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0b38b5e1d0
When userspace executes a syscall or gets interrupted,
BEAR contains a kernel address when returning to userspace.
This make it pretty easy to figure out where the kernel is
mapped even with KASLR enabled. To fix this, add lpswe to
lowcore and always execute it there, so userspace sees only
the lowcore address of lpswe. For this we have to extend
both critical_cleanup and the SWITCH_ASYNC macro to also check
for lpswe addresses in lowcore.
Fixes: b2d24b97b2 ("s390/kernel: add support for kernel address space layout randomization (KASLR)")
Cc: <stable@vger.kernel.org> # v5.2+
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
449 lines
10 KiB
C
449 lines
10 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright IBM Corp. 2006
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* Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>
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*/
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#include <linux/memblock.h>
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#include <linux/pfn.h>
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#include <linux/mm.h>
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#include <linux/init.h>
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#include <linux/list.h>
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#include <linux/hugetlb.h>
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#include <linux/slab.h>
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#include <asm/cacheflush.h>
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#include <asm/pgalloc.h>
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#include <asm/pgtable.h>
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#include <asm/setup.h>
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#include <asm/tlbflush.h>
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#include <asm/sections.h>
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#include <asm/set_memory.h>
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static DEFINE_MUTEX(vmem_mutex);
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struct memory_segment {
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struct list_head list;
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unsigned long start;
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unsigned long size;
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};
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static LIST_HEAD(mem_segs);
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static void __ref *vmem_alloc_pages(unsigned int order)
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{
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unsigned long size = PAGE_SIZE << order;
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if (slab_is_available())
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return (void *)__get_free_pages(GFP_KERNEL, order);
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return (void *) memblock_phys_alloc(size, size);
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}
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void *vmem_crst_alloc(unsigned long val)
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{
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unsigned long *table;
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table = vmem_alloc_pages(CRST_ALLOC_ORDER);
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if (table)
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crst_table_init(table, val);
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return table;
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}
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pte_t __ref *vmem_pte_alloc(void)
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{
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unsigned long size = PTRS_PER_PTE * sizeof(pte_t);
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pte_t *pte;
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if (slab_is_available())
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pte = (pte_t *) page_table_alloc(&init_mm);
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else
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pte = (pte_t *) memblock_phys_alloc(size, size);
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if (!pte)
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return NULL;
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memset64((u64 *)pte, _PAGE_INVALID, PTRS_PER_PTE);
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return pte;
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}
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/*
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* Add a physical memory range to the 1:1 mapping.
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*/
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static int vmem_add_mem(unsigned long start, unsigned long size)
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{
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unsigned long pgt_prot, sgt_prot, r3_prot;
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unsigned long pages4k, pages1m, pages2g;
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unsigned long end = start + size;
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unsigned long address = start;
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pgd_t *pg_dir;
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p4d_t *p4_dir;
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pud_t *pu_dir;
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pmd_t *pm_dir;
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pte_t *pt_dir;
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int ret = -ENOMEM;
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pgt_prot = pgprot_val(PAGE_KERNEL);
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sgt_prot = pgprot_val(SEGMENT_KERNEL);
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r3_prot = pgprot_val(REGION3_KERNEL);
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if (!MACHINE_HAS_NX) {
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pgt_prot &= ~_PAGE_NOEXEC;
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sgt_prot &= ~_SEGMENT_ENTRY_NOEXEC;
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r3_prot &= ~_REGION_ENTRY_NOEXEC;
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}
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pages4k = pages1m = pages2g = 0;
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while (address < end) {
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pg_dir = pgd_offset_k(address);
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if (pgd_none(*pg_dir)) {
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p4_dir = vmem_crst_alloc(_REGION2_ENTRY_EMPTY);
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if (!p4_dir)
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goto out;
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pgd_populate(&init_mm, pg_dir, p4_dir);
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}
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p4_dir = p4d_offset(pg_dir, address);
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if (p4d_none(*p4_dir)) {
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pu_dir = vmem_crst_alloc(_REGION3_ENTRY_EMPTY);
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if (!pu_dir)
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goto out;
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p4d_populate(&init_mm, p4_dir, pu_dir);
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}
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pu_dir = pud_offset(p4_dir, address);
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if (MACHINE_HAS_EDAT2 && pud_none(*pu_dir) && address &&
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!(address & ~PUD_MASK) && (address + PUD_SIZE <= end) &&
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!debug_pagealloc_enabled()) {
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pud_val(*pu_dir) = address | r3_prot;
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address += PUD_SIZE;
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pages2g++;
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continue;
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}
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if (pud_none(*pu_dir)) {
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pm_dir = vmem_crst_alloc(_SEGMENT_ENTRY_EMPTY);
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if (!pm_dir)
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goto out;
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pud_populate(&init_mm, pu_dir, pm_dir);
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}
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pm_dir = pmd_offset(pu_dir, address);
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if (MACHINE_HAS_EDAT1 && pmd_none(*pm_dir) && address &&
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!(address & ~PMD_MASK) && (address + PMD_SIZE <= end) &&
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!debug_pagealloc_enabled()) {
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pmd_val(*pm_dir) = address | sgt_prot;
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address += PMD_SIZE;
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pages1m++;
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continue;
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}
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if (pmd_none(*pm_dir)) {
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pt_dir = vmem_pte_alloc();
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if (!pt_dir)
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goto out;
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pmd_populate(&init_mm, pm_dir, pt_dir);
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}
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pt_dir = pte_offset_kernel(pm_dir, address);
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pte_val(*pt_dir) = address | pgt_prot;
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address += PAGE_SIZE;
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pages4k++;
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}
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ret = 0;
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out:
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update_page_count(PG_DIRECT_MAP_4K, pages4k);
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update_page_count(PG_DIRECT_MAP_1M, pages1m);
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update_page_count(PG_DIRECT_MAP_2G, pages2g);
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return ret;
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}
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/*
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* Remove a physical memory range from the 1:1 mapping.
