linux-kernel - Re: [RFC perf/core 03/11] uprobes: Add len argument to uprobe_write

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Message-ID: <CAEf4BzbM+warM65tnYampngqOGzQ-FS7frH88Hayx7veMjpjZA@mail.gmail.com>
Date: Thu, 14 Nov 2024 15:41:03 -0800
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Jiri Olsa <jolsa@...nel.org>
Cc: Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org, Song Liu <songliubraving@...com>, 
	Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, Hao Luo <haoluo@...gle.com>, 
	Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu <mhiramat@...nel.org>, 
	Alan Maguire <alan.maguire@...cle.com>, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org
Subject: Re: [RFC perf/core 03/11] uprobes: Add len argument to uprobe_write_opcode

On Tue, Nov 5, 2024 at 5:34 AM Jiri Olsa <jolsa@...nel.org> wrote:
>
> Adding len argument to uprobe_write_opcode as preparation
> fo writing longer instructions in following changes.

typo: for

>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  include/linux/uprobes.h |  3 ++-
>  kernel/events/uprobes.c | 14 ++++++++------
>  2 files changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h
> index 28068f9fcdc1..7d23a4fee6f4 100644
> --- a/include/linux/uprobes.h
> +++ b/include/linux/uprobes.h
> @@ -181,7 +181,8 @@ extern bool is_swbp_insn(uprobe_opcode_t *insn);
>  extern bool is_trap_insn(uprobe_opcode_t *insn);
>  extern unsigned long uprobe_get_swbp_addr(struct pt_regs *regs);
>  extern unsigned long uprobe_get_trap_addr(struct pt_regs *regs);
> -extern int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr, uprobe_opcode_t);
> +extern int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
> +                              unsigned long vaddr, uprobe_opcode_t *insn, int len);

is len in sizeof(uprobe_opcode_t) units or in bytes? it would be good
to make this clearer

it feels like passing `void *` for insns would be better, tbh...



>  extern struct uprobe *uprobe_register(struct inode *inode, loff_t offset, loff_t ref_ctr_offset, struct uprobe_consumer *uc);
>  extern int uprobe_apply(struct uprobe *uprobe, struct uprobe_consumer *uc, bool);
>  extern void uprobe_unregister_nosync(struct uprobe *uprobe, struct uprobe_consumer *uc);
> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> index e9308649bba3..3e275717789b 100644
> --- a/kernel/events/uprobes.c
> +++ b/kernel/events/uprobes.c
> @@ -471,7 +471,7 @@ static int update_ref_ctr(struct uprobe *uprobe, struct mm_struct *mm,
>   * Return 0 (success) or a negative errno.
>   */
>  int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
> -                       unsigned long vaddr, uprobe_opcode_t opcode)
> +                       unsigned long vaddr, uprobe_opcode_t *insn, int len)
>  {
>         struct uprobe *uprobe;
>         struct page *old_page, *new_page;
> @@ -480,7 +480,7 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
>         bool orig_page_huge = false;
>         unsigned int gup_flags = FOLL_FORCE;
>
> -       is_register = is_swbp_insn(&opcode);
> +       is_register = is_swbp_insn(insn);
>         uprobe = container_of(auprobe, struct uprobe, arch);
>
>  retry:
> @@ -491,7 +491,7 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
>         if (IS_ERR(old_page))
>                 return PTR_ERR(old_page);
>
> -       ret = verify_opcode(old_page, vaddr, &opcode);
> +       ret = verify_opcode(old_page, vaddr, insn);
>         if (ret <= 0)
>                 goto put_old;
>
> @@ -525,7 +525,7 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
>
>         __SetPageUptodate(new_page);
>         copy_highpage(new_page, old_page);
> -       copy_to_page(new_page, vaddr, &opcode, UPROBE_SWBP_INSN_SIZE);
> +       copy_to_page(new_page, vaddr, insn, len);
>
>         if (!is_register) {
>                 struct page *orig_page;
> @@ -582,7 +582,9 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct mm_struct *mm,
>   */
>  int __weak set_swbp(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
>  {
> -       return uprobe_write_opcode(auprobe, mm, vaddr, UPROBE_SWBP_INSN);
> +       uprobe_opcode_t insn = UPROBE_SWBP_INSN;
> +
> +       return uprobe_write_opcode(auprobe, mm, vaddr, &insn, UPROBE_SWBP_INSN_SIZE);
>  }
>
>  /**
> @@ -598,7 +600,7 @@ int __weak
>  set_orig_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long vaddr)
>  {
>         return uprobe_write_opcode(auprobe, mm, vaddr,
> -                       *(uprobe_opcode_t *)&auprobe->insn);
> +                       (uprobe_opcode_t *)&auprobe->insn, UPROBE_SWBP_INSN_SIZE);
>  }
>
>  /* uprobe should have guaranteed positive refcount */
> --
> 2.47.0
>