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2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/arch/riscv/kernel/ftrace.c
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@@ -1,4 +1,4 @@
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-/* SPDX-License-Identifier: GPL-2.0 */
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+// SPDX-License-Identifier: GPL-2.0
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 /*
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  * Copyright (C) 2013 Linaro Limited
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  * Author: AKASHI Takahiro <takahiro.akashi@linaro.org>
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@@ -7,9 +7,33 @@
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 #include <linux/ftrace.h>
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 #include <linux/uaccess.h>
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+#include <linux/memory.h>
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 #include <asm/cacheflush.h>
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+#include <asm/patch.h>
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 #ifdef CONFIG_DYNAMIC_FTRACE
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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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+
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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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+
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 static int ftrace_check_current_call(unsigned long hook_pos,
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 				     unsigned int *expected)
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 {
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@@ -24,7 +48,8 @@
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 	 * Read the text we want to modify;
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 	 * return must be -EFAULT on read error
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 	 */
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-	if (probe_kernel_read(replaced, (void *)hook_pos, MCOUNT_INSN_SIZE))
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+	if (copy_from_kernel_nofault(replaced, (void *)hook_pos,
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+			MCOUNT_INSN_SIZE))
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 		return -EFAULT;
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 	/*
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@@ -32,7 +57,7 @@
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 	 * return must be -EINVAL on failed comparison
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 	 */
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 	if (memcmp(expected, replaced, sizeof(replaced))) {
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-		pr_err("%p: expected (%08x %08x) but get (%08x %08x)",
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+		pr_err("%p: expected (%08x %08x) but got (%08x %08x)\n",
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 		       (void *)hook_pos, expected[0], expected[1], replaced[0],
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 		       replaced[1]);
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 		return -EINVAL;
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@@ -46,19 +71,13 @@
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 {
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 	unsigned int call[2];
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 	unsigned int nops[2] = {NOP4, NOP4};
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-	int ret = 0;
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 	make_call(hook_pos, target, call);
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-	/* replace the auipc-jalr pair at once */
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-	ret = probe_kernel_write((void *)hook_pos, enable ? call : nops,
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-				 MCOUNT_INSN_SIZE);
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-	/* return must be -EPERM on write error */
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-	if (ret)
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+	/* Replace the auipc-jalr pair at once. Return -EPERM on write error. */
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+	if (patch_text_nosync
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+	    ((void *)hook_pos, enable ? call : nops, MCOUNT_INSN_SIZE))
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 		return -EPERM;
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-
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-	smp_mb();
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-	flush_icache_range((void *)hook_pos, (void *)hook_pos + MCOUNT_INSN_SIZE);
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 	return 0;
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 }
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@@ -100,9 +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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 }