RISC-V: Setup initial page tables in two stages
Currently, the setup_vm() does initial page table setup in one-shot very early before enabling MMU. Due to this, the setup_vm() has to map all possible kernel virtual addresses since it does not know size and location of RAM. This means we have kernel mappings for non-existent RAM and any buggy driver (or kernel) code doing out-of-bound access to RAM will not fault and cause underterministic behaviour. Further, the setup_vm() creates PMD mappings (i.e. 2M mappings) for RV64 systems. This means for PAGE_OFFSET=0xffffffe000000000 (i.e. MAXPHYSMEM_128GB=y), the setup_vm() will require 129 pages (i.e. 516 KB) of memory for initial page tables which is never freed. The memory required for initial page tables will further increase if we chose a lower value of PAGE_OFFSET (e.g. 0xffffff0000000000) This patch implements two-staged initial page table setup, as follows: 1. Early (i.e. setup_vm()): This stage maps kernel image and DTB in a early page table (i.e. early_pg_dir). The early_pg_dir will be used only by boot HART so it can be freed as-part of init memory free-up. 2. Final (i.e. setup_vm_final()): This stage maps all possible RAM banks in the final page table (i.e. swapper_pg_dir). The boot HART will start using swapper_pg_dir at the end of setup_vm_final(). All non-boot HARTs directly use the swapper_pg_dir created by boot HART. We have following advantages with this new approach: 1. Kernel mappings for non-existent RAM don't exists anymore. 2. Memory consumed by initial page tables is now indpendent of the chosen PAGE_OFFSET. 3. Memory consumed by initial page tables on RV64 system is 2 pages (i.e. 8 KB) which has significantly reduced and these pages will be freed as-part of the init memory free-up. The patch also provides a foundation for implementing strict kernel mappings where we protect kernel text and rodata using PTE permissions. Suggested-by: Mike Rapoport <rppt@linux.ibm.com> Signed-off-by: Anup Patel <anup.patel@wdc.com> [paul.walmsley@sifive.com: updated to apply; fixed a checkpatch warning] Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>alistair/sunxi64-5.4-dsi
Anup Patel
Paul Walmsley
parent
2ebca1cbb4
commit
671f9a3e2e
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@ -21,6 +21,11 @@
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*/
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enum fixed_addresses {
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FIX_HOLE,
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#define FIX_FDT_SIZE SZ_1M
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FIX_FDT_END,
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FIX_FDT = FIX_FDT_END + FIX_FDT_SIZE / PAGE_SIZE - 1,
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FIX_PTE,
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FIX_PMD,
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FIX_EARLYCON_MEM_BASE,
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__end_of_fixed_addresses
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};
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@ -70,6 +70,11 @@ static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t prot)
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return __pmd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
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}
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static inline unsigned long _pmd_pfn(pmd_t pmd)
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{
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return pmd_val(pmd) >> _PAGE_PFN_SHIFT;
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}
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#define pmd_ERROR(e) \
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pr_err("%s:%d: bad pmd %016lx.\n", __FILE__, __LINE__, pmd_val(e))
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@ -59,6 +59,8 @@
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#define PAGE_KERNEL __pgprot(_PAGE_KERNEL)
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#define PAGE_KERNEL_EXEC __pgprot(_PAGE_KERNEL | _PAGE_EXEC)
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#define PAGE_TABLE __pgprot(_PAGE_TABLE)
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extern pgd_t swapper_pg_dir[];
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/* MAP_PRIVATE permissions: xwr (copy-on-write) */
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@ -118,6 +120,11 @@ static inline pgd_t pfn_pgd(unsigned long pfn, pgprot_t prot)
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return __pgd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
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}
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static inline unsigned long _pgd_pfn(pgd_t pgd)
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{
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return pgd_val(pgd) >> _PAGE_PFN_SHIFT;
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}
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#define pgd_index(addr) (((addr) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1))
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/* Locate an entry in the page global directory */
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@ -400,6 +407,7 @@ static inline int ptep_clear_flush_young(struct vm_area_struct *vma,
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#define kern_addr_valid(addr) (1) /* FIXME */
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#endif
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extern void *dtb_early_va;
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extern void setup_bootmem(void);
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extern void paging_init(void);
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@ -55,7 +55,9 @@ clear_bss_done:
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/* Initialize page tables and relocate to virtual addresses */
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la sp, init_thread_union + THREAD_SIZE
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mv a0, s1
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call setup_vm
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la a0, early_pg_dir
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call relocate
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/* Restore C environment */
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@ -64,25 +66,23 @@ clear_bss_done:
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la sp, init_thread_union + THREAD_SIZE
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/* Start the kernel */
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mv a0, s1
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call parse_dtb
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tail start_kernel
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relocate:
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/* Relocate return address */
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li a1, PAGE_OFFSET
