1 files changed, 601 insertions, 0 deletions

diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
new file mode 100644
index 000000000..55fdba8ba
--- /dev/null
+++ b/arch/powerpc/mm/fault.c
@@ -0,0 +1,601 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  PowerPC version
+ *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
+ *
+ *  Derived from "arch/i386/mm/fault.c"
+ *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
+ *
+ *  Modified by Cort Dougan and Paul Mackerras.
+ *
+ *  Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
+ */
+
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/pagemap.h>
+#include <linux/ptrace.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/interrupt.h>
+#include <linux/highmem.h>
+#include <linux/extable.h>
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
+#include <linux/perf_event.h>
+#include <linux/ratelimit.h>
+#include <linux/context_tracking.h>
+#include <linux/hugetlb.h>
+#include <linux/uaccess.h>
+
+#include <asm/firmware.h>
+#include <asm/page.h>
+#include <asm/mmu.h>
+#include <asm/mmu_context.h>
+#include <asm/siginfo.h>
+#include <asm/debug.h>
+#include <asm/kup.h>
+#include <asm/inst.h>
+
+
+/*
+ * do_page_fault error handling helpers
+ */
+
+static int
+__bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code)
+{
+	/*
+	 * If we are in kernel mode, bail out with a SEGV, this will
+	 * be caught by the assembly which will restore the non-volatile
+	 * registers before calling bad_page_fault()
+	 */
+	if (!user_mode(regs))
+		return SIGSEGV;
+
+	_exception(SIGSEGV, regs, si_code, address);
+
+	return 0;
+}
+
+static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address)
+{
+	return __bad_area_nosemaphore(regs, address, SEGV_MAPERR);
+}
+
+static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code)
+{
+	struct mm_struct *mm = current->mm;
+
+	/*
+	 * Something tried to access memory that isn't in our memory map..
+	 * Fix it, but check if it's kernel or user first..
+	 */
+	mmap_read_unlock(mm);
+
+	return __bad_area_nosemaphore(regs, address, si_code);
+}
+
+static noinline int bad_area(struct pt_regs *regs, unsigned long address)
+{
+	return __bad_area(regs, address, SEGV_MAPERR);
+}
+
+#ifdef CONFIG_PPC_MEM_KEYS
+static noinline int bad_access_pkey(struct pt_regs *regs, unsigned long address,
+				    struct vm_area_struct *vma)
+{
+	struct mm_struct *mm = current->mm;
+	int pkey;
+
+	/*
+	 * We don't try to fetch the pkey from page table because reading
+	 * page table without locking doesn't guarantee stable pte value.
+	 * Hence the pkey value that we return to userspace can be different
+	 * from the pkey that actually caused access error.
+	 *
+	 * It does *not* guarantee that the VMA we find here
+	 * was the one that we faulted on.
+	 *
+	 * 1. T1   : mprotect_key(foo, PAGE_SIZE, pkey=4);
+	 * 2. T1   : set AMR to deny access to pkey=4, touches, page
+	 * 3. T1   : faults...
+	 * 4.    T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
+	 * 5. T1   : enters fault handler, takes mmap_lock, etc...
+	 * 6. T1   : reaches here, sees vma_pkey(vma)=5, when we really
+	 *	     faulted on a pte with its pkey=4.
