Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...

[linux-2.6-block.git] / arch / x86 / kernel / unwind_orc.c

diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 33b66b5c5aec3244a11f565ed0334383b8c29fae..332ae6530fa8813e5c6dda09f6457e1ded0eb436 100644 (file)
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -82,9 +82,9 @@ static struct orc_entry *orc_find(unsigned long ip);
  * But they are copies of the ftrace entries that are static and
  * defined in ftrace_*.S, which do have orc entries.
  *
- * If the undwinder comes across a ftrace trampoline, then find the
+ * If the unwinder comes across a ftrace trampoline, then find the
  * ftrace function that was used to create it, and use that ftrace
- * function's orc entrie, as the placement of the return code in
+ * function's orc entry, as the placement of the return code in
  * the stack will be identical.
  */
 static struct orc_entry *orc_ftrace_find(unsigned long ip)
@@ -128,6 +128,16 @@ static struct orc_entry null_orc_entry = {
        .type = ORC_TYPE_CALL
 };
 
+/* Fake frame pointer entry -- used as a fallback for generated code */
+static struct orc_entry orc_fp_entry = {
+       .type           = ORC_TYPE_CALL,
+       .sp_reg         = ORC_REG_BP,
+       .sp_offset      = 16,
+       .bp_reg         = ORC_REG_PREV_SP,
+       .bp_offset      = -16,
+       .end            = 0,
+};
+
 static struct orc_entry *orc_find(unsigned long ip)
 {
        static struct orc_entry *orc;
@@ -392,8 +402,16 @@ bool unwind_next_frame(struct unwind_state *state)
         * calls and calls to noreturn functions.
         */
        orc = orc_find(state->signal ? state->ip : state->ip - 1);
-       if (!orc)
-               goto err;
+       if (!orc) {
+               /*
+                * As a fallback, try to assume this code uses a frame pointer.
+                * This is useful for generated code, like BPF, which ORC
+                * doesn't know about.  This is just a guess, so the rest of
+                * the unwind is no longer considered reliable.
+                */
+               orc = &orc_fp_entry;
+               state->error = true;
+       }
 
        /* End-of-stack check for kernel threads: */
        if (orc->sp_reg == ORC_REG_UNDEFINED) {
@@ -580,7 +598,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
                        goto done;
 
                state->ip = regs->ip;
-               state->sp = kernel_stack_pointer(regs);
+               state->sp = regs->sp;
                state->bp = regs->bp;
                state->regs = regs;
                state->full_regs = true;