[PATCH] ftrace: x86: Fix a compile error about get_kernel_nofault()

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

From: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Fix a compile error about get_kernel_nofault() which is defined in the
linux/uaccess.h. Since asm/ftrace.h is widely used, including
linux/uaccess.h in asm/ftrace.h caused another error. Thus this
moves arch_ftrace_get_symaddr() into arch/x86/kernel/ftrace.c.

The original errors look like:

In file included from ./arch/x86/include/asm/asm-prototypes.h:2,
                 from <stdin>:3:
./arch/x86/include/asm/ftrace.h: In function 'arch_ftrace_get_symaddr':
./arch/x86/include/asm/ftrace.h:46:21: error: implicit declaration of function 'get_kernel_nofault' [-Werror=implicit-function-declaration]
   46 |                 if (get_kernel_nofault(instr, (u32 *)(fentry_ip - ENDBR_INSN_SIZE)))
      |                     ^~~~~~~~~~~~~~~~~~

This also makes ftrace_get_symaddr() available only when
CONFIG_HAVE_FENTRY=y on x86.

Reported-by: Gabriel de Perthuis <g2p.code@gmail.com>
Closes: https://lore.kernel.org/all/a87f98bf-45b1-4ef5-aa77-02f7e61203f4@gmail.com/
Reported-by: Haiyue Wang <haiyuewa@163.com>
Closes: https://lore.kernel.org/all/20250205180116.88644-1-haiyuewa@163.com/
Fixes: 2bc56fdae1ba ("ftrace: Add ftrace_get_symaddr to convert fentry_ip to symaddr")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
 arch/x86/include/asm/ftrace.h |   23 ++++-------------------
 arch/x86/kernel/ftrace.c      |   26 +++++++++++++++++++++++++-
 2 files changed, 29 insertions(+), 20 deletions(-)

diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index f9cb4d07df58..1ed08f2de366 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -34,26 +34,11 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
 	return addr;
 }
 
-static inline unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)
-{
-#ifdef CONFIG_X86_KERNEL_IBT
-	u32 instr;
-
-	/* We want to be extra safe in case entry ip is on the page edge,
-	 * but otherwise we need to avoid get_kernel_nofault()'s overhead.
-	 */
-	if ((fentry_ip & ~PAGE_MASK) < ENDBR_INSN_SIZE) {
-		if (get_kernel_nofault(instr, (u32 *)(fentry_ip - ENDBR_INSN_SIZE)))
-			return fentry_ip;
-	} else {
-		instr = *(u32 *)(fentry_ip - ENDBR_INSN_SIZE);
-	}
-	if (is_endbr(instr))
-		fentry_ip -= ENDBR_INSN_SIZE;
-#endif
-	return fentry_ip;
-}
+/* This does not support mcount. */
+#ifdef CONFIG_HAVE_FENTRY
+unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip);
 #define ftrace_get_symaddr(fentry_ip)	arch_ftrace_get_symaddr(fentry_ip)
+#endif
 
 #ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
 
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 166bc0ea3bdf..7250118005fc 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -29,11 +29,35 @@
 
 #include <trace/syscall.h>
 
-#include <asm/kprobes.h>
 #include <asm/ftrace.h>
+#include <asm/ibt.h>
+#include <asm/kprobes.h>
 #include <asm/nops.h>
 #include <asm/text-patching.h>
 
+#ifdef CONFIG_HAVE_FENTRY
+/* Convert fentry address to the symbol address. */
+unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)
+{
+#ifdef CONFIG_X86_KERNEL_IBT
+	u32 instr;
+
+	/* We want to be extra safe in case entry ip is on the page edge,
+	 * but otherwise we need to avoid get_kernel_nofault()'s overhead.
+	 */
+	if ((fentry_ip & ~PAGE_MASK) < ENDBR_INSN_SIZE) {
+		if (get_kernel_nofault(instr, (u32 *)(fentry_ip - ENDBR_INSN_SIZE)))
+			return fentry_ip;
+	} else {
+		instr = *(u32 *)(fentry_ip - ENDBR_INSN_SIZE);
+	}
+	if (is_endbr(instr))
+		fentry_ip -= ENDBR_INSN_SIZE;
+#endif
+	return fentry_ip;
+}
+#endif
+
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 static int ftrace_poke_late = 0;