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powerpc/mm: Make bad_area* helper functions

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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: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Benjamin Herrenschmidt 2017-07-19 14:49:35 +10:00 committed by Michael Ellerman
parent d3ca587404
commit c3350602e8
1 changed files with 50 additions and 28 deletions
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78
arch/powerpc/mm/fault.c
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@ -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;
}
/*
@ -492,20 +527,7 @@ 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;
return 0;
}
NOKPROBE_SYMBOL(__do_page_fault);