+	 */
+	pkey = vma_pkey(vma);
+
+	mmap_read_unlock(mm);
+
+	/*
+	 * If we are in kernel mode, bail out with a SEGV, this will
+	 * be caught by the assembly which will restore the non-volatile
+	 * registers before calling bad_page_fault()
+	 */
+	if (!user_mode(regs))
+		return SIGSEGV;
+
+	_exception_pkey(regs, address, pkey);
+
+	return 0;
+}
+#endif
+
+static noinline int bad_access(struct pt_regs *regs, unsigned long address)
+{
+	return __bad_area(regs, address, SEGV_ACCERR);
+}
+
+static int do_sigbus(struct pt_regs *regs, unsigned long address,
+		     vm_fault_t fault)
+{
+	if (!user_mode(regs))
+		return SIGBUS;
+
+	current->thread.trap_nr = BUS_ADRERR;
+#ifdef CONFIG_MEMORY_FAILURE
+	if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
+		unsigned int lsb = 0; /* shutup gcc */
+
+		pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
+			current->comm, current->pid, address);
+
+		if (fault & VM_FAULT_HWPOISON_LARGE)
+			lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
+		if (fault & VM_FAULT_HWPOISON)
+			lsb = PAGE_SHIFT;
+
+		force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
+		return 0;
+	}
+
+#endif
+	force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
+	return 0;
+}
+
+static int mm_fault_error(struct pt_regs *regs, unsigned long addr,
+				vm_fault_t fault)
+{
+	/*
+	 * Kernel page fault interrupted by SIGKILL. We have no reason to
+	 * continue processing.
+	 */
+	if (fatal_signal_pending(current) && !user_mode(regs))
+		return SIGKILL;
+
+	/* Out of memory */
+	if (fault & VM_FAULT_OOM) {
+		/*
+		 * We ran out of memory, or some other thing happened to us that
+		 * made us unable to handle the page fault gracefully.
+		 */
+		if (!user_mode(regs))
+			return SIGSEGV;
+		pagefault_out_of_memory();
+	} else {
+		if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
+			     VM_FAULT_HWPOISON_LARGE))
+			return do_sigbus(regs, addr, fault);
+		else if (fault & VM_FAULT_SIGSEGV)
+			return bad_area_nosemaphore(regs, addr);
+		else
+			BUG();
+	}
+	return 0;
+}
+
+/* Is this a bad kernel fault ? */
+static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
+			     unsigned long address, bool is_write)
+{
+	int is_exec = TRAP(regs) == 0x400;
+
+	if (is_exec) {
+		pr_crit_ratelimited("kernel tried to execute %s page (%lx) - exploit attempt? (uid: %d)\n",
+				    address >= TASK_SIZE ? "exec-protected" : "user",
+				    address,
+				    from_kuid(&init_user_ns, current_uid()));
+
+		// Kernel exec fault is always bad
+		return true;
+	}
+
+	if (!is_exec && address < TASK_SIZE && (error_code & DSISR_PROTFAULT) &&
+	    !search_exception_tables(regs->nip)) {
+		pr_crit_ratelimited("Kernel attempted to access user page (%lx) - exploit attempt? (uid: %d)\n",
+				    address,
+				    from_kuid(&init_user_ns, current_uid()));
+	}
+
+	// Kernel fault on kernel address is bad
+	if (address >= TASK_SIZE)
+		return true;
+
+	// Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad
+	if (!search_exception_tables(regs->nip))
+		return true;
+
+	// Read/write fault in a valid region (the exception table search passed
+	// above), but blocked by KUAP is bad, it can never succeed.
+	if (bad_kuap_fault(regs, address, is_write))
+		return true;
+
+	// What's left? Kernel fault on user in well defined regions (extable
+	// matched), and allowed by KUAP in the faulting context.
+	return false;
+}
+
+#ifdef CONFIG_PPC_MEM_KEYS
+static bool access_pkey_error(bool is_write, bool is_exec, bool is_pkey,
+			      struct vm_area_struct *vma)
+{
+	/*
+	 * Make sure to check the VMA so that we do not perform
+	 * faults just to hit a pkey fault as soon as we fill in a
+	 * page. Only called for current mm, hence foreign == 0
+	 */
+	if (!arch_vma_access_permitted(vma, is_write, is_exec, 0))
+		return true;
+
+	return false;
+}
+#endif
+
+static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma)
+{
+	/*
+	 * Allow execution from readable areas if the MMU does not
+	 * provide separate controls over reading and executing.
+	 *
+	 * Note: That code used to not be enabled for 4xx/BookE.
+	 * It is now as I/D cache coherency for these is done at
+	 * set_pte_at() time and I see no reason why the test
+	 * below wouldn't be valid on those processors. This -may-
+	 * break programs compiled with a really old ABI though.
