[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAPhsuW4au6v8k8Ab7Ff6Yj64rGvZ7wkz=Xrgh8ZZtLyscpChqQ@mail.gmail.com>
Date: Thu, 18 Apr 2024 09:13:27 -0700
From: Song Liu <song@...nel.org>
To: Mike Rapoport <rppt@...nel.org>
Cc: Mark Rutland <mark.rutland@....com>, Peter Zijlstra <peterz@...radead.org>,
linux-kernel@...r.kernel.org, Alexandre Ghiti <alexghiti@...osinc.com>,
Andrew Morton <akpm@...ux-foundation.org>, Bjorn Topel <bjorn@...nel.org>,
Catalin Marinas <catalin.marinas@....com>, Christophe Leroy <christophe.leroy@...roup.eu>,
"David S. Miller" <davem@...emloft.net>, Dinh Nguyen <dinguyen@...nel.org>,
Donald Dutile <ddutile@...hat.com>, Eric Chanudet <echanude@...hat.com>,
Heiko Carstens <hca@...ux.ibm.com>, Helge Deller <deller@....de>, Huacai Chen <chenhuacai@...nel.org>,
Kent Overstreet <kent.overstreet@...ux.dev>, Luis Chamberlain <mcgrof@...nel.org>,
Michael Ellerman <mpe@...erman.id.au>, Nadav Amit <nadav.amit@...il.com>,
Palmer Dabbelt <palmer@...belt.com>, Puranjay Mohan <puranjay12@...il.com>,
Rick Edgecombe <rick.p.edgecombe@...el.com>, Russell King <linux@...linux.org.uk>,
Steven Rostedt <rostedt@...dmis.org>, Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
Thomas Gleixner <tglx@...utronix.de>, Will Deacon <will@...nel.org>, bpf@...r.kernel.org,
linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-mips@...r.kernel.org, linux-mm@...ck.org, linux-modules@...r.kernel.org,
linux-parisc@...r.kernel.org, linux-riscv@...ts.infradead.org,
linux-s390@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, loongarch@...ts.linux.dev,
netdev@...r.kernel.org, sparclinux@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v4 05/15] mm: introduce execmem_alloc() and execmem_free()
On Thu, Apr 18, 2024 at 8:37 AM Mike Rapoport <rppt@...nel.org> wrote:
>
[...]
> >
> > Is +/- 2G enough for all realistic use cases? If so, I guess we don't
> > really need
> > EXECMEM_ANYWHERE below?
> >
> > > >
> > > > * I'm not sure about BPF's requirements; it seems happy doing the same as
> > > > modules.
> > >
> > > BPF are happy with vmalloc().
> > >
> > > > So if we *must* use a common execmem allocator, what we'd reall want is our own
> > > > types, e.g.
> > > >
> > > > EXECMEM_ANYWHERE
> > > > EXECMEM_NOPLT
> > > > EXECMEM_PREL32
> > > >
> > > > ... and then we use those in arch code to implement module_alloc() and friends.
> > >
> > > I'm looking at execmem_types more as definition of the consumers, maybe I
> > > should have named the enum execmem_consumer at the first place.
> >
> > I think looking at execmem_type from consumers' point of view adds
> > unnecessary complexity. IIUC, for most (if not all) archs, ftrace, kprobe,
> > and bpf (and maybe also module text) all have the same requirements.
> > Did I miss something?
>
> It's enough to have one architecture with different constrains for kprobes
> and bpf to warrant a type for each.
>
AFAICT, some of these constraints can be changed without too much work.
> Where do you see unnecessary complexity?
>
> > IOW, we have
> >
> > enum execmem_type {
> > EXECMEM_DEFAULT,
> > EXECMEM_TEXT,
> > EXECMEM_KPROBES = EXECMEM_TEXT,
> > EXECMEM_FTRACE = EXECMEM_TEXT,
> > EXECMEM_BPF = EXECMEM_TEXT, /* we may end up without
> > _KPROBE, _FTRACE, _BPF */
> > EXECMEM_DATA, /* rw */
> > EXECMEM_RO_DATA,
> > EXECMEM_RO_AFTER_INIT,
> > EXECMEM_TYPE_MAX,
> > };
> >
> > Does this make sense?
>
> How do you suggest to deal with e.g. riscv that has separate address spaces
> for modules, kprobes and bpf?
IIUC, modules and bpf use the same address space on riscv, while kprobes use
vmalloc address. I haven't tried this yet, but I think we can let
kprobes use the
same space as modules and bpf, which is:
ffffffff00000000 | -4 GB | ffffffff7fffffff | 2 GB | modules, BPF
Did I get this right?
Thanks,
Song
Powered by blists - more mailing lists