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la a0, _start
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sub a1, a1, a0
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la a2, _start
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sub a1, a1, a2
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add ra, ra, a1
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/* Point stvec to virtual address of intruction after satp write */
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la a0, 1f
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add a0, a0, a1
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csrw CSR_STVEC, a0
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la a2, 1f
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add a2, a2, a1
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csrw CSR_STVEC, a2
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/* Compute satp for kernel page tables, but don't load it yet */
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la a2, swapper_pg_dir
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srl a2, a2, PAGE_SHIFT
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srl a2, a0, PAGE_SHIFT
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li a1, SATP_MODE
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or a2, a2, a1
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@ -148,6 +148,7 @@ relocate:
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fence
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/* Enable virtual memory and relocate to virtual address */
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la a0, swapper_pg_dir
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call relocate
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tail smp_callin
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@ -39,11 +39,9 @@ struct screen_info screen_info = {
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atomic_t hart_lottery;
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unsigned long boot_cpu_hartid;
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void __init parse_dtb(phys_addr_t dtb_phys)
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void __init parse_dtb(void)
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{
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void *dtb = __va(dtb_phys);
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if (early_init_dt_scan(dtb))
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if (early_init_dt_scan(dtb_early_va))
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return;
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pr_err("No DTB passed to the kernel\n");
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@ -1,6 +1,7 @@
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Copyright (C) 2012 Regents of the University of California
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* Copyright (C) 2019 Western Digital Corporation or its affiliates.
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*/
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#include <linux/init.h>
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@ -41,13 +42,6 @@ void setup_zero_page(void)
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memset((void *)empty_zero_page, 0, PAGE_SIZE);
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}
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void __init paging_init(void)
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{
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setup_zero_page();
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local_flush_tlb_all();
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zone_sizes_init();
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}
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void __init mem_init(void)
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{
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#ifdef CONFIG_FLATMEM
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@ -143,17 +137,15 @@ EXPORT_SYMBOL(va_pa_offset);
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unsigned long pfn_base;
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EXPORT_SYMBOL(pfn_base);
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void *dtb_early_va;
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pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
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pgd_t trampoline_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
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#ifndef __PAGETABLE_PMD_FOLDED
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#define NUM_SWAPPER_PMDS ((uintptr_t)-PAGE_OFFSET >> PGDIR_SHIFT)
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pmd_t swapper_pmd[PTRS_PER_PMD*((-PAGE_OFFSET)/PGDIR_SIZE)] __page_aligned_bss;
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pmd_t trampoline_pmd[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
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pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
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#endif
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pgd_t trampoline_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
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pte_t fixmap_pte[PTRS_PER_PTE] __page_aligned_bss;
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static bool mmu_enabled;
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#define MAX_EARLY_MAPPING_SIZE SZ_128M
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pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
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void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
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{
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@ -172,6 +164,156 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
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}
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}
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static pte_t *__init get_pte_virt(phys_addr_t pa)
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{
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if (mmu_enabled) {
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clear_fixmap(FIX_PTE);
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return (pte_t *)set_fixmap_offset(FIX_PTE, pa);
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} else {
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return (pte_t *)((uintptr_t)pa);
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}
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}
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static phys_addr_t __init alloc_pte(uintptr_t va)
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{
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/*
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* We only create PMD or PGD early mappings so we
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* should never reach here with MMU disabled.
