cregit-Linux how code gets into the kernel

Release 4.14 arch/nios2/kernel/module.c

/*
 * Kernel module support for Nios II.
 *
 * Copyright (C) 2004 Microtronix Datacom Ltd.
 *   Written by Wentao Xu <xuwentao@microtronix.com>
 * Copyright (C) 2001, 2003 Rusty Russell
 *
 * This file is subject to the terms and conditions of the GNU General
 * Public License.  See the file COPYING in the main directory of this
 * archive for more details.
 */

#include <linux/moduleloader.h>
#include <linux/elf.h>
#include <linux/mm.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/kernel.h>

#include <asm/pgtable.h>
#include <asm/cacheflush.h>

/*
 * Modules should NOT be allocated with kmalloc for (obvious) reasons.
 * But we do it for now to avoid relocation issues. CALL26/PCREL26 cannot reach
 * from 0x80000000 (vmalloc area) to 0xc00000000 (kernel) (kmalloc returns
 * addresses in 0xc0000000)
 */

void *module_alloc(unsigned long size) { if (size == 0) return NULL; return kmalloc(size, GFP_KERNEL); }

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/* Free memory returned from module_alloc */
void module_memfree(void *module_region) { kfree(module_region); }

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int apply_relocate_add(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex, unsigned int relsec, struct module *mod) { unsigned int i; Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr; pr_debug("Applying relocate section %u to %u\n", relsec, sechdrs[relsec].sh_info); for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) { /* This is where to make the change */ uint32_t word; uint32_t *loc = ((void *)sechdrs[sechdrs[relsec].sh_info].sh_addr + rela[i].r_offset); /* This is the symbol it is referring to. Note that all undefined symbols have been resolved. */ Elf32_Sym *sym = ((Elf32_Sym *)sechdrs[symindex].sh_addr + ELF32_R_SYM(rela[i].r_info)); uint32_t v = sym->st_value + rela[i].r_addend; pr_debug("reltype %d 0x%x name:<%s>\n", ELF32_R_TYPE(rela[i].r_info), rela[i].r_offset, strtab + sym->st_name); switch (ELF32_R_TYPE(rela[i].r_info)) { case R_NIOS2_NONE: break; case R_NIOS2_BFD_RELOC_32: *loc += v; break; case R_NIOS2_PCREL16: v -= (uint32_t)loc + 4; if ((int32_t)v > 0x7fff || (int32_t)v < -(int32_t)0x8000) { pr_err("module %s: relocation overflow\n", mod->name); return -ENOEXEC; } word = *loc; *loc = ((((word >> 22) << 16) | (v & 0xffff)) << 6) | (word & 0x3f); break; case R_NIOS2_CALL26: if (v & 3) { pr_err("module %s: dangerous relocation\n", mod->name); return -ENOEXEC; } if ((v >> 28) != ((uint32_t)loc >> 28)) { pr_err("module %s: relocation overflow\n", mod->name); return -ENOEXEC; } *loc = (*loc & 0x3f) | ((v >> 2) << 6); break; case R_NIOS2_HI16: word = *loc; *loc = ((((word >> 22) << 16) | ((v >> 16) & 0xffff)) << 6) | (word & 0x3f); break; case R_NIOS2_LO16: word = *loc; *loc = ((((word >> 22) << 16) | (v & 0xffff)) << 6) | (word & 0x3f); break; case R_NIOS2_HIADJ16: { Elf32_Addr word2; word = *loc; word2 = ((v >> 16) + ((v >> 15) & 1)) & 0xffff; *loc = ((((word >> 22) << 16) | word2) << 6) | (word & 0x3f); } break; default: pr_err("module %s: Unknown reloc: %u\n", mod->name, ELF32_R_TYPE(rela[i].r_info)); return -ENOEXEC; } } return 0; }

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int module_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs, struct module *me) { flush_cache_all(); return 0; }

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