[PATCH] uprobe: Do not use UPROBE_SWBP_INSN as static initializer

[Jiri Olsa]

Nathan reported compilation fail for loongarch arch:

  kernel/events/uprobes.c: In function 'arch_uprobe_trampoline':
  arch/loongarch/include/asm/uprobes.h:12:33: error: initializer element is not 
constant
     12 | #define UPROBE_SWBP_INSN        larch_insn_gen_break(BRK_UPROBE_BP)
        |                                 ^~~~~~~~~~~~~~~~~~~~
  kernel/events/uprobes.c:1479:39: note: in expansion of macro 
'UPROBE_SWBP_INSN'
   1479 |         static uprobe_opcode_t insn = UPROBE_SWBP_INSN;

Loongarch defines UPROBE_SWBP_INSN as function call, so we can't
use it to initialize static variable.

Cc: Oleg Nesterov <o...@redhat.com>
Fixes: ff474a78cef5 ("uprobe: Add uretprobe syscall to speed up return probe")
Reported-by: Nathan Chancellor <nat...@kernel.org>
Signed-off-by: Jiri Olsa <jo...@kernel.org>
---
 kernel/events/uprobes.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 2816e65729ac..6986bd993702 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1476,8 +1476,9 @@ static int xol_add_vma(struct mm_struct *mm, struct 
xol_area *area)
 
 void * __weak arch_uprobe_trampoline(unsigned long *psize)
 {
-       static uprobe_opcode_t insn = UPROBE_SWBP_INSN;
+       static uprobe_opcode_t insn;
 
+       insn = insn ?: UPROBE_SWBP_INSN;
        *psize = UPROBE_SWBP_INSN_SIZE;
        return &insn;
 }
-- 
2.45.1