linux-kernel - Re: [PATCH] LoongArch: make the users of larch_insn_gen

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Message-ID: <CAAhV-H5Pr2UmOTezMtO8GfAWEbWkSJ4aUJFusLWxDNn3VyTXXA@mail.gmail.com>
Date: Mon, 1 Jul 2024 23:01:27 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc: Oleg Nesterov <oleg@...hat.com>, andrii.nakryiko@...il.com, andrii@...nel.org, 
	bpf@...r.kernel.org, jolsa@...nel.org, kernel@...0n.name, 
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	loongarch@...ts.linux.dev, mhiramat@...nel.org, nathan@...nel.org, 
	rostedt@...dmis.org
Subject: Re: [PATCH] LoongArch: make the users of larch_insn_gen_break() constant

On Mon, Jul 1, 2024 at 2:22 PM Tiezhu Yang <yangtiezhu@...ngson.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@...nel.org>
> > Closes: https://lore.kernel.org/all/20240614174822.GA1185149@thelio-3990X/
> > Suggested-by: Andrii Nakryiko <andrii@...nel.org>
> > Signed-off-by: Oleg Nesterov <oleg@...hat.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@...ngson.cn>
Queued, thanks.

Huacai
>
> Thanks,
> Tiezhu
>
>