Re: [PATCH] LoongArch: uprobes: make UPROBE_SWBP_INSN/UPROBE_XOLBP_INSN constant

Andrii Nakryiko
2024-06-27T16:51:48Z

On Thu, Jun 27, 2024 at 9:04 AM Oleg Nesterov <oleg@redhat.com> wrote:
>
> LoongArch defines UPROBE_SWBP_INSN as a function call and this breaks
> arch_uprobe_trampoline() which uses it to initialize a static variable.
>
> Fixes: ff474a78cef5 ("uprobe: Add uretprobe syscall to speed up return probe")
> Reported-by: Nathan Chancellor <nathan@kernel.org>
> Closes: https://lore.kernel.org/all/20240614174822.GA1185149@thelio-3990X/
> Suggested-by: Andrii Nakryiko <andrii@kernel.org>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> ---
> arch/loongarch/include/asm/uprobes.h | 6 ++++--
> arch/loongarch/kernel/uprobes.c | 8 ++++++++
> 2 files changed, 12 insertions(+), 2 deletions(-)
>

LGTM.

Acked-by: Andrii Nakryiko <andrii@kernel.org>

> diff --git a/arch/loongarch/include/asm/uprobes.h b/arch/loongarch/include/asm/uprobes.h
> index c8f59983f702..18221eb9a8b0 100644
> --- a/arch/loongarch/include/asm/uprobes.h
> +++ b/arch/loongarch/include/asm/uprobes.h
> @@ -6,13 +6,15 @@
>
> typedef u32 uprobe_opcode_t;
>
> +#define __emit_break(imm) (uprobe_opcode_t)((imm) | (break_op << 15))
> +
> #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 __emit_break(BRK_UPROBE_BP)
> #define UPROBE_SWBP_INSN_SIZE LOONGARCH_INSN_SIZE
>
> -#define UPROBE_XOLBP_INSN larch_insn_gen_break(BRK_UPROBE_XOLBP)
> +#define UPROBE_XOLBP_INSN __emit_break(BRK_UPROBE_XOLBP)
>

this looks correct (but based on pure code inspection)

> struct arch_uprobe {
> unsigned long resume_era;
> diff --git a/arch/loongarch/kernel/uprobes.c b/arch/loongarch/kernel/uprobes.c
> index 87abc7137b73..90462d94c28f 100644
> --- a/arch/loongarch/kernel/uprobes.c
> +++ b/arch/loongarch/kernel/uprobes.c
> @@ -7,6 +7,14 @@
>
> #define UPROBE_TRAP_NR UINT_MAX
>
> +static __init int check_emit_break(void)
> +{
> + BUG_ON(UPROBE_SWBP_INSN != larch_insn_gen_break(BRK_UPROBE_BP));
> + BUG_ON(UPROBE_XOLBP_INSN != larch_insn_gen_break(BRK_UPROBE_XOLBP));
> + return 0;
> +}
> +arch_initcall(check_emit_break);
> +

I wouldn't even bother with this, but whatever.

> int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe,
> struct mm_struct *mm, unsigned long addr)
> {
> --
> 2.25.1.362.g51ebf55
>
>