+	 */
+	if (is_exec) {
+		return !(vma->vm_flags & VM_EXEC) &&
+			(cpu_has_feature(CPU_FTR_NOEXECUTE) ||
+			 !(vma->vm_flags & (VM_READ | VM_WRITE)));
+	}
+
+	if (is_write) {
+		if (unlikely(!(vma->vm_flags & VM_WRITE)))
+			return true;
+		return false;
+	}
+
+	if (unlikely(!vma_is_accessible(vma)))
+		return true;
+	/*
+	 * We should ideally do the vma pkey access check here. But in the
+	 * fault path, handle_mm_fault() also does the same check. To avoid
+	 * these multiple checks, we skip it here and handle access error due
+	 * to pkeys later.
+	 */
+	return false;
+}
+
+#ifdef CONFIG_PPC_SMLPAR
+static inline void cmo_account_page_fault(void)
+{
+	if (firmware_has_feature(FW_FEATURE_CMO)) {
+		u32 page_ins;
+
+		preempt_disable();
+		page_ins = be32_to_cpu(get_lppaca()->page_ins);
+		page_ins += 1 << PAGE_FACTOR;
+		get_lppaca()->page_ins = cpu_to_be32(page_ins);
+		preempt_enable();
+	}
+}
+#else
+static inline void cmo_account_page_fault(void) { }
+#endif /* CONFIG_PPC_SMLPAR */
+
+static void sanity_check_fault(bool is_write, bool is_user,
+			       unsigned long error_code, unsigned long address)
+{
+	/*
+	 * Userspace trying to access kernel address, we get PROTFAULT for that.
+	 */
+	if (is_user && address >= TASK_SIZE) {
+		if ((long)address == -1)
+			return;
+
+		pr_crit_ratelimited("%s[%d]: User access of kernel address (%lx) - exploit attempt? (uid: %d)\n",
+				   current->comm, current->pid, address,
+				   from_kuid(&init_user_ns, current_uid()));
+		return;
+	}
+
+	if (!IS_ENABLED(CONFIG_PPC_BOOK3S))
+		return;
+
+	/*
+	 * For hash translation mode, we should never get a
+	 * PROTFAULT. Any update to pte to reduce access will result in us
+	 * removing the hash page table entry, thus resulting in a DSISR_NOHPTE
+	 * fault instead of DSISR_PROTFAULT.
+	 *
+	 * A pte update to relax the access will not result in a hash page table
+	 * entry invalidate and hence can result in DSISR_PROTFAULT.
+	 * ptep_set_access_flags() doesn't do a hpte flush. This is why we have
+	 * the special !is_write in the below conditional.
+	 *
+	 * For platforms that doesn't supports coherent icache and do support
+	 * per page noexec bit, we do setup things such that we do the
+	 * sync between D/I cache via fault. But that is handled via low level
+	 * hash fault code (hash_page_do_lazy_icache()) and we should not reach
+	 * here in such case.
+	 *
+	 * For wrong access that can result in PROTFAULT, the above vma->vm_flags
+	 * check should handle those and hence we should fall to the bad_area
+	 * handling correctly.
+	 *
+	 * For embedded with per page exec support that doesn't support coherent
+	 * icache we do get PROTFAULT and we handle that D/I cache sync in
+	 * set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON
+	 * is conditional for server MMU.
+	 *
+	 * For radix, we can get prot fault for autonuma case, because radix
+	 * page table will have them marked noaccess for user.
+	 */
+	if (radix_enabled() || is_write)
+		return;
+
+	WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
+}
+
+/*
+ * Define the correct "is_write" bit in error_code based
+ * on the processor family
+ */
+#if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
+#define page_fault_is_write(__err)	((__err) & ESR_DST)
+#define page_fault_is_bad(__err)	(0)
+#else
+#define page_fault_is_write(__err)	((__err) & DSISR_ISSTORE)
+#if defined(CONFIG_PPC_8xx)
+#define page_fault_is_bad(__err)	((__err) & DSISR_NOEXEC_OR_G)
+#elif defined(CONFIG_PPC64)
+#define page_fault_is_bad(__err)	((__err) & DSISR_BAD_FAULT_64S)
+#else
+#define page_fault_is_bad(__err)	((__err) & DSISR_BAD_FAULT_32S)
+#endif
+#endif
+
+/*
+ * For 600- and 800-family processors, the error_code parameter is DSISR
+ * for a data fault, SRR1 for an instruction fault. For 400-family processors
+ * the error_code parameter is ESR for a data fault, 0 for an instruction
+ * fault.
