1 files changed, 55 insertions, 7 deletions

diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index c7861c9864e6..52ee273afeec 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -82,6 +82,49 @@ static inline int notify_page_fault(struct pt_regs *regs, unsigned int esr)
 }
 #endif
 
+static void data_abort_decode(unsigned int esr)
+{
+	pr_alert("Data abort info:\n");
+
+	if (esr & ESR_ELx_ISV) {
+		pr_alert("  Access size = %u byte(s)\n",
+			 1U << ((esr & ESR_ELx_SAS) >> ESR_ELx_SAS_SHIFT));
+		pr_alert("  SSE = %lu, SRT = %lu\n",
+			 (esr & ESR_ELx_SSE) >> ESR_ELx_SSE_SHIFT,
+			 (esr & ESR_ELx_SRT_MASK) >> ESR_ELx_SRT_SHIFT);
+		pr_alert("  SF = %lu, AR = %lu\n",
+			 (esr & ESR_ELx_SF) >> ESR_ELx_SF_SHIFT,
+			 (esr & ESR_ELx_AR) >> ESR_ELx_AR_SHIFT);
+	} else {
+		pr_alert("  ISV = 0, ISS = 0x%08lu\n", esr & ESR_ELx_ISS_MASK);
+	}
+
+	pr_alert("  CM = %lu, WnR = %lu\n",
+		 (esr & ESR_ELx_CM) >> ESR_ELx_CM_SHIFT,
+		 (esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT);
+}
+
+/*
+ * Decode mem abort information
+ */
+static void mem_abort_decode(unsigned int esr)
+{
+	pr_alert("Mem abort info:\n");
+
+	pr_alert("  Exception class = %s, IL = %u bits\n",
+		 esr_get_class_string(esr),
+		 (esr & ESR_ELx_IL) ? 32 : 16);
+	pr_alert("  SET = %lu, FnV = %lu\n",
+		 (esr & ESR_ELx_SET_MASK) >> ESR_ELx_SET_SHIFT,
+		 (esr & ESR_ELx_FnV) >> ESR_ELx_FnV_SHIFT);
+	pr_alert("  EA = %lu, S1PTW = %lu\n",
+		 (esr & ESR_ELx_EA) >> ESR_ELx_EA_SHIFT,
+		 (esr & ESR_ELx_S1PTW) >> ESR_ELx_S1PTW_SHIFT);
+
+	if (esr_is_data_abort(esr))
+		data_abort_decode(esr);
+}
+
 /*
  * Dump out the page tables associated with 'addr' in the currently active mm.
  */
@@ -163,26 +206,27 @@ int ptep_set_access_flags(struct vm_area_struct *vma,
 	/* only preserve the access flags and write permission */
 	pte_val(entry) &= PTE_AF | PTE_WRITE | PTE_DIRTY;
 
-	/*
-	 * PTE_RDONLY is cleared by default in the asm below, so set it in
-	 * back if necessary (read-only or clean PTE).
-	 */
+	/* set PTE_RDONLY if actual read-only or clean PTE */
 	if (!pte_write(entry) || !pte_sw_dirty(entry))
 		pte_val(entry) |= PTE_RDONLY;
 
 	/*
 	 * Setting the flags must be done atomically to avoid racing with the
-	 * hardware update of the access/dirty state.
+	 * hardware update of the access/dirty state. The PTE_RDONLY bit must
+	 * be set to the most permissive (lowest value) of *ptep and entry
+	 * (calculated as: a & b == ~(~a | ~b)).
 	 */
+	pte_val(entry) ^= PTE_RDONLY;
 	asm volatile("//	ptep_set_access_flags\n"
 	"	prfm	pstl1strm, %2\n"
 	"1:	ldxr	%0, %2\n"
-	"	and	%0, %0, %3		// clear PTE_RDONLY\n"
+	"	eor	%0, %0, %3		// negate PTE_RDONLY in *ptep\n"
 	"	orr	%0, %0, %4		// set flags\n"
+	"	eor	%0, %0, %3		// negate final PTE_RDONLY\n"
 	"	stxr	%w1, %0, %2\n"
 	"	cbnz	%w1, 1b\n"
 	: "=&r" (old_pteval), "=&r" (tmp), "+Q" (pte_val(*ptep))
-	: "L" (~PTE_RDONLY), "r" (pte_val(entry)));
+	: "L" (PTE_RDONLY), "r" (pte_val(entry)));
 
 	flush_tlb_fix_spurious_fault(vma, address);
 	return 1;
@@ -247,6 +291,8 @@ static void __do_kernel_fault(unsigned long addr, unsigned int esr,
 	pr_alert("Unable to handle kernel %s at virtual address %08lx\n", msg,
 		 addr);
 
+	mem_abort_decode(esr);
+
 	show_pte(addr);
 	die("Oops", regs, esr);
 	bust_spinlocks(0);
@@ -701,6 +747,8 @@ asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
 	pr_alert("Unhandled fault: %s (0x%08x) at 0x%016lx\n",
 		 inf->name, esr, addr);
 
+	mem_abort_decode(esr);
+
 	info.si_signo = inf->sig;
 	info.si_errno = 0;
 	info.si_code  = inf->code;