cregit-Linux how code gets into the kernel

Release 4.14 arch/x86/mm/fault.c

Directory: arch/x86/mm
// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1995  Linus Torvalds
 *  Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
 *  Copyright (C) 2008-2009, Red Hat Inc., Ingo Molnar
 */
#include <linux/sched.h>		/* test_thread_flag(), ...      */
#include <linux/sched/task_stack.h>	/* task_stack_*(), ...          */
#include <linux/kdebug.h>		/* oops_begin/end, ...          */
#include <linux/extable.h>		/* search_exception_tables      */
#include <linux/bootmem.h>		/* max_low_pfn                  */
#include <linux/kprobes.h>		/* NOKPROBE_SYMBOL, ...         */
#include <linux/mmiotrace.h>		/* kmmio_handler, ...           */
#include <linux/perf_event.h>		/* perf_sw_event                */
#include <linux/hugetlb.h>		/* hstate_index_to_shift        */
#include <linux/prefetch.h>		/* prefetchw                    */
#include <linux/context_tracking.h>	/* exception_enter(), ...       */
#include <linux/uaccess.h>		/* faulthandler_disabled()      */

#include <asm/cpufeature.h>		/* boot_cpu_has, ...            */
#include <asm/traps.h>			/* dotraplinkage, ...           */
#include <asm/pgalloc.h>		/* pgd_*(), ...                 */
#include <asm/kmemcheck.h>		/* kmemcheck_*(), ...           */
#include <asm/fixmap.h>			/* VSYSCALL_ADDR                */
#include <asm/vsyscall.h>		/* emulate_vsyscall             */
#include <asm/vm86.h>			/* struct vm86                  */
#include <asm/mmu_context.h>		/* vma_pkey()                   */


#define CREATE_TRACE_POINTS
#include <asm/trace/exceptions.h>

/*
 * Page fault error code bits:
 *
 *   bit 0 ==    0: no page found       1: protection fault
 *   bit 1 ==    0: read access         1: write access
 *   bit 2 ==    0: kernel-mode access  1: user-mode access
 *   bit 3 ==                           1: use of reserved bit detected
 *   bit 4 ==                           1: fault was an instruction fetch
 *   bit 5 ==                           1: protection keys block access
 */

enum x86_pf_error_code {

	
PF_PROT		=		1 << 0,
	
PF_WRITE	=		1 << 1,
	
PF_USER		=		1 << 2,
	
PF_RSVD		=		1 << 3,
	
PF_INSTR	=		1 << 4,
	
PF_PK		=		1 << 5,
};

/*
 * Returns 0 if mmiotrace is disabled, or if the fault is not
 * handled by mmiotrace:
 */


static nokprobe_inline int

kmmio_fault(struct pt_regs *regs, unsigned long addr)
{
	if (unlikely(is_kmmio_active()))
		if (kmmio_handler(regs, addr) == 1)
			return -1;
	return 0;
}


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Pekka Paalanen4197.62%375.00%


Masami Hiramatsu12.38%125.00%


Total42100.00%4100.00%






static nokprobe_inline int kprobes_fault(struct pt_regs *regs)
{
	int ret = 0;

	/* kprobe_running() needs smp_processor_id() */
	if (kprobes_built_in() && !user_mode(regs)) {
		preempt_disable();
		if (kprobe_running() && kprobe_fault_handler(regs, 14))
			ret = 1;
		preempt_enable();
	}

	return ret;
}


Contributors
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Christoph Hellwig2748.21%111.11%


Anil S Keshavamurthy1221.43%111.11%


Harvey Harrison916.07%222.22%


Ingo Molnar35.36%111.11%


Andi Kleen23.57%111.11%


Peter Zijlstra11.79%111.11%


Masami Hiramatsu11.79%111.11%


Andrew Lutomirski11.79%111.11%


Total56100.00%9100.00%



/*
 * Prefetch quirks:
 *
 * 32-bit mode:
 *
 *   Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
 *   Check that here and ignore it.
 *
 * 64-bit mode:
 *
 *   Sometimes the CPU reports invalid exceptions on prefetch.
 *   Check that here and ignore it.
 *
 * Opcode checker based on code by Richard Brunner.
 */


static inline int

check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
		      unsigned char opcode, int *prefetch)
{
	unsigned char instr_hi = opcode & 0xf0;
	unsigned char instr_lo = opcode & 0x0f;

	switch (instr_hi) {
	case 0x20:
	case 0x30:
		/*
                 * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
                 * In X86_64 long mode, the CPU will signal invalid
                 * opcode if some of these prefixes are present so
                 * X86_64 will never get here anyway
                 */
		return ((instr_lo & 7) == 0x6);
#ifdef CONFIG_X86_64
	case 0x40:
		/*
                 * In AMD64 long mode 0x40..0x4F are valid REX prefixes
                 * Need to figure out under what instruction mode the
                 * instruction was issued. Could check the LDT for lm,
                 * but for now it's good enough to assume that long
                 * mode only uses well known segments or kernel.
                 */
		return (!user_mode(regs) || user_64bit_mode(regs));
#endif
	case 0x60:
		/* 0x64 thru 0x67 are valid prefixes in all modes. */
		return (instr_lo & 0xC) == 0x4;
	case 0xF0:
		/* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
		return !instr_lo || (instr_lo>>1) == 1;
	case 0x00:
		/* Prefetch instruction is 0x0F0D or 0x0F18 */
		if (probe_kernel_address(instr, opcode))
			return 0;

		*prefetch = (instr_lo == 0xF) &&
			(opcode == 0x0D || opcode == 0x18);
		return 0;
	default:
		return 0;
	}
}


Contributors
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Andi Kleen10767.30%225.00%


Ingo Molnar3924.53%225.00%


Harvey Harrison63.77%225.00%


Vincent Hanquez42.52%112.50%


Andrew Lutomirski31.89%112.50%


Total159100.00%8100.00%





static int

is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
{
	unsigned char *max_instr;
	unsigned char *instr;
	int prefetch = 0;

	/*
         * If it was a exec (instruction fetch) fault on NX page, then
         * do not ignore the fault:
         */
	if (error_code & PF_INSTR)
		return 0;

	instr = (void *)convert_ip_to_linear(current, regs);
	max_instr = instr + 15;

	if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE_MAX)
		return 0;

	while (instr < max_instr) {
		unsigned char opcode;

		if (probe_kernel_address(instr, opcode))
			break;

		instr++;

		if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
			break;
	}
	return prefetch;
}


Contributors
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Ingo Molnar11692.06%133.33%


Andi Kleen97.14%133.33%


Andrew Lutomirski10.79%133.33%


Total126100.00%3100.00%



/*
 * A protection key fault means that the PKRU value did not allow
 * access to some PTE.  Userspace can figure out what PKRU was
 * from the XSAVE state, and this function fills out a field in
 * siginfo so userspace can discover which protection key was set
 * on the PTE.
 *
 * If we get here, we know that the hardware signaled a PF_PK
 * fault and that there was a VMA once we got in the fault
 * handler.  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 PKRU 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_sem, etc...
 * 6. T1   : reaches here, sees vma_pkey(vma)=5, when we really
 *           faulted on a pte with its pkey=4.
 */



static void fill_sig_info_pkey(int si_code, siginfo_t *info, u32 *pkey)
{
	/* This is effectively an #ifdef */
	if (!boot_cpu_has(X86_FEATURE_OSPKE))
		return;

