cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
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fault.c (4388B)

      1// SPDX-License-Identifier: GPL-2.0-only
      2/* Page Fault Handling for ARC (TLB Miss / ProtV)
      3 *
      4 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
      5 */
      6
      7#include <linux/signal.h>
      8#include <linux/interrupt.h>
      9#include <linux/sched/signal.h>
     10#include <linux/errno.h>
     11#include <linux/ptrace.h>
     12#include <linux/uaccess.h>
     13#include <linux/kdebug.h>
     14#include <linux/perf_event.h>
     15#include <linux/mm_types.h>
     16#include <asm/mmu.h>
     17
     18/*
     19 * kernel virtual address is required to implement vmalloc/pkmap/fixmap
     20 * Refer to asm/processor.h for System Memory Map
     21 *
     22 * It simply copies the PMD entry (pointer to 2nd level page table or hugepage)
     23 * from swapper pgdir to task pgdir. The 2nd level table/page is thus shared
     24 */
     25noinline static int handle_kernel_vaddr_fault(unsigned long address)
     26{
     27	/*
     28	 * Synchronize this task's top level page-table
     29	 * with the 'reference' page table.
     30	 */
     31	pgd_t *pgd, *pgd_k;
     32	p4d_t *p4d, *p4d_k;
     33	pud_t *pud, *pud_k;
     34	pmd_t *pmd, *pmd_k;
     35
     36	pgd = pgd_offset(current->active_mm, address);
     37	pgd_k = pgd_offset_k(address);
     38
     39	if (pgd_none (*pgd_k))
     40		goto bad_area;
     41	if (!pgd_present(*pgd))
     42		set_pgd(pgd, *pgd_k);
     43
     44	p4d = p4d_offset(pgd, address);
     45	p4d_k = p4d_offset(pgd_k, address);
     46	if (p4d_none(*p4d_k))
     47		goto bad_area;
     48	if (!p4d_present(*p4d))
     49		set_p4d(p4d, *p4d_k);
     50
     51	pud = pud_offset(p4d, address);
     52	pud_k = pud_offset(p4d_k, address);
     53	if (pud_none(*pud_k))
     54		goto bad_area;
     55	if (!pud_present(*pud))
     56		set_pud(pud, *pud_k);
     57
     58	pmd = pmd_offset(pud, address);
     59	pmd_k = pmd_offset(pud_k, address);
     60	if (pmd_none(*pmd_k))
     61		goto bad_area;
     62	if (!pmd_present(*pmd))
     63		set_pmd(pmd, *pmd_k);
     64
     65	/* XXX: create the TLB entry here */
     66	return 0;
     67
     68bad_area:
     69	return 1;
     70}
     71
     72void do_page_fault(unsigned long address, struct pt_regs *regs)
     73{
     74	struct vm_area_struct *vma = NULL;
     75	struct task_struct *tsk = current;
     76	struct mm_struct *mm = tsk->mm;
     77	int sig, si_code = SEGV_MAPERR;
     78	unsigned int write = 0, exec = 0, mask;
     79	vm_fault_t fault = VM_FAULT_SIGSEGV;	/* handle_mm_fault() output */
     80	unsigned int flags;			/* handle_mm_fault() input */
     81
     82	/*
     83	 * NOTE! We MUST NOT take any locks for this case. We may
     84	 * be in an interrupt or a critical region, and should
     85	 * only copy the information from the master page table,
     86	 * nothing more.
     87	 */
     88	if (address >= VMALLOC_START && !user_mode(regs)) {
     89		if (unlikely(handle_kernel_vaddr_fault(address)))
     90			goto no_context;
     91		else
     92			return;
     93	}
     94
     95	/*
     96	 * If we're in an interrupt or have no user
     97	 * context, we must not take the fault..
     98	 */
     99	if (faulthandler_disabled() || !mm)
    100		goto no_context;
    101
    102	if (regs->ecr_cause & ECR_C_PROTV_STORE)	/* ST/EX */
    103		write = 1;
    104	else if ((regs->ecr_vec == ECR_V_PROTV) &&
    105	         (regs->ecr_cause == ECR_C_PROTV_INST_FETCH))
    106		exec = 1;
    107
    108	flags = FAULT_FLAG_DEFAULT;
    109	if (user_mode(regs))
    110		flags |= FAULT_FLAG_USER;
    111	if (write)
    112		flags |= FAULT_FLAG_WRITE;
    113
    114	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
    115retry:
    116	mmap_read_lock(mm);
    117
    118	vma = find_vma(mm, address);
    119	if (!vma)
    120		goto bad_area;
    121	if (unlikely(address < vma->vm_start)) {
    122		if (!(vma->vm_flags & VM_GROWSDOWN) || expand_stack(vma, address))
    123			goto bad_area;
    124	}
    125
    126	/*
    127	 * vm_area is good, now check permissions for this memory access
    128	 */
    129	mask = VM_READ;
    130	if (write)
    131		mask = VM_WRITE;
    132	if (exec)
    133		mask = VM_EXEC;
    134
    135	if (!(vma->vm_flags & mask)) {
    136		si_code = SEGV_ACCERR;
    137		goto bad_area;
    138	}
    139
    140	fault = handle_mm_fault(vma, address, flags, regs);
    141
    142	/* Quick path to respond to signals */
    143	if (fault_signal_pending(fault, regs)) {
    144		if (!user_mode(regs))
    145			goto no_context;
    146		return;
    147	}
    148
    149	/*
    150	 * Fault retry nuances, mmap_lock already relinquished by core mm
    151	 */
    152	if (unlikely(fault & VM_FAULT_RETRY)) {
    153		flags |= FAULT_FLAG_TRIED;
    154		goto retry;
    155	}
    156
    157bad_area:
    158	mmap_read_unlock(mm);
    159
    160	/*
    161	 * Major/minor page fault accounting
    162	 * (in case of retry we only land here once)
    163	 */
    164	if (likely(!(fault & VM_FAULT_ERROR)))
    165		/* Normal return path: fault Handled Gracefully */
    166		return;
    167
    168	if (!user_mode(regs))
    169		goto no_context;
    170
    171	if (fault & VM_FAULT_OOM) {
    172		pagefault_out_of_memory();
    173		return;
    174	}
    175
    176	if (fault & VM_FAULT_SIGBUS) {
    177		sig = SIGBUS;
    178		si_code = BUS_ADRERR;
    179	}
    180	else {
    181		sig = SIGSEGV;
    182	}
    183
    184	tsk->thread.fault_address = address;
    185	force_sig_fault(sig, si_code, (void __user *)address);
    186	return;
    187
    188no_context:
    189	if (fixup_exception(regs))
    190		return;
    191
    192	die("Oops", regs, address);
    193}