xtensa: dump userspace code around the exception PC

In the absence of other debug facilities dumping user code around the
unhandled exception address may help debugging the issue.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

diff --git a/arch/xtensa/Kconfig.debug b/arch/xtensa/Kconfig.debug
index 83cc8d12fa0e1e1373a1f51f5fb0138d8ed1c846..e84172a7763c9d11736d55d66a19a2140159915c 100644 (file)
--- a/arch/xtensa/Kconfig.debug
+++ b/arch/xtensa/Kconfig.debug
@@ -38,3 +38,11 @@ config PRINT_STACK_DEPTH
        help
          This option allows you to set the stack depth that the kernel
          prints in stack traces.
+
+config PRINT_USER_CODE_ON_UNHANDLED_EXCEPTION
+       bool "Dump user code around unhandled exception address"
+       help
+         Enable this option to display user code around PC of the unhandled
+         exception (starting at address aligned on 16 byte boundary).
+         This may simplify finding faulting code in the absence of other
+         debug facilities.

diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index a2a9a460ec9e6c3c9240f8182edee0755189efb8..17eb180eff7c0d61595971781167ab929eb3ca19 100644 (file)
--- a/arch/xtensa/kernel/traps.c
+++ b/arch/xtensa/kernel/traps.c
@@ -175,6 +175,23 @@ __die_if_kernel(const char *str, struct pt_regs *regs, long err)
                die(str, regs, err);
 }
 
+#ifdef CONFIG_PRINT_USER_CODE_ON_UNHANDLED_EXCEPTION
+static inline void dump_user_code(struct pt_regs *regs)
+{
+       char buf[32];
+
+       if (copy_from_user(buf, (void __user *)(regs->pc & -16), sizeof(buf)) == 0) {
+               print_hex_dump(KERN_INFO, " ", DUMP_PREFIX_NONE,
+                              32, 1, buf, sizeof(buf), false);
+
+       }
+}
+#else
+static inline void dump_user_code(struct pt_regs *regs)
+{
+}
+#endif
+
 /*
  * Unhandled Exceptions. Kill user task or panic if in kernel space.
  */
@@ -190,6 +207,7 @@ void do_unhandled(struct pt_regs *regs)
                            "\tEXCCAUSE is %ld\n",
                            current->comm, task_pid_nr(current), regs->pc,
                            regs->exccause);
+       dump_user_code(regs);
        force_sig(SIGILL);
 }