/* * linux/arch/arm/mm/mmu.c * * Copyright (C) 1995-2005 Russell King * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "mm.h" #include "tcm.h" /* * empty_zero_page is a special page that is used for * zero-initialized data and COW. */ struct page *empty_zero_page; EXPORT_SYMBOL(empty_zero_page); /* * The pmd table for the upper-most set of pages. */ pmd_t *top_pmd; pmdval_t user_pmd_table = _PAGE_USER_TABLE; #define CPOLICY_UNCACHED 0 #define CPOLICY_BUFFERED 1 #define CPOLICY_WRITETHROUGH 2 #define CPOLICY_WRITEBACK 3 #define CPOLICY_WRITEALLOC 4 static unsigned int cachepolicy __initdata = CPOLICY_WRITEBACK; static unsigned int ecc_mask __initdata = 0; pgprot_t pgprot_user; pgprot_t pgprot_kernel; pgprot_t pgprot_hyp_device; pgprot_t pgprot_s2; pgprot_t pgprot_s2_device; EXPORT_SYMBOL(pgprot_user); EXPORT_SYMBOL(pgprot_kernel); struct cachepolicy { const char policy[16]; unsigned int cr_mask; pmdval_t pmd; pteval_t pte; pteval_t pte_s2; }; #ifdef CONFIG_ARM_LPAE #define s2_policy(policy) policy #else #define s2_policy(policy) 0 #endif static struct cachepolicy cache_policies[] __initdata = { { .policy = "uncached", .cr_mask = CR_W|CR_C, .pmd = PMD_SECT_UNCACHED, .pte = L_PTE_MT_UNCACHED, .pte_s2 = s2_policy(L_PTE_S2_MT_UNCACHED), }, { .policy = "buffered", .cr_mask = CR_C, .pmd = PMD_SECT_BUFFERED, .pte = L_PTE_MT_BUFFERABLE, .pte_s2 = s2_policy(L_PTE_S2_MT_UNCACHED), }, { .policy = "writethrough", .cr_mask = 0, .pmd = PMD_SECT_WT, .pte = L_PTE_MT_WRITETHROUGH, .pte_s2 = s2_policy(L_PTE_S2_MT_WRITETHROUGH), }, { .policy = "writeback", .cr_mask = 0, .pmd = PMD_SECT_WB, .pte = L_PTE_MT_WRITEBACK, .pte_s2 = s2_policy(L_PTE_S2_MT_WRITEBACK), }, { .policy = "writealloc", .cr_mask = 0, .pmd = PMD_SECT_WBWA, .pte = L_PTE_MT_WRITEALLOC, .pte_s2 = s2_policy(L_PTE_S2_MT_WRITEBACK), } }; #ifdef CONFIG_CPU_CP15 static unsigned long initial_pmd_value __initdata = 0; /* * Initialise the cache_policy variable with the initial state specified * via the "pmd" value. This is used to ensure that on ARMv6 and later, * the C code sets the page tables up with the same policy as the head * assembly code, which avoids an illegal state where the TLBs can get * confused. See comments in early_cachepolicy() for more information. */ void __init init_default_cache_policy(unsigned long pmd) { int i; initial_pmd_value = pmd; pmd &= PMD_SECT_TEX(1) | PMD_SECT_BUFFERABLE | PMD_SECT_CACHEABLE; for (i = 0; i < ARRAY_SIZE(cache_policies); i++) if (cache_policies[i].pmd == pmd) { cachepolicy = i; break; } if (i == ARRAY_SIZE(cache_policies)) pr_err("ERROR: could not find cache policy\n"); } /* * These are useful for identifying cache coherency problems by allowing * the cache or the cache and writebuffer to be turned off. (Note: the * write buffer should not be on and the cache off). */ static int __init early_cachepolicy(char *p) { int i, selected = -1; for (i = 0; i < ARRAY_SIZE(cache_policies); i++) { int len = strlen(cache_policies[i].policy); if (memcmp(p, cache_policies[i].policy, len) == 0) { selected = i; break; } } if (selected == -1) pr_err("ERROR: unknown or unsupported cache policy\n"); /* * This restriction is partly to do with the way we boot; it is * unpredictable to have memory mapped using two different sets of * memory attributes (shared, type, and cache attribs). We can not * change these attributes once the initial assembly has setup the * page tables. */ if (cpu_architecture() >= CPU_ARCH_ARMv6 && selected != cachepolicy) { pr_warn("Only cachepolicy=%s supported on ARMv6 and later\n", cache_policies[cachepolicy].policy); return 0; } if (selected != cachepolicy) { unsigned long cr = __clear_cr(cache_policies[selected].cr_mask); cachepolicy = selected; flush_cache_all(); set_cr(cr); } return 0; } early_param("cachepolicy", early_cachepolicy); static int __init early_nocache(char *__unused) { char *p = "buffered"; pr_warn("nocache is deprecated; use cachepolicy=%s\n", p); early_cachepolicy(p); return 0; } early_param("nocache", early_nocache); static int __init early_nowrite(char *__unused) { char *p = "uncached"; pr_warn("nowb is deprecated; use cachepolicy=%s\n", p); early_cachepolicy(p); return 0; } early_param("nowb", early_nowrite); #ifndef CONFIG_ARM_LPAE static int __init early_ecc(char *p) { if (memcmp(p, "on", 2) == 0) ecc_mask = PMD_PROTECTION; else if (memcmp(p, "off", 3) == 0) ecc_mask = 0; return 0; } early_param("ecc", early_ecc); #endif #else /* ifdef CONFIG_CPU_CP15 */ static int __init early_cachepolicy(char *p) { pr_warn("cachepolicy kernel parameter not supported without cp15\n"); } early_param("cachepolicy", early_cachepolicy); static int __init noalign_setup(char *__unused) { pr_warn("noalign kernel parameter not supported without cp15\n"); } __setup("noalign", noalign_setup); #endif /* ifdef CONFIG_CPU_CP15 / else */ #define PROT_PTE_DEVICE L_PTE_PRESENT|L_PTE_YOUNG|L_PTE_DIRTY|L_PTE_XN #define PROT_PTE_S2_DEVICE PROT_PTE_DEVICE #define PROT_SECT_DEVICE PMD_TYPE_SECT|PMD_SECT_AP_WRITE static struct mem_type mem_types[] = { [MT_DEVICE] = { /* Strongly ordered / ARMv6 shared device */ .prot_pte = PROT_PTE_DEVICE | L_PTE_MT_DEV_SHARED | L_PTE_SHARED, .prot_pte_s2 = s2_policy(PROT_PTE_S2_DEVICE) | s2_policy(L_PTE_S2_MT_DEV_SHARED) | L_PTE_SHARED, .prot_l1 = PMD_TYPE_TABLE, .prot_sect = PROT_SECT_DEVICE | PMD_SECT_S, .domain = DOMAIN_IO, }, [MT_DEVICE_NONSHARED] = { /* ARMv6 non-shared device */ .prot_pte = PROT_PTE_DEVICE | L_PTE_MT_DEV_NONSHARED, .prot_l1 = PMD_TYPE_TABLE, .prot_sect = PROT_SECT_DEVICE, .domain = DOMAIN_IO, }, [MT_DEVICE_CACHED] = { /* ioremap_cached */ .prot_pte = PROT_PTE_DEVICE | L_PTE_MT_DEV_CACHED, .prot_l1 = PMD_TYPE_TABLE, .prot_sect = PROT_SECT_DEVICE | PMD_SECT_WB, .domain = DOMAIN_IO, }, [MT_DEVICE_WC] = { /* ioremap_wc */ .prot_pte = PROT_PTE_DEVICE | L_PTE_MT_DEV_WC, .prot_l1 = PMD_TYPE_TABLE, .prot_sect = PROT_SECT_DEVICE, .domain = DOMAIN_IO, }, [MT_UNCACHED] = { .prot_pte = PROT_PTE_DEVICE, .prot_l1 = PMD_TYPE_TABLE, .prot_sect = PMD_TYPE_SECT | PMD_SECT_XN, .domain = DOMAIN_IO, }, [MT_CACHECLEAN] = { .prot_sect = PMD_TYPE_SECT | PMD_SECT_XN, .domain = DOMAIN_KERNEL, }, #ifndef CONFIG_ARM_LPAE [MT_MINICLEAN] = { .prot_sect = PMD_TYPE_SECT | PMD_SECT_XN | PMD_SECT_MINICACHE, .domain = DOMAIN_KERNEL, }, #endif [MT_LOW_VECTORS] = { .prot_pte = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY | L_PTE_RDONLY, .prot_l1 = PMD_TYPE_TABLE, .domain = DOMAIN_USER, }, [MT_HIGH_VECTORS] = { .prot_pte = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY | L_PTE_USER | L_PTE_RDONLY, .prot_l1 = PMD_TYPE_TABLE, .domain = DOMAIN_USER, }, [MT_MEMORY_RWX] = { .prot_pte = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY, .prot_l1 = PMD_TYPE_TABLE, .prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE, .domain = DOMAIN_KERNEL, }, [MT_MEMORY_RW] = { .prot_pte = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY | L_PTE_XN, .prot_l1 = PMD_TYPE_TABLE, .prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE, .domain = DOMAIN_KERNEL, }, [MT_ROM] = { .prot_sect = PMD_TYPE_SECT, .domain = DOMAIN_KERNEL, }, [MT_MEMORY_RWX_NONCACHED] = { .prot_pte = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY | L_PTE_MT_BUFFERABLE, .prot_l1 = PMD_TYPE_TABLE, .prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE, .domain = DOMAIN_KERNEL, }, [MT_MEMORY_RW_DTCM] = { .prot_pte = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY | L_PTE_XN, .prot_l1 = PMD_TYPE_TABLE, .prot_sect = PMD_TYPE_SECT | PMD_SECT_XN, .domain = DOMAIN_KERNEL, }, [MT_MEMORY_RWX_ITCM] = { .prot_pte = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY, .prot_l1 = PMD_TYPE_TABLE, .domain = DOMAIN_KERNEL, }, [MT_MEMORY_RW_SO] = { .prot_pte = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY | L_PTE_MT_UNCACHED | L_PTE_XN, .prot_l1 = PMD_TYPE_TABLE, .prot_sect = PMD_TYPE_SECT | PMD_SECT_AP_WRITE | PMD_SECT_S | PMD_SECT_UNCACHED | PMD_SECT_XN, .domain = DOMAIN_KERNEL, }, [MT_MEMORY_DMA_READY] = { .prot_pte = L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY | L_PTE_XN, .prot_l1 = PMD_TYPE_TABLE, .domain = DOMAIN_KERNEL, }, }; const struct mem_type *get_mem_type(unsigned int type) { return type < ARRAY_SIZE(mem_types) ? &mem_types[type] : NULL; } EXPORT_SYMBOL(get_mem_type); /* * To avoid TLB flush broadcasts, this uses local_flush_tlb_kernel_range(). * As a result, this can only be called with preemption disabled, as under * stop_machine(). */ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot) { unsigned long vaddr = __fix_to_virt(idx); pte_t *pte = pte_offset_kernel(pmd_off_k(vaddr), vaddr); /* Make sure fixmap region does not exceed available allocation. */ BUILD_BUG_ON(FIXADDR_START + (__end_of_fixed_addresses * PAGE_SIZE) > FIXADDR_END); BUG_ON(idx >= __end_of_fixed_addresses); if (pgprot_val(prot)) set_pte_at(NULL, vaddr, pte, pfn_pte(phys >> PAGE_SHIFT, prot)); else pte_clear(NULL, vaddr, pte); local_flush_tlb_kernel_range(vaddr, vaddr + PAGE_SIZE); } /* * Adjust the PMD section entries according to the CPU in use. */ static void __init build_mem_type_table(void) { struct cachepolicy *cp; unsigned int cr = get_cr(); pteval_t user_pgprot, kern_pgprot, vecs_pgprot; pteval_t hyp_device_pgprot, s2_pgprot, s2_device_pgprot; int cpu_arch = cpu_architecture(); int i; if (cpu_arch < CPU_ARCH_ARMv6) { #if defined(CONFIG_CPU_DCACHE_DISABLE) if (cachepolicy > CPOLICY_BUFFERED) cachepolicy = CPOLICY_BUFFERED; #elif defined(CONFIG_CPU_DCACHE_WRITETHROUGH) if (cachepolicy > CPOLICY_WRITETHROUGH) cachepolicy = CPOLICY_WRITETHROUGH; #endif } if (cpu_arch < CPU_ARCH_ARMv5) { if (cachepolicy >= CPOLICY_WRITEALLOC) cachepolicy = CPOLICY_WRITEBACK; ecc_mask = 0; } if (is_smp()) { if (cachepolicy != CPOLICY_WRITEALLOC) { pr_warn("Forcing write-allocate cache policy for SMP\n"); cachepolicy = CPOLICY_WRITEALLOC; } if (!