traps.c

linux 内核源代码

	printk(KERN_CRIT "Bad mode in %s handler detected\n", handler[reason]);

	die("Oops - bad mode", regs, 0);
	local_irq_disable();
	panic("bad mode");
}

static int bad_syscall(int n, struct pt_regs *regs)
{
	struct thread_info *thread = current_thread_info();
	siginfo_t info;

	if (current->personality != PER_LINUX &&
	    current->personality != PER_LINUX_32BIT &&
	    thread->exec_domain->handler) {
		thread->exec_domain->handler(n, regs);
		return regs->ARM_r0;
	}

#ifdef CONFIG_DEBUG_USER
	if (user_debug & UDBG_SYSCALL) {
		printk(KERN_ERR "[%d] %s: obsolete system call %08x.\n",
			task_pid_nr(current), current->comm, n);
		dump_instr(regs);
	}
#endif

	info.si_signo = SIGILL;
	info.si_errno = 0;
	info.si_code  = ILL_ILLTRP;
	info.si_addr  = (void __user *)instruction_pointer(regs) -
			 (thumb_mode(regs) ? 2 : 4);

	arm_notify_die("Oops - bad syscall", regs, &info, n, 0);

	return regs->ARM_r0;
}

static inline void
do_cache_op(unsigned long start, unsigned long end, int flags)
{
	struct vm_area_struct *vma;

	if (end < start || flags)
		return;

	vma = find_vma(current->active_mm, start);
	if (vma && vma->vm_start < end) {
		if (start < vma->vm_start)
			start = vma->vm_start;
		if (end > vma->vm_end)
			end = vma->vm_end;

		flush_cache_user_range(vma, start, end);
	}
}

/*
 * Handle all unrecognised system calls.
 *  0x9f0000 - 0x9fffff are some more esoteric system calls
 */
#define NR(x) ((__ARM_NR_##x) - __ARM_NR_BASE)
asmlinkage int arm_syscall(int no, struct pt_regs *regs)
{
	struct thread_info *thread = current_thread_info();
	siginfo_t info;

	if ((no >> 16) != (__ARM_NR_BASE>> 16))
		return bad_syscall(no, regs);

	switch (no & 0xffff) {
	case 0: /* branch through 0 */
		info.si_signo = SIGSEGV;
		info.si_errno = 0;
		info.si_code  = SEGV_MAPERR;
		info.si_addr  = NULL;

		arm_notify_die("branch through zero", regs, &info, 0, 0);
		return 0;

	case NR(breakpoint): /* SWI BREAK_POINT */
		regs->ARM_pc -= thumb_mode(regs) ? 2 : 4;
		ptrace_break(current, regs);
		return regs->ARM_r0;

	/*
	 * Flush a region from virtual address 'r0' to virtual address 'r1'
	 * _exclusive_.  There is no alignment requirement on either address;
	 * user space does not need to know the hardware cache layout.
	 *
	 * r2 contains flags.  It should ALWAYS be passed as ZERO until it
	 * is defined to be something else.  For now we ignore it, but may
	 * the fires of hell burn in your belly if you break this rule. ;)
	 *
	 * (at a later date, we may want to allow this call to not flush
	 * various aspects of the cache.  Passing '0' will guarantee that
	 * everything necessary gets flushed to maintain consistency in
	 * the specified region).
	 */
	case NR(cacheflush):
		do_cache_op(regs->ARM_r0, regs->ARM_r1, regs->ARM_r2);
		return 0;

	case NR(usr26):
		if (!(elf_hwcap & HWCAP_26BIT))
			break;
		regs->ARM_cpsr &= ~MODE32_BIT;
		return regs->ARM_r0;

	case NR(usr32):
		if (!(elf_hwcap & HWCAP_26BIT))
			break;
		regs->ARM_cpsr |= MODE32_BIT;
		return regs->ARM_r0;

	case NR(set_tls):
		thread->tp_value = regs->ARM_r0;
#if defined(CONFIG_HAS_TLS_REG)
		asm ("mcr p15, 0, %0, c13, c0, 3" : : "r" (regs->ARM_r0) );
#elif !defined(CONFIG_TLS_REG_EMUL)
		/*
		 * User space must never try to access this directly.
		 * Expect your app to break eventually if you do so.
		 * The user helper at 0xffff0fe0 must be used instead.
		 * (see entry-armv.S for details)
		 */
		*((unsigned int *)0xffff0ff0) = regs->ARM_r0;
#endif
		return 0;

