s390/jump_label: Use "jdd" constraint on gcc9

BugLink: https://bugs.launchpad.net/bugs/1838824
[ Upstream commit 146448524bddbf6dfc62de31957e428de001cbda ]

[heiko.carstens@de.ibm.com]:
-----
Laura Abbott reported that the kernel doesn't build anymore with gcc 9,
due to the "X" constraint. Ilya provided the gcc 9 patch "S/390:
Introduce jdd constraint" which introduces the new "jdd" constraint
which fixes this.
-----

The support for section anchors on S/390 introduced in gcc9 has changed
the behavior of "X" constraint, which can now produce register
references. Since existing constraints, in particular, "i", do not fit
the intended use case on S/390, the new machine-specific "jdd"
constraint was introduced. This patch makes jump labels use "jdd"
constraint when building with gcc9.

Reported-by: Laura Abbott <labbott@redhat.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/s390/include/asm/jump_label.h b/arch/s390/include/asm/jump_label.h
index 40f651292aa78997232c74ae5f91afc0bbea035e..9c7dc970e96653fd739f3daa1435a670a409b197 100644 (file)
--- a/arch/s390/include/asm/jump_label.h
+++ b/arch/s390/include/asm/jump_label.h
@@ -10,6 +10,12 @@
 #define JUMP_LABEL_NOP_SIZE 6
 #define JUMP_LABEL_NOP_OFFSET 2
 
+#if __GNUC__ < 9
+#define JUMP_LABEL_STATIC_KEY_CONSTRAINT "X"
+#else
+#define JUMP_LABEL_STATIC_KEY_CONSTRAINT "jdd"
+#endif
+
 /*
  * We use a brcl 0,2 instruction for jump labels at compile time so it
  * can be easily distinguished from a hotpatch generated instruction.
@@ -19,9 +25,9 @@ static __always_inline bool arch_static_branch(struct static_key *key, bool bran
        asm_volatile_goto("0:   brcl 0,"__stringify(JUMP_LABEL_NOP_OFFSET)"\n"
                ".pushsection __jump_table, \"aw\"\n"
                ".balign 8\n"
-               ".quad 0b, %l[label], %0\n"
+               ".quad 0b, %l[label], %0+%1\n"
                ".popsection\n"
-               : : "X" (&((char *)key)[branch]) : : label);
+               : : JUMP_LABEL_STATIC_KEY_CONSTRAINT (key), "i" (branch) : : label);
 
        return false;
 label:
@@ -33,9 +39,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, bool
        asm_volatile_goto("0:   brcl 15, %l[label]\n"
                ".pushsection __jump_table, \"aw\"\n"
                ".balign 8\n"
-               ".quad 0b, %l[label], %0\n"
+               ".quad 0b, %l[label], %0+%1\n"
                ".popsection\n"
-               : : "X" (&((char *)key)[branch]) : : label);
+               : : JUMP_LABEL_STATIC_KEY_CONSTRAINT (key), "i" (branch) : : label);
 
        return false;
 label: