ftrace: Add ftrace_get_symaddr to convert fentry_ip to symaddr

This introduces ftrace_get_symaddr() which tries to convert fentry_ip
passed by ftrace or fgraph callback to symaddr without calling
kallsyms API. It returns the symbol address or 0 if it fails to
convert it.

Cc: Alexei Starovoitov <[email protected]>
Cc: Florent Revest <[email protected]>
Cc: Martin KaFai Lau <[email protected]>
Cc: bpf <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Alan Maguire <[email protected]>
Cc: Mark Rutland <[email protected]>
Link: https://lore.kernel.org/173519011487.391279.5450806886342723151.stgit@devnote2
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Signed-off-by: Steven Rostedt (Google) <[email protected]>

1 files changed, 21 insertions, 0 deletions

diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index cc92c99ef276..f9cb4d07df58 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -34,6 +34,27 @@ 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;
+}
+#define ftrace_get_symaddr(fentry_ip)	arch_ftrace_get_symaddr(fentry_ip)
+
 #ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
 
 #include <linux/ftrace_regs.h>