(initial_pmd_value & PMD_SECT_S)) { pr_warn("Forcing shared mappings for SMP\n"); initial_pmd_value |= PMD_SECT_S; } } /* * Strip out features not present on earlier architectures. * Pre-ARMv5 CPUs don't have TEX bits. Pre-ARMv6 CPUs or those * without extended page tables don't have the 'Shared' bit. */ if (cpu_arch < CPU_ARCH_ARMv5) for (i = 0; i < ARRAY_SIZE(mem_types); i++) mem_types[i].prot_sect &= ~PMD_SECT_TEX(7); if ((cpu_arch < CPU_ARCH_ARMv6 || !(cr & CR_XP)) && !cpu_is_xsc3()) for (i = 0; i < ARRAY_SIZE(mem_types); i++) mem_types[i].prot_sect &= ~PMD_SECT_S; /* * ARMv5 and lower, bit 4 must be set for page tables (was: cache * "update-able on write" bit on ARM610). However, Xscale and * Xscale3 require this bit to be cleared. */ if (cpu_is_xscale() || cpu_is_xsc3()) { for (i = 0; i < ARRAY_SIZE(mem_types); i++) { mem_types[i].prot_sect &= ~PMD_BIT4; mem_types[i].prot_l1 &= ~PMD_BIT4; } } else if (cpu_arch < CPU_ARCH_ARMv6) { for (i = 0; i < ARRAY_SIZE(mem_types); i++) { if (mem_types[i].prot_l1) mem_types[i].prot_l1 |= PMD_BIT4; if (mem_types[i].prot_sect) mem_types[i].prot_sect |= PMD_BIT4; } } /* * Mark the device areas according to the CPU/architecture. */ if (cpu_is_xsc3() || (cpu_arch >= CPU_ARCH_ARMv6 && (cr & CR_XP))) { if (!cpu_is_xsc3()) { /* * Mark device regions on ARMv6+ as execute-never * to prevent speculative instruction fetches. */ mem_types[MT_DEVICE].prot_sect |= PMD_SECT_XN; mem_types[MT_DEVICE_NONSHARED].prot_sect |= PMD_SECT_XN; mem_types[MT_DEVICE_CACHED].prot_sect |= PMD_SECT_XN; mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_XN; /* Also setup NX memory mapping */ mem_types[MT_MEMORY_RW].prot_sect |= PMD_SECT_XN; } if (cpu_arch >= CPU_ARCH_ARMv7 && (cr & CR_TRE)) { /* * For ARMv7 with TEX remapping, * - shared device is SXCB=1100 * - nonshared device is SXCB=0100 * - write combine device mem is SXCB=0001 * (Uncached Normal memory) */ mem_types[MT_DEVICE].prot_sect |= PMD_SECT_TEX(1); mem_types[MT_DEVICE_NONSHARED].prot_sect |= PMD_SECT_TEX(1); mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_BUFFERABLE; } else if (cpu_is_xsc3()) { /* * For Xscale3, * - shared device is TEXCB=00101 * - nonshared device is TEXCB=01000 * - write combine device mem is TEXCB=00100 * (Inner/Outer Uncacheable in xsc3 parlance) */ mem_types[MT_DEVICE].prot_sect |= PMD_SECT_TEX(1) | PMD_SECT_BUFFERED; mem_types[MT_DEVICE_NONSHARED].prot_sect |= PMD_SECT_TEX(2); mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_TEX(1); } else { /* * For ARMv6 and ARMv7 without TEX remapping, * - shared device is TEXCB=00001 * - nonshared device is TEXCB=01000 * - write combine device mem is TEXCB=00100 * (Uncached Normal in ARMv6 parlance). */ mem_types[MT_DEVICE].prot_sect |= PMD_SECT_BUFFERED; mem_types[MT_DEVICE_NONSHARED].prot_sect |= PMD_SECT_TEX(2); mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_TEX(1); } } else { /* * On others, write combining is "Uncached/Buffered" */ mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_BUFFERABLE; } /* * Now deal with the memory-type mappings */ cp = &cache_policies[cachepolicy]; vecs_pgprot = kern_pgprot = user_pgprot = cp->pte; s2_pgprot = cp->pte_s2; hyp_device_pgprot = mem_types[MT_DEVICE].prot_pte; s2_device_pgprot = mem_types[MT_DEVICE].prot_pte_s2; #ifndef CONFIG_ARM_LPAE /* * We don't use domains on ARMv6 (since this causes problems with * v6/v7 kernels), so we must use a separate memory type for user * r/o, kernel r/w to map the vectors page. */ if (cpu_arch == CPU_ARCH_ARMv6) vecs_pgprot |= L_PTE_MT_VECTORS; /* * Check is it with support for the PXN bit * in the Short-descriptor translation table format descriptors. */ if (cpu_arch == CPU_ARCH_ARMv7 && (read_cpuid_ext(CPUID_EXT_MMFR0) & 0xF) == 4) { user_pmd_table |= PMD_PXNTABLE; } #endif /* * ARMv6 and above have extended page tables. */ if (cpu_arch >= CPU_ARCH_ARMv6 && (cr & CR_XP)) { #ifndef CONFIG_ARM_LPAE /* * Mark cache clean areas and XIP ROM read only * from SVC mode and no access from userspace. */ mem_types[MT_ROM].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE; mem_types[MT_MINICLEAN].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE; mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_APX|PMD_SECT_AP_WRITE; #endif /* * If the initial page tables were created with the S bit * set, then we need to do the same here for the same * reasons given in early_cachepolicy(). */ if (initial_pmd_value & PMD_SECT_S) { user_pgprot |= L_PTE_SHARED; kern_pgprot |= L_PTE_SHARED; vecs_pgprot |= L_PTE_SHARED; s2_pgprot |= L_PTE_SHARED; mem_types[MT_DEVICE_WC].prot_sect |= PMD_SECT_S; mem_types[MT_DEVICE_WC].prot_pte |= L_PTE_SHARED; mem_types[MT_DEVICE_CACHED].prot_sect |= PMD_SECT_S; mem_types[MT_DEVICE_CACHED].prot_pte |= L_PTE_SHARED; mem_types[MT_MEMORY_RWX].prot_sect |= PMD_SECT_S; mem_types[MT_MEMORY_RWX].prot_pte |= L_PTE_SHARED; mem_types[MT_MEMORY_RW].prot_sect |= PMD_SECT_S; mem_types[MT_MEMORY_RW].prot_pte |= L_PTE_SHARED; mem_types[MT_MEMORY_DMA_READY].prot_pte |= L_PTE_SHARED; mem_types[MT_MEMORY_RWX_NONCACHED].prot_sect |= PMD_SECT_S; mem_types[MT_MEMORY_RWX_NONCACHED].prot_pte |= L_PTE_SHARED; } } /* * Non-cacheable Normal - intended for memory areas that must * not cause dirty cache line writebacks when used */ if (cpu_arch >= CPU_ARCH_ARMv6) { if (cpu_arch >= CPU_ARCH_ARMv7 && (cr & CR_TRE)) { /* Non-cacheable Normal is XCB = 001 */ mem_types[MT_MEMORY_RWX_NONCACHED].prot_sect |= PMD_SECT_BUFFERED; } else { /* For both ARMv6 and non-TEX-remapping ARMv7 */ mem_types[MT_MEMORY_RWX_NONCACHED].prot_sect |= PMD_SECT_TEX(1); } } else { mem_types[MT_MEMORY_RWX_NONCACHED].prot_sect |= PMD_SECT_BUFFERABLE; } #ifdef CONFIG_ARM_LPAE /* * Do not generate access flag faults for the kernel mappings. */ for (i = 0; i < ARRAY_SIZE(mem_types); i++) { mem_types[i].prot_pte |= PTE_EXT_AF; if (mem_types[i].prot_sect) mem_types[i].prot_sect |= PMD_SECT_AF; } kern_pgprot |= PTE_EXT_AF; vecs_pgprot |= PTE_EXT_AF; /* * Set PXN for user mappings */ user_pgprot |= PTE_EXT_PXN; #endif for (i = 0; i < 16; i++) { pteval_t v = pgprot_val(protection_map[i]); protection_map[i] = __pgprot(v | user_pgprot); } mem_types[MT_LOW_VECTORS].prot_pte |= vecs_pgprot; mem_types[MT_HIGH_VECTORS].prot_pte |= vecs_pgprot; pgprot_user = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | user_pgprot); pgprot_kernel = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | L_PTE_DIRTY | kern_pgprot); pgprot_s2 = __pgprot(L_PTE_PRESENT | L_PTE_YOUNG | s2_pgprot); pgprot_s2_device = __pgprot(s2_device_pgprot); pgprot_hyp_device = __pgprot(hyp_device_pgprot); mem_types[MT_LOW_VECTORS].prot_l1 |= ecc_mask; mem_types[MT_HIGH_VECTORS].prot_l1 |= ecc_mask; mem_types[MT_MEMORY_RWX].prot_sect |= ecc_mask | cp->pmd; mem_types[MT_MEMORY_RWX].prot_pte |= kern_pgprot; mem_types[MT_MEMORY_RW].prot_sect |= ecc_mask | cp->pmd; mem_types[MT_MEMORY_RW].prot_pte |= kern_pgprot; mem_types[MT_MEMORY_DMA_READY].prot_pte |= kern_pgprot; mem_types[MT_MEMORY_RWX_NONCACHED].prot_sect |= ecc_mask; mem_types[MT_ROM].prot_sect |= cp->pmd; switch (cp->pmd) { case PMD_SECT_WT: mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_WT; break; case PMD_SECT_WB: case PMD_SECT_WBWA: mem_types[MT_CACHECLEAN].prot_sect |= PMD_SECT_WB; break; } pr_info("Memory policy: %sData cache %s\n", ecc_mask ? "ECC enabled, " : "", cp->policy); for (i = 0; i < ARRAY_SIZE(mem_types); i++) { struct mem_type *t = &mem_types[i]; if (t->prot_l1) t->prot_l1 |= PMD_DOMAIN(t->domain); if (t->prot_sect) t->prot_sect |= PMD_DOMAIN(t->domain); } } #ifdef CONFIG_ARM_DMA_MEM_BUFFERABLE pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn, unsigned long size, pgprot_t vma_prot) { if (!pfn_valid(pfn)) return pgprot_noncached(vma_prot); else if (file->f_flags & O_SYNC) return pgprot_writecombine(vma_prot); return vma_prot; } EXPORT_SYMBOL(phys_mem_access_prot); #endif #define vectors_base() (vectors_high() ? 0xffff0000 : 0) static void __init *early_alloc_aligned(unsigned long sz, unsigned long align) { void *ptr = __va(memblock_alloc(sz, align)); memset(ptr, 0, sz); return ptr; } static void __init *early_alloc(unsigned long sz) { return early_alloc_aligned(sz, sz); } static pte_t * __init early_pte_alloc(pmd_t *pmd, unsigned long addr, unsigned long prot) { if (pmd_none(*pmd)) { pte_t *pte = early_alloc(PTE_HWTABLE_OFF + PTE_HWTABLE_SIZE); __pmd_populate(pmd, __pa(pte), prot); } BUG_ON(pmd_bad(*pmd)); return pte_offset_kernel(pmd, addr); } static void __init alloc_init_pte(pmd_t *pmd, unsigned long addr, unsigned long end, unsigned long pfn, const struct mem_type *type) { pte_t *pte = early_pte_alloc(pmd, addr, type->prot_l1); do { set_pte_ext(pte, pfn_pte(pfn, __pgprot(type->prot_pte)), 0); pfn++; } while (pte++, addr += PAGE_SIZE, addr != end); } static void __init __map_init_section(pmd_t *pmd, unsigned long addr, unsigned long end, phys_addr_t phys, const struct mem_type *type) { pmd_t *p = pmd; #ifndef CONFIG_ARM_LPAE /* * In classic MMU format, puds and pmds are folded in to * the pgds. pmd_offset gives the PGD entry. PGDs refer to a * group of L1 entries making up one logical pointer to * an L2 table (2MB), where as PMDs refer to the individual * L1 entries (1MB). Hence increment to get the correct * offset for odd 1MB sections. * (See arch/arm/include/asm/pgtable-2level.h) */ if (addr & SECTION_SIZE) pmd++; #endif do { *pmd = __pmd(phys | type->prot_sect); phys += SECTION_SIZE; } while (pmd++, addr += SECTION_SIZE, addr != end); flush_pmd_entry(p); } static void __init alloc_init_pmd(pud_t *pud, unsigned long addr, unsigned long end, phys_addr_t phys, const struct mem_type *type) { pmd_t *pmd = pmd_offset(pud, addr); unsigned long next; do { /* * With LPAE, we must loop over to map * all the pmds for the given range. */ next = pmd_addr_end(addr, end); /* * Try a section mapping - addr, next and phys must all be * aligned to a section boundary. */ if (type->prot_sect && ((addr | next | phys) & ~SECTION_MASK) == 0) { __map_init_section(pmd, addr, next, phys, type); } else { alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys), type); } phys += next - addr; } while (pmd++, addr = next, addr != end); } static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr, unsigned long end, phys_addr_t phys, const struct mem_type *type) { pud_t *pud = pud_offset(pgd, addr); unsigned long next; do { next = pud_addr_end(addr, end); alloc_init_pmd(pud, addr, next, phys, type); phys += next - addr; } while (pud++, addr = next, addr != end); } #ifndef CONFIG_ARM_LPAE static void __init create_36bit_mapping(struct map_desc *md, const struct mem_type *type) { unsigned long addr, length, end; phys_addr_t phys; pgd_t *pgd; addr = md->virtual; phys = __pfn_to_phys(md->pfn); length = PAGE_ALIGN(md->length); if (!(cpu_architecture() >= CPU_ARCH_ARMv6 || cpu_is_xsc3())) { pr_err("MM: CPU does not support supersection mapping for 0x%08llx at 0x%08lx\n", (long long)__pfn_to_phys((u64)md->pfn), addr); return; } /* N.B. ARMv6 supersections are only defined to work with domain 0. * Since domain assignments can in fact be arbitrary, the * 'domain == 0' check below is required to insure that ARMv6 * supersections are only allocated for domain 0 regardless * of the actual domain assignments in use. */ if (type->domain) { pr_err("MM: invalid domain in supersection mapping for 0x%08llx at 0x%08lx\n", (long long)__pfn_to_phys((u64)md->pfn), addr); return; } if ((addr | length | __pfn_to_phys(md->pfn)) & ~SUPERSECTION_MASK) { pr_err("MM: cannot create mapping for 0x%08llx at 0x%08lx invalid alignment\n", (long long)__pfn_to_phys((u64)md->pfn), addr); return; } /* * Shift bits [35:32] of address into bits [23:20] of PMD * (See ARMv6 spec). */ phys |= (((md->pfn >> (32 - PAGE_SHIFT)) & 0xF) << 20); pgd = pgd_offset_k(addr); end = addr + length; do { pud_t *pud = pud_offset(pgd, addr); pmd_t *pmd = pmd_offset(pud, addr); int i; for (i = 0; i < 16; i++) *pmd++ = __pmd(phys | type->prot_sect | PMD_SECT_SUPER); addr += SUPERSECTION_SIZE; phys += SUPERSECTION_SIZE; pgd += SUPERSECTION_SIZE >> PGDIR_SHIFT; } while (addr != end); } #endif /* !CONFIG_ARM_LPAE */ /* * Create the page directory entries and any necessary * page tables for the mapping specified by `md'. We * are able to cope here with varying sizes and address * offsets, and we take full advantage of sections and * supersections. */ static void __init create_mapping(struct map_desc *md) { unsigned long addr, length, end; phys_addr_t phys; const struct mem_type *type; pgd_t *pgd; if (md->virtual != vectors_base() && md->virtual < TASK_SIZE) { pr_warn("BUG: not creating mapping for 0x%08llx at 0x%08lx in user region\n", (long long)__pfn_to_phys((u64)md->pfn), md->virtual); return; } if ((md->type == MT_DEVICE || md->type == MT_ROM) && md->virtual >= PAGE_OFFSET && (md->virtual < VMALLOC_START || md->virtual >= VMALLOC_END)) { pr_warn("BUG: mapping for 0x%08llx at 0x%08lx out of vmalloc space\n", (long long)__pfn_to_phys((u64)md->pfn), md->virtual); } type = &mem_types[md->type]; #ifndef CONFIG_ARM_LPAE /* * Catch 36-bit addresses */ if (md->pfn >= 0x100000) { create_36bit_mapping(md, type); return; } #endif addr = md->virtual & PAGE_MASK; phys = __pfn_to_phys(md->pfn); length = PAGE_ALIGN(md->length + (md->virtual & ~PAGE_MASK)); if (type->prot_l1 == 0 && ((addr | phys | length) & ~SECTION_MASK)) { pr_warn("BUG: map for 0x%08llx at 0x%08lx can not be mapped using pages, ignoring.\n", (long long)__pfn_to_phys(md->pfn), addr); return; } pgd = pgd_offset_k(addr); end = addr + length; do { unsigned long next = pgd_addr_end(addr, end); alloc_init_pud(pgd, addr, next, phys, type); phys += next - addr; addr = next; } while (pgd++, addr != end); } /* * Create the architecture specific mappings */ void __init iotable_init(struct map_desc *io_desc, int nr) { struct map_desc *md; struct vm_struct *vm; struct static_vm *svm; if (!nr) return; svm = early_alloc_aligned(sizeof(*svm) * nr, __alignof__(*svm)); for (md = io_desc; nr; md++, nr--) { create_mapping(md); vm = &svm->vm; vm->addr = (void *)(md->virtual & PAGE_MASK); vm->size = PAGE_ALIGN(md->length + (md->virtual & ~PAGE_MASK)); vm->phys_addr = __pfn_to_phys(md->pfn); vm->flags = VM_IOREMAP | VM_ARM_STATIC_MAPPING; vm->flags |= VM_ARM_MTYPE(md->type); vm->caller = iotable_init; add_static_vm_early(svm++); } } void __init vm_reserve_area_early(unsigned long addr, unsigned long size, void *caller) { struct vm_struct *vm; struct static_vm *svm; svm = early_alloc_aligned(sizeof(*svm), __alignof__(*svm)); vm = &svm->vm; vm->addr = (void *)addr; vm->size = size; vm->flags = VM_IOREMAP | VM_ARM_EMPTY_MAPPING; vm->caller = caller; add_static_vm_early(svm); } #ifndef CONFIG_ARM_LPAE /* * The Linux PMD is made of two consecutive section entries covering 2MB * (see definition in include/asm/pgtable-2level.h). However a call