Re: [PATCH v3 02/13] mm: introduce execmem_text_alloc() and execmem_free()

[Song Liu]

On Sat, Sep 23, 2023 at 8:39 AM Mike Rapoport <rppt@xxxxxxxxxx> 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@xxxxxxxxxx> 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