Re: [PATCH v2 04/12] mm/execmem, arch: convert remaining overrides of module_alloc to execmem

Mike Rapoport
2023-06-17T06:15:35Z

On Fri, Jun 16, 2023 at 11:53:54AM -0700, Song Liu wrote:
> On Fri, Jun 16, 2023 at 1:51 AM Mike Rapoport <rppt@kernel.org> wrote:
> [...]
> > diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
> > index 5af4975caeb5..c3d999f3a3dd 100644
> > --- a/arch/arm64/kernel/module.c
> > +++ b/arch/arm64/kernel/module.c
> > @@ -17,56 +17,50 @@
> > #include <linux/moduleloader.h>
> > #include <linux/scs.h>
> > #include <linux/vmalloc.h>
> > +#include <linux/execmem.h>
> > #include <asm/alternative.h>
> > #include <asm/insn.h>
> > #include <asm/scs.h>
> > #include <asm/sections.h>
> >
> > -void *module_alloc(unsigned long size)
> > +static struct execmem_params execmem_params = {
> > + .modules = {
> > + .flags = EXECMEM_KASAN_SHADOW,
> > + .text = {
> > + .alignment = MODULE_ALIGN,
> > + },
> > + },
> > +};
> > +
> > +struct execmem_params __init *execmem_arch_params(void)
> > {
> > u64 module_alloc_end = module_alloc_base + MODULES_VSIZE;
> > - gfp_t gfp_mask = GFP_KERNEL;
> > - void *p;
> > -
> > - /* Silence the initial allocation */
> > - if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS))
> > - gfp_mask |= __GFP_NOWARN;
> >
> > - if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
> > - IS_ENABLED(CONFIG_KASAN_SW_TAGS))
> > - /* don't exceed the static module region - see below */
> > - module_alloc_end = MODULES_END;
> > + execmem_params.modules.text.pgprot = PAGE_KERNEL;
> > + execmem_params.modules.text.start = module_alloc_base;
>
> I think I mentioned this earlier. For arm64 with CONFIG_RANDOMIZE_BASE,
> module_alloc_base is not yet set when execmem_arch_params() is
> called. So we will need some extra logic for this.

Right, this is taken care of in a later patch, but it actually belongs here.
Good catch!

> Thanks,
> Song
>
>
> > + execmem_params.modules.text.end = module_alloc_end;
> >
> > - p = __vmalloc_node_range(size, MODULE_ALIGN, module_alloc_base,
> > - module_alloc_end, gfp_mask, PAGE_KERNEL, VM_DEFER_KMEMLEAK,
> > - NUMA_NO_NODE, __builtin_return_address(0));
> > -
> > - if (!p && IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
> > + /*
> > + * KASAN without KASAN_VMALLOC can only deal with module
> > + * allocations being served from the reserved module region,
> > + * since the remainder of the vmalloc region is already
> > + * backed by zero shadow pages, and punching holes into it
> > + * is non-trivial. Since the module region is not randomized
> > + * when KASAN is enabled without KASAN_VMALLOC, it is even
> > + * less likely that the module region gets exhausted, so we
> > + * can simply omit this fallback in that case.
> > + */
> > + if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
> > (IS_ENABLED(CONFIG_KASAN_VMALLOC) ||
> > (!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
> > - !IS_ENABLED(CONFIG_KASAN_SW_TAGS))))
> > - /*
> > - * KASAN without KASAN_VMALLOC can only deal with module
> > - * allocations being served from the reserved module region,
> > - * since the remainder of the vmalloc region is already
> > - * backed by zero shadow pages, and punching holes into it
> > - * is non-trivial. Since the module region is not randomized
> > - * when KASAN is enabled without KASAN_VMALLOC, it is even
> > - * less likely that the module region gets exhausted, so we
> > - * can simply omit this fallback in that case.
> > - */
> > - p = __vmalloc_node_range(size, MODULE_ALIGN, module_alloc_base,
> > - module_alloc_base + SZ_2G, GFP_KERNEL,
> > - PAGE_KERNEL, 0, NUMA_NO_NODE,
> > - __builtin_return_address(0));
> > -
> > - if (p && (kasan_alloc_module_shadow(p, size, gfp_mask) < 0)) {
> > - vfree(p);
> > - return NULL;
> > + !IS_ENABLED(CONFIG_KASAN_SW_TAGS)))) {
> > + unsigned long end = module_alloc_base + SZ_2G;
> > +
> > + execmem_params.modules.text.fallback_start = module_alloc_base;
> > + execmem_params.modules.text.fallback_end = end;
> > }
> >
> > - /* Memory is intended to be executable, reset the pointer tag. */
> > - return kasan_reset_tag(p);
> > + return &execmem_params;
> > }
> >
> > enum aarch64_reloc_op {

--
Sincerely yours,
Mike.