to * create_mapping() may optimize static mappings by using individual * 1MB section mappings. This leaves the actual PMD potentially half * initialized if the top or bottom section entry isn't used, leaving it * open to problems if a subsequent ioremap() or vmalloc() tries to use * the virtual space left free by that unused section entry. * * Let's avoid the issue by inserting dummy vm entries covering the unused * PMD halves once the static mappings are in place. */ static void __init pmd_empty_section_gap(unsigned long addr) { vm_reserve_area_early(addr, SECTION_SIZE, pmd_empty_section_gap); } static void __init fill_pmd_gaps(void) { struct static_vm *svm; struct vm_struct *vm; unsigned long addr, next = 0; pmd_t *pmd; list_for_each_entry(svm, &static_vmlist, list) { vm = &svm->vm; addr = (unsigned long)vm->addr; if (addr < next) continue; /* * Check if this vm starts on an odd section boundary. * If so and the first section entry for this PMD is free * then we block the corresponding virtual address. */ if ((addr & ~PMD_MASK) == SECTION_SIZE) { pmd = pmd_off_k(addr); if (pmd_none(*pmd)) pmd_empty_section_gap(addr & PMD_MASK); } /* * Then check if this vm ends on an odd section boundary. * If so and the second section entry for this PMD is empty * then we block the corresponding virtual address. */ addr += vm->size; if ((addr & ~PMD_MASK) == SECTION_SIZE) { pmd = pmd_off_k(addr) + 1; if (pmd_none(*pmd)) pmd_empty_section_gap(addr); } /* no need to look at any vm entry until we hit the next PMD */ next = (addr + PMD_SIZE - 1) & PMD_MASK; } } #else #define fill_pmd_gaps() do { } while (0) #endif #if defined(CONFIG_PCI) && !defined(CONFIG_NEED_MACH_IO_H) static void __init pci_reserve_io(void) { struct static_vm *svm; svm = find_static_vm_vaddr((void *)PCI_IO_VIRT_BASE); if (svm) return; vm_reserve_area_early(PCI_IO_VIRT_BASE, SZ_2M, pci_reserve_io); } #else #define pci_reserve_io() do { } while (0) #endif #ifdef CONFIG_DEBUG_LL void __init debug_ll_io_init(void) { struct map_desc map; debug_ll_addr(&map.pfn, &map.virtual); if (!map.pfn || !map.virtual) return; map.pfn = __phys_to_pfn(map.pfn); map.virtual &= PAGE_MASK; map.length = PAGE_SIZE; map.type = MT_DEVICE; iotable_init(&map, 1); } #endif static void * __initdata vmalloc_min = (void *)(VMALLOC_END - (240 << 20) - VMALLOC_OFFSET); /* * vmalloc=size forces the vmalloc area to be exactly 'size' * bytes. This can be used to increase (or decrease) the vmalloc * area - the default is 240m. */ static int __init early_vmalloc(char *arg) { unsigned long vmalloc_reserve = memparse(arg, NULL); if (vmalloc_reserve < SZ_16M) { vmalloc_reserve = SZ_16M; pr_warn("vmalloc area too small, limiting to %luMB\n", vmalloc_reserve >> 20); } if (vmalloc_reserve > VMALLOC_END - (PAGE_OFFSET + SZ_32M)) { vmalloc_reserve = VMALLOC_END - (PAGE_OFFSET + SZ_32M); pr_warn("vmalloc area is too big, limiting to %luMB\n", vmalloc_reserve >> 20); } vmalloc_min = (void *)(VMALLOC_END - vmalloc_reserve); return 0; } early_param("vmalloc", early_vmalloc); phys_addr_t arm_lowmem_limit __initdata = 0; void __init sanity_check_meminfo(void) { phys_addr_t memblock_limit = 0; int highmem = 0; phys_addr_t vmalloc_limit = __pa(vmalloc_min - 1) + 1; struct memblock_region *reg; for_each_memblock(memory, reg) { phys_addr_t block_start = reg->base; phys_addr_t block_end = reg->base + reg->size; phys_addr_t size_limit = reg->size; if (reg->base >= vmalloc_limit) highmem = 1; else size_limit = vmalloc_limit - reg->base; if (!IS_ENABLED(CONFIG_HIGHMEM) || cache_is_vipt_aliasing()) { if (highmem) { pr_notice("Ignoring RAM at %pa-%pa (!CONFIG_HIGHMEM)\n", &block_start, &block_end); memblock_remove(reg->base, reg->size); continue; } if (reg->size > size_limit) { phys_addr_t overlap_size = reg->size - size_limit; pr_notice("Truncating RAM at %pa-%pa to -%pa", &block_start, &block_end, &vmalloc_limit); memblock_remove(vmalloc_limit, overlap_size); block_end = vmalloc_limit; } } if (!highmem) { if (block_end > arm_lowmem_limit) { if (reg->size > size_limit) arm_lowmem_limit = vmalloc_limit; else arm_lowmem_limit = block_end; } /* * Find the first non-pmd-aligned page, and point * memblock_limit at it. This relies on rounding the * limit down to be pmd-aligned, which happens at the * end of this function. * * With this algorithm, the start or end of almost any * bank can be non-pmd-aligned. The only exception is * that the start of the bank 0 must be section- * aligned, since otherwise memory would need to be * allocated when mapping the start of bank 0, which * occurs before any free memory is mapped. */ if (!memblock_limit) { if (!IS_ALIGNED(block_start, PMD_SIZE)) memblock_limit = block_start; else if (!IS_ALIGNED(block_end, PMD_SIZE)) memblock_limit = arm_lowmem_limit; } } } high_memory = __va(arm_lowmem_limit - 1) + 1; /* * Round the memblock limit down to a pmd size. This * helps to ensure that we will allocate memory from