linux-kernel - Re: [PATCH v3 02/13] mm: introduce execmem_text_alloc() and execmem

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Date:   Sat, 23 Sep 2023 15:36:01 -0700
From:   Song Liu <song@...nel.org>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Björn Töpel <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>,
        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>,
        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>,
        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-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 v3 02/13] mm: introduce execmem_text_alloc() and execmem_free()

On Sat, Sep 23, 2023 at 8:39 AM Mike Rapoport <rppt@...nel.org> wrote:
>
> On Thu, Sep 21, 2023 at 03:34:18PM -0700, Song Liu wrote:
> > On Mon, Sep 18, 2023 at 12:30 AM Mike Rapoport <rppt@...nel.org> wrote:
> > >
> >
> > [...]
> >
> > > diff --git a/arch/s390/kernel/module.c b/arch/s390/kernel/module.c
> > > index 42215f9404af..db5561d0c233 100644
> > > --- a/arch/s390/kernel/module.c
> > > +++ b/arch/s390/kernel/module.c
> > > @@ -21,6 +21,7 @@
> > >  #include <linux/moduleloader.h>
> > >  #include <linux/bug.h>
> > >  #include <linux/memory.h>
> > > +#include <linux/execmem.h>
> > >  #include <asm/alternative.h>
> > >  #include <asm/nospec-branch.h>
> > >  #include <asm/facility.h>
> > > @@ -76,7 +77,7 @@ void *module_alloc(unsigned long size)
> > >  #ifdef CONFIG_FUNCTION_TRACER
> > >  void module_arch_cleanup(struct module *mod)
> > >  {
> > > -       module_memfree(mod->arch.trampolines_start);
> > > +       execmem_free(mod->arch.trampolines_start);
> > >  }
> > >  #endif
> > >
> > > @@ -510,7 +511,7 @@ static int module_alloc_ftrace_hotpatch_trampolines(struct module *me,
> > >
> > >         size = FTRACE_HOTPATCH_TRAMPOLINES_SIZE(s->sh_size);
> > >         numpages = DIV_ROUND_UP(size, PAGE_SIZE);
> > > -       start = module_alloc(numpages * PAGE_SIZE);
> > > +       start = execmem_text_alloc(EXECMEM_FTRACE, numpages * PAGE_SIZE);
> >
> > This should be EXECMEM_MODULE_TEXT?
>
> This is an ftrace trampoline, so I think it should be FTRACE type of
> allocation.

Yeah, I was aware of the ftrace trampoline. My point was, ftrace trampoline
doesn't seem to have any special requirements. Therefore, it is probably not
necessary to have a separate type just for it.

AFAICT, kprobe, ftrace, and BPF (JIT and trampoline) can share the same
execmem_type. We may need some work for some archs, but nothing is
fundamentally different among these.

Thanks,
Song