	/* Fault not from Protection Keys: nothing to do */
	if (si_code != SEGV_PKUERR)
		return;
	/*
         * force_sig_info_fault() is called from a number of
         * contexts, some of which have a VMA and some of which
         * do not.  The PF_PK handing happens after we have a
         * valid VMA, so we should never reach this without a
         * valid VMA.
         */
	if (!pkey) {
		WARN_ONCE(1, "PKU fault with no VMA passed in");
		info->si_pkey = 0;
		return;
	}
	/*
         * si_pkey should be thought of as a strong hint, but not
         * absolutely guranteed to be 100% accurate because of
         * the race explained above.
         */
	info->si_pkey = *pkey;
}


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Dave Hansen6092.31%150.00%


Laurent Dufour57.69%150.00%


Total65100.00%2100.00%





static void

force_sig_info_fault(int si_signo, int si_code, unsigned long address,
		     struct task_struct *tsk, u32 *pkey, int fault)
{
	unsigned lsb = 0;
	siginfo_t info;

	info.si_signo	= si_signo;
	info.si_errno	= 0;
	info.si_code	= si_code;
	info.si_addr	= (void __user *)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;
	info.si_addr_lsb = lsb;

	fill_sig_info_pkey(si_code, &info, pkey);

	force_sig_info(si_signo, &info, tsk);
}


Contributors
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Harvey Harrison6353.85%116.67%


Andi Kleen4034.19%233.33%


Dave Hansen119.40%233.33%


Laurent Dufour32.56%116.67%


Total117100.00%6100.00%




DEFINE_SPINLOCK(pgd_lock);

LIST_HEAD(pgd_list);

#ifdef CONFIG_X86_32



static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
{
	unsigned index = pgd_index(address);
	pgd_t *pgd_k;
	p4d_t *p4d, *p4d_k;
	pud_t *pud, *pud_k;
	pmd_t *pmd, *pmd_k;

	pgd += index;
	pgd_k = init_mm.pgd + index;

	if (!pgd_present(*pgd_k))
		return NULL;

	/*
         * set_pgd(pgd, *pgd_k); here would be useless on PAE
         * and redundant with the set_pmd() on non-PAE. As would
         * set_p4d/set_pud.
         */
	p4d = p4d_offset(pgd, address);
	p4d_k = p4d_offset(pgd_k, address);
	if (!p4d_present(*p4d_k))
		return NULL;

	pud = pud_offset(p4d, address);
	pud_k = pud_offset(p4d_k, address);
	if (!pud_present(*pud_k))
		return NULL;

	pmd = pmd_offset(pud, address);
	pmd_k = pmd_offset(pud_k, address);
	if (!pmd_present(*pmd_k))
		return NULL;

	if (!pmd_present(*pmd))
		set_pmd(pmd, *pmd_k);
	else
		BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));

	return pmd_k;
}


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Ingo Molnar16080.00%150.00%


Kirill A. Shutemov4020.00%150.00%


Total200100.00%2100.00%






void vmalloc_sync_all(void)
{
	unsigned long address;

	if (SHARED_KERNEL_PMD)
		return;

	for (address = VMALLOC_START & PMD_MASK;
	     address >= TASK_SIZE_MAX && address < FIXADDR_TOP;
	     address += PMD_SIZE) {
		struct page *page;

		spin_lock(&pgd_lock);
		list_for_each_entry(page, &pgd_list, lru) {
			spinlock_t *pgt_lock;
			pmd_t *ret;

			/* the pgt_lock only for Xen */
			pgt_lock = &pgd_page_get_mm(page)->page_table_lock;

			spin_lock(pgt_lock);
			ret = vmalloc_sync_one(page_address(page), address);
			spin_unlock(pgt_lock);

			if (!ret)
				break;
		}
		spin_unlock(&pgd_lock);
	}
}


Contributors
PersonTokensPropCommitsCommitProp
Ingo Molnar7365.18%120.00%


Jeremy Fitzhardinge3329.46%120.00%


Andrea Arcangeli32.68%120.00%


Borislav Petkov21.79%120.00%


Andrew Lutomirski10.89%120.00%


Total112100.00%5100.00%



/*
 * 32-bit:
 *
 *   Handle a fault on the vmalloc or module mapping area
 */



static noinline int vmalloc_fault(unsigned long address)
{
	unsigned long pgd_paddr;
	pmd_t *pmd_k;
	pte_t *pte_k;

	/* Make sure we are in vmalloc area: */
	if (!(address >= VMALLOC_START && address < VMALLOC_END))
		return -1;

	WARN_ON_ONCE(in_nmi());

	/*
         * Synchronize this task's top level page-table
         * with the 'reference' page table.
         *
         * Do _not_ use "current" here. We might be inside
         * an interrupt in the middle of a task switch..
         */
	pgd_paddr = read_cr3_pa();
	pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
	if (!pmd_k)
		return -1;

	if (pmd_huge(*pmd_k))
		return 0;

	pte_k = pte_offset_kernel(pmd_k, address);
	if (!pte_present(*pte_k))
		return -1;

	return 0;
}

Contributors
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Ingo Molnar9283.64%125.00%


Toshi Kani1110.00%125.00%


Frédéric Weisbecker65.45%125.00%


Andrew Lutomirski10.91%125.00%


Total110100.00%4100.00%




NOKPROBE_SYMBOL(vmalloc_fault);

/*
 * Did it hit the DOS screen memory VA from vm86 mode?
 */


static inline void

check_v8086_mode(struct pt_regs *regs, unsigned long address,
		 struct task_struct *tsk)
{
#ifdef CONFIG_VM86
	unsigned long bit;

	if (!v8086_mode(regs) || !tsk->thread.vm86)
		return;

	bit = (address - 0xA0000) >> PAGE_SHIFT;
	if (bit < 32)
		tsk->thread.vm86->screen_bitmap |= 1 << bit;
#endif
}


Contributors
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Ingo Molnar4864.86%133.33%


Brian Gerst1418.92%133.33%


Andi Kleen1216.22%133.33%


Total74100.00%3100.00%






static bool low_pfn(unsigned long pfn)
{
	return pfn < max_low_pfn;
}


Contributors
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Akinobu Mita15100.00%1100.00%


Total15100.00%1100.00%






static void dump_pagetable(unsigned long address)
{
	pgd_t *base = __va(read_cr3_pa());
	pgd_t *pgd = &base[pgd_index(address)];
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

#ifdef CONFIG_X86_PAE
	pr_info("*pdpt = %016Lx ", pgd_val(*pgd));
	if (!low_pfn(pgd_val(*pgd) >> PAGE_SHIFT) || !pgd_present(*pgd))
		goto out;

#define pr_pde pr_cont
#else
#define pr_pde pr_info
#endif
	p4d = p4d_offset(pgd, address);
	pud = pud_offset(p4d, address);
	pmd = pmd_offset(pud, address);
	pr_pde("*pde = %0*Lx ", sizeof(*pmd) * 2, (u64)pmd_val(*pmd));