+ * For 64-bit processors, the error_code parameter is
+ *  - DSISR for a non-SLB data access fault,
+ *  - SRR1 & 0x08000000 for a non-SLB instruction access fault
+ *  - 0 any SLB fault.
+ *
+ * The return value is 0 if the fault was handled, or the signal
+ * number if this is a kernel fault that can't be handled here.
+ */
+static int __do_page_fault(struct pt_regs *regs, unsigned long address,
+			   unsigned long error_code)
+{
+	struct vm_area_struct * vma;
+	struct mm_struct *mm = current->mm;
+	unsigned int flags = FAULT_FLAG_DEFAULT;
+ 	int is_exec = TRAP(regs) == 0x400;
+	int is_user = user_mode(regs);
+	int is_write = page_fault_is_write(error_code);
+	vm_fault_t fault, major = 0;
+	bool kprobe_fault = kprobe_page_fault(regs, 11);
+
+	if (unlikely(debugger_fault_handler(regs) || kprobe_fault))
+		return 0;
+
+	if (unlikely(page_fault_is_bad(error_code))) {
+		if (is_user) {
+			_exception(SIGBUS, regs, BUS_OBJERR, address);
+			return 0;
+		}
+		return SIGBUS;
+	}
+
+	/* Additional sanity check(s) */
+	sanity_check_fault(is_write, is_user, error_code, address);
+
+	/*
+	 * The kernel should never take an execute fault nor should it
+	 * take a page fault to a kernel address or a page fault to a user
+	 * address outside of dedicated places
+	 */
+	if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write)))
+		return SIGSEGV;
+
+	/*
+	 * If we're in an interrupt, have no user context or are running
+	 * in a region with pagefaults disabled then we must not take the fault
+	 */
+	if (unlikely(faulthandler_disabled() || !mm)) {
+		if (is_user)
+			printk_ratelimited(KERN_ERR "Page fault in user mode"
+					   " with faulthandler_disabled()=%d"
+					   " mm=%p\n",
+					   faulthandler_disabled(), mm);
+		return bad_area_nosemaphore(regs, address);
+	}
+
+	/* We restore the interrupt state now */
+	if (!arch_irq_disabled_regs(regs))
+		local_irq_enable();
+
+	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
+
+	/*
+	 * We want to do this outside mmap_lock, because reading code around nip
+	 * can result in fault, which will cause a deadlock when called with
+	 * mmap_lock held
+	 */
+	if (is_user)
+		flags |= FAULT_FLAG_USER;
+	if (is_write)
+		flags |= FAULT_FLAG_WRITE;
+	if (is_exec)
+		flags |= FAULT_FLAG_INSTRUCTION;
+
+	/* When running in the kernel we expect faults to occur only to
+	 * addresses in user space.  All other faults represent errors in the
+	 * kernel and should generate an OOPS.  Unfortunately, in the case of an
+	 * erroneous fault occurring in a code path which already holds mmap_lock
+	 * we will deadlock attempting to validate the fault against the
+	 * address space.  Luckily the kernel only validly references user
+	 * space from well defined areas of code, which are listed in the
+	 * exceptions table.
+	 *
+	 * As the vast majority of faults will be valid we will only perform
+	 * the source reference check when there is a possibility of a deadlock.
+	 * Attempt to lock the address space, if we cannot we then validate the
+	 * source.  If this is invalid we can skip the address space check,
+	 * thus avoiding the deadlock.
