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

Oleg Nesterov
2024-06-21T12:03:31Z

On 06/20, Andrii Nakryiko wrote:
>
> On Thu, Jun 20, 2024 at 12:40 PM Oleg Nesterov <oleg@redhat.com> wrote:
> >
> > But I can't understand what does it do, it calls emit_break() and
> > git grep -w emit_break finds nothing.
> >
>
> It's DEF_EMIT_REG0I15_FORMAT(break, break_op) in
> arch/loongarch/include/asm/inst.h
>
> A bunch of macro magic, but in the end it produces some constant
> value, of course.

I see, thanks!

Then perhaps something like below?

Oleg.

--- x/arch/loongarch/include/asm/uprobes.h
+++ x/arch/loongarch/include/asm/uprobes.h
@@ -9,7 +9,7 @@ typedef u32 uprobe_opcode_t;
#define MAX_UINSN_BYTES 8
#define UPROBE_XOL_SLOT_BYTES MAX_UINSN_BYTES

-#define UPROBE_SWBP_INSN larch_insn_gen_break(BRK_UPROBE_BP)
+#define UPROBE_SWBP_INSN (uprobe_opcode_t)(BRK_UPROBE_BP | (break_op << 15))
#define UPROBE_SWBP_INSN_SIZE LOONGARCH_INSN_SIZE

#define UPROBE_XOLBP_INSN larch_insn_gen_break(BRK_UPROBE_XOLBP)
--- x/arch/loongarch/kernel/uprobes.c
+++ x/arch/loongarch/kernel/uprobes.c
@@ -7,6 +7,13 @@

#define UPROBE_TRAP_NR UINT_MAX

+static __init int __ck_insn(void)
+{
+ BUG_ON(UPROBE_SWBP_INSN != larch_insn_gen_break(BRK_UPROBE_BP));
+ return 0;
+}
+late_initcall(__ck_insn);
+
int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe,
struct mm_struct *mm, unsigned long addr)
{