#undef pr_pde

	/*
         * We must not directly access the pte in the highpte
         * case if the page table is located in highmem.
         * And let's rather not kmap-atomic the pte, just in case
         * it's allocated already:
         */
	if (!low_pfn(pmd_pfn(*pmd)) || !pmd_present(*pmd) || pmd_large(*pmd))
		goto out;

	pte = pte_offset_kernel(pmd, address);
	pr_cont("*pte = %0*Lx ", sizeof(*pte) * 2, (u64)pte_val(*pte));
out:
	pr_cont("\n");
}


Contributors
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Akinobu Mita10648.62%111.11%


Harvey Harrison3415.60%111.11%


Ingo Molnar2712.39%222.22%


Kirill A. Shutemov2411.01%111.11%


Jan Beulich177.80%111.11%


Andi Kleen83.67%111.11%


Andrew Lutomirski10.46%111.11%


Adrian Bunk10.46%111.11%


Total218100.00%9100.00%



#else /* CONFIG_X86_64: */




void vmalloc_sync_all(void)
{
	sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END);
}


Contributors
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Ingo Molnar1168.75%133.33%


Haicheng Li318.75%133.33%


Harvey Harrison212.50%133.33%


Total16100.00%3100.00%



/*
 * 64-bit:
 *
 *   Handle a fault on the vmalloc area
 */



static noinline int vmalloc_fault(unsigned long address)
{
	pgd_t *pgd, *pgd_ref;
	p4d_t *p4d, *p4d_ref;
	pud_t *pud, *pud_ref;
	pmd_t *pmd, *pmd_ref;
	pte_t *pte, *pte_ref;

	/* Make sure we are in vmalloc area: */
	if (!(address >= VMALLOC_START && address < VMALLOC_END))
		return -1;

	WARN_ON_ONCE(in_nmi());

	/*
         * Copy kernel mappings over when needed. This can also
         * happen within a race in page table update. In the later
         * case just flush:
         */
	pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address);
	pgd_ref = pgd_offset_k(address);
	if (pgd_none(*pgd_ref))
		return -1;

	if (pgd_none(*pgd)) {
		set_pgd(pgd, *pgd_ref);
		arch_flush_lazy_mmu_mode();
	} else if (CONFIG_PGTABLE_LEVELS > 4) {
		/*
                 * With folded p4d, pgd_none() is always false, so the pgd may
                 * point to an empty page table entry and pgd_page_vaddr()
                 * will return garbage.
                 *
                 * We will do the correct sanity check on the p4d level.
                 */
		BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
	}

	/* With 4-level paging, copying happens on the p4d level. */
	p4d = p4d_offset(pgd, address);
	p4d_ref = p4d_offset(pgd_ref, address);
	if (p4d_none(*p4d_ref))
		return -1;

	if (p4d_none(*p4d)) {
		set_p4d(p4d, *p4d_ref);
		arch_flush_lazy_mmu_mode();
	} else {
		BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_ref));
	}

	/*
         * Below here mismatches are bugs because these lower tables
         * are shared:
         */

	pud = pud_offset(p4d, address);
	pud_ref = pud_offset(p4d_ref, address);
	if (pud_none(*pud_ref))
		return -1;

	if (pud_none(*pud) || pud_pfn(*pud) != pud_pfn(*pud_ref))
		BUG();

	if (pud_huge(*pud))
		return 0;

	pmd = pmd_offset(pud, address);
	pmd_ref = pmd_offset(pud_ref, address);
	if (pmd_none(*pmd_ref))
		return -1;

	if (pmd_none(*pmd) || pmd_pfn(*pmd) != pmd_pfn(*pmd_ref))
		BUG();

	if (pmd_huge(*pmd))
		return 0;

	pte_ref = pte_offset_kernel(pmd_ref, address);
	if (!pte_present(*pte_ref))
		return -1;

	pte = pte_offset_kernel(pmd, address);

	/*
         * Don't use pte_page here, because the mappings can point
         * outside mem_map, and the NUMA hash lookup cannot handle
         * that:
         */
	if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
		BUG();

	return 0;
}

Contributors
PersonTokensPropCommitsCommitProp
Ingo Molnar16038.93%15.88%


Kirill A. Shutemov8721.17%15.88%


Andi Kleen8420.44%635.29%


Toshi Kani266.33%15.88%


Andrew Morton184.38%15.88%


Andrew Lutomirski112.68%211.76%


Jan Beulich102.43%211.76%


Samu Kallio71.70%15.88%


Frédéric Weisbecker61.46%15.88%


Glauber de Oliveira Costa20.49%15.88%


Total411100.00%17100.00%




NOKPROBE_SYMBOL(vmalloc_fault);

#ifdef CONFIG_CPU_SUP_AMD

static const char errata93_warning[] =
KERN_ERR 
"******* Your BIOS seems to not contain a fix for K8 errata #93\n"
"******* Working around it, but it may cause SEGVs or burn power.\n"
"******* Please consider a BIOS update.\n"
"******* Disabling USB legacy in the BIOS may also help.\n";
#endif

/*
 * No vm86 mode in 64-bit mode:
 */


static inline void

check_v8086_mode(struct pt_regs *regs, unsigned long address,
		 struct task_struct *tsk)
{
}


Contributors
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Ingo Molnar1260.00%150.00%


Harvey Harrison840.00%150.00%


Total20100.00%2100.00%






static int bad_address(void *p)
{
	unsigned long dummy;

	return probe_kernel_address((unsigned long *)p, dummy);
}


Contributors
PersonTokensPropCommitsCommitProp
Ingo Molnar2281.48%150.00%


Harvey Harrison518.52%150.00%


Total27100.00%2100.00%






static void dump_pagetable(unsigned long address)
{
	pgd_t *base = __va(read_cr3_pa());
	pgd_t *pgd = base + pgd_index(address);
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;

	if (bad_address(pgd))
		goto bad;

	pr_info("PGD %lx ", pgd_val(*pgd));

	if (!pgd_present(*pgd))
		goto out;

	p4d = p4d_offset(pgd, address);
	if (bad_address(p4d))
		goto bad;

	pr_cont("P4D %lx ", p4d_val(*p4d));
	if (!p4d_present(*p4d) || p4d_large(*p4d))
		goto out;

	pud = pud_offset(p4d, address);
	if (bad_address(pud))
		goto bad;

	pr_cont("PUD %lx ", pud_val(*pud));
	if (!pud_present(*pud) || pud_large(*pud))
		goto out;

	pmd = pmd_offset(pud, address);
	if (bad_address(pmd))
		goto bad;

	pr_cont("PMD %lx ", pmd_val(*pmd));
	if (!pmd_present(*pmd) || pmd_large(*pmd))
		goto out;

	pte = pte_offset_kernel(pmd, address);
	if (bad_address(pte))
		goto bad;

	pr_cont("PTE %lx", pte_val(*pte));
out:
	pr_cont("\n");
	return;
bad:
	pr_info("BAD\n");
}


Contributors
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Ingo Molnar12847.58%228.57%