+	 */
+	if (unlikely(!mmap_read_trylock(mm))) {
+		if (!is_user && !search_exception_tables(regs->nip))
+			return bad_area_nosemaphore(regs, address);
+
+retry:
+		mmap_read_lock(mm);
+	} else {
+		/*
+		 * The above down_read_trylock() might have succeeded in
+		 * which case we'll have missed the might_sleep() from
+		 * down_read():
+		 */
+		might_sleep();
+	}
+
+	vma = find_vma(mm, address);
+	if (unlikely(!vma))
+		return bad_area(regs, address);
+
+	if (unlikely(vma->vm_start > address)) {
+		if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
+			return bad_area(regs, address);
+
+		if (unlikely(expand_stack(vma, address)))
+			return bad_area(regs, address);
+	}
+
+#ifdef CONFIG_PPC_MEM_KEYS
+	if (unlikely(access_pkey_error(is_write, is_exec,
+				       (error_code & DSISR_KEYFAULT), vma)))
+		return bad_access_pkey(regs, address, vma);
+#endif /* CONFIG_PPC_MEM_KEYS */
+
+	if (unlikely(access_error(is_write, is_exec, vma)))
+		return bad_access(regs, address);
+
+	/*
+	 * If for any reason at all we couldn't handle the fault,
+	 * make sure we exit gracefully rather than endlessly redo
+	 * the fault.
+	 */
+	fault = handle_mm_fault(vma, address, flags, regs);
+
+	major |= fault & VM_FAULT_MAJOR;
+
+	if (fault_signal_pending(fault, regs))
+		return user_mode(regs) ? 0 : SIGBUS;
+
+	/*
+	 * Handle the retry right now, the mmap_lock has been released in that
+	 * case.
+	 */
+	if (unlikely(fault & VM_FAULT_RETRY)) {
+		if (flags & FAULT_FLAG_ALLOW_RETRY) {
+			flags |= FAULT_FLAG_TRIED;
+			goto retry;
+		}
+	}
+
+	mmap_read_unlock(current->mm);
+
+	if (unlikely(fault & VM_FAULT_ERROR))
+		return mm_fault_error(regs, address, fault);
+
+	/*
+	 * Major/minor page fault accounting.
+	 */
+	if (major)
+		cmo_account_page_fault();
+
+	return 0;
+}
+NOKPROBE_SYMBOL(__do_page_fault);
+
+int do_page_fault(struct pt_regs *regs, unsigned long address,
+		  unsigned long error_code)
+{
+	enum ctx_state prev_state = exception_enter();
+	int rc = __do_page_fault(regs, address, error_code);
+	exception_exit(prev_state);
+	return rc;
+}
+NOKPROBE_SYMBOL(do_page_fault);
+
+/*
+ * bad_page_fault is called when we have a bad access from the kernel.
+ * It is called from the DSI and ISI handlers in head.S and from some
+ * of the procedures in traps.c.
+ */
+void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
+{
+	const struct exception_table_entry *entry;
+	int is_write = page_fault_is_write(regs->dsisr);
+
+	/* Are we prepared to handle this fault?  */
+	if ((entry = search_exception_tables(regs->nip)) != NULL) {
+		regs->nip = extable_fixup(entry);
+		return;
+	}
+
+	/* kernel has accessed a bad area */
+
+	switch (TRAP(regs)) {
+	case 0x300:
+	case 0x380:
+	case 0xe00:
+		pr_alert("BUG: %s on %s at 0x%08lx\n",
+			 regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
+			 "Unable to handle kernel data access",
+			 is_write ? "write" : "read", regs->dar);
+		break;
+	case 0x400:
+	case 0x480:
+		pr_alert("BUG: Unable to handle kernel instruction fetch%s",
+			 regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n");
+		break;
+	case 0x600:
+		pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n",
+			 regs->dar);
+		break;
+	default:
+		pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n",
+			 regs->dar);
+		break;
+	}
+	printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
+		regs->nip);
+
+	if (task_stack_end_corrupted(current))
+		printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
+
+	die("Kernel access of bad area", regs, sig);
+}