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

[Shea Levy]

Hi Palmer,

Palmer Dabbelt <palmer at sifive.com> writes:

> 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.

Thanks, I'll include this fix when I resolve the RISCV_ALIGN issue, and
see if it makes sense to make generic.
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