Harvey Harrison6524.16%114.29%


Kirill A. Shutemov5219.33%114.29%


Akinobu Mita165.95%114.29%


Jan Beulich72.60%114.29%


Andrew Lutomirski10.37%114.29%


Total269100.00%7100.00%



#endif /* CONFIG_X86_64 */

/*
 * Workaround for K8 erratum #93 & buggy BIOS.
 *
 * BIOS SMM functions are required to use a specific workaround
 * to avoid corruption of the 64bit RIP register on C stepping K8.
 *
 * A lot of BIOS that didn't get tested properly miss this.
 *
 * The OS sees this as a page fault with the upper 32bits of RIP cleared.
 * Try to work around it here.
 *
 * Note we only handle faults in kernel here.
 * Does nothing on 32-bit.
 */



static int is_errata93(struct pt_regs *regs, unsigned long address)
{
#if defined(CONFIG_X86_64) && defined(CONFIG_CPU_SUP_AMD)
	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD
	    || boot_cpu_data.x86 != 0xf)
		return 0;

	if (address != regs->ip)
		return 0;

	if ((address >> 32) != 0)
		return 0;

	address |= 0xffffffffUL << 32;
	if ((address >= (u64)_stext && address <= (u64)_etext) ||
	    (address >= MODULES_VADDR && address <= MODULES_END)) {
		printk_once(errata93_warning);
		regs->ip = address;
		return 1;
	}
#endif
	return 0;
}


Contributors
PersonTokensPropCommitsCommitProp
Andi Kleen8972.95%120.00%


Jan Beulich2722.13%120.00%


Harvey Harrison32.46%120.00%


H. Peter Anvin21.64%120.00%


Ingo Molnar10.82%120.00%


Total122100.00%5100.00%



/*
 * Work around K8 erratum #100 K8 in compat mode occasionally jumps
 * to illegal addresses >4GB.
 *
 * We catch this in the page fault handler because these addresses
 * are not reachable. Just detect this case and return.  Any code
 * segment in LDT is compatibility mode.
 */



static int is_errata100(struct pt_regs *regs, unsigned long address)
{
#ifdef CONFIG_X86_64
	if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
		return 1;
#endif
	return 0;
}


Contributors
PersonTokensPropCommitsCommitProp
Harvey Harrison54100.00%1100.00%


Total54100.00%1100.00%






static int is_f00f_bug(struct pt_regs *regs, unsigned long address)
{
#ifdef CONFIG_X86_F00F_BUG
	unsigned long nr;

	/*
         * Pentium F0 0F C7 C8 bug workaround:
         */
	if (boot_cpu_has_bug(X86_BUG_F00F)) {
		nr = (address - idt_descr.address) >> 3;

		if (nr == 6) {
			do_invalid_op(regs, 0);
			return 1;
		}
	}
#endif
	return 0;
}


Contributors
PersonTokensPropCommitsCommitProp
Harvey Harrison6292.54%250.00%


Borislav Petkov45.97%125.00%


Ingo Molnar11.49%125.00%


Total67100.00%4100.00%




static const char nx_warning[] = KERN_CRIT
"kernel tried to execute NX-protected page - exploit attempt? (uid: %d)\n";

static const char smep_warning[] = KERN_CRIT
"unable to execute userspace code (SMEP?) (uid: %d)\n";



static void

show_fault_oops(struct pt_regs *regs, unsigned long error_code,
		unsigned long address)
{
	if (!oops_may_print())
		return;

	if (error_code & PF_INSTR) {
		unsigned int level;
		pgd_t *pgd;
		pte_t *pte;

		pgd = __va(read_cr3_pa());
		pgd += pgd_index(address);

		pte = lookup_address_in_pgd(pgd, address, &level);

		if (pte && pte_present(*pte) && !pte_exec(*pte))
			printk(nx_warning, from_kuid(&init_user_ns, current_uid()));
		if (pte && pte_present(*pte) && pte_exec(*pte) &&
				(pgd_flags(*pgd) & _PAGE_USER) &&
				(__read_cr4() & X86_CR4_SMEP))
			printk(smep_warning, from_kuid(&init_user_ns, current_uid()));
	}

	printk(KERN_ALERT "BUG: unable to handle kernel ");
	if (address < PAGE_SIZE)
		printk(KERN_CONT "NULL pointer dereference");
	else
		printk(KERN_CONT "paging request");

	printk(KERN_CONT " at %p\n", (void *) address);
	printk(KERN_ALERT "IP: %pS\n", (void *)regs->ip);

	dump_pagetable(address);
}


Contributors
PersonTokensPropCommitsCommitProp
Harvey Harrison11455.07%430.77%


Jiri Kosina4622.22%17.69%


Matt Fleming2512.08%17.69%


Josh Poimboeuf62.90%17.69%


Eric W. Biedermann62.90%17.69%


Vegard Nossum52.42%17.69%


Andrew Lutomirski20.97%215.38%


David Howells20.97%17.69%


Ingo Molnar10.48%17.69%


Total207100.00%13100.00%





static noinline void

pgtable_bad(struct pt_regs *regs, unsigned long error_code,
	    unsigned long address)
{
	struct task_struct *tsk;
	unsigned long flags;
	int sig;

	flags = oops_begin();
	tsk = current;
	sig = SIGKILL;

	printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
	       tsk->comm, address);
	dump_pagetable(address);

	tsk->thread.cr2		= address;
	tsk->thread.trap_nr	= X86_TRAP_PF;
	tsk->thread.error_code	= error_code;

	if (__die("Bad pagetable", regs, error_code))
		sig = 0;

	oops_end(flags, regs, sig);
}


Contributors
PersonTokensPropCommitsCommitProp
Andi Kleen4440.00%112.50%


Jan Beulich3632.73%337.50%


Ingo Molnar1614.55%112.50%


Alexander van Heukelum65.45%112.50%


Nicholas Piggin65.45%112.50%


Srikar Dronamraju21.82%112.50%


Total110100.00%8100.00%





static noinline void

no_context(struct pt_regs *regs, unsigned long error_code,
	   unsigned long address, int signal, int si_code)
{
	struct task_struct *tsk = current;
	unsigned long flags;
	int sig;

	/* Are we prepared to handle this kernel fault? */
	if (fixup_exception(regs, X86_TRAP_PF)) {
		/*
                 * Any interrupt that takes a fault gets the fixup. This makes
                 * the below recursive fault logic only apply to a faults from
                 * task context.
                 */
		if (in_interrupt())
			return;

		/*
                 * Per the above we're !in_interrupt(), aka. task context.
                 *
                 * In this case we need to make sure we're not recursively
                 * faulting through the emulate_vsyscall() logic.
                 */
		if (current->thread.sig_on_uaccess_err && signal) {
			tsk->thread.trap_nr = X86_TRAP_PF;
			tsk->thread.error_code = error_code | PF_USER;
			tsk->thread.cr2 = address;

			/* XXX: hwpoison faults will set the wrong code. */
			force_sig_info_fault(signal, si_code, address,
					     tsk, NULL, 0);
		}

		/*
                 * Barring that, we can do the fixup and be happy.
                 */
		return;
	}

