// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/arch/arm/mm/fault.c
*
* Copyright (C) 1995 Linus Torvalds
* Modifications for ARM processor (c) 1995-2004 Russell King
*/
#include <linux/extable.h>
#include <linux/signal.h>
#include <linux/mm.h>
#include <linux/hardirq.h>
#include <linux/init.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <linux/page-flags.h>
#include <linux/sched/signal.h>
#include <linux/sched/debug.h>
#include <linux/highmem.h>
#include <linux/perf_event.h>
#include <linux/kfence.h>
#include <asm/system_misc.h>
#include <asm/system_info.h>
#include <asm/tlbflush.h>
#include "fault.h"
#ifdef CONFIG_MMU
bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size)
{
unsigned long addr = (unsigned long)unsafe_src;
return addr >= TASK_SIZE && ULONG_MAX - addr >= size;
}
/*
* This is useful to dump out the page tables associated with
* 'addr' in mm 'mm'.
*/
void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
{
pgd_t *pgd;
if (!mm)
mm = &init_mm;
pgd = pgd_offset(mm, addr);
printk("%s[%08lx] *pgd=%08llx", lvl, addr, (long long)pgd_val(*pgd));
do {
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
p4d = p4d_offset(pgd, addr);
if (p4d_none(*p4d))
break;
if (p4d_bad(*p4d)) {
pr_cont("(bad)");
break;
}
pud = pud_offset(p4d, addr);
if (PTRS_PER_PUD != 1)
pr_cont(", *pud=%08llx", (long long)pud_val(*pud));
if (pud_none(*pud))
break;
if (pud_bad(*pud)) {
pr_cont("(bad)");
break;
}
pmd = pmd_offset(pud, addr);
if (PTRS_PER_PMD != 1)
pr_cont(", *pmd=%08llx", (long long)pmd_val(*pmd));
if (pmd_none(*pmd))
break;
if (pmd_bad(*pmd)) {
pr_cont("(bad)");
break;
}
/* We must not map this if we have highmem enabled */
if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
break;
pte = pte_offset_map(pmd, addr);
if (!pte)
break;
pr_cont(", *pte=%08llx", (long long)pte_val(*pte));
#ifndef CONFIG_ARM_LPAE
pr_cont(", *ppte=%08llx",
(long long)pte_val(pte[PTE_HWTABLE_PTRS]));
#endif
pte_unmap(pte);
} while(0);
pr_cont("\n");
}
#else /* CONFIG_MMU */
void show_pte(const char *lvl, struct mm_struct *mm, unsigned long addr)
{ }
#endif /* CONFIG_MMU */
static inline bool is_write_fault(unsigned int fsr)
{
return (fsr & FSR_WRITE) && !(fsr & FSR_CM);
}
static inline bool is_translation_fault(unsigned int fsr)
{
int fs = fsr_fs(fsr);
#ifdef CONFIG_ARM_LPAE
if ((fs & FS_MMU_NOLL_MASK) == FS_TRANS_NOLL)
return true;
#else
if (fs == FS_L1_TRANS || fs == FS_L2_TRANS)
return true;
#endif
return false;
}
static void die_kernel_fault(const char *msg, struct mm_struct *mm,
unsigned long addr, unsigned int fsr,
struct pt_regs *regs)
{
bust_spinlocks(1);
pr_alert("8<--- cut here ---\n");
pr_alert("Unable to handle kernel %s at virtual address %08lx when %s\n",
msg, addr, fsr & FSR_LNX_PF ? "execute" :
fsr & FSR_WRITE ? "write" : "read");
show_pte(KERN_ALERT, mm, addr);
die("Oops", regs, fsr);
bust_spinlocks(0);
make_task_dead(SIGKILL);
}
/*
* Oops. The kernel tried to access some page that wasn't present.
*/
static void
__do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
struct pt_regs *regs)
{
const char *msg;
/*
* Are we prepared to handle this kernel fault?
*/
if (fixup_exception(regs))
return;
/*
* No handler, we'll have to terminate things with extreme prejudice.
*/
if (addr < PAGE_SIZE) {
msg = "NULL pointer dereference";
} else {
if (is_translation_fault(fsr) &&
kfence_handle_page_fault(addr, is_write_fault(fsr), regs))
return;
msg = "paging request";
}
die_kernel_fault(msg, mm, addr, fsr, regs);
}
/*
* Something tried to access memory that isn't in our memory map..