the * last full pmd, which should be mapped. */ if (memblock_limit) memblock_limit = round_down(memblock_limit, PMD_SIZE); if (!memblock_limit) memblock_limit = arm_lowmem_limit; memblock_set_current_limit(memblock_limit); } static inline void prepare_page_table(void) { unsigned long addr; phys_addr_t end; /* * Clear out all the mappings below the kernel image. */ for (addr = 0; addr < MODULES_VADDR; addr += PMD_SIZE) pmd_clear(pmd_off_k(addr)); #ifdef CONFIG_XIP_KERNEL /* The XIP kernel is mapped in the module area -- skip over it */ addr = ((unsigned long)_etext + PMD_SIZE - 1) & PMD_MASK; #endif for ( ; addr < PAGE_OFFSET; addr += PMD_SIZE) pmd_clear(pmd_off_k(addr)); /* * Find the end of the first block of lowmem. */ end = memblock.memory.regions[0].base + memblock.memory.regions[0].size; if (end >= arm_lowmem_limit) end = arm_lowmem_limit; /* * Clear out all the kernel space mappings, except for the first * memory bank, up to the vmalloc region. */ for (addr = __phys_to_virt(end); addr < VMALLOC_START; addr += PMD_SIZE) pmd_clear(pmd_off_k(addr)); } #ifdef CONFIG_ARM_LPAE /* the first page is reserved for pgd */ #define SWAPPER_PG_DIR_SIZE (PAGE_SIZE + \ PTRS_PER_PGD * PTRS_PER_PMD * sizeof(pmd_t)) #else #define SWAPPER_PG_DIR_SIZE (PTRS_PER_PGD * sizeof(pgd_t)) #endif /* * Reserve the special regions of memory */ void __init arm_mm_memblock_reserve(void) { /* * Reserve the page tables. These are already in use, * and can only be in node 0. */ memblock_reserve(__pa(swapper_pg_dir), SWAPPER_PG_DIR_SIZE); #ifdef CONFIG_SA1111 /* * Because of the SA1111 DMA bug, we want to preserve our * precious DMA-able memory... */ memblock_reserve(PHYS_OFFSET, __pa(swapper_pg_dir) - PHYS_OFFSET); #endif } /* * Set up the device mappings. Since we clear out the page tables for all * mappings above VMALLOC_START, we will remove any debug device mappings. * This means you have to be careful how you debug this function, or any * called function. This means you can't use any function or debugging * method which may touch any device, otherwise the kernel _will_ crash. */ static void __init devicemaps_init(const struct machine_desc *mdesc) { struct map_desc map; unsigned long addr; void *vectors; /* * Allocate the vector page early. */ vectors = early_alloc(PAGE_SIZE * 2); early_trap_init(vectors); for (addr = VMALLOC_START; addr; addr += PMD_SIZE) pmd_clear(pmd_off_k(addr)); /* * Map the kernel if it is XIP. * It is always first in the modulearea. */ #ifdef CONFIG_XIP_KERNEL map.pfn = __phys_to_pfn(CONFIG_XIP_PHYS_ADDR & SECTION_MASK); map.virtual = MODULES_VADDR; map.length = ((unsigned long)_etext - map.virtual + ~SECTION_MASK) & SECTION_MASK; map.type = MT_ROM; create_mapping(&map); #endif /* * Map the cache flushing regions. */ #ifdef FLUSH_BASE map.pfn = __phys_to_pfn(FLUSH_BASE_PHYS); map.virtual = FLUSH_BASE; map.length = SZ_1M; map.type = MT_CACHECLEAN; create_mapping(&map); #endif #ifdef FLUSH_BASE_MINICACHE map.pfn = __phys_to_pfn(FLUSH_BASE_PHYS + SZ_1M); map.virtual = FLUSH_BASE_MINICACHE; map.length = SZ_1M; map.type = MT_MINICLEAN; create_mapping(&map); #endif /* * Create a mapping for the machine vectors at the high-vectors * location (0xffff0000). If we aren't using high-vectors, also * create a mapping at the low-vectors virtual address. */ map.pfn = __phys_to_pfn(virt_to_phys(vectors)); map.virtual = 0xffff0000; map.length = PAGE_SIZE; #ifdef CONFIG_KUSER_HELPERS map.type = MT_HIGH_VECTORS; #else map.type = MT_LOW_VECTORS; #endif create_mapping(&map); if (!vectors_high()) { map.virtual = 0; map.length = PAGE_SIZE * 2; map.type = MT_LOW_VECTORS; create_mapping(&map); } /* Now create a kernel read-only mapping */ map.pfn += 1; map.virtual = 0xffff0000 + PAGE_SIZE; map.length = PAGE_SIZE; map.type = MT_LOW_VECTORS; create_mapping(&map); /* * Ask the machine support to map in the statically mapped devices. */ if (mdesc->map_io) mdesc->map_io(); else debug_ll_io_init(); fill_pmd_gaps(); /* Reserve fixed i/o space in VMALLOC region */ pci_reserve_io(); /* * Finally flush the caches and tlb to ensure that we're in a * consistent state wrt the writebuffer. This also ensures that * any write-allocated cache lines in the vector page are written * back. After this point, we can start to touch devices again. */ local_flush_tlb_all(); flush_cache_all(); } static void __init kmap_init(void) { #ifdef CONFIG_HIGHMEM pkmap_page_table = early_pte_alloc(pmd_off_k(PKMAP_BASE), PKMAP_BASE, _PAGE_KERNEL_TABLE); #endif early_pte_alloc(pmd_off_k(FIXADDR_START), FIXADDR_START, _PAGE_KERNEL_TABLE); } static void __init map_lowmem(void) { struct memblock_region *reg; phys_addr_t kernel_x_start = round_down(__pa(_stext), SECTION_SIZE); phys_addr_t kernel_x_end = round_up(__pa(__init_end), SECTION_SIZE); /* Map all the lowmem memory banks. */ for_each_memblock(memory, reg) { phys_addr_t start = reg->base; phys_addr_t end = start + reg->size; struct map_desc