[tip:core/urgent] objtool: Add mcsafe_handle_tail() to the uaccess safe list

[tip-bot for Josh Poimboeuf]

Commit-ID:  a7e47f26039c26312a4144c3001b4e9fa886bd45
Gitweb:     https://git.kernel.org/tip/a7e47f26039c26312a4144c3001b4e9fa886bd45
Author:     Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
AuthorDate: Wed, 17 Jul 2019 20:36:46 -0500
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Thu, 18 Jul 2019 21:01:06 +0200

objtool: Add mcsafe_handle_tail() to the uaccess safe list

After an objtool improvement, it's reporting that __memcpy_mcsafe() is
calling mcsafe_handle_tail() with AC=1:

  arch/x86/lib/memcpy_64.o: warning: objtool: .fixup+0x13: call to mcsafe_handle_tail() with UACCESS enabled
  arch/x86/lib/memcpy_64.o: warning: objtool:   __memcpy_mcsafe()+0x34: (alt)
  arch/x86/lib/memcpy_64.o: warning: objtool:   __memcpy_mcsafe()+0xb: (branch)
  arch/x86/lib/memcpy_64.o: warning: objtool:   __memcpy_mcsafe()+0x0: <=== (func)

mcsafe_handle_tail() is basically an extension of __memcpy_mcsafe(), so
AC=1 is supposed to be set.  Add mcsafe_handle_tail() to the uaccess
safe list.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/035c38f7eac845281d3c3d36749144982e06e58c.1563413318.git.jpoimboe@xxxxxxxxxx

---
 tools/objtool/check.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 2f8ba0368231..f9494ff8c286 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -490,6 +490,7 @@ static const char *uaccess_safe_builtin[] = {
 	/* misc */
 	"csum_partial_copy_generic",
 	"__memcpy_mcsafe",
+	"mcsafe_handle_tail",
 	"ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
 	NULL
 };