1 files changed, 250 insertions, 0 deletions
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
new file mode 100644
index 000000000..c90c20904
--- /dev/null
+++ b/arch/x86/mm/mmap.c
@@ -0,0 +1,250 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Flexible mmap layout support
+ *
+ * Based on code by Ingo Molnar and Andi Kleen, copyrighted
+ * as follows:
+ *
+ * Copyright 2003-2009 Red Hat Inc.
+ * All Rights Reserved.
+ * Copyright 2005 Andi Kleen, SUSE Labs.
+ * Copyright 2007 Jiri Kosina, SUSE Labs.
+ */
+
+#include <linux/personality.h>
+#include <linux/mm.h>
+#include <linux/random.h>
+#include <linux/limits.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/mm.h>
+#include <linux/compat.h>
+#include <linux/elf-randomize.h>
+#include <asm/elf.h>
+#include <asm/io.h>
+
+#include "physaddr.h"
+
+struct va_alignment __read_mostly va_align = {
+	.flags = -1,
+};
+
+unsigned long task_size_32bit(void)
+{
+	return IA32_PAGE_OFFSET;
+}
+
+unsigned long task_size_64bit(int full_addr_space)
+{
+	return full_addr_space ? TASK_SIZE_MAX : DEFAULT_MAP_WINDOW;
+}
+
+static unsigned long stack_maxrandom_size(unsigned long task_size)
+{
+	unsigned long max = 0;
+	if (current->flags & PF_RANDOMIZE) {
+		max = (-1UL) & __STACK_RND_MASK(task_size == task_size_32bit());
+		max <<= PAGE_SHIFT;
+	}
+
+	return max;
+}
+
+#ifdef CONFIG_COMPAT
+# define mmap32_rnd_bits  mmap_rnd_compat_bits
+# define mmap64_rnd_bits  mmap_rnd_bits
+#else
+# define mmap32_rnd_bits  mmap_rnd_bits
+# define mmap64_rnd_bits  mmap_rnd_bits
+#endif
+
+#define SIZE_128M    (128 * 1024 * 1024UL)
+
+static int mmap_is_legacy(void)
+{
+	if (current->personality & ADDR_COMPAT_LAYOUT)
+		return 1;
+
+	return sysctl_legacy_va_layout;
+}
+
+static unsigned long arch_rnd(unsigned int rndbits)
+{
+	if (!(current->flags & PF_RANDOMIZE))
+		return 0;
+	return (get_random_long() & ((1UL << rndbits) - 1)) << PAGE_SHIFT;
+}
+
+unsigned long arch_mmap_rnd(void)
+{
+	return arch_rnd(mmap_is_ia32() ? mmap32_rnd_bits : mmap64_rnd_bits);
+}
+
+static unsigned long mmap_base(unsigned long rnd, unsigned long task_size,
+			       struct rlimit *rlim_stack)
+{
+	unsigned long gap = rlim_stack->rlim_cur;
+	unsigned long pad = stack_maxrandom_size(task_size) + stack_guard_gap;
+	unsigned long gap_min, gap_max;
+
+	/* Values close to RLIM_INFINITY can overflow. */
+	if (gap + pad > gap)
+		gap += pad;
+
+	/*
+	 * Top of mmap area (just below the process stack).
+	 * Leave an at least ~128 MB hole with possible stack randomization.
+	 */
+	gap_min = SIZE_128M;
+	gap_max = (task_size / 6) * 5;
+
+	if (gap < gap_min)
+		gap = gap_min;
+	else if (gap > gap_max)
+		gap = gap_max;
+
+	return PAGE_ALIGN(task_size - gap - rnd);
+}
+
+static unsigned long mmap_legacy_base(unsigned long rnd,
+				      unsigned long task_size)
+{
+	return __TASK_UNMAPPED_BASE(task_size) + rnd;
+}
+
+/*
+ * This function, called very early during the creation of a new
+ * process VM image, sets up which VM layout function to use:
+ */
+static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base,
+		unsigned long random_factor, unsigned long task_size,
+		struct rlimit *rlim_stack)
+{
+	*legacy_base = mmap_legacy_base(random_factor, task_size);
+	if (mmap_is_legacy())
+		*base = *legacy_base;
+	else
+		*base = mmap_base(random_factor, task_size, rlim_stack);
+}
+
+void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
+{
+	if (mmap_is_legacy())
+		mm->get_unmapped_area = arch_get_unmapped_area;
+	else
+		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
+
+	arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base,
+			arch_rnd(mmap64_rnd_bits), task_size_64bit(0),
+			rlim_stack);
+
+#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
+	/*
+	 * The mmap syscall mapping base decision depends solely on the
+	 * syscall type (64-bit or compat). This applies for 64bit
+	 * applications and 32bit applications. The 64bit syscall uses
+	 * mmap_base, the compat syscall uses mmap_compat_base.
