arch/arm26/mm/fault.c - linux - Git at Google

 /*
  *  linux/arch/arm26/mm/fault.c
  *
  *  Copyright (C) 1995  Linus Torvalds
  *  Modifications for ARM processor (c) 1995-2001 Russell King
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  */
 #include <linux/signal.h>
 #include <linux/sched.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/string.h>
 #include <linux/types.h>
 #include <linux/ptrace.h>
 #include <linux/mman.h>
 #include <linux/mm.h>
 #include <linux/interrupt.h>
 #include <linux/proc_fs.h>
 #include <linux/init.h>

 #include <asm/system.h>
 #include <asm/pgtable.h>
 #include <asm/uaccess.h> //FIXME this header may be bogusly included

 #include "fault.h"

 #define FAULT_CODE_LDRSTRPOST   0x80
 #define FAULT_CODE_LDRSTRPRE    0x40
 #define FAULT_CODE_LDRSTRREG    0x20
 #define FAULT_CODE_LDMSTM       0x10
 #define FAULT_CODE_LDCSTC       0x08
 #define FAULT_CODE_PREFETCH     0x04
 #define FAULT_CODE_WRITE        0x02
 #define FAULT_CODE_FORCECOW     0x01

 #define DO_COW(m)               ((m) & (FAULT_CODE_WRITE|FAULT_CODE_FORCECOW))
 #define READ_FAULT(m)           (!((m) & FAULT_CODE_WRITE))
 #define DEBUG
 /*
  * This is useful to dump out the page tables associated with
  * 'addr' in mm 'mm'.
  */
 void show_pte(struct mm_struct *mm, unsigned long addr)
 {
 	pgd_t *pgd;

 	if (!mm)
 		mm = &init_mm;

 	printk(KERN_ALERT "pgd = %p\n", mm->pgd);
 	pgd = pgd_offset(mm, addr);
 	printk(KERN_ALERT "[%08lx] *pgd=%08lx", addr, pgd_val(*pgd));

 	do {
 		pmd_t *pmd;
 		pte_t *pte;

 		pmd = pmd_offset(pgd, addr);

 		if (pmd_none(*pmd))
 			break;

 		if (pmd_bad(*pmd)) {
 			printk("(bad)");
 			break;
 		}

 		/* We must not map this if we have highmem enabled */
 		/* FIXME */
 		pte = pte_offset_map(pmd, addr);
 		printk(", *pte=%08lx", pte_val(*pte));
 		pte_unmap(pte);
 	} while(0);

 	printk("\n");
 }

 /*
  * 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)
 {
 	/*
          * Are we prepared to handle this kernel fault?
          */
         if (fixup_exception(regs))
                 return;

 	/*
 	 * No handler, we'll have to terminate things with extreme prejudice.
 	 */
 	bust_spinlocks(1);
 	printk(KERN_ALERT
 		"Unable to handle kernel %s at virtual address %08lx\n",
 		(addr < PAGE_SIZE) ? "NULL pointer dereference" :
 		"paging request", addr);

 	show_pte(mm, addr);
 	die("Oops", regs, fsr);
 	bust_spinlocks(0);
 	do_exit(SIGKILL);
 }

 /*
  * Something tried to access memory that isn't in our memory map..
  * User mode accesses just cause a SIGSEGV
  */
 static void
 __do_user_fault(struct task_struct *tsk, unsigned long addr,
 		unsigned int fsr, int code, struct pt_regs *regs)
 {
 	struct siginfo si;

 #ifdef CONFIG_DEBUG_USER
 	printk("%s: unhandled page fault at 0x%08lx, code 0x%03x\n",
 	       tsk->comm, addr, fsr);
 	show_pte(tsk->mm, addr);
 	show_regs(regs);
 	//dump_backtrace(regs, tsk); // FIXME ARM32 dropped this - why?
 	while(1); //FIXME - hack to stop debug going nutso
 #endif

 	tsk->thread.address = addr;
 	tsk->thread.error_code = fsr;
 	tsk->thread.trap_no = 14;
 	si.si_signo = SIGSEGV;
 	si.si_errno = 0;
 	si.si_code = code;
 	si.si_addr = (void *)addr;
 	force_sig_info(SIGSEGV, &si, tsk);
 }

 static int
 __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
 		struct task_struct *tsk)
 {
 	struct vm_area_struct *vma;
 	int fault, mask;

 	vma = find_vma(mm, addr);
 	fault = -2; /* bad map area */
 	if (!vma)
 		goto out;
 	if (vma->vm_start > addr)
 		goto check_stack;