#ifdef CONFIG_VMAP_STACK
	/*
         * Stack overflow?  During boot, we can fault near the initial
         * stack in the direct map, but that's not an overflow -- check
         * that we're in vmalloc space to avoid this.
         */
	if (is_vmalloc_addr((void *)address) &&
	    (((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
	     address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
		unsigned long stack = this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *);
		/*
                 * We're likely to be running with very little stack space
                 * left.  It's plausible that we'd hit this condition but
                 * double-fault even before we get this far, in which case
                 * we're fine: the double-fault handler will deal with it.
                 *
                 * We don't want to make it all the way into the oops code
                 * and then double-fault, though, because we're likely to
                 * break the console driver and lose most of the stack dump.
                 */
		asm volatile ("movq %[stack], %%rsp\n\t"
                              "call handle_stack_overflow\n\t"
                              "1: jmp 1b"
                              : ASM_CALL_CONSTRAINT
                              : "D" ("kernel stack overflow (page fault)"),
                                "S" (regs), "d" (address),
                                [stack] "rm" (stack));
		unreachable();
	}
#endif

	/*
         * 32-bit:
         *
         *   Valid to do another page fault here, because if this fault
         *   had been triggered by is_prefetch fixup_exception would have
         *   handled it.
         *
         * 64-bit:
         *
         *   Hall of shame of CPU/BIOS bugs.
         */
	if (is_prefetch(regs, error_code, address))
		return;

	if (is_errata93(regs, address))
		return;

	/*
         * Oops. The kernel tried to access some bad page. We'll have to
         * terminate things with extreme prejudice:
         */
	flags = oops_begin();

	show_fault_oops(regs, error_code, address);

	if (task_stack_end_corrupted(tsk))
		printk(KERN_EMERG "Thread overran stack, or stack corrupted\n");

	tsk->thread.cr2		= address;
	tsk->thread.trap_nr	= X86_TRAP_PF;
	tsk->thread.error_code	= error_code;

	sig = SIGKILL;
	if (__die("Oops", regs, error_code))
		sig = 0;

	/* Executive summary in case the body of the oops scrolled away */
	printk(KERN_DEFAULT "CR2: %016lx\n", address);

	oops_end(flags, regs, sig);
}


Contributors
PersonTokensPropCommitsCommitProp
Andrew Lutomirski13644.16%316.67%


Nicholas Piggin8326.95%15.56%


Jeremy Fitzhardinge4313.96%15.56%


Thomas Gleixner165.19%15.56%


Peter Zijlstra92.92%15.56%


Ingo Molnar82.60%316.67%


Srikar Dronamraju41.30%15.56%


Prarit Bhargava20.65%15.56%


Tony Luck20.65%15.56%


Josh Poimboeuf10.32%15.56%


Laurent Dufour10.32%15.56%


Aaron Tomlin10.32%15.56%


Dave Hansen10.32%15.56%


Jan Beulich10.32%15.56%


Total308100.00%18100.00%



/*
 * Print out info about fatal segfaults, if the show_unhandled_signals
 * sysctl is set:
 */


static inline void

show_signal_msg(struct pt_regs *regs, unsigned long error_code,
		unsigned long address, struct task_struct *tsk)
{
	if (!unhandled_signal(tsk, SIGSEGV))
		return;

	if (!printk_ratelimit())
		return;

	printk("%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
		task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
		tsk->comm, task_pid_nr(tsk), address,
		(void *)regs->ip, (void *)regs->sp, error_code);

	print_vma_addr(KERN_CONT " in ", regs->ip);

	printk(KERN_CONT "\n");
}


Contributors
PersonTokensPropCommitsCommitProp
Nicholas Piggin5855.77%116.67%


Andi Kleen1918.27%116.67%


Ingo Molnar1110.58%116.67%


Harvey Harrison109.62%233.33%


Jan Beulich65.77%116.67%


Total104100.00%6100.00%





static void

__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
		       unsigned long address, u32 *pkey, int si_code)
{
	struct task_struct *tsk = current;

	/* User mode accesses just cause a SIGSEGV */
	if (error_code & PF_USER) {
		/*
                 * It's possible to have interrupts off here:
                 */
		local_irq_enable();

		/*
                 * Valid to do another page fault here because this one came
                 * from user space:
                 */
		if (is_prefetch(regs, error_code, address))
			return;

		if (is_errata100(regs, address))
			return;

#ifdef CONFIG_X86_64
		/*
                 * Instruction fetch faults in the vsyscall page might need
                 * emulation.
                 */
		if (unlikely((error_code & PF_INSTR) &&
			     ((address & ~0xfff) == VSYSCALL_ADDR))) {
			if (emulate_vsyscall(regs, address))
				return;
		}
#endif

		/*
                 * To avoid leaking information about the kernel page table
                 * layout, pretend that user-mode accesses to kernel addresses
                 * are always protection faults.
                 */
		if (address >= TASK_SIZE_MAX)
			error_code |= PF_PROT;

		if (likely(show_unhandled_signals))
			show_signal_msg(regs, error_code, address, tsk);

		tsk->thread.cr2		= address;
		tsk->thread.error_code	= error_code;
		tsk->thread.trap_nr	= X86_TRAP_PF;

		force_sig_info_fault(SIGSEGV, si_code, address, tsk, pkey, 0);

		return;
	}

	if (is_f00f_bug(regs, address))
		return;

	no_context(regs, error_code, address, SIGSEGV, si_code);
}


Contributors
PersonTokensPropCommitsCommitProp
Ingo Molnar8039.80%18.33%


Andrew Lutomirski4622.89%433.33%


Nicholas Piggin3316.42%18.33%


Andi Kleen2411.94%216.67%


Kees Cook104.98%18.33%


Laurent Dufour31.49%18.33%


Dave Hansen31.49%18.33%


Srikar Dronamraju21.00%18.33%


Total201100.00%12100.00%





static noinline void

bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
		     unsigned long address, u32 *pkey)
{
	__bad_area_nosemaphore(regs, error_code, address, pkey, SEGV_MAPERR);
}


Contributors
PersonTokensPropCommitsCommitProp
Andi Kleen1745.95%240.00%


Nicholas Piggin1437.84%120.00%


Laurent Dufour38.11%120.00%


Dave Hansen38.11%120.00%


Total37100.00%5100.00%





static void

__bad_area(struct pt_regs *regs, unsigned long error_code,
	   unsigned long address,  struct vm_area_struct *vma, int si_code)
{
	struct mm_struct *mm = current->mm;
	u32 pkey;

	if (vma)
		pkey = vma_pkey(vma);

	/*
         * 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);

	__bad_area_nosemaphore(regs, error_code, address,
			       (vma) ? &pkey : NULL, si_code);
}


Contributors
PersonTokensPropCommitsCommitProp
Nicholas Piggin2329.11%18.33%


Laurent Dufour2126.58%18.33%


Andi Kleen1012.66%216.67%


Dave Hansen78.86%18.33%


Arjan van de Ven67.59%18.33%


Jeremy Fitzhardinge33.80%18.33%


Pekka Paalanen33.80%18.33%


Jan Beulich22.53%18.33%


Ingo Molnar22.53%18.33%


Harvey Harrison11.27%18.33%


Alexander van Heukelum11.27%18.33%


Total79100.00%12100.00%





static noinline void

bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
{
	__bad_area(regs, error_code, address, NULL, SEGV_MAPERR);
}


