add new system file

hc

2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/arch/riscv/kernel/ftrace.c
..
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@@ -15,11 +15,21 @@
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 int ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex)
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 {
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 	mutex_lock(&text_mutex);
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+
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+	/*
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+	 * The code sequences we use for ftrace can't be patched while the
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+	 * kernel is running, so we need to use stop_machine() to modify them
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+	 * for now.  This doesn't play nice with text_mutex, we use this flag
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+	 * to elide the check.
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+	 */
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+	riscv_patch_in_stop_machine = true;
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+
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 	return 0;
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 }
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 int ftrace_arch_code_modify_post_process(void) __releases(&text_mutex)
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 {
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+	riscv_patch_in_stop_machine = false;
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 	mutex_unlock(&text_mutex);
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 	return 0;
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 }
..
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@@ -109,9 +119,9 @@
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 {
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 	int out;
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-	ftrace_arch_code_modify_prepare();
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+	mutex_lock(&text_mutex);
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 	out = ftrace_make_nop(mod, rec, MCOUNT_ADDR);
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-	ftrace_arch_code_modify_post_process();
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+	mutex_unlock(&text_mutex);
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 	return out;
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 }