From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 489173DAC0F; Tue, 26 Mar 2024 16:38:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711471093; cv=none; b=OQ4H8oXosRQ66njrzRAMQACwG2mt2LjiYmN8tGDi1cz2/vIgMHRi6fkMYffmKlXId+ONiojOUY01cOpioZQagichW1GV2sJEPEQeth0yo1nBfV4kk2bBI9Vj5+Hty38CRnKMh9rVLBb7KSXDJqRtLHL6YUpn6asgy64x8SoNicY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711471093; c=relaxed/simple; bh=1VUl5T3Hy9/wKjGM7Ekj16noT58ordY8L5XY+CsT5wE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OAMvyH0vVZDZ4ABlXPwhZ3fvIZAhEdf/MLjS7QFO4H47WGd1u6WwpskeHxpcC5/+8m6cmfbOX6z3GihZOBP73WOa3Fb4RjW472PawNKnkUBiejljHQZabbB+DxPRErE5ERhzvZGhVQn3X5h4YEET84q4AxjkgyELNcXm+3lV24A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6E6452F4; Tue, 26 Mar 2024 09:38:45 -0700 (PDT) Received: from FVFF77S0Q05N.cambridge.arm.com (FVFF77S0Q05N.cambridge.arm.com [10.1.35.184]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2A34C3F694; Tue, 26 Mar 2024 09:38:10 -0700 (PDT) Date: Tue, 26 Mar 2024 16:38:07 +0000 From: Mark Rutland To: Masami Hiramatsu Cc: Jarkko Sakkinen , linux-riscv@lists.infradead.org, Paul Walmsley , Palmer Dabbelt , Albert Ou , linux-kernel@vger.kernel.org, "Naveen N . Rao" , Anil S Keshavamurthy , "David S . Miller" , linux-trace-kernel@vger.kernel.org, Calvin Owens Subject: Re: [PATCH v2] arch/riscv: Enable kprobes when CONFIG_MODULES=n Message-ID: References: <20240323232908.13261-1-jarkko@kernel.org> <20240325115632.04e37297491cadfbbf382767@kernel.org> <20240327002403.62649aee45508b7a16caedba@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240327002403.62649aee45508b7a16caedba@kernel.org> On Wed, Mar 27, 2024 at 12:24:03AM +0900, Masami Hiramatsu wrote: > On Tue, 26 Mar 2024 14:46:10 +0000 > Mark Rutland wrote: > > > > On Mon, Mar 25, 2024 at 11:56:32AM +0900, Masami Hiramatsu wrote: > > > I think, we'd better to introduce `alloc_execmem()`, > > > CONFIG_HAVE_ALLOC_EXECMEM and CONFIG_ALLOC_EXECMEM at first > > > > > > config HAVE_ALLOC_EXECMEM > > > bool > > > > > > config ALLOC_EXECMEM > > > bool "Executable trampline memory allocation" > > > depends on MODULES || HAVE_ALLOC_EXECMEM > > > > > > And define fallback macro to module_alloc() like this. > > > > > > #ifndef CONFIG_HAVE_ALLOC_EXECMEM > > > #define alloc_execmem(size, gfp) module_alloc(size) > > > #endif > > > > Please can we *not* do this? I think this is abstracting at the wrong level (as > > I mentioned on the prior execmem proposals). > > > > Different exectuable allocations can have different requirements. For example, > > on arm64 modules need to be within 2G of the kernel image, but the kprobes XOL > > areas can be anywhere in the kernel VA space. > > > > Forcing those behind the same interface makes things *harder* for architectures > > and/or makes the common code more complicated (if that ends up having to track > > all those different requirements). From my PoV it'd be much better to have > > separate kprobes_alloc_*() functions for kprobes which an architecture can then > > choose to implement using a common library if it wants to. > > > > I took a look at doing that using the core ifdeffery fixups from Jarkko's v6, > > and it looks pretty clean to me (and works in testing on arm64): > > > > https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=kprobes/without-modules > > > > Could we please start with that approach, with kprobe-specific alloc/free code > > provided by the architecture? > > OK, as far as I can read the code, this method also works and neat! > (and minimum intrusion). I actually found that exposing CONFIG_ALLOC_EXECMEM > to user does not help, it should be an internal change. So hiding this change > from user is better choice. Then there is no reason to introduce the new > alloc_execmem, but just expand kprobe_alloc_insn_page() is reasonable. > > Mark, can you send this series here, so that others can review/test it? I've written up a cover letter and sent that out: https://lore.kernel.org/lkml/20240326163624.3253157-1-mark.rutland@arm.com/ Mark.