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

Jiri Olsa
2024-06-21T13:18:02Z

On Fri, Jun 21, 2024 at 02:01:50PM +0200, Oleg Nesterov wrote:
> 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?

lgtm, added loong arch list/folks

for context:
https://lore.kernel.org/bpf/20240614174822.GA1185149@thelio-3990X/

thanks,
jirka

>
> 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)
> {
>