* User mode accesses just cause a SIGSEGV
*/
static void
__do_user_fault(unsigned long addr, unsigned int fsr, unsigned int sig,
int code, struct pt_regs *regs)
{
struct task_struct *tsk = current;
if (addr > TASK_SIZE)
harden_branch_predictor();
#ifdef CONFIG_DEBUG_USER
if (((user_debug & UDBG_SEGV) && (sig == SIGSEGV)) ||
((user_debug & UDBG_BUS) && (sig == SIGBUS))) {
pr_err("8<--- cut here ---\n");
pr_err("%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
tsk->comm, sig, addr, fsr);
show_pte(KERN_ERR, tsk->mm, addr);
show_regs(regs);
}
#endif
#ifndef CONFIG_KUSER_HELPERS
if ((sig == SIGSEGV) && ((addr & PAGE_MASK) == 0xffff0000))
printk_ratelimited(KERN_DEBUG
"%s: CONFIG_KUSER_HELPERS disabled at 0x%08lx\n",
tsk->comm, addr);
#endif
tsk->thread.address = addr;
tsk->thread.error_code = fsr;
tsk->thread.trap_no = 14;
force_sig_fault(sig, code, (void __user *)addr);
}
void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
{
struct task_struct *tsk = current;
struct mm_struct *mm = tsk->active_mm;
/*
* If we are in kernel mode at this point, we
* have no context to handle this fault with.
*/
if (user_mode(regs))
__do_user_fault(addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
else
__do_kernel_fault(mm, addr, fsr, regs);
}
#ifdef CONFIG_MMU
static inline bool is_permission_fault(unsigned int fsr)
{
int fs = fsr_fs(fsr);
#ifdef CONFIG_ARM_LPAE
if ((fs & FS_MMU_NOLL_MASK) == FS_PERM_NOLL)
return true;
#else
if (fs == FS_L1_PERM || fs == FS_L2_PERM)
return true;
#endif
return false;
}
#ifdef CONFIG_CPU_TTBR0_PAN
static inline bool ttbr0_usermode_access_allowed(struct pt_regs *regs)
{
struct svc_pt_regs *svcregs;
/* If we are in user mode: permission granted */
if (user_mode(regs))
return true;
/* uaccess state saved above pt_regs on SVC exception entry */
svcregs = to_svc_pt_regs(regs);
return !(svcregs->ttbcr & TTBCR_EPD0);
}
#else
static inline bool ttbr0_usermode_access_allowed(struct pt_regs *regs)
{
return true;
}
#endif
static int __kprobes
do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
int sig, code;
vm_fault_t fault;
unsigned int flags = FAULT_FLAG_DEFAULT;
unsigned long vm_flags = VM_ACCESS_FLAGS;
if (kprobe_page_fault(regs, fsr))
return 0;
/* Enable interrupts if they were enabled in the parent context. */
if (interrupts_enabled(regs))
local_irq_enable();
/*
* If we're in an interrupt or have no user
* context, we must not take the fault..
*/
if (faulthandler_disabled() || !mm)
goto no_context;
if (user_mode(regs))
flags |= FAULT_FLAG_USER;
if (is_write_fault(fsr)) {
flags |= FAULT_FLAG_WRITE;
vm_flags = VM_WRITE;
}
if (fsr & FSR_LNX_PF) {
vm_flags = VM_EXEC;
if (is_permission_fault(fsr) && !user_mode(regs))
die_kernel_fault("execution of memory",
mm, addr, fsr, regs);
}
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
/*
* Privileged access aborts with CONFIG_CPU_TTBR0_PAN enabled are
* routed via the translation fault mechanism. Check whether uaccess
* is disabled while in kernel mode.
