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-rw-r--r--arch/powerpc/mm/fault.c664
1 files changed, 664 insertions, 0 deletions
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
new file mode 100644
index 000000000..eb5252177
--- /dev/null
+++ b/arch/powerpc/mm/fault.c
@@ -0,0 +1,664 @@
+/*
+ * 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)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#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/pgtable.h>
+#include <asm/mmu.h>
+#include <asm/mmu_context.h>
+#include <asm/siginfo.h>
+#include <asm/debug.h>
+
+static inline bool notify_page_fault(struct pt_regs *regs)
+{
+ bool ret = false;
+
+#ifdef CONFIG_KPROBES
+ /* kprobe_running() needs smp_processor_id() */
+ if (!user_mode(regs)) {
+ preempt_disable();
+ if (kprobe_running() && kprobe_fault_handler(regs, 11))
+ ret = true;
+ preempt_enable();
+ }
+#endif /* CONFIG_KPROBES */
+
+ if (unlikely(debugger_fault_handler(regs)))
+ ret = true;
+
+ return ret;
+}
+
+/*
+ * Check whether the instruction inst is a store using
+ * an update addressing form which will update r1.
+ */
+static bool store_updates_sp(unsigned int inst)
+{
+ /* check for 1 in the rA field */
+ if (((inst >> 16) & 0x1f) != 1)
+ return false;
+ /* check major opcode */
+ switch (inst >> 26) {
+ case OP_STWU:
+ case OP_STBU:
+ case OP_STHU:
+ case OP_STFSU:
+ case OP_STFDU:
+ return true;
+ case OP_STD: /* std or stdu */
+ return (inst & 3) == 1;
+ case OP_31:
+ /* check minor opcode */
+ switch ((inst >> 1) & 0x3ff) {
+ case OP_31_XOP_STDUX:
+ case OP_31_XOP_STWUX:
+ case OP_31_XOP_STBUX:
+ case OP_31_XOP_STHUX:
+ case OP_31_XOP_STFSUX:
+ case OP_31_XOP_STFDUX:
+ return true;
+ }
+ }
+ return false;
+}
+/*
+ * do_page_fault error handling helpers
+ */
+
+static int
+__bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code,
+ int pkey)
+{
+ /*
+ * 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(SIGSEGV, regs, si_code, address, pkey);
+
+ return 0;
+}
+
+static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address)
+{
+ return __bad_area_nosemaphore(regs, address, SEGV_MAPERR, 0);
+}
+
+static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code,
+ int pkey)
+{
+ 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..
+ */
+ up_read(&mm->mmap_sem);
+
+ return __bad_area_nosemaphore(regs, address, si_code, pkey);
+}
+
+static noinline int bad_area(struct pt_regs *regs, unsigned long address)
+{
+ return __bad_area(regs, address, SEGV_MAPERR, 0);
+}
+
+static int bad_key_fault_exception(struct pt_regs *regs, unsigned long address,
+ int pkey)
+{
+ return __bad_area_nosemaphore(regs, address, SEGV_PKUERR, pkey);
+}
+
+static noinline int bad_access(struct pt_regs *regs, unsigned long address)
+{
+ return __bad_area(regs, address, SEGV_ACCERR, 0);
+}
+
+static int do_sigbus(struct pt_regs *regs, unsigned long address,
+ vm_fault_t fault)
+{
+ siginfo_t info;
+ unsigned int lsb = 0;
+
+ if (!user_mode(regs))
+ return SIGBUS;
+
+ current->thread.trap_nr = BUS_ADRERR;
+ clear_siginfo(&info);
+ info.si_signo = SIGBUS;
+ info.si_errno = 0;
+ info.si_code = BUS_ADRERR;
+ info.si_addr = (void __user *)address;
+#ifdef CONFIG_MEMORY_FAILURE
+ if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
+ pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
+ current->comm, current->pid, address);
+ info.si_code = BUS_MCEERR_AR;
+ }
+
+ if (fault & VM_FAULT_HWPOISON_LARGE)
+ lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
+ if (fault & VM_FAULT_HWPOISON)
+ lsb = PAGE_SHIFT;
+#endif
+ info.si_addr_lsb = lsb;
+ force_sig_info(SIGBUS, &info, current);
+ 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(bool is_exec, unsigned long error_code,
+ unsigned long address)
+{
+ /* NX faults set DSISR_PROTFAULT on the 8xx, DSISR_NOEXEC_OR_G on others */
+ if (is_exec && (error_code & (DSISR_NOEXEC_OR_G | DSISR_KEYFAULT |
+ DSISR_PROTFAULT))) {
+ printk_ratelimited(KERN_CRIT "kernel tried to execute"
+ " exec-protected page (%lx) -"
+ "exploit attempt? (uid: %d)\n",
+ address, from_kuid(&init_user_ns,
+ current_uid()));
+ }
+ return is_exec || (address >= TASK_SIZE);
+}
+
+// This comes from 64-bit struct rt_sigframe + __SIGNAL_FRAMESIZE
+#define SIGFRAME_MAX_SIZE (4096 + 128)
+
+static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address,
+ struct vm_area_struct *vma, unsigned int flags,
+ bool *must_retry)
+{
+ /*
+ * N.B. The POWER/Open ABI allows programs to access up to
+ * 288 bytes below the stack pointer.
+ * The kernel signal delivery code writes a bit over 4KB
+ * below the stack pointer (r1) before decrementing it.