#ifdef CONFIG_NEEDS_SYSCALL_FOR_CMPXCHG
	/*
	 * Atomically store r1 in *r2 if *r2 is equal to r0 for user space.
	 * Return zero in r0 if *MEM was changed or non-zero if no exchange
	 * happened.  Also set the user C flag accordingly.
	 * If access permissions have to be fixed up then non-zero is
	 * returned and the operation has to be re-attempted.
	 *
	 * *NOTE*: This is a ghost syscall private to the kernel.  Only the
	 * __kuser_cmpxchg code in entry-armv.S should be aware of its
	 * existence.  Don't ever use this from user code.
	 */
	case 0xfff0:
	for (;;) {
		extern void do_DataAbort(unsigned long addr, unsigned int fsr,
					 struct pt_regs *regs);
		unsigned long val;
		unsigned long addr = regs->ARM_r2;
		struct mm_struct *mm = current->mm;
		pgd_t *pgd; pmd_t *pmd; pte_t *pte;
		spinlock_t *ptl;

		regs->ARM_cpsr &= ~PSR_C_BIT;
		down_read(&mm->mmap_sem);
		pgd = pgd_offset(mm, addr);
		if (!pgd_present(*pgd))
			goto bad_access;
		pmd = pmd_offset(pgd, addr);
		if (!pmd_present(*pmd))
			goto bad_access;
		pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
		if (!pte_present(*pte) || !pte_dirty(*pte)) {
			pte_unmap_unlock(pte, ptl);
			goto bad_access;
		}
		val = *(unsigned long *)addr;
		val -= regs->ARM_r0;
		if (val == 0) {
			*(unsigned long *)addr = regs->ARM_r1;
			regs->ARM_cpsr |= PSR_C_BIT;
		}
		pte_unmap_unlock(pte, ptl);
		up_read(&mm->mmap_sem);
		return val;

		bad_access:
		up_read(&mm->mmap_sem);
		/* simulate a write access fault */
		do_DataAbort(addr, 15 + (1 << 11), regs);
	}
#endif

	default:
		/* Calls 9f00xx..9f07ff are defined to return -ENOSYS
		   if not implemented, rather than raising SIGILL.  This
		   way the calling program can gracefully determine whether
		   a feature is supported.  */
		if (no <= 0x7ff)
			return -ENOSYS;
		break;
	}
#ifdef CONFIG_DEBUG_USER
	/*
	 * experience shows that these seem to indicate that
	 * something catastrophic has happened
	 */
	if (user_debug & UDBG_SYSCALL) {
		printk("[%d] %s: arm syscall %d\n",
		       task_pid_nr(current), current->comm, no);
		dump_instr(regs);
		if (user_mode(regs)) {
			__show_regs(regs);
			c_backtrace(regs->ARM_fp, processor_mode(regs));
		}
	}
#endif
	info.si_signo = SIGILL;
	info.si_errno = 0;
	info.si_code  = ILL_ILLTRP;
	info.si_addr  = (void __user *)instruction_pointer(regs) -
			 (thumb_mode(regs) ? 2 : 4);

	arm_notify_die("Oops - bad syscall(2)", regs, &info, no, 0);
	return 0;
}

#ifdef CONFIG_TLS_REG_EMUL

/*
 * We might be running on an ARMv6+ processor which should have the TLS
 * register but for some reason we can't use it, or maybe an SMP system
 * using a pre-ARMv6 processor (there are apparently a few prototypes like
 * that in existence) and therefore access to that register must be
 * emulated.
 */

static int get_tp_trap(struct pt_regs *regs, unsigned int instr)
{
	int reg = (instr >> 12) & 15;
	if (reg == 15)
		return 1;
	regs->uregs[reg] = current_thread_info()->tp_value;
	regs->ARM_pc += 4;
	return 0;
}

static struct undef_hook arm_mrc_hook = {
	.instr_mask	= 0x0fff0fff,
	.instr_val	= 0x0e1d0f70,
	.cpsr_mask	= PSR_T_BIT,
	.cpsr_val	= 0,
	.fn		= get_tp_trap,
};

static int __init arm_mrc_hook_init(void)
{
	register_undef_hook(&arm_mrc_hook);
	return 0;
}

late_initcall(arm_mrc_hook_init);