map; if (end > arm_lowmem_limit) end = arm_lowmem_limit; if (start >= end) break; if (end < kernel_x_start) { map.pfn = __phys_to_pfn(start); map.virtual = __phys_to_virt(start); map.length = end - start; map.type = MT_MEMORY_RWX; create_mapping(&map); } else if (start >= kernel_x_end) { map.pfn = __phys_to_pfn(start); map.virtual = __phys_to_virt(start); map.length = end - start; map.type = MT_MEMORY_RW; create_mapping(&map); } else { /* This better cover the entire kernel */ if (start < kernel_x_start) { map.pfn = __phys_to_pfn(start); map.virtual = __phys_to_virt(start); map.length = kernel_x_start - start; map.type = MT_MEMORY_RW; create_mapping(&map); } map.pfn = __phys_to_pfn(kernel_x_start); map.virtual = __phys_to_virt(kernel_x_start); map.length = kernel_x_end - kernel_x_start; map.type = MT_MEMORY_RWX; create_mapping(&map); if (kernel_x_end < end) { map.pfn = __phys_to_pfn(kernel_x_end); map.virtual = __phys_to_virt(kernel_x_end); map.length = end - kernel_x_end; map.type = MT_MEMORY_RW; create_mapping(&map); } } } } #ifdef CONFIG_ARM_LPAE /* * early_paging_init() recreates boot time page table setup, allowing machines * to switch over to a high (>4G) address space on LPAE systems */ void __init early_paging_init(const struct machine_desc *mdesc, struct proc_info_list *procinfo) { pmdval_t pmdprot = procinfo->__cpu_mm_mmu_flags; unsigned long map_start, map_end; pgd_t *pgd0, *pgdk; pud_t *pud0, *pudk, *pud_start; pmd_t *pmd0, *pmdk; phys_addr_t phys; int i; if (!(mdesc->init_meminfo)) return; /* remap kernel code and data */ map_start = init_mm.start_code & PMD_MASK; map_end = ALIGN(init_mm.brk, PMD_SIZE); /* get a handle on things... */ pgd0 = pgd_offset_k(0); pud_start = pud0 = pud_offset(pgd0, 0); pmd0 = pmd_offset(pud0, 0); pgdk = pgd_offset_k(map_start); pudk = pud_offset(pgdk, map_start); pmdk = pmd_offset(pudk, map_start); mdesc->init_meminfo(); /* Run the patch stub to update the constants */ fixup_pv_table(&__pv_table_begin, (&__pv_table_end - &__pv_table_begin) << 2); /* * Cache cleaning operations for self-modifying code * We should clean the entries by MVA but running a * for loop over every pv_table entry pointer would * just complicate the code. */ flush_cache_louis(); dsb(ishst); isb(); /* * FIXME: This code is not architecturally compliant: we modify * the mappings in-place, indeed while they are in use by this * very same code. This may lead to unpredictable behaviour of * the CPU. * * Even modifying the mappings in a separate page table does * not resolve this. * * The architecture strongly recommends that when a mapping is * changed, that it is changed by first going via an invalid * mapping and back to the new mapping. This is to ensure that * no TLB conflicts (caused by the TLB having more than one TLB * entry match a translation) can occur. However, doing that * here will result in unmapping the code we are running. */ pr_warn("WARNING: unsafe modification of in-place page tables - tainting kernel\n"); add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK); /* * Remap level 1 table. This changes the physical addresses * used to refer to the level 2 page tables to the high * physical address alias, leaving everything else the same. */ for (i = 0; i < PTRS_PER_PGD; pud0++, i++) { set_pud(pud0, __pud(__pa(pmd0) | PMD_TYPE_TABLE | L_PGD_SWAPPER)); pmd0 += PTRS_PER_PMD; } /* * Remap the level 2 table, pointing the mappings at the high * physical address alias of these pages. */ phys = __pa(map_start); do { *pmdk++ = __pmd(phys | pmdprot); phys += PMD_SIZE; } while (phys < map_end); /* * Ensure that the above updates are flushed out of the cache. * This is not strictly correct; on a system where the caches * are coherent with each other, but the MMU page table walks * may not be coherent, flush_cache_all() may be a no-op, and * this will fail. */ flush_cache_all(); /* * Re-write the TTBR values to point them at the high physical * alias of the page tables. We expect __va() will work on * cpu_get_pgd(), which returns the value of TTBR0. */ cpu_switch_mm(pgd0, &init_mm); cpu_set_ttbr(1, __pa(pgd0) + TTBR1_OFFSET); /* Finally flush any stale TLB values. */ local_flush_bp_all(); local_flush_tlb_all(); } #else void __init early_paging_init(const struct machine_desc *mdesc, struct proc_info_list *procinfo) { if (mdesc->init_meminfo) mdesc->init_meminfo(); } #endif /* * paging_init() sets up the page tables, initialises the zone memory * maps, and sets up the zero page, bad page and bad page tables. */ void __init paging_init(const struct machine_desc *mdesc) { void *zero_page; build_mem_type_table(); prepare_page_table(); map_lowmem(); dma_contiguous_remap(); devicemaps_init(mdesc); kmap_init(); tcm_init(); top_pmd = pmd_off_k(0xffff0000); /* allocate the zero page. */ zero_page = early_alloc(PAGE_SIZE); bootmem_init(); empty_zero_page = virt_to_page(zero_page); __flush_dcache_page(NULL, empty_zero_page); }