[PATCH v2 3/7] ARM: mm: Cleanup access_error()

Kefeng Wang
2021-06-02T06:54:11Z

Now the write fault check in do_page_fault() and access_error() twice,
we can cleanup access_error(), and make the fault check and vma flags set
into do_page_fault() directly, then pass the vma flags to __do_page_fault.

No functional change.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
arch/arm/mm/fault.c | 38 ++++++++++++++------------------------
1 file changed, 14 insertions(+), 24 deletions(-)

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 249db395bdf0..9a6d74f6ea1d 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -183,26 +183,9 @@ void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
#define VM_FAULT_BADMAP 0x010000
#define VM_FAULT_BADACCESS 0x020000

-/*
- * Check that the permissions on the VMA allow for the fault which occurred.
- * If we encountered a write fault, we must have write permission, otherwise
- * we allow any permission.
- */
-static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
-{
- unsigned int mask = VM_ACCESS_FLAGS;
-
- if ((fsr & FSR_WRITE) && !(fsr & FSR_CM))
- mask = VM_WRITE;
- if (fsr & FSR_LNX_PF)
- mask = VM_EXEC;
-
- return vma->vm_flags & mask ? false : true;
-}
-
static vm_fault_t __kprobes
-__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
- unsigned int flags, struct pt_regs *regs)
+__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int flags,
+ unsigned long vma_flags, struct pt_regs *regs)
{
struct vm_area_struct *vma = find_vma(mm, addr);
if (unlikely(!vma))
@@ -218,10 +201,10 @@ __do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
}

/*
- * Ok, we have a good vm_area for this
- * memory access, so we can handle it.
+ * ok, we have a good vm_area for this memory access, check the
+ * permissions on the VMA allow for the fault which occurred.
*/
- if (access_error(fsr, vma))
+ if (!(vma->vm_flags & vma_flags))
return VM_FAULT_BADACCESS;

return handle_mm_fault(vma, addr & PAGE_MASK, flags, regs);
@@ -234,6 +217,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
int sig, code;
vm_fault_t fault;
unsigned int flags = FAULT_FLAG_DEFAULT;
+ unsigned long vm_flags = VM_ACCESS_FLAGS;

if (kprobe_page_fault(regs, fsr))
return 0;
@@ -252,8 +236,14 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)

if (user_mode(regs))
flags |= FAULT_FLAG_USER;
- if ((fsr & FSR_WRITE) && !(fsr & FSR_CM))
+
+ if ((fsr & FSR_WRITE) && !(fsr & FSR_CM)) {
flags |= FAULT_FLAG_WRITE;
+ vm_flags = VM_WRITE;
+ }
+
+ if (fsr & FSR_LNX_PF)
+ vm_flags = VM_EXEC;

perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);

@@ -281,7 +271,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
#endif
}

- fault = __do_page_fault(mm, addr, fsr, flags, regs);
+ fault = __do_page_fault(mm, addr, flags, vm_flags, regs);

/* If we need to retry but a fatal signal is pending, handle the
* signal first. We do not need to release the mmap_lock because
--
2.26.2