From: Song Liu <song@kernel.org>
To: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org,
Alexandre Ghiti <alexghiti@rivosinc.com>,
Andrew Morton <akpm@linux-foundation.org>,
Bjorn Topel <bjorn@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
"David S. Miller" <davem@davemloft.net>,
Dinh Nguyen <dinguyen@kernel.org>,
Donald Dutile <ddutile@redhat.com>,
Eric Chanudet <echanude@redhat.com>,
Heiko Carstens <hca@linux.ibm.com>, Helge Deller <deller@gmx.de>,
Huacai Chen <chenhuacai@kernel.org>,
Kent Overstreet <kent.overstreet@linux.dev>,
Luis Chamberlain <mcgrof@kernel.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Nadav Amit <nadav.amit@gmail.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Puranjay Mohan <puranjay12@gmail.com>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
Russell King <linux@armlinux.org.uk>,
Steven Rostedt <rostedt@goodmis.org>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>,
bpf@vger.kernel.org, linux-arch@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-mips@vger.kernel.org, linux-mm@kvack.org,
linux-modules@vger.kernel.org, linux-parisc@vger.kernel.org,
linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org,
linux-trace-kernel@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, loongarch@lists.linux.dev,
netdev@vger.kernel.org, sparclinux@vger.kernel.org,
x86@kernel.org
Subject: Re: [PATCH v4 05/15] mm: introduce execmem_alloc() and execmem_free()
Date: Mon, 22 Apr 2024 11:32:02 -0700 [thread overview]
Message-ID: <CAPhsuW5RYfq8FOtMkO69cdQ3Bc1p2kQPWE2crts1UMhqJr+7sQ@mail.gmail.com> (raw)
In-Reply-To: <20240420181121.d6c7be11a6f98dc2462f8b41@kernel.org>
Hi Masami and Mike,
On Sat, Apr 20, 2024 at 2:11 AM Masami Hiramatsu <mhiramat@kernel.org> wrote:
[...]
> > >
> > > IIUC, we need to update __execmem_cache_alloc() to take a range pointer as
> > > input. module text will use "range" for EXECMEM_MODULE_TEXT, while kprobe
> > > will use "range" for EXECMEM_KPROBE. Without "map to" concept or sharing
> > > the "range" object, we will have to compare different range parameters to check
> > > we can share cached pages between module text and kprobe, which is not
> > > efficient. Did I miss something?
>
> Song, thanks for trying to eplain. I think I need to explain why I used
> module_alloc() originally.
>
> This depends on how kprobe features are implemented on the architecture, and
> how much features are supported on kprobes.
>
> Because kprobe jump optimization and kprobe jump-back optimization need to
> use a jump instruction to jump into the trampoline and jump back from the
> trampoline directly, if the architecuture jmp instruction supports +-2GB range
> like x86, it needs to allocate the trampoline buffer inside such address space.
> This requirement is similar to the modules (because module function needs to
> call other functions in the kernel etc.), at least kprobes on x86 used
> module_alloc().
>
> However, if an architecture only supports breakpoint/trap based kprobe,
> it does not need to consider whether the execmem is allocated.
>
> >
> > We can always share large ROX pages as long as they are within the correct
> > address space. The permissions for them are ROX and the alignment
> > differences are due to KASAN and this is handled during allocation of the
> > large page to refill the cache. __execmem_cache_alloc() only needs to limit
> > the search for the address space of the range.
>
> So I don't think EXECMEM_KPROBE always same as EXECMEM_MODULE_TEXT, it
> should be configured for each arch. Especially, if it is only used for
> searching parameter, it looks OK to me.
Thanks for the explanation!
I was thinking "we can have EXECMEM_KPROBE share the same parameters as
EXECMEM_MODULE_TEXT for all architectures". But this thought is built on top
of assumptions on future changes/improvements within multiple sub systems.
At this moment, I have no objections moving forward with current execmem APIs.
Thanks,
Song
next prev parent reply other threads:[~2024-04-22 18:32 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-11 16:00 [PATCH v4 00/15] mm: jit/text allocator Mike Rapoport
2024-04-11 16:00 ` [PATCH v4 01/15] arm64: module: remove uneeded call to kasan_alloc_module_shadow() Mike Rapoport
2024-04-11 16:00 ` [PATCH v4 02/15] mips: module: rename MODULE_START to MODULES_VADDR Mike Rapoport
2024-04-11 16:00 ` [PATCH v4 03/15] nios2: define virtual address space for modules Mike Rapoport
2024-04-11 16:00 ` [PATCH v4 04/15] module: make module_memory_{alloc,free} more self-contained Mike Rapoport
2024-04-11 16:00 ` [PATCH v4 05/15] mm: introduce execmem_alloc() and execmem_free() Mike Rapoport
2024-04-11 19:42 ` Luis Chamberlain
2024-04-14 6:53 ` Mike Rapoport
2024-04-12 9:16 ` Ingo Molnar
2024-04-14 6:54 ` Mike Rapoport
2024-04-15 7:52 ` Peter Zijlstra
2024-04-15 16:51 ` Mike Rapoport
2024-04-15 17:36 ` Mark Rutland
2024-04-16 7:22 ` Mike Rapoport
2024-04-17 23:32 ` Song Liu
2024-04-18 15:35 ` Mike Rapoport
2024-04-18 16:13 ` Song Liu
2024-04-18 17:52 ` Mike Rapoport
2024-04-18 21:01 ` Song Liu
2024-04-19 6:55 ` Mike Rapoport
2024-04-19 15:54 ` Song Liu
2024-04-19 17:02 ` Mike Rapoport
2024-04-19 17:32 ` Song Liu
2024-04-19 19:59 ` Mike Rapoport
2024-04-19 21:42 ` Song Liu
2024-04-20 4:22 ` Mike Rapoport
2024-04-20 9:11 ` Masami Hiramatsu
2024-04-22 18:32 ` Song Liu [this message]
2024-04-17 21:06 ` Masami Hiramatsu
2024-04-11 16:00 ` [PATCH v4 06/15] mm/execmem, arch: convert simple overrides of module_alloc to execmem Mike Rapoport
2024-04-11 20:53 ` Sam Ravnborg
2024-04-14 7:26 ` Mike Rapoport
2024-04-15 8:03 ` Peter Zijlstra
2024-04-11 16:00 ` [PATCH v4 07/15] mm/execmem, arch: convert remaining " Mike Rapoport
2024-04-15 9:36 ` Peter Zijlstra
2024-04-11 16:00 ` [PATCH v4 08/15] arm64: extend execmem_info for generated code allocations Mike Rapoport
2024-04-11 16:00 ` [PATCH v4 09/15] riscv: extend execmem_params " Mike Rapoport
2024-04-11 16:00 ` [PATCH v4 10/15] powerpc: extend execmem_params for kprobes allocations Mike Rapoport
2024-04-11 16:00 ` [PATCH v4 11/15] arch: make execmem setup available regardless of CONFIG_MODULES Mike Rapoport
2024-04-11 16:00 ` [PATCH v4 12/15] x86/ftrace: enable dynamic ftrace without CONFIG_MODULES Mike Rapoport
2024-04-11 16:00 ` [PATCH v4 13/15] powerpc: use CONFIG_EXECMEM instead of CONFIG_MODULES where appropiate Mike Rapoport
2024-04-11 16:00 ` [PATCH v4 14/15] kprobes: remove dependency on CONFIG_MODULES Mike Rapoport
2024-04-17 21:16 ` Masami Hiramatsu
2024-04-18 15:37 ` Mike Rapoport
2024-04-19 15:49 ` Mike Rapoport
2024-04-19 15:59 ` Christophe Leroy
2024-04-20 7:33 ` Mike Rapoport
2024-04-20 9:15 ` Masami Hiramatsu
2024-04-20 10:52 ` Mike Rapoport
2024-04-11 16:00 ` [PATCH v4 15/15] bpf: remove CONFIG_BPF_JIT dependency on CONFIG_MODULES of Mike Rapoport
2024-04-11 18:00 ` [PATCH v4 00/15] mm: jit/text allocator Kent Overstreet
2024-04-11 19:45 ` Luis Chamberlain
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