Re: [PATCH bpf-next 4/5] module: introduce module_alloc_huge

[Song Liu <songliubraving@fb.com>]

Hi Luis,

> On May 15, 2022, at 10:40 PM, Song Liu <song@kernel.org> wrote:
> 
> Introduce module_alloc_huge, which allocates huge page backed memory in
> module memory space. The primary user of this memory is bpf_prog_pack
> (multiple BPF programs sharing a huge page).
> 
> Cc: Stephen Rothwell <sfr@canb.auug.org.au>
> Cc: Luis Chamberlain <mcgrof@kernel.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Song Liu <song@kernel.org>
> 
> ---
> Note: This conflicts with the module.c => module/ split in modules-next.
> Current patch is for module.c in the bpf-next tree. After the split,
> __weak module_alloc_huge() should be added to kernel/module/main.c.

Could you please share your feedback on this patch? I guess we need
to address the conflict with module.c split in the merge window?

Thanks,
Song


> ---
> arch/x86/kernel/module.c     | 21 +++++++++++++++++++++
> include/linux/moduleloader.h |  5 +++++
> kernel/module.c              |  8 ++++++++
> 3 files changed, 34 insertions(+)
> 
> diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
> index b98ffcf4d250..63f6a16c70dc 100644
> --- a/arch/x86/kernel/module.c
> +++ b/arch/x86/kernel/module.c
> @@ -86,6 +86,27 @@ void *module_alloc(unsigned long size)
> 	return p;
> }
> 
> +void *module_alloc_huge(unsigned long size)
> +{
> +	gfp_t gfp_mask = GFP_KERNEL;
> +	void *p;
> +
> +	if (PAGE_ALIGN(size) > MODULES_LEN)
> +		return NULL;
> +
> +	p = __vmalloc_node_range(size, MODULE_ALIGN,
> +				 MODULES_VADDR + get_module_load_offset(),
> +				 MODULES_END, gfp_mask, PAGE_KERNEL,
> +				 VM_DEFER_KMEMLEAK | VM_ALLOW_HUGE_VMAP,
> +				 NUMA_NO_NODE, __builtin_return_address(0));
> +	if (p && (kasan_alloc_module_shadow(p, size, gfp_mask) < 0)) {
> +		vfree(p);
> +		return NULL;
> +	}
> +
> +	return p;
> +}
> +
> #ifdef CONFIG_X86_32
> int apply_relocate(Elf32_Shdr *sechdrs,
> 		   const char *strtab,
> diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
> index 9e09d11ffe5b..d34743a88938 100644
> --- a/include/linux/moduleloader.h
> +++ b/include/linux/moduleloader.h
> @@ -26,6 +26,11 @@ unsigned int arch_mod_section_prepend(struct module *mod, unsigned int section);
>    sections.  Returns NULL on failure. */
> void *module_alloc(unsigned long size);
> 
> +/* Allocator used for allocating memory in module memory space. If size is
> + * greater than PMD_SIZE, allow using huge pages. Returns NULL on failure.
> + */
> +void *module_alloc_huge(unsigned long size);
> +
> /* Free memory returned from module_alloc. */
> void module_memfree(void *module_region);
> 
> diff --git a/kernel/module.c b/kernel/module.c
> index 6cea788fd965..2af20ac3209c 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2839,6 +2839,14 @@ void * __weak module_alloc(unsigned long size)
> 			NUMA_NO_NODE, __builtin_return_address(0));
> }
> 
> +void * __weak module_alloc_huge(unsigned long size)
> +{
> +	return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
> +				    GFP_KERNEL, PAGE_KERNEL_EXEC,
> +				    VM_FLUSH_RESET_PERMS | VM_ALLOW_HUGE_VMAP,
> +				    NUMA_NO_NODE, __builtin_return_address(0));
> +}
> +
> bool __weak module_init_section(const char *name)
> {
> 	return strstarts(name, ".init");
> -- 
> 2.30.2
>