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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2020-2022 Loongson Technology Corporation Limited
*
* Derived from MIPS:
* Copyright (C) 1995 - 2000 by Ralf Baechle
*/
#include <linux/context_tracking.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/entry-common.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/ptrace.h>
#include <linux/ratelimit.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kdebug.h>
#include <linux/perf_event.h>
#include <linux/uaccess.h>
#include <linux/kfence.h>
#include <asm/branch.h>
#include <asm/exception.h>
#include <asm/mmu_context.h>
#include <asm/ptrace.h>
int show_unhandled_signals = 1;
static void __kprobes no_context(struct pt_regs *regs,
unsigned long write, unsigned long address)
{
const int field = sizeof(unsigned long) * 2;
/* Are we prepared to handle this kernel fault? */
if (fixup_exception(regs))
return;
if (kfence_handle_page_fault(address, write, regs))
return;
/*
* Oops. The kernel tried to access some bad page. We'll have to
* terminate things with extreme prejudice.
*/
bust_spinlocks(1);
pr_alert("CPU %d Unable to handle kernel paging request at "
"virtual address %0*lx, era == %0*lx, ra == %0*lx\n",
raw_smp_processor_id(), field, address, field, regs->csr_era,
field, regs->regs[1]);
die("Oops", regs);
}
static void __kprobes do_out_of_memory(struct pt_regs *regs,
unsigned long write, unsigned long address)
{
/*
* We ran out of memory, call the OOM killer, and return the userspace
* (which will retry the fault, or kill us if we got oom-killed).
*/
if (!user_mode(regs)) {
no_context(regs, write, address);
return;
}
pagefault_out_of_memory();
}
static void __kprobes do_sigbus(struct pt_regs *regs,
unsigned long write, unsigned long address, int si_code)
{
/* Kernel mode? Handle exceptions or die */
if (!user_mode(regs)) {
no_context(regs, write, address);
return;
}
/*
* Send a sigbus, regardless of whether we were in kernel
* or user mode.
*/
current->thread.csr_badvaddr = address;
current->thread.trap_nr = read_csr_excode();
force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
}
static void __kprobes do_sigsegv(struct pt_regs *regs,
unsigned long write, unsigned long address, int si_code)
{
const int field = sizeof(unsigned long) * 2;
static DEFINE_RATELIMIT_STATE(ratelimit_state, 5 * HZ, 10);
/* Kernel mode? Handle exceptions or die */
if (!user_mode(regs)) {
no_context(regs, write, address);
return;
}
/* User mode accesses just cause a SIGSEGV */
current->thread.csr_badvaddr = address;
if (!write)
current->thread.error_code = 1;
else
current->thread.error_code = 2;
current->thread.trap_nr = read_csr_excode();
if (show_unhandled_signals &&
unhandled_signal(current, SIGSEGV) && __ratelimit(&ratelimit_state)) {
pr_info("do_page_fault(): sending SIGSEGV to %s for invalid %s %0*lx\n",
current->comm,
write ? "write access to" : "read access from",
field, address);
pr_info("era = %0*lx in", field,
(unsigned long) regs->csr_era);
print_vma_addr(KERN_CONT " ", regs->csr_era);
pr_cont("\n");
pr_info("ra = %0*lx in", field,
(unsigned long) regs->regs[1]);
print_vma_addr(KERN_CONT " ", regs->regs[1]);
pr_cont("\n");
}
force_sig_fault(SIGSEGV, si_code, (void __user *)address);
}
/*
* This routine handles page faults. It determines the address,
* and the problem, and then passes it off to one of the appropriate
* routines.
*/
static void __kprobes __do_page_fault(struct pt_regs *regs,
unsigned long write, unsigned long address)
{
int si_code = SEGV_MAPERR;
unsigned int flags = FAULT_FLAG_DEFAULT;
struct task_struct *tsk = current;
struct mm_struct *mm = tsk->mm;
struct vm_area_struct *vma = NULL;
vm_fault_t fault;
if (kprobe_page_fault(regs, current->thread.trap_nr))
return;
/*
* We fault-in kernel-space virtual memory on-demand. The
* 'reference' page table is init_mm.pgd.
*
* 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.
*/
if (address & __UA_LIMIT) {
if (!user_mode(regs))
no_context(regs, write, address);
else
do_sigsegv(regs, write, address, si_code);
return;
}
/*
* If we're in an interrupt or have no user
* context, we must not take the fault..
*/
if (faulthandler_disabled() || !mm) {
do_sigsegv(regs, write, address, si_code);
return;
}
if (user_mode(regs))
flags |= FAULT_FLAG_USER;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
retry:
vma = lock_mm_and_find_vma(mm, address, regs);
if (unlikely(!vma))
goto bad_area_nosemaphore;
goto good_area;
/*
* Something tried to access memory that isn't in our memory map..
* Fix it, but check if it's kernel or user first..
*/
bad_area:
mmap_read_unlock(mm);
bad_area_nosemaphore:
do_sigsegv(regs, write, address, si_code);
return;
/*
* Ok, we have a good vm_area for this memory access, so
* we can handle it..
*/
good_area:
si_code = SEGV_ACCERR;
if (write) {
flags |= FAULT_FLAG_WRITE;
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
} else {
if (!(vma->vm_flags & VM_EXEC) && address == exception_era(regs))
goto bad_area;
if (!(vma->vm_flags & (VM_READ | VM_WRITE)) && address != exception_era(regs))
goto bad_area;
}
/*
* 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);
if (fault_signal_pending(fault, regs)) {
if (!user_mode(regs))
no_context(regs, write, address);
return;
}
/* The fault is fully completed (including releasing mmap lock) */
if (fault & VM_FAULT_COMPLETED)
return;
if (unlikely(fault & VM_FAULT_RETRY)) {
flags |= FAULT_FLAG_TRIED;
/*
* No need to mmap_read_unlock(mm) as we would
* have already released it in __lock_page_or_retry
* in mm/filemap.c.
*/
goto retry;
}
if (unlikely(fault & VM_FAULT_ERROR)) {
mmap_read_unlock(mm);
if (fault & VM_FAULT_OOM) {
do_out_of_memory(regs, write, address);
return;
} else if (fault & VM_FAULT_SIGSEGV) {
do_sigsegv(regs, write, address, si_code);
return;
} else if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
do_sigbus(regs, write, address, si_code);
return;
}
BUG();
}
mmap_read_unlock(mm);
}
asmlinkage void __kprobes do_page_fault(struct pt_regs *regs,
unsigned long write, unsigned long address)
{
irqentry_state_t state = irqentry_enter(regs);
/* Enable interrupt if enabled in parent context */
if (likely(regs->csr_prmd & CSR_PRMD_PIE))
local_irq_enable();
__do_page_fault(regs, write, address);
local_irq_disable();
irqentry_exit(regs, state);
}
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