[PATCH 2/2] ARM: Proper prefetch abort handling on ARMv7

[Kirill A. Shutemov]

Currently, on ARMv7, if an application tries to execute code
(or garbage) on non-executable page it hangs. It caused by incorrect
prefetch abort handling. Now every prefetch abort processes as
a translation fault.

To fix this we have to analize instruction fault status register
to figure out reason why we've got the abort and process it
accordingly.

Signed-off-by: Kirill A. Shutemov <kirill at shutemov.name>
---
 arch/arm/mm/fault.c |   51 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 50 insertions(+), 1 deletions(-)

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 5e27462..5abb9a5 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -505,9 +505,58 @@ do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 	arm_notify_die("", regs, &info, fsr, 0);
 }
 
+
+static struct fsr_info ifsr_info[] = {
+	{ do_bad,		SIGBUS,  0,		"unknown 0"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 1"			   },
+	{ do_bad,		SIGBUS,  0,		"debug event"			   },
+	{ do_bad,		SIGSEGV, SEGV_ACCERR,	"section access flag fault"	   },
+	{ do_bad,		SIGBUS,  0,		"unknown 4"			   },
+	{ do_translation_fault,	SIGSEGV, SEGV_MAPERR,	"section translation fault"	   },
+	{ do_bad,		SIGSEGV, SEGV_ACCERR,	"page access flag fault"	   },
+	{ do_page_fault,	SIGSEGV, SEGV_MAPERR,	"page translation fault"	   },
+	{ do_bad,		SIGBUS,	 0,		"external abort on non-linefetch"  },
+	{ do_bad,		SIGSEGV, SEGV_ACCERR,	"section domain fault"		   },
+	{ do_bad,		SIGBUS,  0,		"unknown 10"			   },
+	{ do_bad,		SIGSEGV, SEGV_ACCERR,	"page domain fault"		   },
+	{ do_bad,		SIGBUS,	 0,		"external abort on translation"	   },
+	{ do_bad,		SIGSEGV, SEGV_ACCERR,	"section permission fault"	   },
+	{ do_bad,		SIGBUS,	 0,		"external abort on translation"	   },
+	{ do_bad,		SIGSEGV, SEGV_ACCERR,	"page permission fault"		   },
+	{ do_bad,		SIGBUS,  0,		"unknown 16"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 17"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 18"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 19"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 20"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 21"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 22"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 23"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 24"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 25"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 26"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 27"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 28"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 29"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 30"			   },
+	{ do_bad,		SIGBUS,  0,		"unknown 31"			   },
+};
+
 asmlinkage void __exception
 do_PrefetchAbort(unsigned long addr, int ifsr, struct pt_regs *regs)
 {
-	do_translation_fault(addr, 0, regs);
+	const struct fsr_info *inf = ifsr_info + (ifsr & 15) + ((ifsr & (1 << 10)) >> 6);
+	struct siginfo info;
+
+	if (!inf->fn(addr, ifsr, regs))
+		return;
+
+	printk(KERN_ALERT "Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
+		inf->name, ifsr, addr);
+
+	info.si_signo = inf->sig;
+	info.si_errno = 0;
+	info.si_code  = inf->code;
+	info.si_addr  = (void __user *)addr;
+	arm_notify_die("", regs, &info, ifsr, 0);
 }
 
-- 
1.6.4.4