Commit c3350602 authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt Committed by Michael Ellerman
Browse files

powerpc/mm: Make bad_area* helper functions 



Instead of goto labels, instead call those functions and return.

This gets us closer to x86 and allows us to shring do_page_fault()
even more.

The main difference with x86 is that those function return a value
which we then return from do_page_fault(). That value is our
return value from do_page_fault() which we use to generate
kernel faults.

Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent d3ca5874

arch/powerpc/mm/fault.c

+50 −28
Original line number Diff line number Diff line
@@ -108,6 +108,45 @@ static int store_updates_sp(struct pt_regs *regs) 
 * do_page_fault error handling helpers

 */



static int

__bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code)

{

	/*

	 * If we are in kernel mode, bail out with a SEGV, this will

	 * be caught by the assembly which will restore the non-volatile

	 * registers before calling bad_page_fault()

	 */

	if (!user_mode(regs))

		return SIGSEGV;



	_exception(SIGSEGV, regs, si_code, address);



	return 0;

}



static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address)

{

	return __bad_area_nosemaphore(regs, address, SEGV_MAPERR);

}



static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code)

{

	struct mm_struct *mm = current->mm;



	/*

	 * 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);



	return __bad_area_nosemaphore(regs, address, si_code);

}



static noinline int bad_area(struct pt_regs *regs, unsigned long address)

{

	return __bad_area(regs, address, SEGV_MAPERR);

}



#define MM_FAULT_RETURN		0

#define MM_FAULT_CONTINUE	-1

#define MM_FAULT_ERR(sig)	(sig)
@@ -231,7 +270,6 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address, 
	struct vm_area_struct * vma;

	struct mm_struct *mm = current->mm;

	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;

	int code = SEGV_MAPERR;

 	int is_exec = TRAP(regs) == 0x400;

	int is_user = user_mode(regs);

	int is_write = page_fault_is_write(error_code);
@@ -317,7 +355,7 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address, 
	 */

	if (!down_read_trylock(&mm->mmap_sem)) {

		if (!is_user && !search_exception_tables(regs->nip))

			goto bad_area_nosemaphore;

			return bad_area_nosemaphore(regs, address);



retry:

		down_read(&mm->mmap_sem);
@@ -332,11 +370,11 @@ retry: 


	vma = find_vma(mm, address);

	if (!vma)

		goto bad_area;

		return bad_area(regs, address);

	if (vma->vm_start <= address)

		goto good_area;

	if (!(vma->vm_flags & VM_GROWSDOWN))

		goto bad_area;

		return bad_area(regs, address);



	/*

	 * N.B. The POWER/Open ABI allows programs to access up to
@@ -351,7 +389,7 @@ retry: 
		/* get user regs even if this fault is in kernel mode */

		struct pt_regs *uregs = current->thread.regs;

		if (uregs == NULL)

			goto bad_area;

			return bad_area(regs, address);



		/*

		 * A user-mode access to an address a long way below
@@ -366,14 +404,12 @@ retry: 
		 * expand the stack rather than segfaulting.

		 */

		if (address + 2048 < uregs->gpr[1] && !store_update_sp)

			goto bad_area;

			return bad_area(regs, address);

	}

	if (expand_stack(vma, address))

		goto bad_area;

		return bad_area(regs, address);



good_area:

	code = SEGV_ACCERR;



	if (is_exec) {

		/*

		 * Allow execution from readable areas if the MMU does not
@@ -388,16 +424,16 @@ good_area: 
		if (!(vma->vm_flags & VM_EXEC) &&

		    (cpu_has_feature(CPU_FTR_NOEXECUTE) ||

		     !(vma->vm_flags & (VM_READ | VM_WRITE))))

			goto bad_area;

			return bad_area(regs, address);

	/* a write */

	} else if (is_write) {

		if (!(vma->vm_flags & VM_WRITE))

			goto bad_area;

			return bad_area(regs, address);

		flags |= FAULT_FLAG_WRITE;

	/* a read */

	} else {

		if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))

			goto bad_area;

			return bad_area(regs, address);

	}

#ifdef CONFIG_PPC_STD_MMU

	/*
@@ -462,11 +498,10 @@ good_area: 


	if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {

		if (fault & VM_FAULT_SIGSEGV)

			goto bad_area_nosemaphore;

			return bad_area_nosemaphore(regs, address);

		rc = mm_fault_error(regs, address, fault);

		if (rc >= MM_FAULT_RETURN)

			return rc;

		rc = 0;

	}



	/*
@@ -492,21 +527,8 @@ good_area: 
		perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,

			      regs, address);

	}



	return rc;



bad_area:

	up_read(&mm->mmap_sem);



bad_area_nosemaphore:

	/* User mode accesses cause a SIGSEGV */

	if (is_user) {

		_exception(SIGSEGV, regs, code, address);

	return 0;

}



	return SIGSEGV;

}

NOKPROBE_SYMBOL(__do_page_fault);



int do_page_fault(struct pt_regs *regs, unsigned long address,

CRA Git | Maintained and supported by SUSTech CRA and CCSE