riscv: avoid the PIC offset of static percpu data in module beyond 2G limits
The compiler uses the PIC-relative method to access static variables instead of GOT when the code model is PIC. Therefore, the limitation of the access range from the instruction to the symbol address is +-2GB. Under this circumstance, the kernel cannot load a kernel module if this module has static per-CPU symbols declared by DEFINE_PER_CPU(). The reason is that kernel relocates the .data..percpu section of the kernel module to the end of kernel's .data..percpu. Hence, the distance between the per-CPU symbols and the instruction will exceed the 2GB limits. To solve this problem, the kernel should place the loaded module in the memory area [&_end-2G, VMALLOC_END]. Signed-off-by: Vincent Chen <vincent.chen@sifive.com> Suggested-by: Alexandre Ghiti <alex@ghiti.fr> Suggested-by: Anup Patel <anup@brainfault.org> Tested-by: Alexandre Ghiti <alex@ghiti.fr> Tested-by: Carlos de Paula <me@carlosedp.com> Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
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@ -8,6 +8,10 @@
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#include <linux/err.h>
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#include <linux/errno.h>
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#include <linux/moduleloader.h>
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#include <linux/vmalloc.h>
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#include <linux/sizes.h>
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#include <asm/pgtable.h>
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#include <asm/sections.h>
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static int apply_r_riscv_32_rela(struct module *me, u32 *location, Elf_Addr v)
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{
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@ -386,3 +390,15 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
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return 0;
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}
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#if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
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#define VMALLOC_MODULE_START \
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max(PFN_ALIGN((unsigned long)&_end - SZ_2G), VMALLOC_START)
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void *module_alloc(unsigned long size)
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{
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return __vmalloc_node_range(size, 1, VMALLOC_MODULE_START,
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VMALLOC_END, GFP_KERNEL,
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PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
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__builtin_return_address(0));
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}
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#endif
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