 	/*
 	 * Ok, we have a good vm_area for this
 	 * memory access, so we can handle it.
 	 */
 good_area:
 	if (READ_FAULT(fsr)) /* read? */
 		mask = VM_READ|VM_EXEC;
 	else
 		mask = VM_WRITE;

 	fault = -1; /* bad access type */
 	if (!(vma->vm_flags & mask))
 		goto out;

 	/*
 	 * If for any reason at all we couldn't handle
 	 * the fault, make sure we exit gracefully rather
 	 * than endlessly redo the fault.
 	 */
 survive:
 	fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, DO_COW(fsr));

 	/*
 	 * Handle the "normal" cases first - successful and sigbus
 	 */
 	switch (fault) {
 	case VM_FAULT_MAJOR:
 		tsk->maj_flt++;
 		return fault;
 	case VM_FAULT_MINOR:
 		tsk->min_flt++;
 	case VM_FAULT_SIGBUS:
 		return fault;
 	}

 	fault = -3; /* out of memory */
 	if (tsk->pid != 1)
 		goto out;

 	/*
 	 * If we are out of memory for pid1,
 	 * sleep for a while and retry
 	 */
 	yield();
 	goto survive;

 check_stack:
 	if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
 		goto good_area;
 out:
 	return fault;
 }

 int do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 {
 	struct task_struct *tsk;
 	struct mm_struct *mm;
 	int fault;

 	tsk = current;
 	mm  = tsk->mm;

 	/*
 	 * If we're in an interrupt or have no user
 	 * context, we must not take the fault..
 	 */
 	if (in_interrupt() || !mm)
 		goto no_context;

 	down_read(&mm->mmap_sem);
 	fault = __do_page_fault(mm, addr, fsr, tsk);
 	up_read(&mm->mmap_sem);

 	/*
 	 * Handle the "normal" case first
 	 */
 	switch (fault) {
 	case VM_FAULT_MINOR:
 	case VM_FAULT_MAJOR:
 		return 0;
 	case VM_FAULT_SIGBUS:
 		goto do_sigbus;
 	}

 	/*
 	 * If we are in kernel mode at this point, we
 	 * have no context to handle this fault with.
          * FIXME - is this test right?
 	 */
 	if (!user_mode(regs)){
 		goto no_context;
 	}

 	if (fault == -3) {
 		/*
 		 * We ran out of memory, or some other thing happened to
 		 * us that made us unable to handle the page fault gracefully.
 		 */
 		printk("VM: killing process %s\n", tsk->comm);
 		do_exit(SIGKILL);
 	}
 	else{
 		__do_user_fault(tsk, addr, fsr, fault == -1 ? SEGV_ACCERR : SEGV_MAPERR, regs);
 	}

 	return 0;


 /*
  * We ran out of memory, or some other thing happened to us that made
  * us unable to handle the page fault gracefully.
  */
 do_sigbus:
 	/*
 	 * Send a sigbus, regardless of whether we were in kernel
 	 * or user mode.
 	 */
 	tsk->thread.address = addr;  //FIXME - need other bits setting?
 	tsk->thread.error_code = fsr;
 	tsk->thread.trap_no = 14;
 	force_sig(SIGBUS, tsk);
 #ifdef CONFIG_DEBUG_USER
 	printk(KERN_DEBUG "%s: sigbus at 0x%08lx, pc=0x%08lx\n",
 		current->comm, addr, instruction_pointer(regs));
 #endif

 	/* Kernel mode? Handle exceptions or die */
 	if (user_mode(regs))
 		return 0;

 no_context:
 	__do_kernel_fault(mm, addr, fsr, regs);
 	return 0;
 }

 /*
  * Handle a data abort.  Note that we have to handle a range of addresses
  * on ARM2/3 for ldm.  If both pages are zero-mapped, then we have to force
  * a copy-on-write.  However, on the second page, we always force COW.
  */
 asmlinkage void
 do_DataAbort(unsigned long min_addr, unsigned long max_addr, int mode, struct pt_regs *regs)
 {
         do_page_fault(min_addr, mode, regs);

         if ((min_addr ^ max_addr) >> PAGE_SHIFT){
                do_page_fault(max_addr, mode | FAULT_CODE_FORCECOW, regs);
 	}
 }