*/
if (!ttbr0_usermode_access_allowed(regs))
goto no_context;
if (!(flags & FAULT_FLAG_USER))
goto lock_mmap;
vma = lock_vma_under_rcu(mm, addr);
if (!vma)
goto lock_mmap;
if (!(vma->vm_flags & vm_flags)) {
vma_end_read(vma);
count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
fault = 0;
code = SEGV_ACCERR;
goto bad_area;
}
fault = handle_mm_fault(vma, addr, flags | FAULT_FLAG_VMA_LOCK, regs);
if (!(fault & (VM_FAULT_RETRY | VM_FAULT_COMPLETED)))
vma_end_read(vma);
if (!(fault & VM_FAULT_RETRY)) {
count_vm_vma_lock_event(VMA_LOCK_SUCCESS);
goto done;
}
count_vm_vma_lock_event(VMA_LOCK_RETRY);
if (fault & VM_FAULT_MAJOR)
flags |= FAULT_FLAG_TRIED;
/* Quick path to respond to signals */
if (fault_signal_pending(fault, regs)) {
if (!user_mode(regs))
goto no_context;
return 0;
}
lock_mmap:
retry:
vma = lock_mm_and_find_vma(mm, addr, regs);
if (unlikely(!vma)) {
fault = 0;
code = SEGV_MAPERR;
goto bad_area;
}
/*
* ok, we have a good vm_area for this memory access, check the
* permissions on the VMA allow for the fault which occurred.
*/
if (!(vma->vm_flags & vm_flags)) {
mmap_read_unlock(mm);
fault = 0;
code = SEGV_ACCERR;
goto bad_area;
}
fault = handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);
/* If we need to retry but a fatal signal is pending, handle the
* signal first. We do not need to release the mmap_lock because
* it would already be released in __lock_page_or_retry in
* mm/filemap.c. */
if (fault_signal_pending(fault, regs)) {
if (!user_mode(regs))
goto no_context;
return 0;
}
/* The fault is fully completed (including releasing mmap lock) */
if (fault & VM_FAULT_COMPLETED)
return 0;
if (!(fault & VM_FAULT_ERROR)) {
if (fault & VM_FAULT_RETRY) {
flags |= FAULT_FLAG_TRIED;
goto retry;
}
}
mmap_read_unlock(mm);
done:
/* Handle the "normal" case first */
if (likely(!(fault & VM_FAULT_ERROR)))
return 0;
code = SEGV_MAPERR;
bad_area:
/*
* If we are in kernel mode at this point, we
* have no context to handle this fault with.
*/
if (!user_mode(regs))
goto no_context;
if (fault & VM_FAULT_OOM) {
/*
* We ran out of memory, call the OOM killer, and return to
* userspace (which will retry the fault, or kill us if we
* got oom-killed)
*/
pagefault_out_of_memory();
return 0;
}
if (fault & VM_FAULT_SIGBUS) {
/*
* We had some memory, but were unable to
* successfully fix up this page fault.
*/
sig = SIGBUS;
code = BUS_ADRERR;
} else {
/*
* Something tried to access memory that
* isn't in our memory map..
*/
sig = SIGSEGV;
}
__do_user_fault(addr, fsr, sig, code, regs);
return 0;
no_context:
__do_kernel_fault(mm, addr, fsr, regs);
return 0;
}
#else /* CONFIG_MMU */
static int
do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
{
return 0;
}
#endif /* CONFIG_MMU */
/*
* First Level Translation Fault Handler
*
* We enter here because the first level page table doesn't contain
* a valid entry for the address.
*
* If the address is in kernel space (>= TASK_SIZE), then we are
* probably faulting in the vmalloc() area.
*
* If the init_task's first level page tables contains the relevant
* entry, we copy the it to this task. If not, we send the process
* a signal, fixup the exception, or oops the kernel.
*
* NOTE! We MUST NOT take any locks for this case. We may be in an
* interrupt or a critical region, and should only copy the information
* from the master page table, nothing more.
*/
#ifdef CONFIG_MMU
static int __kprobes
do_translation_fault(unsigned long addr, unsigned int fsr,
struct pt_regs *regs)
{
unsigned int index;
pgd_t *pgd, *pgd_k;
p4d_t *p4d, *p4d_k;
pud_t *pud, *pud_k;
pmd_t *pmd, *pmd_k;
if (addr < TASK_SIZE)
return do_page_fault(addr, fsr, regs);
if (user_mode(regs))
goto bad_area;
index = pgd_index(addr);
pgd = cpu_get_pgd() + index;
pgd_k = init_mm.pgd + index;
p4d = p4d_offset(pgd, addr);
p4d_k = p4d_offset(pgd_k, addr);
if (p4d_none(*p4d_k))
goto bad_area;
if (!p4d_present(*p4d))
set_p4d(p4d, *p4d_k);
pud = pud_offset(p4d, addr);
pud_k = pud_offset(p4d_k, addr);
if (pud_none(*pud_k))
goto bad_area;
if (!pud_present(*pud))
set_pud(pud, *pud_k);
pmd = pmd_offset(pud, addr);
pmd_k = pmd_offset(pud_k, addr);
#ifdef CONFIG_ARM_LPAE
/*
* Only one hardware entry per PMD with LPAE.