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*/
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BUG_ON(!mmu_enabled);
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return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
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}
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static void __init create_pte_mapping(pte_t *ptep,
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uintptr_t va, phys_addr_t pa,
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phys_addr_t sz, pgprot_t prot)
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{
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uintptr_t pte_index = pte_index(va);
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BUG_ON(sz != PAGE_SIZE);
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if (pte_none(ptep[pte_index]))
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ptep[pte_index] = pfn_pte(PFN_DOWN(pa), prot);
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}
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#ifndef __PAGETABLE_PMD_FOLDED
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pmd_t trampoline_pmd[PTRS_PER_PMD] __page_aligned_bss;
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pmd_t fixmap_pmd[PTRS_PER_PMD] __page_aligned_bss;
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#if MAX_EARLY_MAPPING_SIZE < PGDIR_SIZE
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#define NUM_EARLY_PMDS 1UL
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#else
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#define NUM_EARLY_PMDS (1UL + MAX_EARLY_MAPPING_SIZE / PGDIR_SIZE)
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#endif
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pmd_t early_pmd[PTRS_PER_PMD * NUM_EARLY_PMDS] __initdata __aligned(PAGE_SIZE);
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static pmd_t *__init get_pmd_virt(phys_addr_t pa)
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{
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if (mmu_enabled) {
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clear_fixmap(FIX_PMD);
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return (pmd_t *)set_fixmap_offset(FIX_PMD, pa);
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} else {
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return (pmd_t *)((uintptr_t)pa);
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}
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}
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static phys_addr_t __init alloc_pmd(uintptr_t va)
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{
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uintptr_t pmd_num;
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if (mmu_enabled)
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return memblock_phys_alloc(PAGE_SIZE, PAGE_SIZE);
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pmd_num = (va - PAGE_OFFSET) >> PGDIR_SHIFT;
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BUG_ON(pmd_num >= NUM_EARLY_PMDS);
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return (uintptr_t)&early_pmd[pmd_num * PTRS_PER_PMD];
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}
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static void __init create_pmd_mapping(pmd_t *pmdp,
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uintptr_t va, phys_addr_t pa,
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phys_addr_t sz, pgprot_t prot)
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{
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pte_t *ptep;
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phys_addr_t pte_phys;
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uintptr_t pmd_index = pmd_index(va);
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if (sz == PMD_SIZE) {
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if (pmd_none(pmdp[pmd_index]))
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pmdp[pmd_index] = pfn_pmd(PFN_DOWN(pa), prot);
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return;
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}
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if (pmd_none(pmdp[pmd_index])) {
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pte_phys = alloc_pte(va);
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pmdp[pmd_index] = pfn_pmd(PFN_DOWN(pte_phys), PAGE_TABLE);
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ptep = get_pte_virt(pte_phys);
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memset(ptep, 0, PAGE_SIZE);
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} else {
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pte_phys = PFN_PHYS(_pmd_pfn(pmdp[pmd_index]));
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ptep = get_pte_virt(pte_phys);
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}
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create_pte_mapping(ptep, va, pa, sz, prot);
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}
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#define pgd_next_t pmd_t
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#define alloc_pgd_next(__va) alloc_pmd(__va)
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#define get_pgd_next_virt(__pa) get_pmd_virt(__pa)
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#define create_pgd_next_mapping(__nextp, __va, __pa, __sz, __prot) \
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create_pmd_mapping(__nextp, __va, __pa, __sz, __prot)
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#define PTE_PARENT_SIZE PMD_SIZE
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#define fixmap_pgd_next fixmap_pmd
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#else
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#define pgd_next_t pte_t
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#define alloc_pgd_next(__va) alloc_pte(__va)
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#define get_pgd_next_virt(__pa) get_pte_virt(__pa)
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#define create_pgd_next_mapping(__nextp, __va, __pa, __sz, __prot) \
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create_pte_mapping(__nextp, __va, __pa, __sz, __prot)
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#define PTE_PARENT_SIZE PGDIR_SIZE
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#define fixmap_pgd_next fixmap_pte
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#endif
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static void __init create_pgd_mapping(pgd_t *pgdp,
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uintptr_t va, phys_addr_t pa,
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phys_addr_t sz, pgprot_t prot)
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{
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pgd_next_t *nextp;
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phys_addr_t next_phys;
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uintptr_t pgd_index = pgd_index(va);
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if (sz == PGDIR_SIZE) {
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if (pgd_val(pgdp[pgd_index]) == 0)
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pgdp[pgd_index] = pfn_pgd(PFN_DOWN(pa), prot);
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return;
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}
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if (pgd_val(pgdp[pgd_index]) == 0) {
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next_phys = alloc_pgd_next(va);
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pgdp[pgd_index] = pfn_pgd(PFN_DOWN(next_phys), PAGE_TABLE);
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nextp = get_pgd_next_virt(next_phys);
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memset(nextp, 0, PAGE_SIZE);
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} else {
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next_phys = PFN_PHYS(_pgd_pfn(pgdp[pgd_index]));
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nextp = get_pgd_next_virt(next_phys);
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}
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create_pgd_next_mapping(nextp, va, pa, sz, prot);
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}
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static uintptr_t __init best_map_size(phys_addr_t base, phys_addr_t size)
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{
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uintptr_t map_size = PAGE_SIZE;
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/* Upgrade to PMD/PGDIR mappings whenever possible */
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if (!(base & (PTE_PARENT_SIZE - 1)) &&
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!(size & (PTE_PARENT_SIZE - 1)))
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map_size = PTE_PARENT_SIZE;
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return map_size;
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}
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/*
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* setup_vm() is called from head.S with MMU-off.