 asmlinkage int
 do_PrefetchAbort(unsigned long addr, struct pt_regs *regs)
 {
 #if 0
         if (the memc mapping for this page exists) {
                 printk ("Page in, but got abort (undefined instruction?)\n");
                 return 0;
         }
 #endif
         do_page_fault(addr, FAULT_CODE_PREFETCH, regs);
         return 1;
 }
	/*
	* linux/arch/arm26/mm/fault.c
	*
	* Copyright (C) 1995 Linus Torvalds
	* Modifications for ARM processor (c) 1995-2001 Russell King
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation.
	*/
	#include <linux/signal.h>
	#include <linux/sched.h>
	#include <linux/kernel.h>
	#include <linux/errno.h>
	#include <linux/string.h>
	#include <linux/types.h>
	#include <linux/ptrace.h>
	#include <linux/mman.h>
	#include <linux/mm.h>
	#include <linux/interrupt.h>
	#include <linux/proc_fs.h>
	#include <linux/init.h>

	#include <asm/system.h>
	#include <asm/pgtable.h>
	#include <asm/uaccess.h> //FIXME this header may be bogusly included

	#include "fault.h"

	#define FAULT_CODE_LDRSTRPOST 0x80
	#define FAULT_CODE_LDRSTRPRE 0x40
	#define FAULT_CODE_LDRSTRREG 0x20
	#define FAULT_CODE_LDMSTM 0x10
	#define FAULT_CODE_LDCSTC 0x08
	#define FAULT_CODE_PREFETCH 0x04
	#define FAULT_CODE_WRITE 0x02
	#define FAULT_CODE_FORCECOW 0x01

	#define DO_COW(m) ((m) & (FAULT_CODE_WRITE\|FAULT_CODE_FORCECOW))
	#define READ_FAULT(m) (!((m) & FAULT_CODE_WRITE))
	#define DEBUG
	/*
	* This is useful to dump out the page tables associated with
	* 'addr' in mm 'mm'.
	*/
	void show_pte(struct mm_struct *mm, unsigned long addr)
	{
	pgd_t *pgd;

	if (!mm)
	mm = &init_mm;

	printk(KERN_ALERT "pgd = %p\n", mm->pgd);
	pgd = pgd_offset(mm, addr);
	printk(KERN_ALERT "[%08lx] pgd=%08lx", addr, pgd_val(pgd));

	do {
	pmd_t *pmd;
	pte_t *pte;

	pmd = pmd_offset(pgd, addr);

	if (pmd_none(*pmd))
	break;

	if (pmd_bad(*pmd)) {
	printk("(bad)");
	break;
	}

	/* We must not map this if we have highmem enabled */
	/* FIXME */
	pte = pte_offset_map(pmd, addr);
	printk(", pte=%08lx", pte_val(pte));
	pte_unmap(pte);
	} while(0);

	printk("\n");
	}

	/*
	* 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)
	{
	/*
	* Are we prepared to handle this kernel fault?
	*/
	if (fixup_exception(regs))
	return;

	/*
	* No handler, we'll have to terminate things with extreme prejudice.
	*/
	bust_spinlocks(1);
	printk(KERN_ALERT
	"Unable to handle kernel %s at virtual address %08lx\n",
	(addr < PAGE_SIZE) ? "NULL pointer dereference" :
	"paging request", addr);

	show_pte(mm, addr);
	die("Oops", regs, fsr);
	bust_spinlocks(0);
	do_exit(SIGKILL);
	}

	/*
	* Something tried to access memory that isn't in our memory map..
	* User mode accesses just cause a SIGSEGV
	*/
	static void
	__do_user_fault(struct task_struct *tsk, unsigned long addr,
	unsigned int fsr, int code, struct pt_regs *regs)
	{
	struct siginfo si;

	#ifdef CONFIG_DEBUG_USER
	printk("%s: unhandled page fault at 0x%08lx, code 0x%03x\n",
	tsk->comm, addr, fsr);
	show_pte(tsk->mm, addr);
	show_regs(regs);
	//dump_backtrace(regs, tsk); // FIXME ARM32 dropped this - why?
	while(1); //FIXME - hack to stop debug going nutso
	#endif

	tsk->thread.address = addr;
	tsk->thread.error_code = fsr;
	tsk->thread.trap_no = 14;
	si.si_signo = SIGSEGV;
	si.si_errno = 0;
	si.si_code = code;
	si.si_addr = (void *)addr;
	force_sig_info(SIGSEGV, &si, tsk);
	}

	static int
	__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
	struct task_struct *tsk)
	{
	struct vm_area_struct *vma;
	int fault, mask;

	vma = find_vma(mm, addr);
	fault = -2; /* bad map area */
	if (!vma)
	goto out;
	if (vma->vm_start > addr)
	goto check_stack;

