[PATCH v20 19/19] bpf: Use ftrace_get_symaddr() in get_entry_ip()

[Masami Hiramatsu (Google)]

From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>

Rewrite get_entry_ip() to use ftrace_get_symaddr() macro.

Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
---
 Changes in v19:
  - Use ftrace_get_symaddr() instead of introducing new arch dependent code.
  - Also, replace x86 code with ftrace_get_symaddr(), which does the same
   thing.
---
 kernel/trace/bpf_trace.c |   19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 852400170c5c..9f9a0d666020 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1048,27 +1048,12 @@ static const struct bpf_func_proto bpf_get_func_ip_proto_tracing = {
 	.arg1_type	= ARG_PTR_TO_CTX,
 };
 
-#ifdef CONFIG_X86_KERNEL_IBT
 static unsigned long get_entry_ip(unsigned long fentry_ip)
 {
-	u32 instr;
+	unsigned long ret = ftrace_get_symaddr(fentry_ip);
 
-	/* 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;
-	return fentry_ip;
+	return ret ? : fentry_ip;
 }
-#else
-#define get_entry_ip(fentry_ip) fentry_ip
-#endif
 
 BPF_CALL_1(bpf_get_func_ip_kprobe, struct pt_regs *, regs)
 {