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SubjectRe: [PATCH] RISC-V: Load modules within relative jump range of the kernel text.
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On Sun, 22 Apr 2018 05:53:56 PDT (-0700), shea@shealevy.com wrote:
> Hi Palmer,
>
> Shea Levy <shea@shealevy.com> writes:
>
>> Signed-off-by: Shea Levy <shea@shealevy.com>
>> ---
>>
>> Note that this patch worked in my old modules patchset and seems to be
>> working now, but my kernel boot locks up on top of
>> riscv-for-linus-4.17-mw0 and I don't know if it's due to this patch or
>> something else that's changed in the mean time.
>>
>> ---
>> 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 5dddba301d0a..1b382c7de095 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)
>> {
>> @@ -382,3 +384,12 @@ 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));
>> +}
>> --
>> 2.16.2
>
> Any thoughts on this?

The concept looks good, but does this actually keep the modules within 2GiB of
the text if PAGE_OFFSET is large?

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