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*
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@ -191,54 +333,115 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
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"not use absolute addressing."
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#endif
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asmlinkage void __init setup_vm(void)
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asmlinkage void __init setup_vm(uintptr_t dtb_pa)
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{
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uintptr_t i;
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uintptr_t pa = (uintptr_t) &_start;
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pgprot_t prot = __pgprot(pgprot_val(PAGE_KERNEL) | _PAGE_EXEC);
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uintptr_t va, end_va;
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uintptr_t load_pa = (uintptr_t)(&_start);
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uintptr_t load_sz = (uintptr_t)(&_end) - load_pa;
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uintptr_t map_size = best_map_size(load_pa, MAX_EARLY_MAPPING_SIZE);
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va_pa_offset = PAGE_OFFSET - pa;
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pfn_base = PFN_DOWN(pa);
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va_pa_offset = PAGE_OFFSET - load_pa;
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pfn_base = PFN_DOWN(load_pa);
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/*
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* Enforce boot alignment requirements of RV32 and
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* RV64 by only allowing PMD or PGD mappings.
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*/
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BUG_ON(map_size == PAGE_SIZE);
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/* Sanity check alignment and size */
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BUG_ON((PAGE_OFFSET % PGDIR_SIZE) != 0);
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BUG_ON((pa % (PAGE_SIZE * PTRS_PER_PTE)) != 0);
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BUG_ON((load_pa % map_size) != 0);
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BUG_ON(load_sz > MAX_EARLY_MAPPING_SIZE);
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/* Setup early PGD for fixmap */
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create_pgd_mapping(early_pg_dir, FIXADDR_START,
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(uintptr_t)fixmap_pgd_next, PGDIR_SIZE, PAGE_TABLE);
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#ifndef __PAGETABLE_PMD_FOLDED
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trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] =
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pfn_pgd(PFN_DOWN((uintptr_t)trampoline_pmd),
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__pgprot(_PAGE_TABLE));
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trampoline_pmd[0] = pfn_pmd(PFN_DOWN(pa), prot);
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for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) {
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size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i;
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swapper_pg_dir[o] =
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pfn_pgd(PFN_DOWN((uintptr_t)swapper_pmd) + i,
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__pgprot(_PAGE_TABLE));
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}
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for (i = 0; i < ARRAY_SIZE(swapper_pmd); i++)
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swapper_pmd[i] = pfn_pmd(PFN_DOWN(pa + i * PMD_SIZE), prot);
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swapper_pg_dir[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] =
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pfn_pgd(PFN_DOWN((uintptr_t)fixmap_pmd),
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__pgprot(_PAGE_TABLE));
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fixmap_pmd[(FIXADDR_START >> PMD_SHIFT) % PTRS_PER_PMD] =
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pfn_pmd(PFN_DOWN((uintptr_t)fixmap_pte),
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__pgprot(_PAGE_TABLE));
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/* Setup fixmap PMD */
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create_pmd_mapping(fixmap_pmd, FIXADDR_START,
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(uintptr_t)fixmap_pte, PMD_SIZE, PAGE_TABLE);
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/* Setup trampoline PGD and PMD */
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create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
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(uintptr_t)trampoline_pmd, PGDIR_SIZE, PAGE_TABLE);
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create_pmd_mapping(trampoline_pmd, PAGE_OFFSET,
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load_pa, PMD_SIZE, PAGE_KERNEL_EXEC);
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#else
|
||||
trampoline_pg_dir[(PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD] =
|
||||
pfn_pgd(PFN_DOWN(pa), prot);
|
||||
/* Setup trampoline PGD */
|
||||
create_pgd_mapping(trampoline_pg_dir, PAGE_OFFSET,
|
||||
load_pa, PGDIR_SIZE, PAGE_KERNEL_EXEC);
|
||||
#endif
|
||||
|
||||
for (i = 0; i < (-PAGE_OFFSET)/PGDIR_SIZE; ++i) {
|
||||
size_t o = (PAGE_OFFSET >> PGDIR_SHIFT) % PTRS_PER_PGD + i;
|
||||
/*
|
||||
* Setup early PGD covering entire kernel which will allows
|
||||
* us to reach paging_init(). We map all memory banks later
|
||||
* in setup_vm_final() below.