*/
index = 0;
#else
/*
* On ARM one Linux PGD entry contains two hardware entries (see page
* tables layout in pgtable.h). We normally guarantee that we always
* fill both L1 entries. But create_mapping() doesn't follow the rule.
* It can create inidividual L1 entries, so here we have to call
* pmd_none() check for the entry really corresponded to address, not
* for the first of pair.
*/
index = (addr >> SECTION_SHIFT) & 1;
#endif
if (pmd_none(pmd_k[index]))
goto bad_area;
copy_pmd(pmd, pmd_k);
return 0;
bad_area:
do_bad_area(addr, fsr, regs);
return 0;
}
#else /* CONFIG_MMU */
static int
do_translation_fault(unsigned long addr, unsigned int fsr,
struct pt_regs *regs)
{
return 0;
}
#endif /* CONFIG_MMU */
/*
* Some section permission faults need to be handled gracefully.
* They can happen due to a __{get,put}_user during an oops.
*/
#ifndef CONFIG_ARM_LPAE
static int
do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
{
do_bad_area(addr, fsr, regs);
return 0;
}
#endif /* CONFIG_ARM_LPAE */
/*
* This abort handler always returns "fault".
*/
static int
do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
{
return 1;
}
struct fsr_info {
int (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
int sig;
int code;
const char *name;
};
/* FSR definition */
#ifdef CONFIG_ARM_LPAE
#include "fsr-3level.c"
#else
#include "fsr-2level.c"
#endif
void __init
hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
int sig, int code, const char *name)
{
if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
BUG();
fsr_info[nr].fn = fn;
fsr_info[nr].sig = sig;
fsr_info[nr].code = code;
fsr_info[nr].name = name;
}
/*
* Dispatch a data abort to the relevant handler.
*/
asmlinkage void
do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
{
const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
return;
pr_alert("8<--- cut here ---\n");
pr_alert("Unhandled fault: %s (0x%03x) at 0x%08lx\n",
inf->name, fsr, addr);
show_pte(KERN_ALERT, current->mm, addr);
arm_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
fsr, 0);
}
void __init
hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
int sig, int code, const char *name)
{
if (nr < 0 || nr >= ARRAY_SIZE(ifsr_info))
BUG();
ifsr_info[nr].fn = fn;
ifsr_info[nr].sig = sig;
ifsr_info[nr].code = code;
ifsr_info[nr].name = name;
}
asmlinkage void
do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
{
const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr);
if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
return;
pr_alert("8<--- cut here ---\n");
pr_alert("Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
inf->name, ifsr, addr);
arm_notify_die("", regs, inf->sig, inf->code, (void __user *)addr,
ifsr, 0);
}
/*
* Abort handler to be used only during first unmasking of asynchronous aborts
* on the boot CPU. This makes sure that the machine will not die if the
* firmware/bootloader left an imprecise abort pending for us to trip over.
*/
static int __init early_abort_handler(unsigned long addr, unsigned int fsr,
struct pt_regs *regs)
{
pr_warn("Hit pending asynchronous external abort (FSR=0x%08x) during "
"first unmask, this is most likely caused by a "
"firmware/bootloader bug.\n", fsr);
return 0;
}
void __init early_abt_enable(void)
{
fsr_info[FSR_FS_AEA].fn = early_abort_handler;
local_abt_enable();
fsr_info[FSR_FS_AEA].fn = do_bad;
}
#ifndef CONFIG_ARM_LPAE
static int __init exceptions_init(void)
{
if (cpu_architecture() >= CPU_ARCH_ARMv6) {
hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
"I-cache maintenance fault");
}
if (cpu_architecture() >= CPU_ARCH_ARMv7) {
/*
* TODO: Access flag faults introduced in ARMv6K.
* Runtime check for 'K' extension is needed
*/
hook_fault_code(3, do_bad, SIGSEGV, SEGV_MAPERR,
"section access flag fault");
hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
"section access flag fault");
}
return 0;
}
arch_initcall(exceptions_init);
#endif
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