Contributors
PersonTokensPropCommitsCommitProp
Nicholas Piggin2266.67%112.50%


Ingo Molnar515.15%225.00%


Dave Hansen26.06%112.50%


Harvey Harrison13.03%112.50%


Linus Torvalds13.03%112.50%


Andi Kleen13.03%112.50%


Jan Beulich13.03%112.50%


Total33100.00%8100.00%






static inline bool bad_area_access_from_pkeys(unsigned long error_code,
		struct vm_area_struct *vma)
{
	/* This code is always called on the current mm */
	bool foreign = false;

	if (!boot_cpu_has(X86_FEATURE_OSPKE))
		return false;
	if (error_code & PF_PK)
		return true;
	/* this checks permission keys on the VMA: */
	if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE),
				(error_code & PF_INSTR), foreign))
		return true;
	return false;
}


Contributors
PersonTokensPropCommitsCommitProp
Dave Hansen71100.00%3100.00%


Total71100.00%3100.00%





static noinline void

bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
		      unsigned long address, struct vm_area_struct *vma)
{
	/*
         * This OSPKE check is not strictly necessary at runtime.
         * But, doing it this way allows compiler optimizations
         * if pkeys are compiled out.
         */
	if (bad_area_access_from_pkeys(error_code, vma))
		__bad_area(regs, error_code, address, vma, SEGV_PKUERR);
	else
		__bad_area(regs, error_code, address, vma, SEGV_ACCERR);
}


Contributors
PersonTokensPropCommitsCommitProp
Dave Hansen3150.00%342.86%


Ingo Molnar2337.10%228.57%


Andi Kleen69.68%114.29%


Nicholas Piggin23.23%114.29%


Total62100.00%7100.00%





static void

do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
	  u32 *pkey, unsigned int fault)
{
	struct task_struct *tsk = current;
	int code = BUS_ADRERR;

	/* Kernel mode? Handle exceptions or die: */
	if (!(error_code & PF_USER)) {
		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
		return;
	}

	/* User-space => ok to do another page fault: */
	if (is_prefetch(regs, error_code, address))
		return;

	tsk->thread.cr2		= address;
	tsk->thread.error_code	= error_code;
	tsk->thread.trap_nr	= X86_TRAP_PF;

#ifdef CONFIG_MEMORY_FAILURE
	if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
		printk(KERN_ERR
	"MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
			tsk->comm, tsk->pid, address);
		code = BUS_MCEERR_AR;
	}
#endif
	force_sig_info_fault(SIGBUS, code, address, tsk, pkey, fault);
}


Contributors
PersonTokensPropCommitsCommitProp
Ingo Molnar6038.96%220.00%


Andi Kleen4931.82%220.00%


Nicholas Piggin3019.48%110.00%


Andrew Lutomirski42.60%110.00%


Dave Hansen31.95%110.00%


Laurent Dufour31.95%110.00%


Linus Torvalds31.95%110.00%


Srikar Dronamraju21.30%110.00%


Total154100.00%10100.00%





static noinline void

mm_fault_error(struct pt_regs *regs, unsigned long error_code,
	       unsigned long address, u32 *pkey, unsigned int fault)
{
	if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
		no_context(regs, error_code, address, 0, 0);
		return;
	}

	if (fault & VM_FAULT_OOM) {
		/* Kernel mode? Handle exceptions or die: */
		if (!(error_code & PF_USER)) {
			no_context(regs, error_code, address,
				   SIGSEGV, SEGV_MAPERR);
			return;
		}

		/*
                 * 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):
                 */
		pagefault_out_of_memory();
	} else {
		if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
			     VM_FAULT_HWPOISON_LARGE))
			do_sigbus(regs, error_code, address, pkey, fault);
		else if (fault & VM_FAULT_SIGSEGV)
			bad_area_nosemaphore(regs, error_code, address, pkey);
		else
			BUG();
	}
}


Contributors
PersonTokensPropCommitsCommitProp
Ingo Molnar4732.19%214.29%


Motohiro Kosaki2315.75%17.14%


Andrey Vagin2114.38%17.14%


Linus Torvalds1610.96%17.14%


Andi Kleen106.85%321.43%


Andrew Lutomirski85.48%17.14%


Johannes Weiner74.79%17.14%


David Rientjes42.74%17.14%


Laurent Dufour42.74%17.14%


Dave Hansen42.74%17.14%


Nicholas Piggin21.37%17.14%


Total146100.00%14100.00%






static int spurious_fault_check(unsigned long error_code, pte_t *pte)
{
	if ((error_code & PF_WRITE) && !pte_write(*pte))
		return 0;

	if ((error_code & PF_INSTR) && !pte_exec(*pte))
		return 0;
	/*
         * Note: We do not do lazy flushing on protection key
         * changes, so no spurious fault will ever set PF_PK.
         */
	if ((error_code & PF_PK))
		return 1;

	return 1;
}


Contributors
PersonTokensPropCommitsCommitProp
Ingo Molnar2741.54%133.33%


Nicholas Piggin2640.00%133.33%


Dave Hansen1218.46%133.33%


Total65100.00%3100.00%



/*
 * Handle a spurious fault caused by a stale TLB entry.
 *
 * This allows us to lazily refresh the TLB when increasing the
 * permissions of a kernel page (RO -> RW or NX -> X).  Doing it
 * eagerly is very expensive since that implies doing a full
 * cross-processor TLB flush, even if no stale TLB entries exist
 * on other processors.
 *
 * Spurious faults may only occur if the TLB contains an entry with
 * fewer permission than the page table entry.  Non-present (P = 0)
 * and reserved bit (R = 1) faults are never spurious.
 *
 * There are no security implications to leaving a stale TLB when
 * increasing the permissions on a page.
 *
 * Returns non-zero if a spurious fault was handled, zero otherwise.
 *
 * See Intel Developer's Manual Vol 3 Section 4.10.4.3, bullet 3
 * (Optional Invalidation).
 */


static noinline int

spurious_fault(unsigned long error_code, unsigned long address)
{
	pgd_t *pgd;
	p4d_t *p4d;
	pud_t *pud;
	pmd_t *pmd;
	pte_t *pte;
	int ret;

	/*
         * Only writes to RO or instruction fetches from NX may cause
         * spurious faults.
         *
         * These could be from user or supervisor accesses but the TLB
         * is only lazily flushed after a kernel mapping protection
         * change, so user accesses are not expected to cause spurious
         * faults.
         */
	if (error_code != (PF_WRITE | PF_PROT)
	    && error_code != (PF_INSTR | PF_PROT))
		return 0;

	pgd = init_mm.pgd + pgd_index(address);
	if (!pgd_present(*pgd))
		return 0;

	p4d = p4d_offset(pgd, address);
	if (!p4d_present(*p4d))
		return 0;

	if (p4d_large(*p4d))
		return spurious_fault_check(error_code, (pte_t *) p4d);

	pud = pud_offset(p4d, address);
	if (!pud_present(*pud))
		return 0;

	if (pud_large(*pud))
		return spurious_fault_check(error_code, (pte_t *) pud);

	pmd = pmd_offset(pud, address);
	if (!pmd_present(*pmd))
		return 0;

	if (pmd_large(*pmd))
		return spurious_fault_check(error_code, (pte_t *) pmd);

	pte = pte_offset_kernel(pmd, address);
	if (!pte_present(*pte))
		return 0;

	ret = spurious_fault_check(error_code, pte);
	if (!ret)
		return 0;

