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-rw-r--r--arch/powerpc/mm/fault.c646
1 files changed, 646 insertions, 0 deletions
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
new file mode 100644
index 000000000..644e4ec6c
--- /dev/null
+++ b/arch/powerpc/mm/fault.c
@@ -0,0 +1,646 @@
+// 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 <linux/kfence.h>
+#include <linux/pkeys.h>
+
+#include <asm/firmware.h>
+#include <asm/interrupt.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_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;
+}
+
+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) == INTERRUPT_INST_STORAGE;
+
+ 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;
+ }
+
+ // Kernel fault on kernel address is bad
+ if (address >= TASK_SIZE)
+ return true;
+
+ // Read/write fault blocked by KUAP is bad, it can never succeed.
+ if (bad_kuap_fault(regs, address, is_write)) {
+ pr_crit_ratelimited("Kernel attempted to %s user page (%lx) - exploit attempt? (uid: %d)\n",
+ is_write ? "write" : "read", address,
+ from_kuid(&init_user_ns, current_uid()));
+
+ // 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.
+ return WARN(true, "Bug: %s fault blocked by KUAP!", is_write ? "Write" : "Read");
+ }
+
+ // What's left? Kernel fault on user and allowed by KUAP in the faulting context.
+ return false;
+}
+
+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;
+}
+
+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;
+ }
+
+ /*
+ * VM_READ, VM_WRITE and VM_EXEC all imply read permissions, as
+ * defined in protection_map[]. Read faults can only be caused by
+ * a PROT_NONE mapping, or with a PROT_EXEC-only mapping on Radix.
+ */
+ if (unlikely(!vma_is_accessible(vma)))
+ return true;
+
+ if (unlikely(radix_enabled() && ((vma->vm_flags & VM_ACCESS_FLAGS) == VM_EXEC)))
+ 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)
+#else
+#define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE)
+#endif
+
+#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
+#define page_fault_is_bad(__err) (0)
+#elif defined(CONFIG_PPC_8xx)
+#define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G)
+#elif defined(CONFIG_PPC64)
+static int page_fault_is_bad(unsigned long err)
+{
+ unsigned long flag = DSISR_BAD_FAULT_64S;
+
+ /*
+ * PAPR+ v2.11 ยง 14.15.3.4.1 (unreleased)
+ * If byte 0, bit 3 of pi-attribute-specifier-type in
+ * ibm,pi-features property is defined, ignore the DSI error
+ * which is caused by the paste instruction on the
+ * suspended NX window.
+ */
+ if (mmu_has_feature(MMU_FTR_NX_DSI))
+ flag &= ~DSISR_BAD_COPYPASTE;
+
+ return err & flag;
+}
+#else
+#define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S)
+#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 data access
+ * fault, SRR1 & 0x08000000 for an instruction access 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) == INTERRUPT_INST_STORAGE;
+ 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))) {
+ if (kfence_handle_page_fault(address, is_write, regs))
+ return 0;
+
+ 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);
+ }
+
+ interrupt_cond_local_irq_enable(regs);
+
+ 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. lock_mm_and_find_vma() handles that logic.
+ */
+retry:
+ vma = lock_mm_and_find_vma(mm, address, regs);
+ if (unlikely(!vma))
+ return bad_area_nosemaphore(regs, address);
+
+ if (unlikely(access_pkey_error(is_write, is_exec,
+ (error_code & DSISR_KEYFAULT), vma)))
+ return bad_access_pkey(regs, address, vma);
+
+ 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;
+
+ /* The fault is fully completed (including releasing mmap lock) */
+ if (fault & VM_FAULT_COMPLETED)
+ goto out;
+
+ /*
+ * Handle the retry right now, the mmap_lock has been released in that
+ * case.
+ */
+ if (unlikely(fault & VM_FAULT_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);
+
+out:
+ /*
+ * Major/minor page fault accounting.
+ */
+ if (major)
+ cmo_account_page_fault();
+
+ return 0;
+}
+NOKPROBE_SYMBOL(___do_page_fault);
+
+static __always_inline void __do_page_fault(struct pt_regs *regs)
+{
+ long err;
+
+ err = ___do_page_fault(regs, regs->dar, regs->dsisr);
+ if (unlikely(err))
+ bad_page_fault(regs, err);
+}
+
+DEFINE_INTERRUPT_HANDLER(do_page_fault)
+{
+ __do_page_fault(regs);
+}
+
+#ifdef CONFIG_PPC_BOOK3S_64
+/* Same as do_page_fault but interrupt entry has already run in do_hash_fault */
+void hash__do_page_fault(struct pt_regs *regs)
+{
+ __do_page_fault(regs);
+}
+NOKPROBE_SYMBOL(hash__do_page_fault);
+#endif
+
+/*
+ * 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.
+ */
+static void __bad_page_fault(struct pt_regs *regs, int sig)
+{
+ int is_write = page_fault_is_write(regs->dsisr);
+ const char *msg;
+
+ /* kernel has accessed a bad area */
+
+ if (regs->dar < PAGE_SIZE)
+ msg = "Kernel NULL pointer dereference";
+ else
+ msg = "Unable to handle kernel data access";
+
+ switch (TRAP(regs)) {
+ case INTERRUPT_DATA_STORAGE:
+ case INTERRUPT_H_DATA_STORAGE:
+ pr_alert("BUG: %s on %s at 0x%08lx\n", msg,
+ is_write ? "write" : "read", regs->dar);
+ break;
+ case INTERRUPT_DATA_SEGMENT:
+ pr_alert("BUG: %s at 0x%08lx\n", msg, regs->dar);
+ break;
+ case INTERRUPT_INST_STORAGE:
+ case INTERRUPT_INST_SEGMENT:
+ pr_alert("BUG: Unable to handle kernel instruction fetch%s",
+ regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n");
+ break;
+ case INTERRUPT_ALIGNMENT:
+ 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);
+}
+
+void bad_page_fault(struct pt_regs *regs, int sig)
+{
+ const struct exception_table_entry *entry;
+
+ /* Are we prepared to handle this fault? */
+ entry = search_exception_tables(instruction_pointer(regs));
+ if (entry)
+ instruction_pointer_set(regs, extable_fixup(entry));
+ else
+ __bad_page_fault(regs, sig);
+}
+
+#ifdef CONFIG_PPC_BOOK3S_64
+DEFINE_INTERRUPT_HANDLER(do_bad_page_fault_segv)
+{
+ bad_page_fault(regs, SIGSEGV);
+}
+
+/*
+ * In radix, segment interrupts indicate the EA is not addressable by the
+ * page table geometry, so they are always sent here.
+ *
+ * In hash, this is called if do_slb_fault returns error. Typically it is
+ * because the EA was outside the region allowed by software.
+ */
+DEFINE_INTERRUPT_HANDLER(do_bad_segment_interrupt)
+{
+ int err = regs->result;
+
+ if (err == -EFAULT) {
+ if (user_mode(regs))
+ _exception(SIGSEGV, regs, SEGV_BNDERR, regs->dar);
+ else
+ bad_page_fault(regs, SIGSEGV);
+ } else if (err == -EINVAL) {
+ unrecoverable_exception(regs);
+ } else {
+ BUG();
+ }
+}
+#endif