[PATCH rfc v2 09/10] loongarch: mm: add access_error() helper

[Kefeng Wang]

Add access_error() to check whether vma could be accessible or not,
which will be used __do_page_fault() and later vma locked based page
fault.

Signed-off-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
---
 arch/loongarch/mm/fault.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/arch/loongarch/mm/fault.c b/arch/loongarch/mm/fault.c
index 5d4c742c4bc5..2a45e9f3a485 100644
--- a/arch/loongarch/mm/fault.c
+++ b/arch/loongarch/mm/fault.c
@@ -126,6 +126,22 @@ static void __kprobes do_sigsegv(struct pt_regs *regs,
 	force_sig_fault(SIGSEGV, si_code, (void __user *)address);
 }
 
+static inline bool access_error(unsigned int flags, struct pt_regs *regs,
+				unsigned long addr, struct vm_area_struct *vma)
+{
+	if (flags & FAULT_FLAG_WRITE) {
+		if (!(vma->vm_flags & VM_WRITE))
+			return true;
+	} else {
+		if (!(vma->vm_flags & VM_READ) && addr != exception_era(regs))
+			return true;
+		if (!(vma->vm_flags & VM_EXEC) && addr == exception_era(regs))
+			return true;
+	}
+
+	return false;
+}
+
 /*
  * This routine handles page faults.  It determines the address,
  * and the problem, and then passes it off to one of the appropriate
@@ -169,6 +185,8 @@ static void __kprobes __do_page_fault(struct pt_regs *regs,
 
 	if (user_mode(regs))
 		flags |= FAULT_FLAG_USER;
+	if (write)
+		flags |= FAULT_FLAG_WRITE;
 
 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
 retry:
@@ -178,16 +196,8 @@ static void __kprobes __do_page_fault(struct pt_regs *regs,
 
 	si_code = SEGV_ACCERR;
 
-	if (write) {
-		flags |= FAULT_FLAG_WRITE;
-		if (!(vma->vm_flags & VM_WRITE))
-			goto bad_area;
-	} else {
-		if (!(vma->vm_flags & VM_READ) && address != exception_era(regs))
-			goto bad_area;
-		if (!(vma->vm_flags & VM_EXEC) && address == exception_era(regs))
-			goto bad_area;
-	}
+	if (access_error(flags, regs, vma))
+		goto bad_area;
 
 	/*
 	 * If for any reason at all we couldn't handle the fault,
-- 
2.27.0