	/*
         * Make sure we have permissions in PMD.
         * If not, then there's a bug in the page tables:
         */
	ret = spurious_fault_check(error_code, (pte_t *) pmd);
	WARN_ONCE(!ret, "PMD has incorrect permission bits\n");

	return ret;
}

Contributors
PersonTokensPropCommitsCommitProp
Nicholas Piggin11141.26%116.67%


Ingo Molnar8732.34%116.67%


Kirill A. Shutemov4617.10%116.67%


Andi Kleen124.46%116.67%


David Vrabel124.46%116.67%


Andrea Arcangeli10.37%116.67%


Total269100.00%6100.00%




NOKPROBE_SYMBOL(spurious_fault);


int show_unhandled_signals = 1;



static inline int

access_error(unsigned long error_code, struct vm_area_struct *vma)
{
	/* This is only called for the current mm, so: */
	bool foreign = false;

	/*
         * Read or write was blocked by protection keys.  This is
         * always an unconditional error and can never result in
         * a follow-up action to resolve the fault, like a COW.
         */
	if (error_code & PF_PK)
		return 1;

	/*
         * Make sure to check the VMA so that we do not perform
         * faults just to hit a PF_PK as soon as we fill in a
         * page.
         */
	if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE),
				(error_code & PF_INSTR), foreign))
		return 1;

	if (error_code & PF_WRITE) {
		/* write, present and write, not present: */
		if (unlikely(!(vma->vm_flags & VM_WRITE)))
			return 1;
		return 0;
	}

	/* read, present: */
	if (unlikely(error_code & PF_PROT))
		return 1;

	/* read, not present: */
	if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
		return 1;

	return 0;
}


Contributors
PersonTokensPropCommitsCommitProp
Nicholas Piggin5543.31%112.50%


Dave Hansen4233.07%337.50%


Andi Kleen2015.75%112.50%


Ingo Molnar64.72%112.50%


Michel Lespinasse32.36%112.50%


Chuck Ebbert10.79%112.50%


Total127100.00%8100.00%






static int fault_in_kernel_space(unsigned long address)
{
	return address >= TASK_SIZE_MAX;
}


Contributors
PersonTokensPropCommitsCommitProp
Hiroshi Shimamoto1493.33%150.00%


Ingo Molnar16.67%150.00%


Total15100.00%2100.00%






static inline bool smap_violation(int error_code, struct pt_regs *regs)
{
	if (!IS_ENABLED(CONFIG_X86_SMAP))
		return false;

	if (!static_cpu_has(X86_FEATURE_SMAP))
		return false;

	if (error_code & PF_USER)
		return false;

	if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC))
		return false;

	return true;
}


Contributors
PersonTokensPropCommitsCommitProp
H. Peter Anvin6798.53%266.67%


Andrew Lutomirski11.47%133.33%


Total68100.00%3100.00%



/*
 * This routine handles page faults.  It determines the address,
 * and the problem, and then passes it off to one of the appropriate
 * routines.
 */


static noinline void

__do_page_fault(struct pt_regs *regs, unsigned long error_code,
		unsigned long address)
{
	struct vm_area_struct *vma;
	struct task_struct *tsk;
	struct mm_struct *mm;
	int fault, major = 0;
	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
	u32 pkey;

	tsk = current;
	mm = tsk->mm;

	/*
         * Detect and handle instructions that would cause a page fault for
         * both a tracked kernel page and a userspace page.
         */
	if (kmemcheck_active(regs))
		kmemcheck_hide(regs);
	prefetchw(&mm->mmap_sem);

	if (unlikely(kmmio_fault(regs, address)))
		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.
         *
         * This verifies that the fault happens in kernel space
         * (error_code & 4) == 0, and that the fault was not a
         * protection error (error_code & 9) == 0.
         */
	if (unlikely(fault_in_kernel_space(address))) {
		if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
			if (vmalloc_fault(address) >= 0)
				return;

			if (kmemcheck_fault(regs, address, error_code))
				return;
		}

		/* Can handle a stale RO->RW TLB: */
		if (spurious_fault(error_code, address))
			return;

		/* kprobes don't want to hook the spurious faults: */
		if (kprobes_fault(regs))
			return;
		/*
                 * Don't take the mm semaphore here. If we fixup a prefetch
                 * fault we could otherwise deadlock:
                 */
		bad_area_nosemaphore(regs, error_code, address, NULL);

		return;
	}

	/* kprobes don't want to hook the spurious faults: */
	if (unlikely(kprobes_fault(regs)))
		return;

	if (unlikely(error_code & PF_RSVD))
		pgtable_bad(regs, error_code, address);

	if (unlikely(smap_violation(error_code, regs))) {
		bad_area_nosemaphore(regs, error_code, address, NULL);
		return;
	}

	/*
         * 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)) {
		bad_area_nosemaphore(regs, error_code, address, NULL);
		return;
	}

	/*
         * It's safe to allow irq's after cr2 has been saved and the
         * vmalloc fault has been handled.
         *
         * User-mode registers count as a user access even for any
         * potential system fault or CPU buglet:
         */
	if (user_mode(regs)) {
		local_irq_enable();
		error_code |= PF_USER;
		flags |= FAULT_FLAG_USER;
	} else {
		if (regs->flags & X86_EFLAGS_IF)
			local_irq_enable();
	}

	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);

	if (error_code & PF_WRITE)
		flags |= FAULT_FLAG_WRITE;
	if (error_code & PF_INSTR)
		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 ((error_code & PF_USER) == 0 &&
		    !search_exception_tables(regs->ip)) {
			bad_area_nosemaphore(regs, error_code, address, NULL);
			return;
		}
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)) {
		bad_area(regs, error_code, address);
		return;
	}
	if (likely(vma->vm_start <= address))
		goto good_area;
	if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) {
		bad_area(regs, error_code, address);
		return;
	}
	if (error_code & PF_USER) {
		/*
                 * Accessing the stack below %sp is always a bug.
                 * The large cushion allows instructions like enter
                 * and pusha to work. ("enter $65535, $31" pushes
                 * 32 pointers and then decrements %sp by 65535.)
                 */
		if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
			bad_area(regs, error_code, address);
			return;
		}
	}
	if (unlikely(expand_stack(vma, address))) {
		bad_area(regs, error_code, address);
		return;
	}

	/*
         * Ok, we have a good vm_area for this memory access, so
         * we can handle it..
         */
good_area:
	if (unlikely(access_error(error_code, vma))) {
		bad_area_access_error(regs, error_code, address, vma);
		return;
	}

	/*
         * If for any reason at all we couldn't handle the fault,
         * make sure we exit gracefully rather than endlessly redo
         * the fault.  Since we never set FAULT_FLAG_RETRY_NOWAIT, if
         * we get VM_FAULT_RETRY back, the mmap_sem has been unlocked.
         *
         * Note that handle_userfault() may also release and reacquire mmap_sem
         * (and not return with VM_FAULT_RETRY), when returning to userland to
         * repeat the page fault later with a VM_FAULT_NOPAGE retval
         * (potentially after handling any pending signal during the return to
         * userland). The return to userland is identified whenever
         * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags.
         * Thus we have to be careful about not touching vma after handling the
         * fault, so we read the pkey beforehand.
         */
	pkey = vma_pkey(vma);
	fault = handle_mm_fault(vma, address, flags);
	major |= fault & VM_FAULT_MAJOR;

