From: Sasha Levin <alexander.levin@microsoft.com>
Date: Tue, 20 Mar 2018 20:44:13 +0000 (-0400)
Subject: Revert "kprobes/x86: Disable optimizing on the function jumps to indirect thunk"
X-Git-Tag: v4.1.51~5
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e0e719352ac4c9c94c78cad538ad153afc28e5a8;p=thirdparty%2Fkernel%2Fstable.git

Revert "kprobes/x86: Disable optimizing on the function jumps to indirect thunk"

This reverts commit 3e50641bf84d702a7f82018b07f58cbbdcd3cea5.

Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---

diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index ea8e2b846101d..c9d488f3e4cd4 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -36,7 +36,6 @@
 #include <asm/alternative.h>
 #include <asm/insn.h>
 #include <asm/debugreg.h>
-#include <asm/nospec-branch.h>
 
 #include "common.h"
 
@@ -192,7 +191,7 @@ static int copy_optimized_instructions(u8 *dest, u8 *src)
 }
 
 /* Check whether insn is indirect jump */
-static int __insn_is_indirect_jump(struct insn *insn)
+static int insn_is_indirect_jump(struct insn *insn)
 {
 	return ((insn->opcode.bytes[0] == 0xff &&
 		(X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
@@ -226,26 +225,6 @@ static int insn_jump_into_range(struct insn *insn, unsigned long start, int len)
 	return (start <= target && target <= start + len);
 }
 
-static int insn_is_indirect_jump(struct insn *insn)
-{
-	int ret = __insn_is_indirect_jump(insn);
-
-#ifdef CONFIG_RETPOLINE
-	/*
-	 * Jump to x86_indirect_thunk_* is treated as an indirect jump.
-	 * Note that even with CONFIG_RETPOLINE=y, the kernel compiled with
-	 * older gcc may use indirect jump. So we add this check instead of
-	 * replace indirect-jump check.
-	 */
-	if (!ret)
-		ret = insn_jump_into_range(insn,
-				(unsigned long)__indirect_thunk_start,
-				(unsigned long)__indirect_thunk_end -
-				(unsigned long)__indirect_thunk_start);
-#endif
-	return ret;
-}
-
 /* Decode whole function to ensure any instructions don't jump into target */
 static int can_optimize(unsigned long paddr)
 {