+ * The exec code can write slightly over 640kB to the stack
+ * before setting the user r1. Thus we allow the stack to
+ * expand to 1MB without further checks.
+ */
+ if (address + 0x100000 < vma->vm_end) {
+ unsigned int __user *nip = (unsigned int __user *)regs->nip;
+ /* get user regs even if this fault is in kernel mode */
+ struct pt_regs *uregs = current->thread.regs;
+ if (uregs == NULL)
+ return true;
+
+ /*
+ * A user-mode access to an address a long way below
+ * the stack pointer is only valid if the instruction
+ * is one which would update the stack pointer to the
+ * address accessed if the instruction completed,
+ * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
+ * (or the byte, halfword, float or double forms).
+ *
+ * If we don't check this then any write to the area
+ * between the last mapped region and the stack will
+ * expand the stack rather than segfaulting.
+ */
+ if (address + SIGFRAME_MAX_SIZE >= uregs->gpr[1])
+ return false;
+
+ if ((flags & FAULT_FLAG_WRITE) && (flags & FAULT_FLAG_USER) &&
+ access_ok(VERIFY_READ, nip, sizeof(*nip))) {
+ unsigned int inst;
+ int res;
+
+ pagefault_disable();
+ res = __get_user_inatomic(inst, nip);
+ pagefault_enable();
+ if (!res)
+ return !store_updates_sp(inst);
+ *must_retry = true;
+ }
+ 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;
+ }
+
+ if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
+ 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 */
+
+#ifdef CONFIG_PPC_STD_MMU
+static void sanity_check_fault(bool is_write, unsigned long error_code)
+{
+ /*
+ * 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)
+ WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
+}
+#else
+static void sanity_check_fault(bool is_write, unsigned long error_code) { }
+#endif /* CONFIG_PPC_STD_MMU */
+
+/*
+ * 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_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
+ 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 must_retry = false;
+
+ if (notify_page_fault(regs))
+ 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, error_code);
+
+ /*
+ * The kernel should never take an execute fault nor should it
+ * take a page fault to a kernel address.
+ */
+ if (unlikely(!is_user && bad_kernel_fault(is_exec, error_code, address)))
+ 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);
+
+ if (error_code & DSISR_KEYFAULT)
+ return bad_key_fault_exception(regs, address,
+ get_mm_addr_key(mm, address));
+
+ /*
+ * We want to do this outside mmap_sem, because reading code around nip
+ * can result in fault, which will cause a deadlock when called with
+ * mmap_sem 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_sem
+ * 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(!down_read_trylock(&mm->mmap_sem))) {
+ if (!is_user && !search_exception_tables(regs->nip))
+ return bad_area_nosemaphore(regs, address);
+
+retry:
+ down_read(&mm->mmap_sem);
+ } 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 (likely(vma->vm_start <= address))
+ goto good_area;
+ if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
+ return bad_area(regs, address);
+
+ /* The stack is being expanded, check if it's valid */
+ if (unlikely(bad_stack_expansion(regs, address, vma, flags,
+ &must_retry))) {
+ if (!must_retry)
+ return bad_area(regs, address);
+
+ up_read(&mm->mmap_sem);
+ if (fault_in_pages_readable((const char __user *)regs->nip,
+ sizeof(unsigned int)))
+ return bad_area_nosemaphore(regs, address);
+ goto retry;
+ }
+
+ /* Try to expand it */
+ if (unlikely(expand_stack(vma, address)))
+ return bad_area(regs, address);
+
+good_area:
+ 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);
+
+#ifdef CONFIG_PPC_MEM_KEYS
+ /*
+ * we skipped checking for access error due to key earlier.
+ * Check that using handle_mm_fault error return.
+ */
+ if (unlikely(fault & VM_FAULT_SIGSEGV) &&
+ !arch_vma_access_permitted(vma, is_write, is_exec, 0)) {
+
+ int pkey = vma_pkey(vma);
+
+ up_read(&mm->mmap_sem);
+ return bad_key_fault_exception(regs, address, pkey);
+ }
+#endif /* CONFIG_PPC_MEM_KEYS */
+
+ major |= fault & VM_FAULT_MAJOR;
+
+ /*
+ * Handle the retry right now, the mmap_sem has been released in that
+ * case.
+ */
+ if (unlikely(fault & VM_FAULT_RETRY)) {
+ /* We retry only once */
+ if (flags & FAULT_FLAG_ALLOW_RETRY) {
+ /*
+ * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
+ * of starvation.
+ */
+ flags &= ~FAULT_FLAG_ALLOW_RETRY;
+ flags |= FAULT_FLAG_TRIED;
+ if (!fatal_signal_pending(current))
+ goto retry;
+ }
+
+ /*
+ * User mode? Just return to handle the fatal exception otherwise
+ * return to bad_page_fault
+ */
+ return is_user ? 0 : SIGBUS;
+ }
+
+ up_read(&current->mm->mmap_sem);
+
+ if (unlikely(fault & VM_FAULT_ERROR))
+ return mm_fault_error(regs, address, fault);
+
+ /*
+ * Major/minor page fault accounting.
+ */
+ if (major) {
+ current->maj_flt++;
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
+ cmo_account_page_fault();
+ } else {
+ current->min_flt++;
+ perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
+ }
+ 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;
+
+ /* 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:
+ pr_alert("BUG: %s at 0x%08lx\n",
+ regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
+ "Unable to handle kernel data access", 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);
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-23 23:26:26 +0000