	/*
         * If we need to retry the mmap_sem has already been released,
         * and if there is a fatal signal pending there is no guarantee
         * that we made any progress. Handle this case first.
         */
	if (unlikely(fault & VM_FAULT_RETRY)) {
		/* Retry at most once */
		if (flags & FAULT_FLAG_ALLOW_RETRY) {
			flags &= ~FAULT_FLAG_ALLOW_RETRY;
			flags |= FAULT_FLAG_TRIED;
			if (!fatal_signal_pending(tsk))
				goto retry;
		}

		/* User mode? Just return to handle the fatal exception */
		if (flags & FAULT_FLAG_USER)
			return;

		/* Not returning to user mode? Handle exceptions or die: */
		no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
		return;
	}

	up_read(&mm->mmap_sem);
	if (unlikely(fault & VM_FAULT_ERROR)) {
		mm_fault_error(regs, error_code, address, &pkey, fault);
		return;
	}

	/*
         * Major/minor page fault accounting. If any of the events
         * returned VM_FAULT_MAJOR, we account it as a major fault.
         */
	if (major) {
		tsk->maj_flt++;
		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
	} else {
		tsk->min_flt++;
		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
	}

	check_v8086_mode(regs, address, tsk);
}

Contributors
PersonTokensPropCommitsCommitProp
Nicholas Piggin25735.01%23.64%


Andi Kleen9212.53%712.73%


Linus Torvalds7910.76%35.45%


Peter Zijlstra7810.63%610.91%


Harvey Harrison445.99%712.73%


Vegard Nossum324.36%23.64%


Ingo Molnar253.41%47.27%


H. Peter Anvin253.41%23.64%


Dave Hansen212.86%23.64%


Motohiro Kosaki182.45%23.64%


Johannes Weiner152.04%23.64%


Michel Lespinasse101.36%11.82%


Vlastimil Babka81.09%11.82%


Jan Beulich50.68%23.64%


Laurent Dufour50.68%11.82%


Jiri Olsa40.54%11.82%


Eric Sandeen30.41%11.82%


David Hildenbrand20.27%11.82%


Chuck Ebbert20.27%11.82%


Hiroshi Shimamoto20.27%11.82%


Frédéric Weisbecker20.27%11.82%


Jason Baron10.14%11.82%


Masoud Asgharifard Sharbiani10.14%11.82%


Andrew Lutomirski10.14%11.82%


Masami Hiramatsu10.14%11.82%


Andrew Morton10.14%11.82%


Total734100.00%55100.00%




NOKPROBE_SYMBOL(__do_page_fault);



static nokprobe_inline void

trace_page_fault_entries(unsigned long address, struct pt_regs *regs,
			 unsigned long error_code)
{
	if (user_mode(regs))
		trace_page_fault_user(address, regs, error_code);
	else
		trace_page_fault_kernel(address, regs, error_code);
}


Contributors
PersonTokensPropCommitsCommitProp
Seiji Aguchi3780.43%125.00%


Peter Zijlstra613.04%125.00%


H. Peter Anvin24.35%125.00%


Masami Hiramatsu12.17%125.00%


Total46100.00%4100.00%



/*
 * We must have this function blacklisted from kprobes, tagged with notrace
 * and call read_cr2() before calling anything else. To avoid calling any
 * kind of tracing machinery before we've observed the CR2 value.
 *
 * exception_{enter,exit}() contains all sorts of tracepoints.
 */


dotraplinkage void notrace

do_page_fault(struct pt_regs *regs, unsigned long error_code)
{
	unsigned long address = read_cr2(); /* Get the faulting address */
	enum ctx_state prev_state;

	prev_state = exception_enter();
	if (trace_pagefault_enabled())
		trace_page_fault_entries(address, regs, error_code);

	__do_page_fault(regs, error_code, address);
	exception_exit(prev_state);
}

Contributors
PersonTokensPropCommitsCommitProp
Seiji Aguchi3862.30%233.33%


Jiri Olsa914.75%116.67%


Peter Zijlstra711.48%116.67%


Thomas Gleixner711.48%233.33%


Total61100.00%6100.00%




NOKPROBE_SYMBOL(do_page_fault);

Overall Contributors
PersonTokensPropCommitsCommitProp
Ingo Molnar138125.56%1810.53%


Nicholas Piggin72713.46%21.17%


Andi Kleen67812.55%1810.53%


Harvey Harrison4858.98%158.77%


Dave Hansen2875.31%74.09%


Kirill A. Shutemov2494.61%21.17%


Andrew Lutomirski2234.13%127.02%


Akinobu Mita1372.54%10.58%


Jan Beulich1172.17%95.26%


Linus Torvalds1031.91%74.09%


Peter Zijlstra1011.87%74.09%


H. Peter Anvin961.78%42.34%


Seiji Aguchi811.50%21.17%


Jeremy Fitzhardinge791.46%21.17%


Jiri Kosina551.02%10.58%


Laurent Dufour480.89%10.58%


Pekka Paalanen440.81%31.75%


Motohiro Kosaki410.76%21.17%


Vegard Nossum390.72%21.17%


Toshi Kani380.70%10.58%


Christoph Hellwig290.54%21.17%


Masami Hiramatsu290.54%10.58%


Thomas Gleixner260.48%31.75%


Frédéric Weisbecker250.46%31.75%


Matt Fleming250.46%10.58%


Johannes Weiner220.41%21.17%


Andrey Vagin210.39%10.58%


Andrew Morton190.35%21.17%


Brian Gerst180.33%21.17%


Hiroshi Shimamoto160.30%10.58%


David Vrabel130.24%10.58%


Jiri Olsa130.24%10.58%


Michel Lespinasse130.24%21.17%


Anil S Keshavamurthy120.22%10.58%


Kees Cook100.19%10.58%


Srikar Dronamraju100.19%10.58%


Vlastimil Babka80.15%10.58%


Alexander van Heukelum70.13%10.58%


Samu Kallio70.13%10.58%


Josh Poimboeuf70.13%21.17%


Arjan van de Ven60.11%10.58%


David Hildenbrand60.11%10.58%


Eric W. Biedermann60.11%10.58%


Borislav Petkov60.11%21.17%


Vincent Hanquez40.07%10.58%


David Rientjes40.07%10.58%


Andrea Arcangeli40.07%21.17%


Eric Sandeen30.06%10.58%


Chuck Ebbert30.06%10.58%


Haicheng Li30.06%10.58%


Randy Dunlap20.04%10.58%


Prarit Bhargava20.04%10.58%


Tony Luck20.04%10.58%


Glauber de Oliveira Costa20.04%10.58%


David Howells20.04%10.58%


Prasanna S. Panchamukhi20.04%10.58%


Greg Kroah-Hartman10.02%10.58%


Al Viro10.02%10.58%


Adrian Bunk10.02%10.58%


Jason Baron10.02%10.58%


Masoud Asgharifard Sharbiani10.02%10.58%


Paul Gortmaker10.02%10.58%


Aaron Tomlin10.02%10.58%


Total5403100.00%171100.00%


Directory: arch/x86/mm



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