linux-kernel - Re: [PATCH v2 06/12] mm/execmem: introduce execmem_data

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Date:   Tue, 20 Jun 2023 08:32:33 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Kent Overstreet <kent.overstreet@...ux.dev>,
        Mike Rapoport <rppt@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        "David S. Miller" <davem@...emloft.net>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Helge Deller <deller@....de>,
        Huacai Chen <chenhuacai@...nel.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nadav Amit <nadav.amit@...il.com>,
        "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Puranjay Mohan <puranjay12@...il.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Russell King <linux@...linux.org.uk>,
        Song Liu <song@...nel.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Will Deacon <will@...nel.org>, bpf <bpf@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-mips@...r.kernel.org, linux-mm <linux-mm@...ck.org>,
        linux-modules@...r.kernel.org, linux-parisc@...r.kernel.org,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        linux-trace-kernel@...r.kernel.org,
        ppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        loongarch@...ts.linux.dev,
        Network Development <netdev@...r.kernel.org>,
        sparclinux@...r.kernel.org, X86 ML <x86@...nel.org>
Subject: Re: [PATCH v2 06/12] mm/execmem: introduce execmem_data_alloc()

On Tue, Jun 20, 2023 at 7:51 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Mon, 19 Jun 2023 02:43:58 +0200
> Thomas Gleixner <tglx@...utronix.de> wrote:
>
> > Now you might argue that it _is_ a "hotpath" due to the BPF usage, but
> > then even more so as any intermediate wrapper which converts from one
> > data representation to another data representation is not going to
> > increase performance, right?
>
> Just as a side note. BPF can not attach its return calling code to
> functions that have more than 6 parameters (3 on 32 bit x86), because of
> the way BPF return path trampoline works. It is a requirement that all
> parameters live in registers, and none on the stack.

It's actually 7 and that restriction is being lifted.
The patch set to attach to <= 12 is being discussed.