Re: [PATCH 1/3] module: Rename module_alloc() to text_alloc() and move to kernel proper - Russell King

From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Kefeng Wang <wangkefeng.wang@huawei.com>,
	Paul Mackerras <paulus@samba.org>, Zong Li <zong.li@sifive.com>,
	Andi Kleen <ak@linux.intel.com>,
	Paul Burton <paulburton@kernel.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Vincent Whitchurch <vincent.whitchurch@axis.com>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Petr Mladek <pmladek@suse.com>, Brian Gerst <brgerst@gmail.com>,
	Andy Lutomirski <luto@kernel.org>, Yonghong Song <yhs@fb.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jiri Kosina <jkosina@suse.cz>, Anup Patel <anup.patel@wdc.com>,
	linux-kernel@vger.kernel.org, Philipp Rudo <prudo@linux.ibm.com>,
	Torsten Duwe <duwe@lst.de>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mark Rutland <mark.rutland@arm.com>,
	"James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
	Vincent Chen <deanbo422@gmail.com>,
	"open list:S390" <linux-s390@vger.kernel.org>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Helge Deller <deller@gmx.de>,
	John Fastabend <john.fastabend@gmail.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Iurii Zaikin <yzaikin@google.com>,
	Andrii Nakryiko <andriin@fb.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	"moderated list:ARM PORT" <linux-arm-kernel@lists.infradead.org>,
	Daniel Axtens <dja@axtens.net>,
	Damien Le Moal <damien.lemoal@wdc.com>,
	Peter Oberparleiter <oberpar@linux.ibm.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Atish Patra <atish.patra@wdc.com>, Will Deacon <will@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Nayna Jain <nayna@linux.ibm.com>,
	Ley Foon Tan <ley.foon.tan@intel.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Dmitry Vyukov <dvyukov@google.com>,
	Sami Tolvanen <samitolvanen@google.com>,
	"Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
	Mao Han <han_mao@c-sky.com>, Marco Elver <elver@google.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Babu Moger <Babu.Moger@amd.com>, Borislav Petkov <bp@alien8.de>,
	Greentime Hu <green.hu@gmail.com>,
	Ben Dooks <ben-linux@fluff.org>, Guan Xuetao <gxt@pku.edu.cn>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	"open list:PARISC ARCHITECTURE" <linux-parisc@vger.kernel.org>,
	Jessica Yu <jeyu@kernel.org>,
	"open list:BPF JIT for MIPS \(32-BIT AND 64-BIT\)"
	<bpf@vger.kernel.org>, "David S. Miller" <davem@davemloft.net>,
	Thiago Jung Bauermann <bauerman@linux.ibm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	"open list:SPARC + UltraSPARC \(sparc/sparc64\)"
	<sparclinux@vger.kernel.org>,
	Sandipan Das <sandipan@linux.ibm.com>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Amit Daniel Kachhap <amit.kachhap@arm.com>,
	Tiezhu Yang <yangtiezhu@loongson.cn>,
	Miroslav Benes <mbenes@suse.cz>, Jiri Olsa <jolsa@redhat.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Anders Roxell <anders.roxell@linaro.org>,
	Sven Schnelle <svens@stackframe.org>,
	"maintainer:X86 ARCHITECTURE \(32-BIT AND 64-BIT\)"
	<x86@kernel.org>,
	"open list:RISC-V ARCHITECTURE" <linux-riscv@lists.infradead.org>,
	Mike Rapoport <rppt@linux.ibm.com>,
	Ingo Molnar <mingo@redhat.com>, Albert Ou <aou@eecs.berkeley.edu>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	KP Singh <kpsingh@chromium.org>,
	Gerald Schaefer <gerald.schaefer@de.ibm.com>,
	Nick Hu <nickhu@andestech.com>,
	"open list:BPF JIT for MIPS \(32-BIT AND 64-BIT\)"
	<netdev@vger.kernel.org>,
	"open list:MIPS" <linux-mips@vger.kernel.org>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	"open list:LINUX FOR POWERPC \(32-BIT AND 64-BIT\)"
	<linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH 1/3] module: Rename module_alloc() to text_alloc() and move to kernel proper
Date: Mon, 13 Jul 2020 19:34:10 +0100	[thread overview]
Message-ID: <20200713183410.GY1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <20200713182030.1418041-1-jarkko.sakkinen@linux.intel.com>

On Mon, Jul 13, 2020 at 09:19:37PM +0300, Jarkko Sakkinen wrote:
> Rename module_alloc() to text_alloc() and module_memfree() to
> text_memfree(), and move them to kernel/text.c, which is unconditionally
> compiled to the kernel proper. This allows kprobes, ftrace and bpf to
> allocate space for executable code without requiring to compile the modules
> support (CONFIG_MODULES=y) in.

I'm not sure this is a good idea for 32-bit ARM.  The code you are
moving for 32-bit ARM is quite specific to module use in that it also
supports allocating from the vmalloc area, where the module code
knows to add PLT entries.

If the other proposed users of this text_alloc() do not have the logic
to add PLT entries when branches between kernel code and this
allocation are not reachable by, e.g. a 26-bit signed offset for 32-bit
ARM code, then this code is not suitable for that use.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!

_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv