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Date:   Fri, 10 Jul 2020 15:04:29 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Masami Hiramatsu <mhiramat@kernel.org>,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        linux-kernel@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
        Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
        "David S. Miller" <davem@davemloft.net>,
        Steven Rostedt <rostedt@goodmis.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        Will Deacon <will@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Arnd Bergmann <arnd@arndb.de>, Alexandre Ghiti <alex@ghiti.fr>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Sami Tolvanen <samitolvanen@google.com>,
        Peter Collingbourne <pcc@google.com>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        Stephen Boyd <sboyd@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Jiri Olsa <jolsa@redhat.com>, hch@lst.de
Subject: Re: [PATCH RFC] kprobes: Remove MODULES dependency
Message-ID: <20200710130429.GA8619@lst.de>
References: <20200709234521.194005-1-jarkko.sakkinen@linux.intel.com> <20200710193257.4eeb19e9cd042d99cbca7f9a@kernel.org> <20200710113238.GH4800@hirez.programming.kicks-ass.net>
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On Fri, Jul 10, 2020 at 01:32:38PM +0200, Peter Zijlstra wrote:
> On Fri, Jul 10, 2020 at 07:32:57PM +0900, Masami Hiramatsu wrote:
> > > -	page = module_alloc(PAGE_SIZE);
> > > +	page = vmalloc(PAGE_SIZE);
> > 
> > No, you can not use vmalloc here. The reason why we use module_alloc()
> > is to allocate the executable memory for trampoline code.
> > So, you need to use vmalloc_exec() instead.
> 
> vmalloc_exec() would be broken too, also hch recently got rid of that
> thing.
> 
> module_alloc() really is the only sane choice here.
> 
> We should make module_alloc() unconditionally available, and maybe even
> rename it to text_alloc().

I think unconitionally might be a bit too much, but for
MODULES || KRPOBES or a new symbol select by them makes sense.  As does
the rename.