From: Christoph Hellwig <hch@infradead.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <song@kernel.org>,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-modules@vger.kernel.org,
mcgrof@kernel.org, rostedt@goodmis.org, tglx@linutronix.de,
mingo@redhat.com, bp@alien8.de, mhiramat@kernel.org,
naveen.n.rao@linux.ibm.com, davem@davemloft.net,
anil.s.keshavamurthy@intel.com, keescook@chromium.org,
hch@infradead.org, dave@stgolabs.net, daniel@iogearbox.net,
kernel-team@fb.com, x86@kernel.org, dave.hansen@linux.intel.com,
rick.p.edgecombe@intel.com, akpm@linux-foundation.org
Subject: Re: [PATCH bpf-next 1/3] mm/vmalloc: introduce vmalloc_exec which allocates RO+X memory
Date: Wed, 13 Jul 2022 22:16:36 -0700 [thread overview]
Message-ID: <Ys+mtMUb7lXZ/GaS@infradead.org> (raw)
In-Reply-To: <Ys6cWUMHO8XwyYgr@hirez.programming.kicks-ass.net>
On Wed, Jul 13, 2022 at 12:20:09PM +0200, Peter Zijlstra wrote:
> Start by adding VM_TOPDOWN_VMAP, which instead of returning the lowest
> (leftmost) vmap_area that fits, picks the higests (rightmost).
>
> Then add module_alloc_data() that uses VM_TOPDOWN_VMAP and make
> ARCH_WANTS_MODULE_DATA_IN_VMALLOC use that instead of vmalloc (with a
> weak function doing the vmalloc).
>
> This gets you bottom of module range is RO+X only, top is shattered
> between different !X types.
>
> Then track the boundary between X and !X and ensure module_alloc_data()
> and module_alloc() never cross over and stay strictly separated.
>
> Then change all module_alloc() users to expect RO+X memory, instead of
> RW.
>
> Then make sure any extention of the X range is 2M aligned.
>
> And presto, *everybody* always uses 2M TLB for text, modules, bpf,
> ftrace, the lot and nobody is tracking chunks.
>
> Maybe migration can be eased by instead providing module_alloc_text()
> and ARCH_WANTS_MODULE_ALLOC_TEXT.
This all looks pretty sensible. How are we going to do the initial
write to the executable memory, though?
next prev parent reply other threads:[~2022-07-14 5:16 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20220713071846.3286727-1-song@kernel.org>
[not found] ` <20220713071846.3286727-2-song@kernel.org>
2022-07-13 9:53 ` [PATCH bpf-next 1/3] mm/vmalloc: introduce vmalloc_exec which allocates RO+X memory Peter Zijlstra
2022-07-13 10:08 ` Christoph Hellwig
2022-07-13 15:49 ` Song Liu
2022-07-14 4:23 ` Christoph Hellwig
2022-07-14 4:54 ` Song Liu
2022-07-14 18:15 ` Uladzislau Rezki
2022-07-15 0:24 ` Song Liu
2022-07-13 10:20 ` Peter Zijlstra
2022-07-13 15:48 ` Song Liu
2022-07-13 20:26 ` Peter Zijlstra
2022-07-13 21:20 ` Song Liu
2022-07-14 10:10 ` Peter Zijlstra
2022-07-14 5:16 ` Christoph Hellwig [this message]
2022-07-14 7:26 ` Peter Zijlstra
2022-08-05 5:29 ` Song Liu
2022-08-05 5:29 ` Song Liu
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