|
||||
*/
|
||||
end_va = PAGE_OFFSET + load_sz;
|
||||
for (va = PAGE_OFFSET; va < end_va; va += map_size)
|
||||
create_pgd_mapping(early_pg_dir, va,
|
||||
load_pa + (va - PAGE_OFFSET),
|
||||
map_size, PAGE_KERNEL_EXEC);
|
||||
|
||||
swapper_pg_dir[o] =
|
||||
pfn_pgd(PFN_DOWN(pa + i * PGDIR_SIZE), prot);
|
||||
/* Create fixed mapping for early FDT parsing */
|
||||
end_va = __fix_to_virt(FIX_FDT) + FIX_FDT_SIZE;
|
||||
for (va = __fix_to_virt(FIX_FDT); va < end_va; va += PAGE_SIZE)
|
||||
create_pte_mapping(fixmap_pte, va,
|
||||
dtb_pa + (va - __fix_to_virt(FIX_FDT)),
|
||||
PAGE_SIZE, PAGE_KERNEL);
|
||||
|
||||
/* Save pointer to DTB for early FDT parsing */
|
||||
dtb_early_va = (void *)fix_to_virt(FIX_FDT) + (dtb_pa & ~PAGE_MASK);
|
||||
}
|
||||
|
||||
static void __init setup_vm_final(void)
|
||||
{
|
||||
uintptr_t va, map_size;
|
||||
phys_addr_t pa, start, end;
|
||||
struct memblock_region *reg;
|
||||
|
||||
/* Set mmu_enabled flag */
|
||||
mmu_enabled = true;
|
||||
|
||||
/* Setup swapper PGD for fixmap */
|
||||
create_pgd_mapping(swapper_pg_dir, FIXADDR_START,
|
||||
__pa(fixmap_pgd_next),
|
||||
PGDIR_SIZE, PAGE_TABLE);
|
||||
|
||||
/* Map all memory banks */
|
||||
for_each_memblock(memory, reg) {
|
||||
start = reg->base;
|
||||
end = start + reg->size;
|
||||
|
||||
if (start >= end)
|
||||
break;
|
||||
if (memblock_is_nomap(reg))
|
||||
continue;
|
||||
if (start <= __pa(PAGE_OFFSET) &&
|
||||
__pa(PAGE_OFFSET) < end)
|
||||
start = __pa(PAGE_OFFSET);
|
||||
|
||||
map_size = best_map_size(start, end - start);
|
||||
for (pa = start; pa < end; pa += map_size) {
|
||||
va = (uintptr_t)__va(pa);
|
||||
create_pgd_mapping(swapper_pg_dir, va, pa,
|
||||
map_size, PAGE_KERNEL_EXEC);
|
||||
}
|
||||
}
|
||||
|
||||
swapper_pg_dir[(FIXADDR_START >> PGDIR_SHIFT) % PTRS_PER_PGD] =
|
||||
pfn_pgd(PFN_DOWN((uintptr_t)fixmap_pte),
|
||||
__pgprot(_PAGE_TABLE));
|
||||
#endif
|
||||
/* Clear fixmap PTE and PMD mappings */
|
||||
clear_fixmap(FIX_PTE);
|
||||
clear_fixmap(FIX_PMD);
|
||||
|
||||
/* Move to swapper page table */
|
||||
csr_write(sptbr, PFN_DOWN(__pa(swapper_pg_dir)) | SATP_MODE);
|
||||
local_flush_tlb_all();
|
||||
}
|
||||
|
||||
void __init paging_init(void)
|
||||
{
|
||||
setup_vm_final();
|
||||
setup_zero_page();
|
||||
zone_sizes_init();
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in New Issue