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* Currently only invalidates page table entries.
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*/
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static void vmem_remove_range(unsigned long start, unsigned long size)
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{
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unsigned long pages4k, pages1m, pages2g;
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unsigned long end = start + size;
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unsigned long address = start;
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pgd_t *pg_dir;
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p4d_t *p4_dir;
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pud_t *pu_dir;
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pmd_t *pm_dir;
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pte_t *pt_dir;
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pages4k = pages1m = pages2g = 0;
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while (address < end) {
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pg_dir = pgd_offset_k(address);
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if (pgd_none(*pg_dir)) {
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address += PGDIR_SIZE;
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continue;
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}
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p4_dir = p4d_offset(pg_dir, address);
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if (p4d_none(*p4_dir)) {
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address += P4D_SIZE;
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continue;
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}
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pu_dir = pud_offset(p4_dir, address);
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if (pud_none(*pu_dir)) {
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address += PUD_SIZE;
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continue;
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}
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if (pud_large(*pu_dir)) {
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pud_clear(pu_dir);
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address += PUD_SIZE;
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pages2g++;
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continue;
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}
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pm_dir = pmd_offset(pu_dir, address);
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if (pmd_none(*pm_dir)) {
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address += PMD_SIZE;
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continue;
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}
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if (pmd_large(*pm_dir)) {
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pmd_clear(pm_dir);
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address += PMD_SIZE;
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pages1m++;
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continue;
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}
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pt_dir = pte_offset_kernel(pm_dir, address);
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pte_clear(&init_mm, address, pt_dir);
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address += PAGE_SIZE;
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pages4k++;
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}
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flush_tlb_kernel_range(start, end);
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update_page_count(PG_DIRECT_MAP_4K, -pages4k);
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update_page_count(PG_DIRECT_MAP_1M, -pages1m);
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update_page_count(PG_DIRECT_MAP_2G, -pages2g);
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}
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/*
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* Add a backed mem_map array to the virtual mem_map array.
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*/
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int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
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struct vmem_altmap *altmap)
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{
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unsigned long pgt_prot, sgt_prot;
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unsigned long address = start;
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pgd_t *pg_dir;
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p4d_t *p4_dir;
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pud_t *pu_dir;
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pmd_t *pm_dir;
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pte_t *pt_dir;
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int ret = -ENOMEM;
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pgt_prot = pgprot_val(PAGE_KERNEL);
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sgt_prot = pgprot_val(SEGMENT_KERNEL);
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if (!MACHINE_HAS_NX) {
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pgt_prot &= ~_PAGE_NOEXEC;
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sgt_prot &= ~_SEGMENT_ENTRY_NOEXEC;
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}
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for (address = start; address < end;) {
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pg_dir = pgd_offset_k(address);
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if (pgd_none(*pg_dir)) {
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p4_dir = vmem_crst_alloc(_REGION2_ENTRY_EMPTY);
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if (!p4_dir)
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goto out;
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pgd_populate(&init_mm, pg_dir, p4_dir);
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}
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p4_dir = p4d_offset(pg_dir, address);
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if (p4d_none(*p4_dir)) {
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pu_dir = vmem_crst_alloc(_REGION3_ENTRY_EMPTY);
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if (!pu_dir)
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goto out;
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p4d_populate(&init_mm, p4_dir, pu_dir);
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}
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pu_dir = pud_offset(p4_dir, address);
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if (pud_none(*pu_dir)) {
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pm_dir = vmem_crst_alloc(_SEGMENT_ENTRY_EMPTY);
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if (!pm_dir)
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goto out;
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pud_populate(&init_mm, pu_dir, pm_dir);
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}
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pm_dir = pmd_offset(pu_dir, address);
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if (pmd_none(*pm_dir)) {
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/* Use 1MB frames for vmemmap if available. We always
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* use large frames even if they are only partially
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* used.
