[PATCH 2/9] RISC-V: Load modules within relative jump range of the kernel text.

[Palmer Dabbelt]

On Thu, 22 Feb 2018 19:12:11 PST (-0800), shea at shealevy.com wrote:
> Signed-off-by: Shea Levy <shea at shealevy.com>
> ---
>  arch/riscv/include/asm/pgtable.h |  9 +++++++++
>  arch/riscv/kernel/module.c       | 11 +++++++++++
>  2 files changed, 20 insertions(+)
>
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 16301966d65b..b08ded13364a 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -25,6 +25,7 @@
>  #include <asm/page.h>
>  #include <asm/tlbflush.h>
>  #include <linux/mm_types.h>
> +#include <linux/sizes.h>
>
>  #ifdef CONFIG_64BIT
>  #include <asm/pgtable-64.h>
> @@ -425,6 +426,14 @@ static inline void pgtable_cache_init(void)
>  #define TASK_SIZE VMALLOC_START
>  #endif
>
> +/*
> + * The module space lives between the addresses given by TASK_SIZE
> + * and PAGE_OFFSET - it must be within 2G of the kernel text.
> + */
> +#define MODULES_SIZE		(SZ_128M)
> +#define MODULES_VADDR		(PAGE_OFFSET - MODULES_SIZE)
> +#define MODULES_END		(VMALLOC_END)
> +
>  #include <asm-generic/pgtable.h>
>
>  #endif /* !__ASSEMBLY__ */
> diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
> index e0f05034fc21..8ad24bdf69de 100644
> --- a/arch/riscv/kernel/module.c
> +++ b/arch/riscv/kernel/module.c
> @@ -16,6 +16,8 @@
>  #include <linux/err.h>
>  #include <linux/errno.h>
>  #include <linux/moduleloader.h>
> +#include <linux/vmalloc.h>
> +#include <asm/pgtable.h>
>
>  static int apply_r_riscv_64_rela(struct module *me, u32 *location, Elf_Addr v)
>  {
> @@ -215,3 +217,12 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
>
>  	return 0;
>  }
> +
> +void *module_alloc(unsigned long size)
> +{
> +	return __vmalloc_node_range(size, 1, MODULES_VADDR,
> +				    MODULES_END, GFP_KERNEL,
> +				    PAGE_KERNEL_EXEC, 0,
> +				    NUMA_NO_NODE,
> +				    __builtin_return_address(0));
> +}

arm64 aligns their modules to a page boundary.  I think we need to align them 
to at least whatever the linker is expecting, which should be recorded in each 
segment in the ELF that's provided.

This code otherwise looks exactly teh same as MIPS, maybe we should make it 
generic somewhere?  It's not that much, though, but it looks like it'll get 
bigger as things support KASLR and such.