powerpc/ftrace: Fix inverted check of create_branch()

In commit 24a1bdc35, "Fix ABIv2 issues with __ftrace_make_call", Anton
changed the logic that creates and patches the branch, and added a
thinko in the check of create_branch(). create_branch() returns the
instruction that was generated, so if we get zero then it succeeded.

The result is we can't ftrace modules:

  Branch out of range
  WARNING: at ../kernel/trace/ftrace.c:1638
  ftrace failed to modify [<d000000004ba001c>] fuse_req_init_context+0x1c/0x90 [fuse]

We should probably fix patch_instruction() to do that check and make the
API saner, but that's a separate patch. For now just invert the test.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c
index f5d1a3420192f87ec15a414d1aa9bdde7ac72e55..8fc0c1742498186f3500697d6e8848ba25744765 100644 (file)
--- a/arch/powerpc/kernel/ftrace.c
+++ b/arch/powerpc/kernel/ftrace.c
@@ -320,7 +320,7 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
        }
 
        /* Ensure branch is within 24 bits */
-       if (create_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
+       if (!create_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
                printk(KERN_ERR "Branch out of range");
                return -EINVAL;
        }