Re: [PATCH] LoongArch: make the users of larch_insn_gen_break() constant

[Huacai Chen <chenhuacai@kernel.org>]

On Mon, Jul 1, 2024 at 2:22 PM Tiezhu Yang <yangtiezhu@loongson.cn> wrote:
>
> On 06/29/2024 11:03 PM, Oleg Nesterov wrote:
> > LoongArch defines UPROBE_SWBP_INSN as a function call and this breaks
> > arch_uprobe_trampoline() which uses it to initialize a static variable.
> >
> > Add the new "__builtin_constant_p" helper, __emit_break(), and redefine
> > the current users of larch_insn_gen_break() to use it.
> >
> > The patch adds check_emit_break() into kprobes.c and uprobes.c to test
> > this change. They can be removed if LoongArch boots at least once, but
> > otoh these 2 __init functions will be discarded by free_initmem().
> >
> > 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>
>
> Tested on LoongArch machine with Loongson-3A5000 and Loongson-3A6000
> CPU, based on 6.10-rc3,
>
> KPROBE_BP_INSN == larch_insn_gen_break(BRK_KPROBE_BP)
> KPROBE_SSTEPBP_INSN == larch_insn_gen_break(BRK_KPROBE_SSTEPBP)
> UPROBE_SWBP_INSN  == larch_insn_gen_break(BRK_UPROBE_BP)
> UPROBE_XOLBP_INSN == larch_insn_gen_break(BRK_UPROBE_XOLBP)
>
> The two functions check_emit_break() can be removed in
> arch/loongarch/kernel/kprobes.c and arch/loongarch/kernel/uprobes.c
>
> Tested-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Queued, thanks.

Huacai
>
> Thanks,
> Tiezhu
>
>