From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A116518DB35; Fri, 27 Jun 2025 04:58:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751000291; cv=none; b=DNRaAcNBqogCuAd1KmzmukqH4BFu+9IxPhwXXQJgDGxCqcKPJwlQZe5x8uhp/xTUFWpUOZc0sKwLDQEm6vxsFrHp9TYKDvXYrhz64w016ObdIuEwl0kdtlXrzyeoEqlbJSK4CBGboVflCR+5rPo0WEu5yKVEEJ5fciGKv04Ysx0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751000291; c=relaxed/simple; bh=hh+Pcw6Bm2ZODy21sOTBGqmuusQEsI7aY0o1WB0Nl1c=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=hbaZolug4bh5M/Lh7yVjoE6WEbJ9QumOFEYopu0yQzHD86vwgW0cXFQA/f7Ne0QiKaKYDp/Hr3RKUl5aMemPfOOj6EI9QJcbCccDToxU2YlrejsYyCP5142xbbwZr2lRMz9hxvJtG116qXd1VwGtaZkico6RKOqroLVEwJmGNIY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MAsE4uBQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MAsE4uBQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 24FDEC4CEE3; Fri, 27 Jun 2025 04:58:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1751000291; bh=hh+Pcw6Bm2ZODy21sOTBGqmuusQEsI7aY0o1WB0Nl1c=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=MAsE4uBQf9SAwhj9bFX1fXZozhWsCTxbzvleDxq+MTF5eYPJWzDUxYEDKM0R3vZ4S tnbI0Hs3qmWu474Zuv8EyE0L/ws6cADfKbe4fZ+sdG/kSEASjLuAv7eElKd+qrRCoE uYonxwEDCFhUobdkI1iw7+oyn1QiCJvyzCxxJv9gdXIHboqmCjArGQ+AEmTGBPxNH9 DguOSfCVnDnGax6XYad+DAZKO6JhuMrSB019kM2StIzoBz2DMRfKFrWLxPIRDam1GU b/C8q0E1zxVXFhnJS/DCpGQi5UIFk1XFlnzB9pXbGLlKBV7F/e7LS+XSSanUCVwXKn xF+fpi08z4TNQ== Date: Fri, 27 Jun 2025 13:58:07 +0900 From: Masami Hiramatsu (Google) To: Jiri Olsa Cc: Oleg Nesterov , Peter Zijlstra , Andrii Nakryiko , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org, Song Liu , Yonghong Song , John Fastabend , Hao Luo , Steven Rostedt , Alan Maguire , David Laight , Thomas =?UTF-8?B?V2Vpw59zY2h1aA==?= , Ingo Molnar Subject: Re: [PATCHv3 perf/core 07/22] uprobes: Add do_ref_ctr argument to uprobe_write function Message-Id: <20250627135807.dd97ddf4cb6910df3c56e654@kernel.org> In-Reply-To: References: <20250605132350.1488129-1-jolsa@kernel.org> <20250605132350.1488129-8-jolsa@kernel.org> <20250625154259.4a092f0213739404a0e9b210@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 25 Jun 2025 17:11:09 +0200 Jiri Olsa wrote: > On Wed, Jun 25, 2025 at 03:42:59PM +0900, Masami Hiramatsu wrote: > > On Thu, 5 Jun 2025 15:23:34 +0200 > > Jiri Olsa wrote: > > > > > Making update_ref_ctr call in uprobe_write conditional based > > > on do_ref_ctr argument. This way we can use uprobe_write for > > > instruction update without doing ref_ctr_offset update. > > > > > > > Can we just decouple this update from uprobe_write()? > > If we do this exclusively, I think we can do something like; > > > > lock() > > update_ref_ctr(uprobe, mm, +1); > > ... > > ret = uprobe_write(); > > ... > > if (ret < 0) > > update_ref_ctr(uprobe, mm, -1); > > unlock() > > > > Thank you, > > it was the intention in the v1 but as Oleg pointed out [1] it won't > work, because the set_orig_refctr part of this change does not know > if the refctr should be really updated or not Ah, uprobe_unregister() can not check the given uprobe failed to update the code for each mm.... > > while inside uprobe_write it happens right after