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* Otherwise we would have also page tables since
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* vmemmap_populate gets called for each section
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* separately. */
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if (MACHINE_HAS_EDAT1) {
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void *new_page;
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new_page = vmemmap_alloc_block(PMD_SIZE, node);
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if (!new_page)
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goto out;
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pmd_val(*pm_dir) = __pa(new_page) | sgt_prot;
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address = (address + PMD_SIZE) & PMD_MASK;
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continue;
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}
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pt_dir = vmem_pte_alloc();
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if (!pt_dir)
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goto out;
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pmd_populate(&init_mm, pm_dir, pt_dir);
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} else if (pmd_large(*pm_dir)) {
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address = (address + PMD_SIZE) & PMD_MASK;
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continue;
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}
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pt_dir = pte_offset_kernel(pm_dir, address);
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if (pte_none(*pt_dir)) {
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void *new_page;
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new_page = vmemmap_alloc_block(PAGE_SIZE, node);
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if (!new_page)
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goto out;
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pte_val(*pt_dir) = __pa(new_page) | pgt_prot;
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}
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address += PAGE_SIZE;
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}
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ret = 0;
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out:
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return ret;
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}
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void vmemmap_free(unsigned long start, unsigned long end,
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struct vmem_altmap *altmap)
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{
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}
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/*
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* Add memory segment to the segment list if it doesn't overlap with
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* an already present segment.
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*/
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static int insert_memory_segment(struct memory_segment *seg)
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{
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struct memory_segment *tmp;
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if (seg->start + seg->size > VMEM_MAX_PHYS ||
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seg->start + seg->size < seg->start)
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return -ERANGE;
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list_for_each_entry(tmp, &mem_segs, list) {
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if (seg->start >= tmp->start + tmp->size)
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continue;
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if (seg->start + seg->size <= tmp->start)
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continue;
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return -ENOSPC;
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}
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list_add(&seg->list, &mem_segs);
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return 0;
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}
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/*
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* Remove memory segment from the segment list.
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*/
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static void remove_memory_segment(struct memory_segment *seg)
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{
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list_del(&seg->list);
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}
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static void __remove_shared_memory(struct memory_segment *seg)
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{
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remove_memory_segment(seg);
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vmem_remove_range(seg->start, seg->size);
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}
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int vmem_remove_mapping(unsigned long start, unsigned long size)
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{
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struct memory_segment *seg;
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int ret;
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mutex_lock(&vmem_mutex);
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ret = -ENOENT;
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list_for_each_entry(seg, &mem_segs, list) {
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if (seg->start == start && seg->size == size)
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break;
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}
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if (seg->start != start || seg->size != size)
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goto out;
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ret = 0;
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__remove_shared_memory(seg);
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kfree(seg);
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out:
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mutex_unlock(&vmem_mutex);
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return ret;
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}
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int vmem_add_mapping(unsigned long start, unsigned long size)
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{
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struct memory_segment *seg;
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int ret;
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mutex_lock(&vmem_mutex);
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ret = -ENOMEM;
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seg = kzalloc(sizeof(*seg), GFP_KERNEL);
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if (!seg)
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goto out;
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seg->start = start;
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seg->size = size;
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ret = insert_memory_segment(seg);
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if (ret)
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goto out_free;
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ret = vmem_add_mem(start, size);
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if (ret)
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goto out_remove;
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goto out;
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out_remove:
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__remove_shared_memory(seg);
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out_free:
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kfree(seg);
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out:
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mutex_unlock(&vmem_mutex);
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return ret;
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}
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/*
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* map whole physical memory to virtual memory (identity mapping)
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* we reserve enough space in the vmalloc area for vmemmap to hotplug
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* additional memory segments.
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*/
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void __init vmem_map_init(void)
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{
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struct memblock_region *reg;
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for_each_memblock(memory, reg)
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vmem_add_mem(reg->base, reg->size);
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__set_memory((unsigned long)_stext,
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(unsigned long)(_etext - _stext) >> PAGE_SHIFT,
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SET_MEMORY_RO | SET_MEMORY_X);
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__set_memory((unsigned long)_etext,
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(unsigned long)(__end_rodata - _etext) >> PAGE_SHIFT,
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SET_MEMORY_RO);
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__set_memory((unsigned long)_sinittext,
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(unsigned long)(_einittext - _sinittext) >> PAGE_SHIFT,
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SET_MEMORY_RO | SET_MEMORY_X);
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__set_memory(__stext_dma, (__etext_dma - __stext_dma) >> PAGE_SHIFT,
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SET_MEMORY_RO | SET_MEMORY_X);
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/* we need lowcore executable for our LPSWE instructions */
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set_memory_x(0, 1);
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pr_info("Write protected kernel read-only data: %luk\n",
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(unsigned long)(__end_rodata - _stext) >> 10);
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}
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/*
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* Convert memblock.memory to a memory segment list so there is a single
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* list that contains all memory segments.
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*/
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static int __init vmem_convert_memory_chunk(void)
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{
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struct memblock_region *reg;
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struct memory_segment *seg;
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mutex_lock(&vmem_mutex);
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for_each_memblock(memory, reg) {
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seg = kzalloc(sizeof(*seg), GFP_KERNEL);
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if (!seg)
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panic("Out of memory...\n");
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seg->start = reg->base;
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seg->size = reg->size;
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insert_memory_segment(seg);
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}
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mutex_unlock(&vmem_mutex);
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return 0;
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}
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core_initcall(vmem_convert_memory_chunk);
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