#endif

void __bad_xchg(volatile void *ptr, int size)
{
	printk("xchg: bad data size: pc 0x%p, ptr 0x%p, size %d\n",
		__builtin_return_address(0), ptr, size);
	BUG();
}
EXPORT_SYMBOL(__bad_xchg);

/*
 * A data abort trap was taken, but we did not handle the instruction.
 * Try to abort the user program, or panic if it was the kernel.
 */
asmlinkage void
baddataabort(int code, unsigned long instr, struct pt_regs *regs)
{
	unsigned long addr = instruction_pointer(regs);
	siginfo_t info;

#ifdef CONFIG_DEBUG_USER
	if (user_debug & UDBG_BADABORT) {
		printk(KERN_ERR "[%d] %s: bad data abort: code %d instr 0x%08lx\n",
			task_pid_nr(current), current->comm, code, instr);
		dump_instr(regs);
		show_pte(current->mm, addr);
	}
#endif

	info.si_signo = SIGILL;
	info.si_errno = 0;
	info.si_code  = ILL_ILLOPC;
	info.si_addr  = (void __user *)addr;

	arm_notify_die("unknown data abort code", regs, &info, instr, 0);
}

void __attribute__((noreturn)) __bug(const char *file, int line)
{
	printk(KERN_CRIT"kernel BUG at %s:%d!\n", file, line);
	*(int *)0 = 0;

	/* Avoid "noreturn function does return" */
	for (;;);
}
EXPORT_SYMBOL(__bug);

void __readwrite_bug(const char *fn)
{
	printk("%s called, but not implemented\n", fn);
	BUG();
}
EXPORT_SYMBOL(__readwrite_bug);

void __pte_error(const char *file, int line, unsigned long val)
{
	printk("%s:%d: bad pte %08lx.\n", file, line, val);
}

void __pmd_error(const char *file, int line, unsigned long val)
{
	printk("%s:%d: bad pmd %08lx.\n", file, line, val);
}

void __pgd_error(const char *file, int line, unsigned long val)
{
	printk("%s:%d: bad pgd %08lx.\n", file, line, val);
}

asmlinkage void __div0(void)
{
	printk("Division by zero in kernel.\n");
	dump_stack();
}
EXPORT_SYMBOL(__div0);

void abort(void)
{
	BUG();

	/* if that doesn't kill us, halt */
	panic("Oops failed to kill thread");
}
EXPORT_SYMBOL(abort);

void __init trap_init(void)
{
	unsigned long vectors = CONFIG_VECTORS_BASE;
	extern char __stubs_start[], __stubs_end[];
	extern char __vectors_start[], __vectors_end[];
	extern char __kuser_helper_start[], __kuser_helper_end[];
	int kuser_sz = __kuser_helper_end - __kuser_helper_start;

	/*
	 * Copy the vectors, stubs and kuser helpers (in entry-armv.S)
	 * into the vector page, mapped at 0xffff0000, and ensure these
	 * are visible to the instruction stream.
	 */
	memcpy((void *)vectors, __vectors_start, __vectors_end - __vectors_start);
	memcpy((void *)vectors + 0x200, __stubs_start, __stubs_end - __stubs_start);
	memcpy((void *)vectors + 0x1000 - kuser_sz, __kuser_helper_start, kuser_sz);

	/*
	 * Copy signal return handlers into the vector page, and
	 * set sigreturn to be a pointer to these.
	 */
	memcpy((void *)KERN_SIGRETURN_CODE, sigreturn_codes,
	       sizeof(sigreturn_codes));

	flush_icache_range(vectors, vectors + PAGE_SIZE);
	modify_domain(DOMAIN_USER, DOMAIN_CLIENT);
}