verify callback and > we make sure to update refctr only if the instruction was updated OK. But this is very complicated. Eventually I think uprobe should have a list of mm(or refcnt) to manage whether it is updated the refcounter. Reviewed-by: Masami Hiramatsu (Google) Thanks, > > thanks, > jirka > > > [1] https://lore.kernel.org/bpf/20250427141335.GA9350@redhat.com/ > > > > > > > > Acked-by: Oleg Nesterov > > > Signed-off-by: Jiri Olsa > > > --- > > > include/linux/uprobes.h | 2 +- > > > kernel/events/uprobes.c | 8 ++++---- > > > 2 files changed, 5 insertions(+), 5 deletions(-) > > > > > > diff --git a/include/linux/uprobes.h b/include/linux/uprobes.h > > > index 518b26756469..5080619560d4 100644 > > > --- a/include/linux/uprobes.h > > > +++ b/include/linux/uprobes.h > > > @@ -200,7 +200,7 @@ extern unsigned long uprobe_get_trap_addr(struct pt_regs *regs); > > > extern int uprobe_write_opcode(struct arch_uprobe *auprobe, struct vm_area_struct *vma, unsigned long vaddr, uprobe_opcode_t, > > > bool is_register); > > > extern int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct *vma, const unsigned long opcode_vaddr, > > > - uprobe_opcode_t *insn, int nbytes, uprobe_write_verify_t verify, bool is_register); > > > + uprobe_opcode_t *insn, int nbytes, uprobe_write_verify_t verify, bool is_register, bool do_update_ref_ctr); > > > 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 1e5dc3b30707..6795b8d82b9c 100644 > > > --- a/kernel/events/uprobes.c > > > +++ b/kernel/events/uprobes.c > > > @@ -492,12 +492,12 @@ int uprobe_write_opcode(struct arch_uprobe *auprobe, struct vm_area_struct *vma, > > > bool is_register) > > > { > > > return uprobe_write(auprobe, vma, opcode_vaddr, &opcode, UPROBE_SWBP_INSN_SIZE, > > > - verify_opcode, is_register); > > > + verify_opcode, is_register, true /* do_update_ref_ctr */); > > > } > > > > > > int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct *vma, > > > const unsigned long insn_vaddr, uprobe_opcode_t *insn, int nbytes, > > > - uprobe_write_verify_t verify, bool is_register) > > > + uprobe_write_verify_t verify, bool is_register, bool do_update_ref_ctr) > > > { > > > const unsigned long vaddr = insn_vaddr & PAGE_MASK; > > > struct mm_struct *mm = vma->vm_mm; > > > @@ -538,7 +538,7 @@ int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct *vma, > > > } > > > > > > /* We are going to replace instruction, update ref_ctr. */ > > > - if (!ref_ctr_updated && uprobe->ref_ctr_offset) { > > > + if (do_update_ref_ctr && !ref_ctr_updated && uprobe->ref_ctr_offset) { > > > ret = update_ref_ctr(uprobe, mm, is_register ? 1 : -1); > > > if (ret) { > > > folio_put(folio); > > > @@ -590,7 +590,7 @@ int uprobe_write(struct arch_uprobe *auprobe, struct vm_area_struct *vma, > > > > > > out: > > > /* Revert back reference counter if instruction update failed. */ > > > - if (ret < 0 && ref_ctr_updated) > > > + if (do_update_ref_ctr && ret < 0 && ref_ctr_updated) > > > update_ref_ctr(uprobe, mm, is_register ? -1 : 1); > > > > > > /* try collapse pmd for compound page */ > > > -- > > > 2.49.0 > > > > > > > > > -- > > Masami Hiramatsu (Google) -- Masami Hiramatsu (Google)