @@
11
11
 #include <asm/kprobes.h>
12
12
 #include <asm/cacheflush.h>
13
13
 #include <asm/fixmap.h>
14
+#include <asm/ftrace.h>
14
15
 #include <asm/patch.h>
15
16
 
16
17
 struct patch_insn {
..
..
@@ -18,6 +19,8 @@
18
19
 	u32 insn;
19
20
 	atomic_t cpu_count;
20
21
 };
22
+
23
+int riscv_patch_in_stop_machine = false;
21
24
 
22
25
 #ifdef CONFIG_MMU
23
26
 static void *patch_map(void *addr, int fixmap)
..
..
@@ -55,8 +58,15 @@
55
58
 	 * Before reaching here, it was expected to lock the text_mutex
56
59
 	 * already, so we don't need to give another lock here and could
57
60
 	 * ensure that it was safe between each cores.
61
+	 *
62
+	 * We're currently using stop_machine() for ftrace & kprobes, and while
63
+	 * that ensures text_mutex is held before installing the mappings it
64
+	 * does not ensure text_mutex is held by the calling thread.  That's
65
+	 * safe but triggers a lockdep failure, so just elide it for that
66
+	 * specific case.
58
67
 	 */
59
-	lockdep_assert_held(&text_mutex);
68
+	if (!riscv_patch_in_stop_machine)
69
+		lockdep_assert_held(&text_mutex);
60
70
 
61
71
 	if (across_pages)
62
72
 		patch_map(addr + len, FIX_TEXT_POKE1);
..
..
@@ -117,13 +127,25 @@
117
127
 
118
128
 int patch_text(void *addr, u32 insn)
119
129
 {
130
+	int ret;
120
131
 	struct patch_insn patch = {
121
132
 		.addr = addr,
122
133
 		.insn = insn,
123
134
 		.cpu_count = ATOMIC_INIT(0),
124
135
 	};
125
136
 
126
-	return stop_machine_cpuslocked(patch_text_cb,
127
-				       &patch, cpu_online_mask);
137
+	/*
138
+	 * kprobes takes text_mutex, before calling patch_text(), but as we call
139
+	 * calls stop_machine(), the lockdep assertion in patch_insn_write()
140
+	 * gets confused by the context in which the lock is taken.
141
+	 * Instead, ensure the lock is held before calling stop_machine(), and
142
+	 * set riscv_patch_in_stop_machine to skip the check in
143
+	 * patch_insn_write().
144
+	 */
145
+	lockdep_assert_held(&text_mutex);
146
+	riscv_patch_in_stop_machine = true;
147
+	ret = stop_machine_cpuslocked(patch_text_cb, &patch, cpu_online_mask);
148
+	riscv_patch_in_stop_machine = false;
149
+	return ret;
128
150
 }
129
151
 NOKPROBE_SYMBOL(patch_text);