ARM: show short message on segfault

kernels on some x86 distros do this, it's pretty useful.

diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
index 5378582..1344f5f 100644 (file)
--- a/arch/arm/include/asm/system.h
+++ b/arch/arm/include/asm/system.h
@@ -117,6 +117,7 @@ extern void (*arm_pm_restart)(char str, const char *cmd);
 #define UDBG_BADABORT  (1 << 2)
 #define UDBG_SEGV      (1 << 3)
 #define UDBG_BUS       (1 << 4)
+#define UDBG_SEGV_SHORT        (1 << 8)
 
 extern unsigned int user_debug;
 

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 7d12e73..071772c 100644 (file)
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -48,7 +48,7 @@ static const char *handler[]= {
 void *vectors_page;
 
 #ifdef CONFIG_DEBUG_USER
-unsigned int user_debug;
+unsigned int user_debug = UDBG_SEGV_SHORT;
 
 static int __init user_debug_setup(char *str)
 {

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index 4c9c3b0..ea34eb9 100644 (file)
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -152,6 +152,39 @@ __do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
        do_exit(SIGKILL);
 }
 
+#ifdef CONFIG_DEBUG_USER
+static void
+print_user_faulter_location(const char *name, struct pt_regs *regs)
+{
+       struct mm_struct *mm = current->mm;
+       struct vm_area_struct *vma;
+       char *p, *t, buf[128];
+
+       printk(KERN_DEBUG "%s: pc=%08lx",
+              name, regs->ARM_pc);
+
+       do {
+               if (!mm)
+                       break;
+               vma = find_vma(mm, regs->ARM_pc);
+               if (!vma || !vma->vm_file)
+                       break;
+
+               p = d_path(&vma->vm_file->f_path, buf, sizeof(buf));
+               if (IS_ERR(p))
+                       break;
+
+               t = strrchr(p, '/');
+               if (t)
+                       p = t + 1;
+
+               printk(KERN_CONT " (%s+%lx)", p, regs->ARM_pc - vma->vm_start);
+       } while (0);
+
+       printk(KERN_CONT ", lr=%08lx\n", regs->ARM_lr);
+}
+#endif
+
 /*
  * Something tried to access memory that isn't in our memory map..
  * User mode accesses just cause a SIGSEGV
@@ -164,9 +197,13 @@ __do_user_fault(struct task_struct *tsk, unsigned long addr,
        struct siginfo si;
 
 #ifdef CONFIG_DEBUG_USER
+       if (user_debug & (UDBG_SEGV | UDBG_SEGV_SHORT)) {
+               printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x (%s)\n",
+                      tsk->comm, sig, addr, fsr,
+                      (fsr & FSR_WRITE) ? "write" : "read");
+               print_user_faulter_location(tsk->comm, regs);
+       }
        if (user_debug & UDBG_SEGV) {
-               printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
-                      tsk->comm, sig, addr, fsr);
                show_pte(tsk->mm, addr);
                show_regs(regs);
        }