Re: [PATCH 1/3] ARM: allow __do_kernel_fault() to report execution of memory faults

["Russell King (Oracle)" <linux@armlinux.org.uk>]

On Tue, Dec 09, 2025 at 12:02:23PM +0800, Xie Yuanbin wrote:
> On Mon, 08 Dec 2025 12:34:54 +0000, Russell King wrote:
> > diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
> > index 2bc828a1940c..f0884bf91dfa 100644
> > --- a/arch/arm/mm/fault.c
> > +++ b/arch/arm/mm/fault.c
> > @@ -162,6 +162,8 @@ __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
> >  	 */
> >  	if (addr < PAGE_SIZE) {
> >  		msg = "NULL pointer dereference";
> > +	} else if (is_permission_fault(fsr) && fsr & FSR_LNX_PF) {
> > +		msg = "execution of memory";
> >  	} else {
> >  		if (is_translation_fault(fsr) &&
> >  		    kfence_handle_page_fault(addr, is_write_fault(fsr), regs))
> 
> This patch caused a compilation error, is_permission_fault() is not
> defined. Fixed with:

Thanks - as you've guessed I have some other patches on top of this
which move the is_xxx_fault() into fault.h.

However, for the sake of this series, my preferred fix is to group
all the is_xxx_fault() inline functions together as the first patch
of this series:

8<===
From: "Russell King (Oracle)" <rmk+kernel@armlinux.org.uk>
Subject: [PATCH] ARM: group is_permission_fault() with is_translation_fault()

Group is_permission_fault() with is_translation_fault(), which is
needed to use is_permission_fault() in __do_kernel_fault(). As
this is static inline, there is no need for this to be under
CONFIG_MMU.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---
 arch/arm/mm/fault.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 2bc828a1940c..f87f353e5a8b 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -128,6 +128,19 @@ static inline bool is_translation_fault(unsigned int fsr)
 	return false;
 }
 
+static inline bool is_permission_fault(unsigned int fsr)
+{
+	int fs = fsr_fs(fsr);
+#ifdef CONFIG_ARM_LPAE
+	if ((fs & FS_MMU_NOLL_MASK) == FS_PERM_NOLL)
+		return true;
+#else
+	if (fs == FS_L1_PERM || fs == FS_L2_PERM)
+		return true;
+#endif
+	return false;
+}
+
 static void die_kernel_fault(const char *msg, struct mm_struct *mm,
 			     unsigned long addr, unsigned int fsr,
 			     struct pt_regs *regs)
@@ -225,19 +238,6 @@ void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 }
 
 #ifdef CONFIG_MMU
-static inline bool is_permission_fault(unsigned int fsr)
-{
-	int fs = fsr_fs(fsr);
-#ifdef CONFIG_ARM_LPAE
-	if ((fs & FS_MMU_NOLL_MASK) == FS_PERM_NOLL)
-		return true;
-#else
-	if (fs == FS_L1_PERM || fs == FS_L2_PERM)
-		return true;
-#endif
-	return false;
-}
-
 #ifdef CONFIG_CPU_TTBR0_PAN
 static inline bool ttbr0_usermode_access_allowed(struct pt_regs *regs)
 {
-- 
2.47.3

-- 
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