	/*
	* Ok, we have a good vm_area for this
	* memory access, so we can handle it.
	*/
	good_area:
	if (READ_FAULT(fsr)) /* read? */
	mask = VM_READ\|VM_EXEC;
	else
	mask = VM_WRITE;

	fault = -1; /* bad access type */
	if (!(vma->vm_flags & mask))
	goto out;

	/*
	* If for any reason at all we couldn't handle
	* the fault, make sure we exit gracefully rather
	* than endlessly redo the fault.
	*/
	survive:
	fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, DO_COW(fsr));

	/*
	* Handle the "normal" cases first - successful and sigbus
	*/
	switch (fault) {
	case VM_FAULT_MAJOR:
	tsk->maj_flt++;
	return fault;
	case VM_FAULT_MINOR:
	tsk->min_flt++;
	case VM_FAULT_SIGBUS:
	return fault;
	}

	fault = -3; /* out of memory */
	if (tsk->pid != 1)
	goto out;

	/*
	* If we are out of memory for pid1,
	* sleep for a while and retry
	*/
	yield();
	goto survive;

	check_stack:
	if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
	goto good_area;
	out:
	return fault;
	}

	int do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
	{
	struct task_struct *tsk;
	struct mm_struct *mm;
	int fault;

	tsk = current;
	mm = tsk->mm;

	/*
	* If we're in an interrupt or have no user
	* context, we must not take the fault..
	*/
	if (in_interrupt() \|\| !mm)
	goto no_context;

	down_read(&mm->mmap_sem);
	fault = __do_page_fault(mm, addr, fsr, tsk);
	up_read(&mm->mmap_sem);

	/*
	* Handle the "normal" case first
	*/
	switch (fault) {
	case VM_FAULT_MINOR:
	case VM_FAULT_MAJOR:
	return 0;
	case VM_FAULT_SIGBUS:
	goto do_sigbus;
	}

	/*
	* If we are in kernel mode at this point, we
	* have no context to handle this fault with.
	* FIXME - is this test right?
	*/
	if (!user_mode(regs)){
	goto no_context;
	}

	if (fault == -3) {
	/*
	* We ran out of memory, or some other thing happened to
	* us that made us unable to handle the page fault gracefully.
	*/
	printk("VM: killing process %s\n", tsk->comm);
	do_exit(SIGKILL);
	}
	else{
	__do_user_fault(tsk, addr, fsr, fault == -1 ? SEGV_ACCERR : SEGV_MAPERR, regs);
	}

	return 0;


	/*
	* We ran out of memory, or some other thing happened to us that made
	* us unable to handle the page fault gracefully.
	*/
	do_sigbus:
	/*
	* Send a sigbus, regardless of whether we were in kernel
	* or user mode.
	*/
	tsk->thread.address = addr; //FIXME - need other bits setting?
	tsk->thread.error_code = fsr;
	tsk->thread.trap_no = 14;
	force_sig(SIGBUS, tsk);
	#ifdef CONFIG_DEBUG_USER
	printk(KERN_DEBUG "%s: sigbus at 0x%08lx, pc=0x%08lx\n",
	current->comm, addr, instruction_pointer(regs));
	#endif

	/* Kernel mode? Handle exceptions or die */
	if (user_mode(regs))
	return 0;

	no_context:
	__do_kernel_fault(mm, addr, fsr, regs);
	return 0;
	}

	/*
	* Handle a data abort. Note that we have to handle a range of addresses
	* on ARM2/3 for ldm. If both pages are zero-mapped, then we have to force
	* a copy-on-write. However, on the second page, we always force COW.
	*/
	asmlinkage void
	do_DataAbort(unsigned long min_addr, unsigned long max_addr, int mode, struct pt_regs *regs)
	{
	do_page_fault(min_addr, mode, regs);

	if ((min_addr ^ max_addr) >> PAGE_SHIFT){
	do_page_fault(max_addr, mode \| FAULT_CODE_FORCECOW, regs);
	}
	}

	asmlinkage int
	do_PrefetchAbort(unsigned long addr, struct pt_regs *regs)
	{
	#if 0
	if (the memc mapping for this page exists) {
	printk ("Page in, but got abort (undefined instruction?)\n");
	return 0;
	}
	#endif
	do_page_fault(addr, FAULT_CODE_PREFETCH, regs);
	return 1;
	}