+	 */
+	arch_pick_mmap_base(&mm->mmap_compat_base, &mm->mmap_compat_legacy_base,
+			arch_rnd(mmap32_rnd_bits), task_size_32bit(),
+			rlim_stack);
+#endif
+}
+
+unsigned long get_mmap_base(int is_legacy)
+{
+	struct mm_struct *mm = current->mm;
+
+#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
+	if (in_32bit_syscall()) {
+		return is_legacy ? mm->mmap_compat_legacy_base
+				 : mm->mmap_compat_base;
+	}
+#endif
+	return is_legacy ? mm->mmap_legacy_base : mm->mmap_base;
+}
+
+const char *arch_vma_name(struct vm_area_struct *vma)
+{
+	return NULL;
+}
+
+/**
+ * mmap_address_hint_valid - Validate the address hint of mmap
+ * @addr:	Address hint
+ * @len:	Mapping length
+ *
+ * Check whether @addr and @addr + @len result in a valid mapping.
+ *
+ * On 32bit this only checks whether @addr + @len is <= TASK_SIZE.
+ *
+ * On 64bit with 5-level page tables another sanity check is required
+ * because mappings requested by mmap(@addr, 0) which cross the 47-bit
+ * virtual address boundary can cause the following theoretical issue:
+ *
+ *  An application calls mmap(addr, 0), i.e. without MAP_FIXED, where @addr
+ *  is below the border of the 47-bit address space and @addr + @len is
+ *  above the border.
+ *
+ *  With 4-level paging this request succeeds, but the resulting mapping
+ *  address will always be within the 47-bit virtual address space, because
+ *  the hint address does not result in a valid mapping and is
+ *  ignored. Hence applications which are not prepared to handle virtual
+ *  addresses above 47-bit work correctly.
+ *
+ *  With 5-level paging this request would be granted and result in a
+ *  mapping which crosses the border of the 47-bit virtual address
+ *  space. If the application cannot handle addresses above 47-bit this
+ *  will lead to misbehaviour and hard to diagnose failures.
+ *
+ * Therefore ignore address hints which would result in a mapping crossing
+ * the 47-bit virtual address boundary.
+ *
+ * Note, that in the same scenario with MAP_FIXED the behaviour is
+ * different. The request with @addr < 47-bit and @addr + @len > 47-bit
+ * fails on a 4-level paging machine but succeeds on a 5-level paging
+ * machine. It is reasonable to expect that an application does not rely on
+ * the failure of such a fixed mapping request, so the restriction is not
+ * applied.
+ */
+bool mmap_address_hint_valid(unsigned long addr, unsigned long len)
+{
+	if (TASK_SIZE - len < addr)
+		return false;
+
+	return (addr > DEFAULT_MAP_WINDOW) == (addr + len > DEFAULT_MAP_WINDOW);
+}
+
+/* Can we access it for direct reading/writing? Must be RAM: */
+int valid_phys_addr_range(phys_addr_t addr, size_t count)
+{
+	return addr + count - 1 <= __pa(high_memory - 1);
+}
+
+/* Can we access it through mmap? Must be a valid physical address: */
+int valid_mmap_phys_addr_range(unsigned long pfn, size_t count)
+{
+	phys_addr_t addr = (phys_addr_t)pfn << PAGE_SHIFT;
+
+	return phys_addr_valid(addr + count - 1);
+}
+
+/*
+ * Only allow root to set high MMIO mappings to PROT_NONE.
+ * This prevents an unpriv. user to set them to PROT_NONE and invert
+ * them, then pointing to valid memory for L1TF speculation.
+ *
+ * Note: for locked down kernels may want to disable the root override.
+ */
+bool pfn_modify_allowed(unsigned long pfn, pgprot_t prot)
+{
+	if (!boot_cpu_has_bug(X86_BUG_L1TF))
+		return true;
+	if (!__pte_needs_invert(pgprot_val(prot)))
+		return true;
+	/* If it's real memory always allow */
+	if (pfn_valid(pfn))
+		return true;
+	if (pfn >= l1tf_pfn_limit() && !capable(CAP_SYS_ADMIN))
+		return false;
+	return true;
+}